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The hypothalamus regulates fundamental aspects of physiological homeostasis and behavior, including stress response, reproduction, growth, sleep, and feeding, several of which are affected in patients with Prader–Willi (PWS) and Schaaf–Yang syndrome (SYS). PWS is caused by paternal deletion, maternal uniparental disomy, or imprinting defects that lead to loss of expression of a maternally imprinted region of chromosome 15 encompassing non-coding RNAs and five protein-coding genes; SYS patients have a mutation in one of them, MAGEL2. Throughout life, PWS and SYS patients suffer from musculoskeletal deficiencies, intellectual disabilities, and hormonal abnormalities, which lead to compulsive behaviors like hyperphagia and temper outbursts. Management of PWS and SYS is mostly symptomatic and cures for these debilitating disorders do not exist, highlighting a clear, unmet medical need. Research over several decades into the molecular and cellular roles of PWS genes has uncovered that several impinge on the neuroendocrine system. In this review, we will discuss the expression and molecular functions of PWS genes, connecting them with hormonal imbalances in patients and animal models. Besides the observed hormonal imbalances, we will describe the recent findings about how the loss of individual genes, particularly MAGEL2, affects the molecular mechanisms of hormone secretion. These results suggest that MAGEL2 evolved as a mammalian-specific regulator of hypothalamic neuroendocrine function. [ABSTRACT FROM AUTHOR]

Key Clinical Message: We report two, genotypically identical but phenotypically distinct cases of Schaaf‐Yang syndrome and propose the early use of Genome Sequencing in patients with nonspecific presentations to facilitate the early diagnosis of children with rare genetic diseases and improve overall health care outcomes. [ABSTRACT FROM AUTHOR]

Schaaf‐Yang syndrome (SHFYNG) is a rare pleiotropic disorder, characterized by hypotonia, joint contractures, autism spectrum disorders (ASD), and developmental delay/intellectual disability. Although it shares some common features with Prader‐Willi Syndrome, joint contractures, and ASD were more commonly detected in in this syndrome. Recently, it was shown that truncating variants in the paternal allele of the MAGEL2 gene cause SHFYNG. Here, we present two patients diagnosed with SHFYNG syndrome having two different novel truncating variants in the MAGEL2 gene, one paternally inherited and one de novo. One patient had obesity, brachydactyly and dysmorphic features, and the other patient presented with contractures, severe hypotonia and early death. This is the first report of Turkish SHFYNG syndrome cases presented to emphasize the phenotypic diversity of the syndrome. [ABSTRACT FROM AUTHOR]

Intracellular protein trafficking and sorting are extremely arduous in endocrine and neuroendocrine cells, which synthesize and secrete on-demand substantial quantities of proteins. To ensure that neuroendocrine secretion operates correctly, each step in the secretion pathways is tightly regulated and coordinated both spatially and temporally. At the trans-Golgi network (TGN), intrinsic structural features of proteins and several sorting mechanisms and distinct signals direct newly synthesized proteins into proper membrane vesicles that enter either constitutive or regulated secretion pathways. Furthermore, this anterograde transport is counterbalanced by retrograde transport, which not only maintains membrane homeostasis but also recycles various proteins that function in the sorting of secretory cargo, formation of transport intermediates, or retrieval of resident proteins of secretory organelles. The retromer complex recycles proteins from the endocytic pathway back to the plasma membrane or TGN and was recently identified as a critical player in regulated secretion in the hypothalamus. Furthermore, melanoma antigen protein L2 (MAGEL2) was discovered to act as a tissue-specific regulator of the retromer-dependent endosomal protein recycling pathway and, by doing so, ensures proper secretory granule formation and maturation. MAGEL2 is a mammalian-specific and maternally imprinted gene implicated in Prader-Willi and Schaaf-Yang neurodevelopmental syndromes. In this review, we will briefly discuss the current understanding of the regulated secretion pathway, encompassing anterograde and retrograde traffic. Although our understanding of the retrograde trafficking and sorting in regulated secretion is not yet complete, we will review recent insights into the molecular role of MAGEL2 in hypothalamic neuroendocrine secretion and how its dysregulation contributes to the symptoms of Prader-Willi and Schaaf-Yang patients. Given that the activation of many secreted proteins occurs after they enter secretory granules, modulation of the sorting efficiency in a tissue-specific manner may represent an evolutionary adaptation to environmental cues.

Key Clinical Message We report two, genotypically identical but phenotypically distinct cases of Schaaf‐Yang syndrome and propose the early use of Genome Sequencing in patients with nonspecific presentations to facilitate the early diagnosis of children with rare genetic diseases and improve overall health care outcomes.

Schaaf-Yang syndrome (SYS) is a rare genomic imprinting disorder caused by truncating mutations in the paternally derived MAGE family member L2 (MAGEL2) allele. It is also responsible for Prader-Willi syndrome, characterized by neonatal hypotonia, developmental delay, intellectual disability, respiratory distress in early infancy, and arthrogryposis. More than 250 individuals with approximately 57 different molecular variants have been reported since 2013, but the phenotype-genotype association in SYS is not yet fully understood. Here, we describe the case of a Korean patient diagnosed with SYS harboring a mutation in the paternal allele of MAGEL2: c.2895G>A, resulting in a protein change of p.Trp965*. The patient’s phenotype included respiratory distress, arthrogryposis, hypotonia, and feeding difficulty in the early neonatal period. Mild renal dysfunction and hearing impairment were observed during infancy.

Schaaf-Yang Syndrome (SYS) is a genetic disorder caused by truncating pathogenic variants in the paternal allele of the maternally imprinted, paternally expressed gene MAGEL2 and is characterized by genital hypoplasia, neonatal hypotonia, developmental delay, intellectual disability, autism spectrum disorder (ASD), and other features. In this study, eleven SYS patients from three families were enrolled and comprehensive clinical features were gathered regarding each family. Whole-exome sequencing (WES) was performed for the definitive molecular diagnosis of the disease. Identified variants were validated using Sanger sequencing. Three couples underwent PGT for monogenic diseases (PGT-M) and/or a prenatal diagnosis. Haplotype analysis was performed to deduce the embryo's genotype by using the short tandem repeats (STRs) identified in each sample. The prenatal diagnosis results showed that the fetus in each case did not carry pathogenic variants, and all the babies of the three families were born at full term and were healthy. We also performed a review of SYS cases. In addition to the 11 patients in our study, a total of 127 SYS patients were included in 11 papers. We summarized all variant sites and clinical symptoms thus far, and conducted a genotype–phenotype correlation analysis. Our results also indicated that the variation in phenotypic severity may depend on the specific location of the truncating variant, suggestive of a genotype–phenotype association. [ABSTRACT FROM AUTHOR]

Confronting oxytocin and vasopressin deficits in autism spectrum disorders and rare syndromes brought promises and disappointments for the treatment of social disabilities. We searched downstream of oxytocin and vasopressin for targets alleviating social deficits in a mouse model of Prader-Willi syndrome and Schaaf-Yang syndrome, both associated with high prevalence of autism. We found a population of neurons in the lateral septum-activated on termination of social contacts-which oxytocin and vasopressin inhibit as per degree of peer affiliation. These are somatostatin neurons expressing oxytocin receptors coupled to GABA-B signaling, which are inhibited via GABA-A channels by vasopressin-excited GABA neurons. Loss of oxytocin or vasopressin signaling recapitulated the disease phenotype. By contrast, deactivation of somatostatin neurons or receptor signaling alleviated social deficits of disease models by increasing the duration of contacts with mates and strangers. These findings provide new insights into the treatment framework of social disabilities in neuropsychiatric disorders., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Schaaf‐Yang syndrome (SYS) is a rare hereditary disease caused by truncating point mutations of the paternal allele of melanoma antigen L2 (MAGEL2), one of five protein‐coding genes within the Prader‐Willi syndrome (PWS) critical domain. SYS shares many clinical and molecular characteristics with PWS but has some distinct features, such as joint contractures and autism. Patients with PWS show abnormal electroencephalography (EEG) patterns. However, there are very few reports on EEG findings in patients with SYS. Methods: A SYS patient was included in this study. Detailed neurological examinations and EEG were performed from neonate to infant ages. Sanger sequencing was performed. Results: Our patient presented abnormal EEG findings and had diffuse brain dysfunction symptoms including a reduced level of consciousness, diminished spontaneous movements, hypotonia, feeding difficulties, and hypoventilation from early after birth. As she grew older and her background activity of EEG normalized, her neurodevelopmental symptoms remained but improved. Sanger sequencing of this patient revealed a novel, heterozygous c.2005C > T, truncating mutation in the MEGAL2 gene. Conclusions: We described an SYS‐associated, time‐dependent, EEG pattern in a patient with SYS. Our findings of longitudinal EEG changes in a patient with SYS revealed a specific pattern of how affected individuals develop brain function. [ABSTRACT FROM AUTHOR]

Obesity is a global medical problem; its common form is known as diet-induced obesity (DIO); however, there are several rare genetic disorders, such as Prader–Willi syndrome (PWS), that are also associated with obesity (genetic-induced obesity, GIO). The currently available therapeutics for treating DIO and GIO are very limited, and they result in only a partial improvement. Cannabidiolic acid (CBDA), a constituent of Cannabis sativa, gradually decarboxylates to cannabidiol (CBD). Whereas the anti-obesity properties of CBD have been reasonably identified, our knowledge of the pharmacology of CBDA is more limited due to its instability. To stabilize CBDA, a new derivative, CBDA-O-methyl ester (HU-580, EPM301), was synthesized. The therapeutic potential of EPM301 in appetite reduction, weight loss, and metabolic improvements in DIO and GIO was tested in vivo. EPM301 (40 mg/kg/d, i.p.) successfully resulted in weight loss, increased ambulation, as well as improved glycemic and lipid profiles in DIO mice. Additionally, EPM301 ameliorated DIO-induced hepatic dysfunction and steatosis. Importantly, EPM301 (20 and 40 mg/kg/d, i.p.) effectively reduced body weight and hyperphagia in a high-fat diet-fed Magel2null mouse model for PWS. In addition, when given to standard-diet-fed Magel2null mice as a preventive treatment, EPM301 completely inhibited weight gain and adiposity. Lastly, EPM301 increased the oxidation of different nutrients in each strain. All together, EPM301 ameliorated obesity and its metabolic abnormalities in both DIO and GIO. These results support the idea to further promote this synthetic CBDA derivative toward clinical evaluation in humans. [ABSTRACT FROM AUTHOR]

Abstract Background Schaaf‐Yang syndrome (SYS) is a rare hereditary disease caused by truncating point mutations of the paternal allele of melanoma antigen L2 (MAGEL2), one of five protein‐coding genes within the Prader‐Willi syndrome (PWS) critical domain. SYS shares many clinical and molecular characteristics with PWS but has some distinct features, such as joint contractures and autism. Patients with PWS show abnormal electroencephalography (EEG) patterns. However, there are very few reports on EEG findings in patients with SYS. Methods A SYS patient was included in this study. Detailed neurological examinations and EEG were performed from neonate to infant ages. Sanger sequencing was performed. Results Our patient presented abnormal EEG findings and had diffuse brain dysfunction symptoms including a reduced level of consciousness, diminished spontaneous movements, hypotonia, feeding difficulties, and hypoventilation from early after birth. As she grew older and her background activity of EEG normalized, her neurodevelopmental symptoms remained but improved. Sanger sequencing of this patient revealed a novel, heterozygous c.2005C > T, truncating mutation in the MEGAL2 gene. Conclusions We described an SYS‐associated, time‐dependent, EEG pattern in a patient with SYS. Our findings of longitudinal EEG changes in a patient with SYS revealed a specific pattern of how affected individuals develop brain function.

Abstract Background MAGEL2-associated Schaaf-Yang syndrome (SHFYNG, OMIM #615547, ORPHA: 398069), which was identified in 2013, is a rare disorder caused by truncating variants of the paternal copy of MAGEL2, which is localized in the imprinted region on 15q11.2q13. The phenotype of SHFYNG in childhood partially overlaps with that of the well-established Prader–Willi syndrome (PWS, OMIM #176270). While larger numbers of younger individuals with SHFYNG have been recently published, the phenotype in adulthood is not well established. We recruited 7 adult individuals (aged 18 to 36) with molecularly confirmed SHFYNG and collected data regarding the clinical profile including eating habits, sleep, behavior, personal autonomy, psychiatric abnormalities and other medical conditions, as well as information about the respective phenotypes in childhood. Results Within our small cohort, we identified a range of common features, such as disturbed sleep, hypoactivity, social withdrawal and anxiety, but also noted considerable differences at the level of personal autonomy and skills. Behavioral problems were frequent, and a majority of individuals displayed weight gain and food-seeking behavior, along with mild intellectual disability or borderline intellectual function. Classical symptoms of SHFYNG in childhood were reported for most individuals. Conclusion Our findings indicate a high variability of the functional abilities and social participation of adults with SHFYNG. A high prevalence of obesity within our cohort was notable, and uncontrollable food intake was a major concern for some caregivers. The phenotypes of PWS and SHFYNG in adulthood might be more difficult to discern than the phenotypes in childhood. Molecular genetic testing for SHFYNG should therefore be considered in adults with the suspected diagnosis of PWS, if testing for PWS has been negative.

Background: Prader–Willi syndrome is a rare genetic neurodevelopmental disorder caused by a paternal deficiency of maternally imprinted gene expression located in the chromosome 15q11–q13 region. Previous studies have demonstrated that several classes of neurodevelopmental disorders can be attributed to either over- or under-expression of specific genes that may lead to impairments in neuronal generation, differentiation, maturation and growth. Epigenetic changes that modify gene expression have been highlighted in these disorders. One recent study focused on epigenetic analysis and compared patients with PWS with patients with other imprinting disorders. No study, however, has yet focused on epigenetics in patients with PWS specifically by comparing the mutations associated with this syndrome. Objective: This study investigated the epigenetic modifications in patients with PWS and patients with PWS-related disorders caused by inactivation of two genes of the PWS chromosomal region, SNORD116 and MAGEL2. Our approach also aimed to compare the epigenetic modifications in PWS and PWS-related disorders. Methods: We compared genome-wide methylation analysis (GWAS) in seven blood samples from patients with PWS phenotype (five with deletions of the PWS locus, one with a microdeletion of SNORD116 and one with a frameshift mutation of MAGEL2 presenting with Schaaf–Yang syndrome), as well as two control patients. Controls were infants that had been studied for suspicion of genetic diseases that was not confirmed by the genetic analysis and the clinical follow-up. Results: The analysis identified 29,234 differentially methylated cytosines, corresponding to 5,308 differentially methylated regions (DMRs), which matched with 2,280 genes. The DMRs in patients with PWS were associated with neurodevelopmental pathways, endocrine dysfunction and social and addictive processes consistent with the key features of the PWS phenotype. In addition, the separate analysis for the SNORD116 and MAGEL2 deletions revealed that the DMRs associated with the SNORD116 microdeletion were found in genes implicated in metabolic pathways and nervous system development, whereas MAGEL2 mutations mostly concerned genes involved in macromolecule biosynthesis. Conclusion: The PWS is associated with epigenetic modifications with differences in SNORD116 and MAGEL2 mutations, which seem to be relevant to the different associated phenotypes. [ABSTRACT FROM AUTHOR]

Abstract Background Schaaf-Yang syndrome (SYS) is a newly recognized imprinting related syndrome, which is caused by a truncating variant in maternally imprinted MAGEL2 located in 15q11-q13. Yet, precise pathomechanism remains to be solved. We sequenced MAGEL2 in patients suspected Prader-Willi syndrome (PWS) to delineate clinical presentation of SYS. We examined 105 patients with clinically suspected PWS but without a specific PWS genetic alteration. Sanger sequencing of the entire MAGEL2 gene and methylation-specific restriction enzyme treatment to detect the parent of origin were performed. Clinical presentation was retrospectively assessed in detail. Results Truncating variants in MAGEL2 were detected in six patients (5.7%), including a pair of siblings. All truncating variants in affected patients were on the paternally derived chromosome, while the healthy father of the affected siblings inherited the variant from his mother. Patients with MAGEL2 variants shared several features with PWS, such as neonatal hypotonia, poor suck, and obesity; however, there were also unique features, including arthrogryposis and a failure to acquire meaningful words. Additionally, an episode of neurological deterioration following febrile illness was confirmed in four of the six patients, which caused severe neurological sequalae. Conclusions SYS can be present in infants suspected with PWS but some unique features, such as arthrogryposis, can help discriminate between the two syndromes. An episode of neurological deterioration following febrile illness should be recognized as an important complication.

Prader-Willi and the related Schaaf-Yang Syndromes (PWS/SYS) are rare neurodevelopmental disorders characterized by overlapping phenotypes of high incidence of autism spectrum disorders (ASD) and neonatal feeding difficulties. Based on clinical and basic studies, oxytocin pathway defects are suggested to contribute disease pathogenesis but the mechanism has been poorly understood. Specifically, whether the impairment in oxytocin system is limited to neuropeptide levels and how the functional properties of broader oxytocin neuron circuits affected in PWS/SYS have not been addressed. Using cell type specific electrophysiology, we investigated basic synaptic and cell autonomous properties of oxytocin neurons in the absence of MAGEL2; a hypothalamus enriched ubiquitin ligase regulator that is inactivated in both syndromes. We observed significant suppression of overall ex vivo oxytocin neuron activity, which was largely contributed by altered synaptic input profile; with reduced excitatory and increased inhibitory currents. Our results suggest that dysregulation of oxytocin system goes beyond altered neuropeptide expression and synaptic excitation inhibition imbalance impairs overall oxytocin pathway function.

Background: MAGEL2-associated Schaaf-Yang syndrome (SHFYNG, OMIM #615547, ORPHA: 398069), which was identified in 2013, is a rare disorder caused by truncating variants of the paternal copy of MAGEL2, which is localized in the imprinted region on 15q11.2q13. The phenotype of SHFYNG in childhood partially overlaps with that of the well-established Prader-Willi syndrome (PWS, OMIM #176270). While larger numbers of younger individuals with SHFYNG have been recently published, the phenotype in adulthood is not well established. We recruited 7 adult individuals (aged 18 to 36) with molecularly confirmed SHFYNG and collected data regarding the clinical profile including eating habits, sleep, behavior, personal autonomy, psychiatric abnormalities and other medical conditions, as well as information about the respective phenotypes in childhood.Results: Within our small cohort, we identified a range of common features, such as disturbed sleep, hypoactivity, social withdrawal and anxiety, but also noted considerable differences at the level of personal autonomy and skills. Behavioral problems were frequent, and a majority of individuals displayed weight gain and food-seeking behavior, along with mild intellectual disability or borderline intellectual function. Classical symptoms of SHFYNG in childhood were reported for most individuals.Conclusion: Our findings indicate a high variability of the functional abilities and social participation of adults with SHFYNG. A high prevalence of obesity within our cohort was notable, and uncontrollable food intake was a major concern for some caregivers. The phenotypes of PWS and SHFYNG in adulthood might be more difficult to discern than the phenotypes in childhood. Molecular genetic testing for SHFYNG should therefore be considered in adults with the suspected diagnosis of PWS, if testing for PWS has been negative. [ABSTRACT FROM AUTHOR]

Truncating variants of the MAGEL2 gene, one of the protein-coding genes within the Prader-Willi syndrome (PWS) critical region on chromosome 15q11, cause Schaaf-Yang syndrome (SYS)—a neurodevelopmental disorder that shares several clinical features with PWS. The current study sought to characterize the neurobehavioral phenotype of SYS in a sample of 9 patients with molecularly-confirmed SYS. Participants received an assessment of developmental/intellectual functioning, adaptive functioning, autism symptomatology, and behavioral/emotional functioning. Compared to individuals with PWS, patients with SYS manifested more severe cognitive deficits, no obsessions or compulsions, and increased rates of autism spectrum disorder. [ABSTRACT FROM AUTHOR]

Crisponi/cold‐induced sweating syndrome (CS/CISS) is an autosomal recessive disease characterized by hyperthermia, camptodactyly, feeding and respiratory difficulties often leading to sudden death in the neonatal period. The affected individuals who survived the first critical years of life, develop cold‐induced sweating and scoliosis in early childhood. The disease is caused by variants in the CRLF1 or in the CLCF1 gene. Both proteins form a heterodimeric complex that acts on cells expressing the ciliary neurotrophic factor receptor (CNTFR). CS/CISS belongs to the family of "CNTFR‐related disorders" showing a similar clinical phenotype. Recently, variants in other genes, including KLHL7, NALCN, MAGEL2 and SCN2A, previously linked to other diseases, have been associated with a CS/CISS‐like phenotype. Therefore, retinitis pigmentosa and Bohring‐Optiz syndrome‐like (KLHL7), Congenital contractures of the limbs and face, hypotonia, and developmental delay syndrome (NALCN), Chitayat‐Hall/Schaaf‐Yang syndrome (MAGEL2), and early infantile epileptic encephalopathy‐11 syndrome (SCN2A) all share an overlapping phenotype with CS/CISS, especially in the neonatal period. This review aims to summarize the existing literature on CS/CISS, focusing on the current state of differential diagnosis, pathogenesis and treatment concepts in order to achieve an accurate and rapid diagnosis. This will improve patient management and enable specific treatments for the affected individuals. [ABSTRACT FROM AUTHOR]

Pathogenic MAGEL2 variants result in the phenotypes of Chitayat‐Hall syndrome (CHS), Schaaf‐Yang syndrome (SYS) and Prader‐Willi syndrome (PWS). We present five patients with mutations in MAGEL2, including the first patient reported with a missense variant, adding to the limited literature. Further, we performed a systematic review of the CHS and SYS literature, assess the overlap between CHS, SYS and PWS, and analyze genotype‐phenotype correlations among them. We conclude that there is neither a clinical nor etiological difference between CHS and SYS, and propose that the two syndromes simply be referred to as MAGEL2‐related disorders. [ABSTRACT FROM AUTHOR]

Crisponi/cold‐induced sweating syndrome (CS/CISS) is a rare autosomal recessive disorder characterized by a complex phenotype (hyperthermia and feeding difficulties in the neonatal period, followed by scoliosis and paradoxical sweating induced by cold since early childhood) and a high neonatal lethality. CS/CISS is a genetically heterogeneous disorder caused by mutations in CRLF1 (CS/CISS1), CLCF1 (CS/CISS2) and KLHL7 (CS/CISS‐like). Here, a whole exome sequencing approach in individuals with CS/CISS‐like phenotype with unknown molecular defect revealed unpredicted alternative diagnoses. This approach identified putative pathogenic variations in NALCN, MAGEL2 and SCN2A. They were already found implicated in the pathogenesis of other syndromes, respectively the congenital contractures of the limbs and face, hypotonia, and developmental delay syndrome, the Schaaf‐Yang syndrome, and the early infantile epileptic encephalopathy‐11 syndrome. These results suggest a high neonatal phenotypic overlap among these disorders and will be very helpful for clinicians. Genetic analysis of these genes should be considered for those cases with a suspected CS/CISS during neonatal period who were tested as mutation negative in the known CS/CISS genes, because an expedited and corrected diagnosis can improve patient management and can provide a specific clinical follow‐up. Genetic analysis of NALCN, MAGEL2 and SCN2A should be considered for those cases with a suspected Crisponi/cold‐induced sweating syndrome (CS/CISS) during neonatal period who were tested as mutation negative in the known CS/CISS genes, because an expedited and corrected diagnosis can improve patient management and can provide a specific clinical follow‐up. [ABSTRACT FROM AUTHOR]

Abstract Prader-Willi and the related Schaaf-Yang Syndromes (PWS/SYS) are rare neurodevelopmental disorders characterized by overlapping phenotypes of high incidence of autism spectrum disorders (ASD) and neonatal feeding difficulties. Based on clinical and basic studies, oxytocin pathway defects are suggested to contribute disease pathogenesis but the mechanism has been poorly understood. Specifically, whether the impairment in oxytocin system is limited to neuropeptide levels and how the functional properties of broader oxytocin neuron circuits affected in PWS/SYS have not been addressed. Using cell type specific electrophysiology, we investigated basic synaptic and cell autonomous properties of oxytocin neurons in the absence of MAGEL2; a hypothalamus enriched ubiquitin ligase regulator that is inactivated in both syndromes. We observed significant suppression of overall ex vivo oxytocin neuron activity, which was largely contributed by altered synaptic input profile; with reduced excitatory and increased inhibitory currents. Our results suggest that dysregulation of oxytocin system goes beyond altered neuropeptide expression and synaptic excitation inhibition imbalance impairs overall oxytocin pathway function. Highlights • Loss of Prader-Willi syndrome gene- Magel2 suppresses activity of oxytocin neurons. • Magel2 deficient oxytocin neurons have normal basic membrane properties. • Loss of Magel2 alters excitatory/inhibitory synaptic balance onto oxytocin neurons. • Magel2 mutant oxytocin neurons have selective loss of AMPA but normal NMDA currents. [ABSTRACT FROM AUTHOR]

Among a multitude of hormonal and metabolic complications, individuals with Prader‐Willi syndrome (PWS) exhibit significant bone abnormalities, including decreased BMD, osteoporosis, and subsequent increased fracture risk. Here we show in mice that loss of Magel2, a maternally imprinted gene in the PWS critical region, results in reduced bone mass, density, and strength, corresponding to that observed in humans with PWS, as well as in individuals suffering from Schaaf‐Yang syndrome (SYS), a genetic disorder caused by a disruption of the MAGEL2 gene. The low bone mass phenotype in Magel2‐/‐ mice was attributed to reduced bone formation rate, increased osteoclastogenesis and osteoclast activity, and enhanced trans‐differentiation of osteoblasts to adipocytes. The absence of Magel2 in humans and mice resulted in reduction in the fatty acid amide bone homeostasis regulator, N‐oleoyl serine (OS), whose levels were positively linked with BMD in humans and mice as well as osteoblast activity. Attenuating the skeletal abnormalities in Magel2‐/‐ mice was achieved with chronic administration of a novel synthetic derivative of OS. Taken together, Magel2 plays a key role in modulating bone remodeling and mass in PWS by affecting OS levels and activity. The use of potent synthetic analogs of OS should be further tested clinically as bone therapeutics for treating bone loss. © 2018 American Society for Bone and Mineral Research. [ABSTRACT FROM AUTHOR]

Schaaf‐Yang Syndrome (SYS) is a genetic disorder caused by truncating pathogenic variants in the paternal allele of the maternally imprinted, paternally expressed gene MAGEL2, located in the Prader‐Willi critical region 15q11‐15q13. SYS is a neurodevelopmental disorder that has clinical overlap with Prader‐Willi Syndrome in the initial stages of life but becomes increasingly distinct throughout childhood and adolescence. Here, we describe the phenotype of an international cohort of 78 patients with nonsense or frameshift mutations in MAGEL2. This cohort includes 43 individuals that have been reported previously, as well as 35 newly identified individuals with confirmed pathogenic genetic variants. We emphasize that intellectual disability/developmental delay, autism spectrum disorder, neonatal hypotonia, infantile feeding problems, and distal joint contractures are the most consistently shared features of patients with SYS. Our results also indicate that there is a marked prevalence of infantile respiratory distress, gastroesophageal reflux, chronic constipation, skeletal abnormalities, sleep apnea, and temperature instability. While there are many shared features, patients with SYS are characterized by a wide phenotypic spectrum, including a variable degree of intellectual disability, language development, and motor milestones. Our results indicate that the variation in phenotypic severity may depend on the specific location of the truncating mutation, suggestive of a genotype–phenotype association. This evidence may be useful in both prenatal and pediatric genetic counseling. [ABSTRACT FROM AUTHOR]

Schaaf–Yang syndrome (SYS) was recently identified as a genetic condition resembling Prader–Willi syndrome. It is caused by mutations on the paternal allele of the MAGEL2 gene, a gene that has been mapped in the Prader–Willi critical region. Here, we present an infant with SYS who sadly died because of the combination of hypotonia, sleep apnea, and obesity. A heterozygous premature stop mutation in MAGEL2 was identified in the patient. The main factors reported in the mortality of SYS are lethal arthrogryposis multiplex congenita, fetal akinesia, and pulmonary problems. Our clinical report indicates that obesity and its complications are an important additional factor in the mortality associated with SYS. Therefore, we advise to strictly monitor weight and intensively treat overweight and obesity in SYS. [ABSTRACT FROM AUTHOR]

Abstract We report a novel patient with the phenotypic characteristics of Schaaf-Yang syndrome. In addition, the patient has a severe chronic digestive malfunction, rendering him dependent on intermittent enteral supplementation. To our knowledge, this is the first report of Schaaf-Yang syndrome associated with severe chronic digestive malfunction manifesting with both a malrotation and signs of a chronic intestinal pseudo-obstruction. [ABSTRACT FROM AUTHOR]

Summary: Advance in the exome‐wide sequencing analysis contributes to identifying hundreds of genes that are associated with early‐onset epileptic encephalopathy and neurodevelopmental disorders. On the basis of massive sequencing data, functional interactions among different genes are suggested to explain the common molecular pathway underlying the pathogenic process of these disorders. However, the relevance of such interactions with the phenotypic severity or variety in an affected individual remains elusive. In this report, we present a 45‐year‐old woman with neurofibromatosis type 1 (NF1), infantile‐onset epileptic encephalopathy, and severe developmental delay. Whole‐exome sequencing identified de novo pathogenic mutations in NF1 and the Schaaf‐Yang syndrome‐associated gene, MAGEL2. Literature‐curated interaction data predicted that NF1 and MAGEL2 proteins were closely connected in this network via their common interacting proteins. Direct conversion of fibroblasts into neurons in vitro showed that neuronal cells from 9 patients with NF1 expressed significantly lower levels of MAGEL2 (54%, p = 0.0047) than those from healthy individuals. These data provide the first evidence that pathogenic mutations of NF1 deregulate the expression of other neurodevelopmental disease‐associated genes. De novo mutations in multiple genes may lead to severe developmental phenotypes through their cumulative effects or synergistic interactions. [ABSTRACT FROM AUTHOR]

MAGEL2 is one of five protein-coding, maternally imprinted, paternally expressed genes in the Prader-Willi syndrome (PWS)-critical domain on chromosome 15q11-q13. Truncating pathogenic variants of MAGEL2 cause Schaaf-Yang syndrome (SHFYNG) ( OMIM #615547), a neurodevelopmental disorder related to PWS. Affected individuals manifest a spectrum of neurocognitive and behavioral phenotypes, including intellectual disability and autism spectrum disorder ( ASD). Magel2 knockout mice carrying a maternally inherited, imprinted wild-type (WT) allele and a paternally inherited Magel2- lacZ knock-in allele, which abolishes endogenous Magel2 gene function, exhibit several features reminiscent of the human Prader-Willi phenotypes, including neonatal growth retardation, excessive weight gain after weaning and increased adiposity in adulthood. They were shown to have altered circadian rhythm, reduced motor activity and reduced fertility. An extensive assessment for autism-like behaviors in this mouse model was warranted, because of the high prevalence of ASD in human patients. The behavior of Magel2 knockout mice and their WT littermates were assayed via open field, elevated plus maze, tube, three-chamber and partition tests. Our studies confirm decreased horizontal activity of male and female mice and increased vertical activity of females, in the open field. Both sexes spent more time in the open arm of the elevated plus maze, suggestive of reductions in anxiety. Both sexes displayed a lack of preference for social novelty, via a lack of discrimination between known and novel partners in the partition test. The in-depth investigation of behavioral profiles caused by Magel2 loss-of-function helps to elucidate the etiology of behavioral phenotypes both for SHFYNG and PWS in general. [ABSTRACT FROM AUTHOR]

Intracellular protein trafficking and sorting are extremely arduous in endocrine and neuroendocrine cells, which synthesize and secrete on-demand substantial quantities of proteins. To ensure that neuroendocrine secretion operates correctly, each step in the secretion pathways is tightly regulated and coordinated both spatially and temporally. At the trans -Golgi network (TGN), intrinsic structural features of proteins and several sorting mechanisms and distinct signals direct newly synthesized proteins into proper membrane vesicles that enter either constitutive or regulated secretion pathways. Furthermore, this anterograde transport is counterbalanced by retrograde transport, which not only maintains membrane homeostasis but also recycles various proteins that function in the sorting of secretory cargo, formation of transport intermediates, or retrieval of resident proteins of secretory organelles. The retromer complex recycles proteins from the endocytic pathway back to the plasma membrane or TGN and was recently identified as a critical player in regulated secretion in the hypothalamus. Furthermore, melanoma antigen protein L2 (MAGEL2) was discovered to act as a tissue-specific regulator of the retromer-dependent endosomal protein recycling pathway and, by doing so, ensures proper secretory granule formation and maturation. MAGEL2 is a mammalian-specific and maternally imprinted gene implicated in Prader-Willi and Schaaf-Yang neurodevelopmental syndromes. In this review, we will briefly discuss the current understanding of the regulated secretion pathway, encompassing anterograde and retrograde traffic. Although our understanding of the retrograde trafficking and sorting in regulated secretion is not yet complete, we will review recent insights into the molecular role of MAGEL2 in hypothalamic neuroendocrine secretion and how its dysregulation contributes to the symptoms of Prader-Willi and Schaaf-Yang patients. Given that the activation of many secreted proteins occurs after they enter secretory granules, modulation of the sorting efficiency in a tissue-specific manner may represent an evolutionary adaptation to environmental cues., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Štepihar, Florke Gee, Hoyos Sanchez and Fon Tacer.)

Background: Schaaf-Yang syndrome (SYS) is a recently identified rare neurodevelopmental disorder characterized by neonatal hypotonia, feeding difficulty, joint contractures, autism spectrum disorder and development delay/intellectual disability. It is mainly caused by truncating variants in maternally imprinted gene MAGEL2 within the Prader-Willi syndrome critical region 15q11-q13. Clinical diagnosis of SYS is difficult for clinicians due to its rarity and highly variable phenotypes, while unique inheritance patterns also complicate genetic diagnosis. To date, no published papers have analyzed the clinical consequences and molecular changes in Chinese patients., Methods: In this study, we retrospectively investigated the mutation spectrums and phenotypic features of 12 SYS infants. The data were from a cohort of critically ill infants from the China neonatal genomes project (CNGP), sponsored by Children's Hospital of Fudan University. We also reviewed relevant literature., Results: Six previously reported mutations and six novel pathogenic variations of MAGEL2 were identified in 12 unrelated infants. Neonatal respiratory problems were the major complaint for hospitalization, which occurred in 91.7% (11/12) cases. All babies displayed feeding difficulties and a poor suck postnatally, and neonatal dystonia was present in 11 of the cases; joint contractures and multiple congenital defects were also observed. Interestingly, we found that 42.5% (57/134) of the reported SYS patients, including ours carried variants in the c.1996 site, particularly the c.1996dupC variant. The mortality rate was 17.2% (23/134), with the median age of death between 24 gestational weeks in fetuses and 1-month-old in infants. Respiratory failure was the leading cause of death in live-born patients (58.8%, 10/17), especially during the neonatal period., Conclusions: Our findings expanded the genotype and phenotype spectrum of neonatal SYS patients. The results demonstrated that respiratory dysfunction was a typical characteristic among Chinese SYS neonates that should attract physicians' attention. The early identification of such disorders allows early intervention and can further provide genetic counseling as well as reproductive options for the affected families., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-22-4396/coif). The authors have no conflicts of interest to declare., (2023 Annals of Translational Medicine. All rights reserved.)

Objective Extreme obesity is a core phenotypic feature of Prader–Willi syndrome (PWS). Among numerous metabolic regulators, the endocannabinoid (eCB) system is critically involved in controlling feeding, body weight, and energy metabolism, and a globally acting cannabinoid-1 receptor (CB 1 R) blockade reverses obesity both in animals and humans. The first-in-class CB 1 R antagonist rimonabant proved effective in inducing weight loss in adults with PWS. However, it is no longer available for clinical use because of its centrally mediated, neuropsychiatric, adverse effects. Methods We studied eCB ‘tone’ in individuals with PWS and in the Magel2 -null mouse model that recapitulates the major metabolic phenotypes of PWS and determined the efficacy of a peripherally restricted CB 1 R antagonist, JD5037 in treating obesity in these mice. Results Individuals with PWS had elevated circulating levels of 2-arachidonoylglycerol and its endogenous precursor and breakdown ligand, arachidonic acid. Increased hypothalamic eCB ‘tone’, manifested by increased eCBs and upregulated CB 1 R, was associated with increased fat mass, reduced energy expenditure, and decreased voluntary activity in Magel2 -null mice. Daily chronic treatment of obese Magel2 -null mice and their littermate wild-type controls with JD5037 (3 mg/kg/d for 28 days) reduced body weight, reversed hyperphagia, and improved metabolic parameters related to their obese phenotype. Conclusions Dysregulation of the eCB/CB 1 R system may contribute to hyperphagia and obesity in Magel2 -null mice and in individuals with PWS. Our results demonstrate that treatment with peripherally restricted CB 1 R antagonists may be an effective strategy for the management of severe obesity in PWS. [ABSTRACT FROM AUTHOR]

Prader-Willi syndrome (PWS) is a genetic neurodevelopmental disorder. Global hypothalamic dysfunction is a core feature of PWS and has been implicated as a driver of many of PWS's phenotypic characteristics (e.g., hyperphagia-induced obesity, hypogonadism, short stature). Although the two neuropeptides (i.e., oxytocin [OXT] and arginine vasopressin [AVP]) most implicated in mammalian prosocial functioning are of hypothalamic origin, and social functioning is markedly impaired in PWS, there has been little consideration of how dysregulation of these neuropeptide signaling pathways may contribute to PWS's social behavior impairments. The present article addresses this gap in knowledge by providing a comprehensive review of the preclinical and clinical PWS literature–spanning endogenous neuropeptide measurement to exogenous neuropeptide administration studies–to better understand the roles of OXT and AVP signaling in this population. The preponderance of evidence indicates that OXT and AVP signaling are indeed dysregulated in PWS, and that these neuropeptide pathways may provide promising targets for therapeutic intervention in a patient population that currently lacks a pharmacological strategy for its debilitating social behavior symptoms. • Prader-Willi syndrome has global hypothalamic dysfunction and social deficits. • Hypothalamic oxytocin and vasopressin signaling are critical for social function. • Oxytocin and vasopressin signaling are abnormal in Prader-Willi syndrome. • Oxytocin or vasopressin administration improves social function in animal models. • These pathways may be therapeutic targets for Prader-Willi syndrome social deficits. [ABSTRACT FROM AUTHOR]

Previous studies in mice have utilized Magel2 gene deletion models to examine the consequences of its absence. We report the generation, molecular validation and phenotypic characterization of a novel rat model with a truncating Magel2 mutation modeling variants associated with Schaaf-Yang syndrome-causing mutations. Within the hypothalamus, a brain region in which human MAGEL2 is paternally expressed, we demonstrated, at the level of transcript and peptide detection, that rat Magel2 exhibits a paternal, parent-of-origin effect. In evaluations of behavioral features across several domains, juvenile Magel2 mutant rats displayed alterations in anxiety-like behavior and sociability measures. Moreover, the analysis of peripheral organ systems detected alterations in body composition, cardiac structure and function, and breathing irregularities in Magel2 mutant rats. Several of these findings are concordant with reported mouse phenotypes, indicating the conservation of MAGEL2 function across rodent species. Our comprehensive analysis revealing impairments across multiple domains demonstrates the tractability of this model system for the study of truncating MAGEL2 mutations., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Background Mutations of MAGEL2 have been reported in patients presenting with autism, and loss of MAGEL2 is also associated with Prader-Willi syndrome, a neurodevelopmental genetic disorder. This study aimed to determine the behavioral phenotype of Magel2 -deficient adult mice, to characterize the central oxytocin (OT) system of these mutant mice, and to test the curative effect of a peripheral OT treatment just after birth. Methods We assessed the social and cognitive behavior of Magel2 -deficient mice, analyzed the OT system of mutant mice treated or not by a postnatal administration of OT, and determined the effect of this treatment on the brain. Results Magel2 inactivation induces a deficit in social recognition and social interaction and a reduced learning ability in adult male mice. In these mice, we reveal anatomical and functional modifications of the OT system and show that these defects change from birth to adulthood. Daily administration of OT in the first postnatal week was sufficient to prevent deficits in social behavior and learning abilities in adult mutant male mice. We show that this OT treatment partly restores a normal OT system. Thus, we report that an alteration of the OT system around birth has long-term consequences on behavior and on cognition. Importantly, an acute OT treatment of Magel2 -deficient pups has a curative effect. Conclusions Our study reveals that OT plays a crucial role in setting social behaviors during a period just after birth. An early OT treatment in this critical period could be a novel therapeutic approach for the treatment of neurodevelopmental disorders such as Prader-Willi syndrome and autism. [ABSTRACT FROM AUTHOR]

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder characterized by neonatal hypotonia, developmental delay/intellectual disability, and characteristic feeding behaviors with failure to thrive during infancy; followed by hyperphagia and excessive weight gain later in childhood. Individuals with PWS also manifest complex behavioral phenotypes. Approximately 25% meet criteria for autism spectrum disorder (ASD). PWS is caused by the absence of paternally expressed, maternally silenced genes at chromosome 15q11-q13. MAGEL2 is one of five protein-coding genes in the PWS-critical domain. Truncating point mutations of the paternal allele of MAGEL2 cause Schaaf-Yang syndrome, which has significant phenotypic overlap with PWS, but is also clinically distinct; based on the presence of joint contractures, and a particularly high prevalence of autism spectrum disorder (up to 75% of affected individuals). The clinical and molecular overlap between PWS and Schaaf-Yang syndrome, but also their distinguishing features provide insight into the pathogenetic mechanisms underlying both disorders.

MAGEL2 (melanoma antigen-like gene 2) is essential for circadian function, metabolism and reproduction in mammals. This study was conducted to investigate transcriptional regulation and functional importance in the placenta of porcine MAGEL2. Quantitative real-time PCR showed that MAGEL2 was highly expressed in porcine hypothalamus, pituitary and placenta (P<0.05). The gene was down-regulated in Meishan but up-regulated in Duroc placentas from 25days post-coitum (dpc) to 105dpc (P<0.01). Dual luciferase assay demonstrated that the region -151/+110 had the highest promoter activity. Of the g. -712C>G and g. -708T>C polymorphisms in MAGEL2 promoter, -712C and -708T were observed to be predominant in Large White, Landrace and Duroc populations, while -712G and -708C were predominant in Meishan and Rongchang populations. Moreover, -712C>G and -708T>C had significant effects on MAGEL2 transcription (P<0.05) and placental efficiency (P<0.01). In conclusion, -151/+110 harbors the basal promoter of porcine MAGEL2. The region upstream the basal promoter contains repressive cis-elements. And, MAGEL2 is essential in porcine placenta. [ABSTRACT FROM AUTHOR]

Abstract: Prader–Willi Syndrome (PWS) is a neurodevelopmental genetic disorder caused by loss of expression of imprinted, paternally inherited genes on chromosome 15q11q13. This imprinted gene cluster has its homologous region on mouse chromosome 7C. The extremely well conserved synteny between the human and the murine regions gave origin to the generation of mouse models for PWS, which facilitated investigations of the role and function of single genes or gene clusters in the pathogenesis of this disease. In this review we will describe which mouse models have been generated so far and how they were developed; we will focus on the consequences of single genes’ (or gene clusters’) loss of expression on the phenotype, highlighting the similarities to the human PWS features. PWS mouse models have brought major improvements in our knowledge about this complex condition, although the mechanisms implicated in its pathogenesis still remain not fully understood. [Copyright &y& Elsevier]

Imprinted genes have important effects on the regulation of fetal growth, development, and postnatal behavior. However, the study of imprinted genes has been limited in mammalian species other than human and mouse. Therefore, the study of porcine imprinted genes is useful for defining the extent of conservation of genomic imprinting among different species. In this study, the imprinting status of porcine NDN, MAGEL2 and MEST genes was determined by direct sequencing of the cDNAs and detection of single nucleotide polymorphisms (SNPs) identified in individuals from reciprocal crosses between Meishan and Large White pigs for allele discrimination. The analysis was carried out in 13 different tissues (skeletal muscle, fat, pituitary gland, heart, lung, liver, kidney, spleen, stomach, small intestine, uterus, ovary and testis) from 12 two-month-old piglets. Imprinting analysis showed that NDN and MAGEL2 were paternally expressed in all tissues where the genes were expressed as in human and mouse. Interestingly, MEST showed tissue-specific imprinting, being paternally expressed in skeletal muscle, fat, pituitary gland, heart, kidney, lung, stomach and uterus, and maternally expressed in spleen and liver. [ABSTRACT FROM AUTHOR]

Imprinted genes play an essential role in the regulation of fetal growth, development and function of the placenta, however only a limited number of imprinted genes have been studied in swine. In this study, we cloned and characterized porcine MAGEL2 (melanoma antigen-like gene 2), and also identified its imprinting status during porcine fetal development. The complete open reading frame (ORF) encoding 1,193 amino acids was isolated and two single nucleotide polymorphisms (SNPs) (g.2592A>C and g.3277T>C) in the coding region were identified. The reciprocal Yorkshire × Meishan F hybrid model and the RT-PCR/RFLP method were used to detect the imprinting status of porcine MAGEL2 gene at two developmental stages of day 30 and 65 of gestation. Imprinting analysis showed that porcine MAGEL2 was paternally expressed in day 65 fetal tissues, including heart, liver, spleen, lung, kidney, stomach, small intestine, skeletal muscle, brain and placenta. Interestingly, we observed an imprinting variance of MAGEL2 gene in 30 dpc fetuses produced by the cross of Yorkshire boar × Meishan sow, in which seven heterozygous fetuses were monoallelically expressed from the paternal allele but two were biallelically expressed from both the paternal and maternal alleles. Association analysis in a Yorkshire × Meishan F resource population showed that the mutation of g.2592A>C was significantly associated with dressed carcass percentage ( P < 0.05) and buttock fat thickness ( P < 0.05). Our results suggest that MAGEL2, as a novel imprinted gene in pig, might be a candidate gene affecting carcass traits and could provide important information for the functional study of imprinted genes during porcine development. [ABSTRACT FROM AUTHOR]

Several investigations have reported that abnormalities in circadian rhythms might be related with the pathophysiology of psychiatric disorders, since many psychiatric patients have insomnia and sleep-awake disturbance. A recent animal study reported that Magel2, which encodes a member of the MAGE/necdin family of proteins, might be associated in the pathophysiology of psychiatric disorders. Magel2 gene knockout mice showed altered concentrations of both dopamine and serotonin in several parts of the brain compared with controls. In addition, the authors of that study detected a bilateral reduction in cortical volume in distinct regions of the Magel2 gene knockout mice brain, including focused regions in the parieto-temporal lobe of the cerebral cortex, the amygdala, the hippocampus, and the nucleus accumbens. These mice were also found to have hypoactivity and abnormalities in circadian rhythms. From this evidence, we considered Magel2 gene ( MAGEL2) to be a good candidate gene for the pathophysiology of schizophrenia and mood disorder, and we conducted a case–control study among Japanese (731 schizophrenia patients, 465 MDD patients, 156 BP patients and 758 controls) using three tagging SNPs in MAGEL2 (rs850815, rs8920 and rs4480754), selected using the HapMap database. We did not find any association between MAGEL2 and schizophrenia, BP or MDD in allele/genotype-wise analysis or haplotype-wise analysis. Our results suggest that MAGEL2 may not play a role in the pathophysiology of schizophrenia and mood disorders in the Japanese population. A replication study using larger samples may be required for conclusive results, since our sample size was small and our study analyzed only three SNPs in MAGEL2. [ABSTRACT FROM AUTHOR]

Prader–Willi syndrome (PWS) is a neurobehavioral disorder that is due to the loss of multiple, paternally-expressed, imprinted genes on human chromosome 15q11-q13. The candidate genes are conserved in mice and are located in an orthologous region on mouse 7C. Several mouse models in which one or more of the PWS candidate genes are silenced do not recapitulate the full PWS phenotype. We examined the expression patterns of the mouse orthologues of PWS candidate genes throughout the development of the brain regions most implicated in PWS, including the hypothalamus, pituitary, forebrain and hindbrain. Snrpn, Ipw and Ndn are widely expressed at high levels throughout the mouse brain, whereas Magel2, Mkrn3 and the snoRNA MBII-85 are preferentially expressed in specific brain regions. Magel2 is most specifically expressed in developing hypothalamus, the region of the brain implicated in PWS hyperphagia and obesity. Although Snrpn, Ipw and MBII-85 are putatively transcribed from the same promoter, the transcripts are differentially detected in neural tissues. The analysis of expression patterns of murine orthologues of human disease genes is valuable for identifying sites of gene expression that correlate with disease phenotype. [Copyright &y& Elsevier]

Prader-Willi syndrome (PWS) is a neurogenetic multifactorial disorder caused by the deletion or inactivation of paternally imprinted genes on human chromosome 15q11-q13. The affected homologous locus is on mouse chromosome 7C. The positional conservation and organization of genes including the imprinting pattern between mice and men implies similar physiological functions of this locus. Therefore, considerable efforts to recreate the pathogenesis of PWS have been accomplished in mouse models. We provide a summary of different mouse models that were generated for the analysis of PWS and discuss their impact on our current understanding of corresponding genes, their putative functions and the pathogenesis of PWS. Murine models of PWS unveiled the contribution of each affected gene to this multi-facetted disease, and also enabled the establishment of the minimal critical genomic region (PWScr) responsible for core symptoms, highlighting the importance of non-protein coding genes in the PWS locus. Although the underlying disease-causing mechanisms of PWS remain widely unresolved and existing mouse models do not fully capture the entire spectrum of the human PWS disorder, continuous improvements of genetically engineered mouse models have proven to be very powerful and valuable tools in PWS research. [ABSTRACT FROM AUTHOR]

Prader–Willi syndrome (PWS) is a rare genetic form of hyperphagia leading to severe obesity, accompanied by endocrine, musculoskeletal, and neurological dysfunction. PWS is caused by the inactivation of contiguous genes on chromosome 15q11-q13, and mice with gene-targeted mutations in one or more of these PWS genes recapitulate PWS-like phenotypes. In addition to evaluating the potential effectiveness of a therapeutic for the treatment of PWS, animal models can be used to elucidate the deficiencies in appetitive and energy balance pathways that lead to hyperphagia and obesity. Various therapeutics have been tested for their effects on ingestive behavior, hyperphagia, and obesity in clinical trials for PWS, with encouraging preliminary results on small groups of participants with PWS. Here, we summarize ingestive behavior-related therapeutics tested in PWS animal models and summarize published data from clinical trials that have evaluated the effect of therapeutics on ingestive behavior in individuals with PWS. We then discuss strategies to accelerate the discovery and translation of therapies into clinical practice in PWS. [ABSTRACT FROM AUTHOR]

Oxytocin contributes to the regulation of cytoskeletal and synaptic proteins and could, therefore, affect the mechanisms of neurodevelopmental disorders, including autism. Both the Prader-Willi syndrome and Schaaf-Yang syndrome exhibit autistic symptoms involving the MAGEL2 gene. Magel2-deficient mice show a deficit in social behavior that is rescued following the postnatal administration of oxytocin. Here, in Magel2-deficient mice, we showed that the neurite outgrowth of primary cultures of immature hippocampal neurons is reduced. Treatment with oxytocin reversed this abnormality. In the hippocampus of Magel2-deficient pups, we further demonstrated that several transcripts of neurite outgrowth-associated proteins, synaptic vesicle proteins, and cell-adhesion molecules are decreased. In the juvenile stage, when neurons are mature, normalization or even overexpression of most of these markers was observed, suggesting a delay in the neuronal maturation of Magel2-deficient pups. Moreover, we found reduced transcripts of the excitatory postsynaptic marker, Psd95 in the hippocampus and we observed a decrease of PSD95/VGLUT2 colocalization in the hippocampal CA1 and CA3 regions in Magel2-deficient mice, indicating a defect in glutamatergic synapses. Postnatal administration of oxytocin upregulated postsynaptic transcripts in pups; however, it did not restore the level of markers of glutamatergic synapses in Magel2-deficient mice. Overall, Magel2 deficiency leads to abnormal neurite outgrowth and reduced glutamatergic synapses during development, suggesting abnormal neuronal maturation. Oxytocin stimulates the expression of numerous genes involved in neurite outgrowth and synapse formation in early development stages. Postnatal oxytocin administration has a strong effect on development that should be considered for certain neuropsychiatric conditions in infancy., (© 2021 Wiley Periodicals LLC.)

Schaaf-Yang syndrome (SHFYNG) is caused by truncating mutations in the paternal allele of the MAGEL2 gene located in the Prader-Willi syndrome region. We report 5 newborns affected with SHFYNG in one family. Trio exome analysis revealed a heterozygous c.1996dupC frameshift mutation in MAGEL2 inherited from the unaffected father. The phenotypes showed strong resemblance, especially for severe respiratory disturbance requiring mechanical ventilation at birth. After discharge from the hospital, 4 of the patients died of respiratory insufficiency within 1 or 2 weeks after birth, and 1 child died after 110 days of aggravated apnea. Apnea or respiratory failure was the main cause of early death in this family. Respiratory distress is a common manifestation of SHFYNG, especially in patients with c.1996dupC mutations. Hypotonia is a main cause of respiratory disturbance, and we propose another possible cause affecting the respiratory center of the brain., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2019 by S. Karger AG, Basel.)

Background: Chitayat-Hall syndrome, initially described in 1990, is a rare condition characterised by distal arthrogryposis, intellectual disability, dysmorphic features and hypopituitarism, in particular growth hormone deficiency. The genetic aetiology has not been identified., Methods and Results: We identified three unrelated families with a total of six affected patients with the clinical manifestations of Chitayat-Hall syndrome. Through whole exome or whole genome sequencing, pathogenic variants in the MAGEL2 gene were identified in all affected patients. All disease-causing sequence variants detected are predicted to result in a truncated protein, including one complex variant that comprised a deletion and inversion., Conclusions: Chitayat-Hall syndrome is caused by pathogenic variants in MAGEL2 and shares a common aetiology with the recently described Schaaf-Yang syndrome. The phenotype of MAGEL2 -related disorders is expanded to include growth hormone deficiency as an important and treatable complication., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: Nonsense and frameshift mutations in the maternally imprinted, paternally expressed gene MAGEL2, located in the Prader-Willi critical region 15q11-15q13, have been reported to cause Schaaf-Yang syndrome (SYS), a genetic disorder that manifests as developmental delay/intellectual disability, hypotonia, feeding difficulties and autism spectrum disorder. Prader-Willi syndrome (PWS) is a genetic disorder characterised by severe infantile hypotonia, hypogonadotrophic hypogonadism, early childhood onset obesity/hyperphagia, developmental delay/intellectual disability and short stature. Scoliosis and growth hormone insufficiency are also prevalent in PWS.There is extensive documentation of the endocrine and metabolic phenotypes for PWS, but not for SYS. This study served to investigate the hormonal, metabolic and body composition phenotype of SYS and its potential overlap with PWS., Methods: In nine individuals with SYS (5 female/4 male; aged 5-17 years), we measured serum ghrelin, glucose, insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 3, follicle-stimulating hormone, luteinising hormone, thyroid-stimulating hormone, free T4, uric acid and testosterone, and performed a comprehensive lipid panel. Patients also underwent X-ray and dual-energy X-ray absorptiometry analyses to assess for scoliosis and bone mineral density., Results: Low IGF-1 levels despite normal weight/adequate nutrition were observed in six patients, suggesting growth hormone deficiency similar to PWS. Fasting ghrelin levels were elevated, as seen in individuals with PWS. X-rays revealed scoliosis >10° in three patients, and abnormal bone mineral density in six patients, indicated by Z-scores of below -2 SDs., Conclusion: This is the first analysis of the hormonal, metabolic and body composition phenotype of SYS. Our findings suggest that there is marked, but not complete overlap between PWS and SYS., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

MAGEL2 is the paternally expressed gene within Prader-Willi syndrome critical region at 15q11.2. We encountered three individuals in whom truncating mutations of MAGEL2 were identified. Patients 1 and 2, siblings born to healthy, non-consanguineous Japanese parents, showed generalized hypotonia, lethargy, severe respiratory difficulty, poor feeding, and multiple anomalies including arthrogryposis soon after birth. We carried out whole-exome sequencing, which detected a MAGEL2 mutation (c.1912C>T, p.Gln638*, heterozygous). The patients' father was heterozygous for the mutation. Patient 3 was a female infant, showed respiratory difficulty reflecting pulmonary hypoplasia, generalized hypotonia, feeding difficulty and multiple anomalies soon after birth. Targeted next-generation sequencing detected a novel heterozygous mutation in MAGEL2 (c.3131C>A, p.Ser1044*). This mutation was not found in the parents. MAGEL2 mutations, first reported to be the cause of the Prader-Willi like syndrome with autism by Schaaf et al. (2013) Nature Genetics, 45: 1405-1408 show the wide range of phenotypic spectrum from lethal arthrogryposis multiplex congenital to autism spectrum disorder (ASD) and mild intellectual disability (ID). Our results indicate that MAGEL2 mutations cause multiple congenital anomalies and intellectual disability accompanied by arthrogryposis multiplex congenita and various endocrinologic abnormalities, supporting that the view that clinical phenotypes of MAGEL2 mutations are variable., (© 2018 Wiley Periodicals, Inc.)

The psychological effects of brain-expressed imprinted genes in humans are virtually unknown. Prader-Willi syndrome (PWS) is a neurogenetic condition mediated by genomic imprinting, which involves high rates of psychosis characterized by hallucinations and paranoia, as well as autism. Altered expression of two brain-expressed imprinted genes, MAGEL2 and NDN , mediates a suite of PWS-related phenotypes, including behaviour, in mice. We phenotyped a large population of typical individuals for schizophrenia-spectrum and autism-spectrum traits, and genotyped them for the single-nucleotide polymorphism rs850807, which is putatively functional and linked with MAGEL2 and NDN Genetic variation in rs850807 was strongly and exclusively associated with the ideas of reference subscale of the schizophrenia spectrum, which is best typified as paranoia. These findings provide a single-locus genetic model for analysing the neurological and psychological bases of paranoid thinking, and implicate imprinted genes, and genomic conflicts, in human mentalistic thought., (© 2018 The Author(s).)