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Current approaches for diagnosing mitochondrial disorders involve specialist clinical assessment, biochemical analyses and targeted molecular genetic testing. There is now a strong rationale for undertaking first-line genome-wide sequencing, accelerating the speed of diagnosis and avoiding the need for expensive and invasive investigations.

Purpose Spinal muscular atrophy (SMA), caused by loss of the SMN1 gene, is a leading cause of early childhood death. Due to the near identical sequences of SMN1 and SMN2 , analysis of this region is challenging. Population-wide SMA screening to quantify the SMN1 copy number (CN) is recommended by the American College of Medical Genetics and Genomics. Methods We developed a method that accurately identifies the CN of SMN1 and SMN2 using genome sequencing (GS) data by analyzing read depth and eight informative reference genome differences between SMN1/2 . Results We characterized SMN1/2 in 12,747 genomes, identified 1568 samples with SMN1 gains or losses and 6615 samples with SMN2 gains or losses, and calculated a pan-ethnic carrier frequency of 2%, consistent with previous studies. Additionally, 99.8% of our SMN1 and 99.7% of SMN2 CN calls agreed with orthogonal methods, with a recall of 100% for SMA and 97.8% for carriers, and a precision of 100% for both SMA and carriers. Conclusion This SMN copy-number caller can be used to identify both carrier and affected status of SMA, enabling SMA testing to be offered as a comprehensive test in neonatal care and an accurate carrier screening tool in GS sequencing projects.

Patients and non-specialist healthcare professionals are increasingly expected to understand and interpret the results of genetic or genomic testing. These results are currently reported using a variety of templates, containing different amounts, levels, and layouts of information. We set out to establish a set of recommendations for communicating genetic test results to non-expert readers. We employed a qualitative-descriptive study design with user-centred design principles, including a mixture of in-person semi-structured interviews and online questionnaires with patients, healthcare professionals and the general public. The resulting recommendations and example template include providing at-a-glance comprehension of what the test results mean for the patient; suggested next steps; and details of further information and support. Separation and inclusion of technical methodological details enhances non-specialists’ understanding, while retaining important information for specialists and the patients’ records. The recommendations address the high-level needs of patients and their non-specialist clinicians when receiving genetic test results. These recommendations provide a solid foundation for the major content and structure of reports, and we recommend further engagement with patients and clinicians to tailor reports to specific types of test and results.

Intellectual disability has a complex effect on the well-being of affected individuals and their families. Previous research has identified multiple risk and protective factors for parental mental health, including socioeconomic circumstances and child behaviour. This study explored whether genetic cause of childhood intellectual disability contributes to parental well-being. Children from across the UK with intellectual disability due to diverse genetic causes were recruited to the IMAGINE-ID study. Primary carers completed the Development and Well-being Assessment, including a measure of parental distress (Everyday Feeling Questionnaire). Genetic diagnoses were broadly categorised into aneuploidy, chromosomal rearrangements, copy number variants (CNVs) and single nucleotide variants. Compared with the UK general population, IMAGINE-ID parents (n = 888) reported significantly elevated emotional distress (Cohen's d = 0.546). Within-sample variation was related to recent life events and the perceived impact of children's difficulties. Impact was predicted by child age, physical disability, autistic characteristics and other behavioural difficulties. Genetic diagnosis also predicted impact, indirectly influencing parental well-being. Specifically, CNVs were associated with higher impact, not explained by CNV inheritance, neighbourhood deprivation or family structure. The mental health of parents caring for a child with intellectual disability is influenced by child and family factors, converging on parental appraisal of impact. We found that genetic aetiologies, broadly categorised, also influence impact and thereby family risks. Recognition of these risk factors could improve access to support for parents, reduce their long-term mental health needs and improve well-being of individuals with intellectual disability.

BackgroundDiagnostic use of gene panel next-generation sequencing (NGS) techniques is commonplace for individuals with inherited retinal dystrophies (IRDs), a highly genetically heterogeneous group of disorders. However, these techniques have often failed to capture the complete spectrum of genomic variation causing IRD, including CNVs. This study assessed the applicability of introducing CNV surveillance into first-tier diagnostic gene panel NGS services for IRD.MethodsThree read-depth algorithms were applied to gene panel NGS data sets for 550 referred individuals, and informatics strategies used for quality assurance and CNV filtering. CNV events were confirmed and reported to referring clinicians through an accredited diagnostic laboratory.ResultsWe confirmed the presence of 33 deletions and 11 duplications, determining these findings to contribute to the confirmed or provisional molecular diagnosis of IRD for 25 individuals. We show that at least 7% of individuals referred for diagnostic testing for IRD have a CNV within genes relevant to their clinical diagnosis, and determined a positive predictive value of 79% for the employed CNV filtering techniques.ConclusionIncorporation of CNV analysis increases diagnostic yield of gene panel NGS diagnostic tests for IRD, increases clarity in diagnostic reporting and expands the spectrum of known disease-causing mutations.

Background Studies have shown that complex structural variants (cxSVs) contribute to human genomic variation and can cause Mendelian disease. We aimed to identify cxSVs relevant to Mendelian disease using short-read whole-genome sequencing (WGS), resolve the precise variant configuration and investigate possible mechanisms of cxSV formation. Methods We performed short-read WGS and analysis of breakpoint junctions to identify cxSVs in a cohort of 1324 undiagnosed rare disease patients. Long-read WGS and gene expression analysis were used to resolve one case. Results We identified three pathogenic cxSVs: a de novo duplication-inversion-inversion-deletion affecting ARID1B , a de novo deletion-inversion-duplication affecting HNRNPU and a homozygous deletion-inversion-deletion affecting CEP78 . Additionally, a de novo duplication-inversion-duplication overlapping CDKL5 was resolved by long-read WGS demonstrating the presence of both a disrupted and an intact copy of CDKL5 on the same allele, and gene expression analysis showed both parental alleles of CDKL5 were expressed. Breakpoint analysis in all the cxSVs revealed both microhomology and longer repetitive elements. Conclusions Our results corroborate that cxSVs cause Mendelian disease, and we recommend their consideration during clinical investigations. We show that resolution of breakpoints can be critical to interpret pathogenicity and present evidence of replication-based mechanisms in cxSV formation.

Deletion and duplication of 16p11.2 (BP4–BP5) have been associated with an increased risk of intellectual disability and psychiatric disorder. This is the first study to compare the frequency of a broad spectrum of psychiatric disorders in children with 16p11.2 deletion and duplication. We aimed to evaluate (1) the nature and prevalence of psychopathology associated with copy number variation (CNV) in children with 16p11.2 by comparing deletion and duplication carriers with family controls; (2) whether deletion and duplication carriers differ in frequency of psychopathology. 217 deletion carriers, 77 deletion family controls, 114 duplication carriers, and 32 duplication family controls participated in the study. Measures included standardized research diagnostic instruments. Deletion carriers had a higher frequency of any psychiatric disorder (OR = 8.9, p < 0.001), attention deficit hyperactivity disorder (ADHD) (OR = 4.0, p = 0.01), and autism spectrum disorder (ASD) (OR = 39.9, p = 0.01) than controls. Duplication carriers had a higher frequency of any psychiatric diagnosis (OR = 5.3, p = 0.01) and ADHD (OR = 7.0, p = 0.02) than controls. The prevalence of ASD in child carriers of deletions and duplications was similar (22% versus 26%). Comparison of the two CNV groups indicated a higher frequency of ADHD in children with the duplication than deletion (OR = 2.7, p = 0.04) as well as a higher frequency of overall psychiatric disorders (OR = 2.8, p = 0.02) and psychotic symptoms (OR = 4.7, p = 0.02). However, no differences between deletion and duplications carriers in the prevalence of ASD were found. Both deletion and duplication are associated with an increased risk of psychiatric disorder, supporting the importance of early recognition, diagnosis, and intervention in these groups.

Purpose Previous studies suggest that ceramide is a proapoptotic lipid as high levels of ceramides can lead to apoptosis of neuronal cells, including photoreceptors. However, no pathogenic variant in ceramide synthases has been identified in human patients and knockout of various ceramide synthases in mice has not led to photoreceptor degeneration. Methods Exome sequencing was used to identify candidate disease genes in patients with vision loss as confirmed by standard evaluation methods, including electroretinography (ERG) and optical coherence tomography. The vision loss phenotype in mice was evaluated by ERG and histological analyses. Results Here we have identified four patients with cone–rod dystrophy or maculopathy from three families carrying pathogenic variants in TLCD3B . Consistent with the phenotype observed in patients, the Tlcd3b KO/KO mice exhibited a significant reduction of the cone photoreceptor light responses, thinning of the outer nuclear layer, and loss of cone photoreceptors across the retina. Conclusion Our results provide a link between loss-of-function variants in a ceramide synthase gene and human retinal dystrophy. Establishment of the Tlcd3b knockout murine model, an in vivo photoreceptor cell degeneration model due to loss of a ceramide synthase, will provide a unique opportunity in probing the role of ceramide in survival and function of photoreceptor cells.

Hyperphagia, Severe Obesity, Impaired Cognitive Function, and Hyperactivity Associated With Functional Loss of One Copy of the Brain-Derived Neurotrophic Factor ( BDNF ) Gene Juliette Gray 1 , Giles S.H. Yeo 1 , James J. Cox 2 , Jenny Morton 3 , Anna-Lynne R. Adlam 4 , Julia M. Keogh 1 , Jack A. Yanovski 5 , Areeg El Gharbawy 5 , Joan C. Han 5 , Y.C. Loraine Tung 1 , John R. Hodges 4 , F. Lucy Raymond 2 , Stephen O’Rahilly 1 and I. Sadaf Farooqi 1 1 University Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge, U.K 2 University Department of Medical Genetics, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge, U.K 3 West Midlands Regional Genetics Service, Birmingham Women’s Hospital, Birmingham, U.K 4 Medical Research Council, Cognition and Brain Sciences Unit, and the Department of Clinical Neurosciences, Addenbrooke’s Hospital, Cambridge, U.K 5 Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland Address correspondence and reprint requests to I. Sadaf Farooqi, University Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge, CB2 2XY, U.K. E-mail: isf20{at}cam.ac.uk Abstract The neurotrophin brain-derived neurotrophic factor (BDNF) inhibits food intake, and rodent models of BDNF disruption all exhibit increased food intake and obesity, as well as hyperactivity. We report an 8-year-old girl with hyperphagia and severe obesity, impaired cognitive function, and hyperactivity who harbored a de novo chromosomal inversion, 46,XX,inv(11)(p13p15.3), a region encompassing the BDNF gene. We have identified the proximal inversion breakpoint that lies 850 kb telomeric of the 5′ end of the BDNF gene. The patient’s genomic DNA was heterozygous for a common coding polymorphism in BDNF , but monoallelic expression was seen in peripheral lymphocytes. Serum concentration of BDNF protein was reduced compared with age- and BMI-matched subjects. Haploinsufficiency for BDNF was associated with increased ad libitum food intake, severe early-onset obesity, hyperactivity, and cognitive impairment. These findings provide direct evidence for the role of the neurotrophin BDNF in human energy homeostasis, as well as in cognitive function, memory, and behavior. BAC, bacterial artificial chromosome BDNF, brain-derived neurotrophic factor FISH, fluorescence in situ hybridization TrkB, tropomyosin-related kinase B Footnotes Additional information for this article can be found in an online appendix at http://diabetes.diabetesjournals.org . The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Accepted August 21, 2006. Received April 24, 2006. DIABETES

Expanded CGG-repeats have been linked to neurodevelopmental and neurodegenerative disorders, including the fragile X syndrome and fragile X-associated tremor/ataxia syndrome (FXTAS). We hypothesized that as of yet uncharacterised CGG-repeat expansions within the genome contribute to human disease. To catalogue the CGG-repeats, 544 human whole genomes were analyzed. In total, 6101 unique CGG-repeats were detected of which more than 93% were highly variable in repeat length. Repeats with a median size of 12 repeat units or more were always polymorphic but shorter repeats were often polymorphic, suggesting a potential intergenerational instability of the CGG region even for repeats units with a median length of four or less. 410 of the CGG repeats were associated with known neurodevelopmental disease genes or with strong candidate genes. Based on their frequency and genomic location, CGG repeats may thus be a currently overlooked cause of human disease.