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MORC2 encodes an ATPase that plays a role in chromatin remodeling, DNA repair, and transcriptional regulation. Heterozygous variants in MORC2 have been reported in individuals with autosomal-dominant Charcot-Marie-Tooth disease type 2Z and spinal muscular atrophy, and the onset of symptoms ranges from infancy to the second decade of life. Here, we present a cohort of 20 individuals referred for exome sequencing who harbor pathogenic variants in the ATPase module of MORC2. Individuals presented with a similar phenotype consisting of developmental delay, intellectual disability, growth retardation, microcephaly, and variable craniofacial dysmorphism. Weakness, hyporeflexia, and electrophysiologic abnormalities suggestive of neuropathy were frequently observed but were not the predominant feature. Five of 18 individuals for whom brain imaging was available had lesions reminiscent of those observed in Leigh syndrome, and five of six individuals who had dilated eye exams had retinal pigmentary abnormalities. Functional assays revealed that these MORC2 variants result in hyperactivation of epigenetic silencing by the HUSH complex, supporting their pathogenicity. The described set of morphological, growth, developmental, and neurological findings and medical concerns expands the spectrum of genetic disorders resulting from pathogenic variants in MORC2.

Von Hippel-Lindau disease (VHL) is a heritable condition caused by pathogenic variants in VHL and is characterized by benign and malignant lesions in the central nervous system (CNS) and abdominal viscera. Due to its variable expressivity, existing efforts to collate VHL patient data do not adequately capture all VHL manifestations. We developed a comprehensive and standardized VHL database in the web-based application, REDCap, that thoroughly captures all VHL manifestation data. As an initial trial, information from 86 VHL patients from the University Health Network/Hospital for Sick Children was populated into the database. Analysis of this cohort showed missense variants occurring with the greatest frequency, with all variants localizing to the α- or β-domains of VHL. The most prevalent manifestations were central nervous system (CNS), renal, and retinal neoplasms, which were associated with frameshift variants and large deletions. We observed greater age-related penetrance for CNS hemangioblastomas with truncating variants compared to missense, while the reverse was true for pheochromocytomas. We demonstrate the utility of a comprehensive VHL database, which supports the standardized collection of clinical and genetic data specific to this patient population. Importantly, we expect that its web-based design will facilitate broader international collaboration and lead to a better understanding of VHL.

BackgroundExome and genome sequencing have been demonstrated to increase diagnostic yield in paediatric populations, improving treatment options and providing risk information for relatives. There are limited studies examining the clinical utility of these tests in adults, who currently have limited access to this technology.MethodsPatients from adult and cancer genetics clinics across Toronto, Ontario, Canada were recruited into a prospective cohort study evaluating the diagnostic utility of exome and genome sequencing in adults. Eligible patients were ≥18 years of age and suspected of having a hereditary disorder but had received previous uninformative genetic test results. In total, we examined the diagnostic utility of exome and genome sequencing in 47 probands and 34 of their relatives who consented to participate and underwent exome or genome sequencing.ResultsOverall, 17% (8/47) of probands had a pathogenic or likely pathogenic variant identified in a gene associated with their primary indication for testing. The diagnostic yield for patients with a cancer history was similar to the yield for patients with a non-cancer history (4/18 (22%) vs 4/29 (14%)). An additional 24 probands (51%) had an inconclusive result. Secondary findings were identified in 10 patients (21%); three had medically actionable results.ConclusionsThis study lends evidence to the diagnostic utility of exome or genome sequencing in an undiagnosed adult population. The significant increase in diagnostic yield warrants the use of this technology. The identification and communication of secondary findings may provide added value when using this testing modality as a first-line test.

SATB2-associated syndrome (SAS) is a multisystemic disorder caused by alterations of the SATB2 gene. We describe the phenotype and genotype of 12 individuals with 10 unique (de novo in 11 of 11 tested) pathogenic variants (1 splice site, 5 frameshift, 3 nonsense, and 2 missense) in SATB2 and review all cases reported in the published literature caused by point alterations thus far. In the cohort here described, developmental delay (DD) with severe speech compromise, facial dysmorphism, and dental anomalies were present in all cases. We also present the third case of tibial bowing in an individual who, just as in the previous 2 individuals in the literature, also had a truncating pathogenic variant of SATB2. We explore early genotype-phenotype correlations and reaffirm the main clinical features of this recognizable syndrome: universal DD with severe speech impediment, mild facial dysmorphism, and high frequency of craniofacial anomalies, behavioral issues, and brain neuroradiographic changes. As the recently proposed surveillance guidelines for individuals with SAS are adopted by providers, further delineation of the frequency and impact of other phenotypic traits will become available. Similarly, as new cases of SAS are identified, further exploration of genotype-phenotype correlations will be possible.

Phenylketonuria (PKU) is an autosomal recessive metabolic disorder characterized by an inability to metabolize the amino acid phenylalanine (Phe). If left untreated, an accumulation of Phe results in neurodevelopmental, neurological and psychological impairments. Advancements in detection and treatment of PKU have improved outcomes and life expectancy for these patients, emphasizing the need for life-long, specialized care. Due to the paucity of adult-focused PKU clinics, patients who are well into adulthood are still being treated in pediatric centers. This retrospective study evaluates the perceived expectations, benefits and challenges of 50 adult PKU patients (mean age 31.3 ± 10.4 years) transitioning from a pediatric to adult care setting using a transition questionnaire administered at the first clinic visit at the adult PKU care center. Patients reported a lack of access to adult resources and adult-specific PKU educational material in their pediatric PKU clinic. In contrast, the established relationships with the pediatric health care team and familiarity with treatment plans were aspects of pediatric care that patients enjoyed. The results from this study will contribute to the optimization of adult PKU patient care, establishment of strategies for transitioning adults with PKU and other metabolic disorders from pediatric to adult care, and support the need to establish adult-only PKU care facilities.

SATB2-associated syndrome (SAS) is an autosomal dominant disorder characterized by significant neurodevelopmental disabilities with limited to absent speech, behavioral issues, and craniofacial anomalies. Previous studies have largely been restricted to case reports and small series without in-depth phenotypic characterization or genotype-phenotype correlations. Seventy two study participants were identified as part of the SAS clinical registry. Individuals with a molecularly confirmed diagnosis of SAS were referred after clinical diagnostic testing. In this series we present the most comprehensive phenotypic and genotypic characterization of SAS to date, including prevalence of each clinical feature, neurodevelopmental milestones, and when available, patient management. We confirm that the most distinctive features are neurodevelopmental delay with invariably severely limited speech, abnormalities of the palate (cleft or high-arched), dental anomalies (crowding, macrodontia, abnormal shape), and behavioral issues with or without bone or brain anomalies. This comprehensive clinical characterization will help clinicians with the diagnosis, counseling and management of SAS and help provide families with anticipatory guidance.

Biochemical analysis and whole-exome sequencing identified mutations in the Golgi-localized UDP-galactose transporter SLC35A2 that define an undiagnosed X-linked congenital disorder of glycosylation (CDG) in three unrelated families. Each mutation reduced UDP-galactose transport, leading to galactose-deficient glycoproteins. Two affected males were somatic mosaics, suggesting that a wild-type SLC35A2 allele may be required for survival. In infancy, the commonly used biomarker transferrin showed abnormal glycosylation, but its appearance became normal later in childhood, without any corresponding clinical improvement. This may indicate selection against cells carrying the mutant allele. To detect other individuals with such mutations, we suggest transferrin testing in infancy. Here, we report somatic mosaicism in CDG, and our work stresses the importance of combining both genetic and biochemical diagnoses.

Chromosome 17p13.3 is a gene rich region that when deleted is associated with the well-known Miller-Dieker syndrome. A recently described duplication syndrome involving this region has been associated with intellectual impairment, autism and occasional brain MRI abnormalities. We report 34 additional patients from 21 families to further delineate the clinical, neurological, behavioral, and brain imaging findings. We found a highly diverse phenotype with inter- and intrafamilial variability, especially in cognitive development. The most specific phenotype occurred in individuals with large duplications that include both the YWHAE and LIS1 genes. These patients had a relatively distinct facial phenotype and frequent structural brain abnormalities involving the corpus callosum, cerebellar vermis, and cranial base. Autism spectrum disorders were seen in a third of duplication probands, most commonly in those with duplications of YWHAE and flanking genes such as CRK. The typical neurobehavioral phenotype was usually seen in those with the larger duplications. We did not confirm the association of early overgrowth with involvement of YWHAE and CRK, or growth failure with duplications of LIS1. Older patients were often overweight. Three variant phenotypes included cleft lip/palate (CLP), split hand/foot with long bone deficiency (SHFLD), and a connective tissue phenotype resembling Marfan syndrome. The duplications in patients with clefts appear to disrupt ABR, while the SHFLD phenotype was associated with duplication of BHLHA9 as noted in two recent reports. The connective tissue phenotype did not have a convincing critical region. Our experience with this large cohort expands knowledge of this diverse duplication syndrome.

Adolescence is a period of challenges that can be more stressful for someone with a genetic condition. The purpose of this descriptive pilot study was to assess the informational needs of adolescents with a genetic condition. To our knowledge, this is the first study that has attempted to identify these needs. A convenience sample of adolescents between 12–19 years of age with either phenylketonuria or congenital adrenal hyperplasia and who had not previously received genetic counseling was recruited. Recruitment ended once the themes were saturated (n=17). A twenty item open/close-ended questionnaire was used to assess participants’ knowledge of their genetic condition, what they wanted to know about their condition and in what manner. Almost all of the adolescents knew the name and genetic basis of their condition while most were aware of the risk of recurrence in a future pregnancy. Parents and doctors respectively, were identified as the primary and secondary sources of genetic information. Despite their evolving independence, almost all of the participants favoured receiving medical information with their parents present. The majority of participants felt that patients should begin receiving genetic information before the age of 12 years. Thematic analysis revealed that adolescents wanted to understand the science behind their condition, how their condition affects them, and how to manage it. The results highlight (i) the importance that adolescents place on parental involvement in their medical care (ii) that adolescents would like information about the genetics of their condition at a much younger age than when they usually receive genetic counseling and (iii) the benefits that can be gained by this patient population from receiving genetic counseling.