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Introduction Guanidinoacetate methyltransferase (GAMT) deficiency is an inherited metabolic disorder that impairs the synthesis of creatine (CRE). Lack of CRE in the brain can cause intellectual disability, autistic-like behavior, seizures, and movement disorders. Identification at birth and immediate therapy can prevent intellectual disability and seizures. Here we report the first two cases of GAMT deficiency identified at birth by newborn screening (NBS) in Utah and New York. Methods NBS dried blood spots were analyzed by tandem mass spectrometry (MS/MS) using either derivatized or non-derivatized assays to detect guanidinoacetate (GUAC) and CRE. For any positive samples, a second-tier test using a more selective method, ultra-performance liquid chromatography (UPLC) combined with MS/MS, was performed to separate GUAC from potential isobaric interferences. Results NBS for GAMT deficiency began in Utah on June 1, 2015 using a derivatized method for the detection of GUAC and CRE. In May 2019, the laboratory and method transitioned to a non-derivatized method. GAMT screening was added to the New York State NBS panel on October 1, 2018 using a derivatized method. In New York, a total of 537,408 babies were screened, 23 infants were referred and one newborn was identified with GAMT deficiency. In Utah, a total of 273,902 infants were screened (195,425 with the derivatized method, 78,477 with the non-derivatized method), three infants referred and one was identified with GAMT deficiency. Mean levels of GUAC and CRE were similar between methods (Utah derivatized: GUAC = 1.20 ± 0.43 μmol/L, CRE = 238 ± 96 μmol/L; Utah non-derivatized: GUAC = 1.23 ± 0.61 μmol/L, CRE = 344 ± 150 μmol/L, New York derivatized: GUAC = 1.34 ± 0.57 μmol/L, CRE = 569 ± 155 μmol/L). With either Utah method, similar concentrations of GUAC are observed in first (collected around 1 day of age) and the second NBS specimens (routinely collected at 7–16 days of age), while CRE concentrations decreased in the second NBS specimens. Both infants identified with GAMT deficiency started therapy by 2 weeks of age and are growing and developing normally at 7 (Utah) and 4 (New York) months of age. Conclusions Newborn screening allows for the prospective identification of GAMT deficiency utilizing elevated GUAC concentration as a marker. First-tier screening may be incorporated into existing methods for amino acids and acylcarnitines without the need for new equipment or staff. Newborn screening performed by either derivatized or non-derivatized methods and coupled with second-tier testing, has a very low false positive rate and can prospectively identify affected children. SummaryCerebral creatine deficiency syndromes caused by defects in creatine synthesis can result in intellectual disability, and are preventable if therapy is initiated early in life. This manuscript reports the identification of two infants with GAMT deficiency (one of the cerebral creatine deficiency syndromes) by newborn screening and demonstrates NBS feasibility using a variety of methods.

Aminoacyl-transfer RNA (tRNA) synthetases ligate amino acids to specific tRNAs and are essential for protein synthesis. Although alanyl-tRNA synthetase (AARS) is a synthetase implicated in a wide range of neurological disorders from Charcot-Marie-Tooth (CMT) disease to infantile epileptic encephalopathy, there have been limited data on their pathogenesis. Here we report loss-of-function mutations in AARS in two siblings with progressive microcephaly with hypomyelination, intractable epilepsy and spasticity. Whole exome sequencing identified that the affected individuals were compound heterozygous for mutations in AARS gene, c.2067dupC (p.Tyr690Leufs*3) and c.2738G>A (p.Gly913Asp). A lymphoblastoid cell line developed from one of the affected individuals showed a strong reduction in AARS abundance. The mutations decrease aminoacylation efficiency by 70–90%. The p.Tyr690Leufs*3 mutation also abolished editing activity required for hydrolyzing misacylated tRNAs, thereby increasing errors during aminoacylation. Our study has extended potential mechanisms underlying AARS-related disorders to include destabilization of the protein, aminoacylation dysfunction, and defective editing activity. This article is protected by copyright. All rights reserved

Early infantile Krabbe disease is rapidly fatal, but hematopoietic stem cell transplantation (HSCT) may improve outcomes if performed soon after birth. New York State began screening all newborns for Krabbe disease in 2006. Infants with abnormal newborn screen results for Krabbe disease were referred to specialty-care centers. Newborns found to be at high risk for Krabbe disease underwent a neurodiagnostic battery to determine the need for emergent HSCT. Almost 2 million infants were screened. Five infants were diagnosed with early infantile Krabbe disease. Three died, two from HSCT-related complications and one from untreated disease. Two children who received HSCT have moderate to severe developmental delays. Forty-six currently asymptomatic children are considered to be at moderate or high risk for development of later-onset Krabbe disease. These results show significant HSCT-associated morbidity and mortality in early infantile Krabbe disease and raise questions about its efficacy when performed in newborns diagnosed through newborn screening. The unanticipated identification of “at risk” children introduces unique ethical and medicolegal issues. New York’s experience raises questions about the risks, benefits, and practicality of screening newborns for Krabbe disease. It is imperative that objective assessments be made on an ongoing basis as additional states begin screening for this disorder. Genet Med 18 12, 1235–1243.

Introduction: The TANGO2 gene encodes a transport and Golgi organization protein of unclear function; mutations should be considered in patients presenting with acute metabolic crisis, hypoglycemic episodes, cardiac arrhythmias, and other endocrinopathies. We report the novel use of a continuous glucose monitor (CGM) to help predict and prevent significant hypoglycemic episodes in a patient with TANGO2 mutation. Clinical Case: A 14-month old previously healthy, developmentally normal female who presented with unresponsive hypoglycemia (glucose 26 mg/dL) was demonstrated by Next Generation Sequencing to have a pathogenic 31.8 kb deletion of exon 3 to 9 in the TANGO-2 gene and a suspected pathogenic hemizygous c.569_592dup, p.Ile190_Leu197dup in TANGO-2. Her hospital course was notable for MRI showing hypoxic ischemic encephalopathy and both physical and electrical cardiac dysfunction. Continuous intravenous dextrose corrected the hypoglycemia, and transient hyperglycemia followed after several days of a glucose infusion rate between 3.2 to 5.8 mg/kg/min. After transitioning to ad lib oral feeds without restrictions, she was discharged. A second admission for acute unresponsive hypoglycemia and metabolic acidosis (glucose 30 mg/dL) occurred at 17 months of age with no clear inciting cause. Continuous IV dextrose at 9.9 mg/kg/min corrected the hypoglycemia and again resulted in transient hyperglycemia up to 271 mg/dl. Levothyroxine was also started for a TSH of 27 mIU/mL and a T4 of 4.6 ug/dL. Immediately after discharge, a DexCom G6 CGM was placed. Data over 2 weeks shows an average glucose of 104 ng/dL with 99% of the BS in target range. Parents report that CGM predictive low alerts have allowed intervention to abort fasting-related metabolic crises. Conclusion: In TANGO-2 deficiency, the liver may not adequately store and/or release glycogen in response to glucagon due to abnormal endoplasmic reticulum, Golgi apparatus, and mitochondrial functioning in states of stress or illness. Recent reports are conflicting with some showing reduced mitochondrial respiration in TANGO-2 patients in steady state with others finding normal values, opening the possibility that a combination of factors in the setting of stress may precipitate a metabolic crisis. Our patient quickly returns to near-normal physiological functioning; consequently, we suggest that use of a CGM can help prevent fasting related metabolic crisis in TANGO2 patients and can help guide feeding schedule and food choices to limit hyper- and hypoglycemia. In addition, CGM data can help further investigate if any beta cell dysregulation exists in non-acute states. References: Bérat CM, ... & de Lonlay P. (2020). Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises.... J Inherit Metab Dis. 2020 Sep 14. doi: 10.1002/jimd.12314.

Neurofibromatosis type 1 (NF1), one of the most common genetic disorders with an estimated prevalence of 1:3000 live births, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and an in-frame 1-amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 patients (129 unrelated probands and 33 affected relatives) carrying a constitutional missense mutation affecting one of five neighboring NF1 codons Leu844, Cys845, Ala846, Leu847 and Gly848, located in the Cysteine-Serine-Rich Domain (CSRD). These recurrent missense mutations affect ~0.8% of unrelated NF1 mutation-positive probands in the UAB cohort. A substantial fraction of these patients presented with a severe phenotype, including plexiform and/or spinal neurofibromas, symptomatic optic pathway gliomas, malignant neoplasms or osseous lesions. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent compared with classic NF1 cohorts (both p

Walker-Warburg syndrome (WWS) is a genetically heterogeneous autosomal recessive disease characterized by congenital muscular dystrophy, cobblestone lissencephaly, and ocular malformations. Mutations in six genes involved in the glycosylation of á-dystroglycan (POMT1, POMT2, POMGNT1, FCMD, FKRP and LARGE) have been identified in WWS patients, but account for only a portion of WWS cases. To better understand the genetics of WWS and establish the frequency and distribution of mutations across WWS genes, we genotyped all known loci in a cohort of 43 WWS patients of varying geographical and ethnic origin. Surprisingly, we reached a molecular diagnosis for 40% of our patients and found mutations in POMT1, POMT2, FCMD and FKRP, many of which were novel alleles, but no mutations in POMGNT1 or LARGE. Notably, the FCMD gene was a more common cause of WWS than previously expected in the European/American subset of our cohort, including all Ashkenazi Jewish cases, who carried the same founder mutation.

Fanconi-Bickel syndrome (FBS) is a rare disorder of glucose transport caused by autosomal recessive mutations in GLUT2. Clinically, FBS results in growth failure, hepatomegaly, renal Fanconi syndrome, and abnormal glucose homeostasis. We report a 23 month old female with FBS characterized by more severe and refractory hypoglycemia than typically seen in this disorder. Although previous reports indicate that FBS patients have diminished insulin secretion, our patient showed evidence of hyperinsulinism (HI). Sequence analysis showed that the patient was homozygous for a known null mutation in GLUT2, confirming the clinical diagnosis of FBS. Parental genotyping showed that the mother was heterozygous for the GLUT2 mutation, while the father was wild type. Tandem repeat marker analysis showed that the patient inherited the GLUT2 mutation via maternal isodisomy of chromosome 3. Further molecular testing showed that the patient was heterozygous for a mutation in ABCC8, a known cause of congenital HI. We discuss the patient's biochemical responses in light of the molecular findings.

Krabbe disease (KD) results from galactocerebrosidase (GALC) deficiency. Infantile KD symptoms include irritability, progressive stiffness, developmental delay, and death. The only potential treatment is hematopoietic stem cell transplantation. New York State (NYS) implemented newborn screening for KD in 2006. Dried blood spots from newborns were assayed for GALC enzyme activity using mass spectrometry, followed by molecular analysis for those with low activity (≤12% of the daily mean). Infants with low enzyme activity and one or more mutations were referred for follow-up diagnostic testing and neurological examination. Of >1.9 million screened, 620 infants were subjected to molecular analysis and 348 were referred for diagnostic testing. Five had enzyme activities and mutations consistent with infantile KD and manifested clinical/neurodiagnostic abnormalities. Four underwent transplantation, two are surviving with moderate to severe handicaps, and two died from transplant-related complications. The significance of many sequence variants identified is unknown. Forty-six asymptomatic infants were found to be at moderate to high risk for disease. The positive predictive value of KD screening in NYS is 1.4% (5/346) considering confirmed infantile cases. The incidence of infantile KD in NYS is approximately 1 in 394,000, but it may be higher for later-onset forms. Genet Med 18 3, 239–248.

Neurofibromatosis type 1 (NF1) is one of the most frequent genetic disorders, affecting 1:3,000 worldwide. Identification of genotype-phenotype correlations is challenging because of the wide range clinical variability, the progressive nature of the disorder, and extreme diversity of the mutational spectrum. We report 136 individuals with a distinct phenotype carrying one of five different NF1 missense mutations affecting p.Arg1809. Patients presented with multiple cafe-au-lait macules (CALM) with or without freckling and Lisch nodules, but no externally visible plexiform neurofibromas or clear cutaneous neurofibromas were found. About 25% of the individuals had Noonan-like features. Pulmonic stenosis and short stature were significantly more prevalent compared with classic cohorts (P, We thank the patients, their family and their referral physicians for the information. We thank the genetics counselor students who helped to re-contact all referral physicians for confirming information. This work was supported though the Children's Tumor Foundation by the Isaac and Sadie Fuchs Genotype-Phenotype Study (to L.M.) and by internal funds from the Medical Genomics Laboratory at UAB.

We describe a 12-year-old boy with mosaic variegated aneuploidy (MVA), subnormal response to growth hormone (GH) stimulation testing, and short stature. In addition to features more commonly described in MVA such as microcephaly, cognitive deficits, and certain facial features, he also has features not commonly reported in MVA, including short limb segments, epidermoid cysts, ventricular septal defect, and subaortic stenosis. Chromosomal analysis revealed hyperdiploid chromosome numbers ranging from 47 to 70; modal number 50, in 24% of the metaphases. This case demonstrates that although the phenotype of MVA almost always includes growth failure, microcephaly, and mental retardation, additional features may vary greatly across individuals. His clinical features and course suggest that in addition to GH deficiency, he may have an intrinsic inability of the growth plate to respond to growth hormone.

Transgenic BDF-1 mice harboring an inducible, tissue-specific transgene for RNA antisense to Galphaq provide a model in which to study a loss-of-function mutant of Galphaq in vivo. Galphaq deficiency induced in liver and white adipose tissue at birth produced increased body mass and hyperadiposity within 5 weeks of birth that persisted throughout adult life. Galphaq-deficient adipocytes display reduced lipolytic responses, shown to reflect a newly discovered, alpha1-adrenergic regulation of lipolysis. This alpha1-adrenergic response via phosphoinositide hydrolysis and activation of protein kinase C is lacking in the Galphaq loss-of-function mutants in vivo and provides a basis for the increased fat accumulation.

We describe a child who has central diabetes insipidus associated with congenital nasal pyriform aperture stenosis without any apparent anterior pituitary dysfunction. This association further strengthens the concept that congenital nasal pyriform aperture stenosis may be a microform of holoprosencephaly.

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is one of the most common inborn errors of metabolism. Affected patients have impaired ability to break down medium chain fatty acids during fasting, and typically present in the early years of life with hypoketotic hypoglycemia, Reye syndrome-like symptoms, brain damage or death. The development of newborn screening (NBS) for MCAD deficiency has greatly improved outcome, but some patients still appear at risk for severe complications. We reviewed the outcome of patients identified with MCAD deficiency by the New York State NBS process to identify biochemical or genotypic markers which might predict outcome.All eight NBS follow-up centers in New York State contributed the cases of MCAD deficiency diagnosed by newborn screen, who received diagnostic and follow-up care in their clinic. Data reviewed included gender, age, birthweight, initial NBS octanoylcarnitine level (C8) and C8/C2 ratio, follow-up C8 and hexanoylglycine, race/ethnicity, and presence of neonatal or later symptoms.We identified 53 cases of MCAD deficiency. More than one quarter of patients had a post-neonatal symptomatic admission (predominantly lethargy associated with an intercurrent illness). No genotype or C8 level was protective for neonatal or later symptoms. There was a relationship between initial C8 level or C8/C2 ratio and occurrence of later symptoms (7.3 micromol/L in the asymptomatic vs. 19.1 micromol/L in the symptomatic, p0.0002 for C8, and 0.26 vs. 0.6, respectively, for C8/C2 ratio, p0.012). Four infants had initial C8 level30 micromol/L; these infants had a high rate of symptomatic or multiple symptomatic episodes or a history of sibling death from "SIDS", and typically had deletion, nonsense or splice sites mutations. Infants having a history of a symptomatic episode were more likely to have higher initial C8 on NBS and a genotype predicted to strongly affect protein function. In our ethnically diverse group of patients, the c.985AG mutation was rarely found in non-Caucasians.No genotype or metabolite profile is protective from symptoms. The strong relationship between initial C8 level and outcome suggests that in at least some cases neonates having high initial C8 levels may be demonstrating an increased susceptibility to catabolic stress, and may merit additional precautions. Our data also suggest that these infants are more likely to carry severe mutations including homozygosity for the common mutation, deletions, nonsense or splice site mutations. The reports of significant lethargy or hypoglycemia during intercurrent illness in over one quarter of cases even when early medical intervention is recommended (and even when initial C8 is not profoundly elevated) underscores the importance of continued vigilance to prevent stressful fasting in this disorder.

Krabbe disease is a rare inherited neurologic disorder affecting the central and peripheral nervous systems. The disease has four phenotypes: early infantile, later onset, adolescent, and adult. The only known treatment is hematopoietic stem cell transplantation, which is, in the early infantile form of the disease, most beneficial if performed before onset of clinical symptoms. In August 2006, New York State began screening all newborns for Krabbe disease. A rapid and accurate technique for assessing galactocerebrosidase activity and performing DNA mutation analysis had been developed. Interpreting these results was limited, however, because neither enzyme activity nor genetic mutation reliably predicts phenotype. A series of initiatives were therefore developed by a multidisciplinary group of neurologists, geneticists, metabolic pediatricians, neurodevelopmental pediatricians, and transplant physicians (the Krabbe Consortium of New York State) to enhance the effectiveness of the newborn screening program. A standardized clinical evaluation protocol was designed based on the available literature, criteria for transplantation for the early infantile phenotype were formulated, a clinical database and registry was developed, and a study of developmental and functional outcomes was instituted. This multidisciplinary standardized approach to evaluating infants who have positive results on newborn screening may serve as a model for other states as they begin the process of screening for Krabbe disease and other lysosomal storage disorders.

Failure-to-thrive (FTT) has been described in patients with organic acidemias treated with low protein diets.To determine if patients with methylmalonic (MMA) or propionic acidemia (PA) can achieve normal growth and nutrition status.A 6-month multicenter outpatient study was conducted with infants and toddlers treated with Propimex-1 Amino Acid-Modified Medical Food With Iron (Ross Products Division, Abbott Laboratories, Columbus, OH). Main outcome measures were anthropometrics, protein status indices, plasma retinol, and alpha-tocopherol.Sixteen patients completed the study. Mean baseline age was 0.54 +/- 0.02 years (range 0.03-3.00 years). By study end, mean National Center for Health Statistics (NCHS) weight centile increased from 26 to 49%; mean crown-heel length centile from 25 to 33%; and mean head circumference centile from 43 to 54%. Mean (+/- SE) protein and energy intakes by6-month-old, 612-month-old, and 14-year-old patients were 15.3 +/- 0.9 g and 645 +/- 10 kcal; 18.3 +/- 1.1 g and 741 +/- 92 kcal; and 25.1 +/- 2.46 g and 1062 +/- 100 kcal, respectively. Plasma glycine concentrations were significantly and negatively correlated with energy intake (r=-0.77, p0.0005). No correlation was found between dietary protein intakes and plasma ammonia concentrations. Protein status indices, retinol and alpha-tocopherol concentrations were within reference ranges at study end.Propimex-1 improved growth and nutrition status in patients with MMA or PA in just 6 months when fed in sufficient amounts. Providing energy and protein for patients with FTT at intakes recommended for catch-up growth may have resulted in even better growth.

The HLXB9 homeobox gene was recently identified as a locus for autosomal dominant Currarino syndrome, also known as hereditary sacral agenesis (HSA). This gene specifies a 403–amino acid protein containing a homeodomain preceded by a very highly conserved 82–amino acid domain of unknown function; the remainder of the protein is not well conserved. Here we report an extensive mutation survey that has identified mutations in the HLXB9 gene in 20 of 21 patients tested with familial Currarino syndrome. Mutations were also detected in two of seven sporadic Currarino syndrome patients; the remainder could be explained by undetected mosaicism for an HLXB9 mutation or by genetic heterogeneity in the sporadic patients. Of the mutations identified in the 22 index patients, 19 were intragenic and included 11 mutations that could lead to the introduction of a premature termination codon. The other eight mutations were missense mutations that were significantly clustered in the homeodomain, resulting, in each patient, in nonconservative substitution of a highly conserved amino acid. All of the intragenic mutations were associated with comparable phenotypes. The only genotype-phenotype correlation appeared to be the occurrence of developmental delay in the case of three patients with microdeletions. HLXB9 expression was analyzed during early human development in a period spanning Carnegie stages 12–21. Signal was detected in the basal plate of the spinal cord and hindbrain and in the pharynx, esophagus, stomach, and pancreas. Significant spatial and temporal expression differences were evident when compared with expression of the mouse Hlxb9 gene, which may partly explain the significant human-mouse differences in mutant phenotype.

This chapter introduces a novel approach to the study of G-protein function in vivo in which transgenic mice are created that harbor α conditional, tissue-specific expression vector that can produce RNA antisense to target mRNA(s). The central role of G proteins in transmembrane signaling from the superfamily of G-protein-linked receptors (GPLRs) to a less populous class of effector molecules that includes adenyl cyclase, phospholipase C (PLC), and various ion channels needs little explanation (see earlier review articles 1–10). Much less obvious is the pivotal role G proteins play in more complex biological processes, such as growth and development. Infectious diseases such as cholera and whooping cough, for example, express elements of their pathology via covalent modification (mono-adenosine diphosphate [ADP]-ribosylation) of G-protein targets. In endocrine tissues, mutations of specific G-protein subunits have been shown to induce tumor growth (11). Finally, genetic mutations of G proteins have been linked to pseudo-hypoparathyroidism, McCune-Albright syndrome (MAS), and Albright’s hereditary osteodystrophy in humans (12).

Summary Antisense RNA technology provides for selective suppression of proteins of interest and thus a new strategy with which to probe the emerging complexity of the various regulatory networks of signal transduction pathways. Considering sheer economics, the use of antisense DNA oligodeoxynucleotides is practical for studies requiring small-scale culture of cells, pilot studies seeking to test the antisense DNA strategy, and in systems in which single-cell assays can be performed (e.g., patch-clamping or histochemical analysis). Vector-driven antisense RNA expression, both constitutive and inducible, in cell culture allows for large-scale cell growth capacities enabling biochemical analyses. Expanding the antisense RNA approach to transgenic mice provides the means to generate unique animal models with which to explore the role of transmembrane signaling elements in complex biological processes in vivo. In our studies, suppression of Gsα with antisense DNA oligodeoxynucleotides provided exciting information concerning the role(s) of this G protein in adipogenesis ( 16 ). Similarly, the role of Giα2 in early mouse development has been addressed in F9 embryonic stem cells stably expressing antisense RNA ( 10 ). Finally, investigation of the role of Giα2 in adipose tissue and liver function as well as its role in whole-body metabolism, growth, and development have been made possible only through the hybrid PEPCK gene construct employed in our laboratory ( 11 ). Using a variety of antisense DNA/RNA-based approaches, investigators are now able to explore the roles of signaling elements at several distinctly different levels, selectively targeting the expression of a protein of interest in vitro or in tissues in vivo. Our knowledge of the role of transmembrane signaling elements in disease is growing rapidly. Our success with antisense DNA/RNA-based approaches in vitro and in vivo highlights the potential applications of this technology for use in gene therapy to treat pathological disorders. Expression of antisense RNA in a global set of tissues by retroviral infection or expression in a tissue-specific manner using selective promoters has implications not only for our basic understanding of how signal transduction pathways impinge on these complex events, but also for the development of new therapeutic agents with which to treat human disease.