Human COQ4 deficiency: delineating the clinical, metabolic and neuroimaging phenotypes.

BACKGROUND: Human coenzyme Q4 (COQ4) is essential for coenzyme Q10 (CoQ10) biosynthesis. Pathogenic variants in COQ4 cause childhood-onset neurodegeneration. We aimed to delineate the clinical spectrum and the cellular consequences of COQ4 deficiency. METHODS: Clinical course and neuroradiological findings in a large cohort of paediatric patients with COQ4 deficiency were analysed. Functional studies in patient-derived cell lines were performed. RESULTS: We characterised 44 individuals from 36 families with COQ4 deficiency (16 newly described). A total of 23 different variants were identified, including four novel variants in COQ4. Correlation analyses of clinical and neuroimaging findings revealed three disease patterns: type 1: early-onset phenotype with neonatal brain anomalies and epileptic encephalopathy; type 2: intermediate phenotype with distinct stroke-like lesions; and type 3: moderate phenotype with non-specific brain pathology and a stable disease course. The functional relevance of COQ4 variants was supported by in vitro studies using patient-derived fibroblast lines. Experiments revealed significantly decreased COQ4 protein levels, reduced levels of cellular CoQ10 and elevated levels of the metabolic intermediate 6-demethoxyubiquinone. CONCLUSION: Our study describes the heterogeneous clinical presentation of COQ4 deficiency and identifies phenotypic subtypes. Cell-based studies support the pathogenic characteristics of COQ4 variants. Due to the insufficient clinical response to oral CoQ10 supplementation, alternative treatment strategies are warranted.

Heterozygous Variants in the Mechanosensitive Ion Channel TMEM63A Result in Transient Hypomyelination during Infancy.

Mechanically activated (MA) ion channels convert physical forces into electrical signals. Despite the importance of this function, the involvement of mechanosensitive ion channels in human disease is poorly understood. Here we report heterozygous missense mutations in the gene encoding the MA ion channel TMEM63A that result in an infantile disorder resembling a hypomyelinating leukodystrophy. Four unrelated individuals presented with congenital nystagmus, motor delay, and deficient myelination on serial scans in infancy, prompting the diagnosis of Pelizaeus-Merzbacher (like) disease. Genomic sequencing revealed that all four individuals carry heterozygous missense variants in the pore-forming domain of TMEM63A. These variants were confirmed to have arisen de novo in three of the four individuals. While the physiological role of TMEM63A is incompletely understood, it is highly expressed in oligodendrocytes and it has recently been shown to be a MA ion channel. Using patch clamp electrophysiology, we demonstrated that each of the modeled variants result in strongly attenuated stretch-activated currents when expressed in naive cells. Unexpectedly, the clinical evolution of all four individuals has been surprisingly favorable, with substantial improvements in neurological signs and developmental progression. In the three individuals with follow-up scans after 4 years of age, the myelin deficit had almost completely resolved. Our results suggest a previously unappreciated role for mechanosensitive ion channels in myelin development.

Investigating rare pathogenic/likely pathogenic exonic variation in bipolar disorder.

Bipolar disorder (BD) is a serious mental illness with substantial common variant heritability. However, the role of rare coding variation in BD is not well established. We examined the protein-coding (exonic) sequences of 3,987 unrelated individuals with BD and 5,322 controls of predominantly European ancestry across four cohorts from the Bipolar Sequencing Consortium (BSC). We assessed the burden of rare, protein-altering, single nucleotide variants classified as pathogenic or likely pathogenic (P-LP) both exome-wide and within several groups of genes with phenotypic or biologic plausibility in BD. While we observed an increased burden of rare coding P-LP variants within 165 genes identified as BD GWAS regions in 3,987 BD cases (meta-analysis OR = 1.9, 95% CI = 1.3-2.8, one-sided p = 6.0 × 10-4), this enrichment did not replicate in an additional 9,929 BD cases and 14,018 controls (OR = 0.9, one-side p = 0.70). Although BD shares common variant heritability with schizophrenia, in the BSC sample we did not observe a significant enrichment of P-LP variants in SCZ GWAS genes, in two classes of neuronal synaptic genes (RBFOX2 and FMRP) associated with SCZ or in loss-of-function intolerant genes. In this study, the largest analysis of exonic variation in BD, individuals with BD do not carry a replicable enrichment of rare P-LP variants across the exome or in any of several groups of genes with biologic plausibility. Moreover, despite a strong shared susceptibility between BD and SCZ through common genetic variation, we do not observe an association between BD risk and rare P-LP coding variants in genes known to modulate risk for SCZ.

Genetic analysis of 20 patients with hypomyelinating leukodystrophy by trio-based whole-exome sequencing.

Hypomyelinating leukodystrophies (HLDs) are a rare group of disorders characterized by myelin deficit of the brain-based on MRI. Here, we studied 20 patients with unexplained HLD to uncover their genetic etiology through whole-exome sequencing (WES). Trio-based WES was performed for 20 unresolved HLDs families after genetic tests for the PLP1 duplication and a panel of 115 known leukodystrophy-related genes. Variants in both known genes that related to HLDs and promising candidate genes were analyzed. Minigene splicing assay was conducted to confirm the effect of splice region variant. All 20 patients were diagnosed with HLDs clinically based on myelin deficit on MRI and impaired motor ability. Through WES, in 11 of 20 trios, 15 causative variants were detected in seven genes TUBB4A, POLR1C, POLR3A, SOX10, TMEM106B, DEGS1, and TMEM63A. The last three genes have just been discovered. Of 15 variants, six were novel. Using minigene splicing assay, splice variant POLR3A c.1770 + 5 G > C was proved to disrupt the normal splicing of intron 13 and led to a premature stop codon at position 618 (p.(P591Vfs*28)). Our analysis determined the molecular diagnosis of 11 HLDs patients. It emphasizes the heterogenicity of HLDs, the diagnostic power of trio-based WES for HLDs. Comprehensive analysis including a focus on candidate genes helps to discover novel disease-causing genes, determine the diagnosis for the first time, and improve the yield of WES. Moreover, novel mutations identified in TUBB4A, POLR3A, and POLR1C expand the mutation spectrum of these genes.

Maternal Overweight and Obesity during Pregnancy Are Associated with Neonatal, but Not Maternal, Hepcidin Concentrations.

BACKGROUND: Overweight or obesity among pregnant women may compromise maternal and neonatal iron status by upregulating hepcidin. OBJECTIVES: This study determined the association of 1) maternal and neonatal iron status with maternal and neonatal hepcidin concentrations, and 2) maternal prepregnancy weight status with maternal and neonatal hepcidin concentrations. METHODS: We examined hematologic data from 405 pregnant women and their infants from the placebo treatment group of a pregnancy iron supplementation trial in rural China. We measured hepcidin, serum ferritin (SF), soluble transferrin receptor (sTfR), and high-sensitivity C-reactive protein in maternal blood samples at mid-pregnancy and in cord blood at delivery. We used regression analysis to examine the association of maternal prepregnancy overweight or obese status with maternal hepcidin concentration in mid-pregnancy and cord hepcidin concentrations. We also used path analysis to examine mediation of the association of maternal prepregnancy overweight or obese status with maternal iron status by maternal hepcidin, as well as with neonatal hepcidin by neonatal iron status. RESULTS: Maternal iron status was positively correlated with maternal hepcidin at mid-pregnancy (SF: r = 0.63, P < 0.001; sTfR: r = -0.37, P < 0.001). Neonatal iron status was also positively correlated with cord hepcidin (SF: r = 0.61, P < 0.001; sTfR: r = -0.39, P < 0.001). In multiple linear regression models, maternal prepregnancy overweight or obese status was not associated with maternal hepcidin at mid-pregnancy but was associated with lower cord hepcidin (coefficient = -0.21, P = 0.004). Using path analysis, we observed a significant indirect effect of maternal prepregnancy overweight or obese status on cord hepcidin, mediated by neonatal iron status. CONCLUSIONS: In both pregnant women and neonates, hepcidin was responsive to iron status. Maternal prepregnancy overweight status, with or without including obese women, was associated with lower cord blood hepcidin, likely driven by lower iron status among the neonates of these mothers.

Review and Consensus on Pharmacogenomic Testing in Psychiatry.

The implementation of pharmacogenomic (PGx) testing in psychiatry remains modest, in part due to divergent perceptions of the quality and completeness of the evidence base and diverse perspectives on the clinical utility of PGx testing among psychiatrists and other healthcare providers. Recognizing the current lack of consensus within the field, the International Society of Psychiatric Genetics assembled a group of experts to conduct a narrative synthesis of the PGx literature, prescribing guidelines, and product labels related to psychotropic medications as well as the key considerations and limitations related to the use of PGx testing in psychiatry. The group concluded that to inform medication selection and dosing of several commonly-used antidepressant and antipsychotic medications, current published evidence, prescribing guidelines, and product labels support the use of PGx testing for 2 cytochrome P450 genes (CYP2D6, CYP2C19). In addition, the evidence supports testing for human leukocyte antigen genes when using the mood stabilizers carbamazepine (HLA-A and HLA-B), oxcarbazepine (HLA-B), and phenytoin (CYP2C9, HLA-B). For valproate, screening for variants in certain genes (POLG, OTC, CSP1) is recommended when a mitochondrial disorder or a urea cycle disorder is suspected. Although barriers to implementing PGx testing remain to be fully resolved, the current trajectory of discovery and innovation in the field suggests these barriers will be overcome and testing will become an important tool in psychiatry.

ß-Arrestin 2 (ARRB2) Polymorphism is Associated With Adverse Consequences of Chronic Heroin Use.

BACKGROUND AND OBJECTIVES: ß-arrestin 2 is an intracellular protein recruited during the activation of G-protein-coupled receptors. In preclinical studies, ß-arrestin 2 has been implicated in µ-opioid receptor desensitization and internalization and the development of opioid tolerance and dependence. The present study investigated relationships between variants in the gene encoding ß-arrestin 2 (ARRB2) and clinically relevant phenotypes among individuals with opioid use disorder (OUD). We hypothesized that ARRB2 variants would be associated with the negative effects of long-term heroin use. METHODS: Chronic heroin users (N = 201; n = 103 African American; n = 98 Caucasian) were genotyped for ARRB2 r1045280 (synonymous, also affecting binding motif of transcription factor GTF2IRD1), rs2036657 (3'UTR) and rs3786047 (intron) and assessed for the past-month frequency of use, injection use, and lifetime duration of heroin use, number of heroin quit-attempts, and heroin use-related consequences. RESULTS: Lifetime heroin-use consequences (especially occupational and health-related) were significantly lower for African American ARRB2 r1045280 C-allele carriers compared with the TT genotype. There was no significant genotype difference in the Caucasian group. ARRB2 rs2036657 was in strong linkage disequilibrium with rs1045280. DISCUSSION AND CONCLUSIONS: These results, consistent with extant data, illustrate a role for ancestry-dependent allelic variation in ARRB2 r1045280 on heroin-use consequences. The ARRB2 r1045280 C-allele played a protective role in African-descent participants. SCIENTIFIC SIGNIFICANCE: These first-in-human findings, which should be replicated, provide support for mechanistic investigations of ARRB2 and related intracellular signaling molecules in OUD etiology, treatment, and relapse prevention. (Am J Addict 2021;00:00-00).

BaiHui: cross-species brain-specific network built with hundreds of hand-curated datasets.

MOTIVATION: Functional gene networks, representing how likely two genes work in the same biological process, are important models for studying gene interactions in complex tissues. However, a limitation of the current network-building scheme is the lack of leveraging evidence from multiple model organisms as well as the lack of expert curation and quality control of the input genomic data. RESULTS: Here, we present BaiHui, a brain-specific functional gene network built by probabilistically integrating expertly-hand-curated (by reading original publications) heterogeneous and multi-species genomic data in human, mouse and rat brains. To facilitate the use of this network, we deployed a web server through which users can query their genes of interest, visualize the network, gain functional insight from enrichment analysis and download network data. We also illustrated how this network could be used to generate testable hypotheses on disease gene prioritization of brain disorders. AVAILABILITY AND IMPLEMENTATION: BaiHui is freely available at: http://guanlab.ccmb.med.umich.edu/BaiHui/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Heroin delay discounting and impulsivity: Modulation by DRD1 genetic variation.

BACKGROUND: Dopamine D1 receptors (encoded by DRD1) are implicated in drug addiction and high-risk behaviors. Delay discounting (DD) procedures measure decisional balance between choosing smaller/sooner rewards vs larger/later rewards. Individuals with higher DD (rapid discounting) are prone to maladaptive behaviors that provide immediate reinforcement (eg, substance use). DRD1 variants have been linked with increased DD (in healthy volunteers) and opioid abuse. This study determined whether four dopaminergic functional variants modulated heroin DD and impulsivity. METHODS: Substance use, DD, and genotype data (DRD1 rs686 and rs5326, DRD3 rs6280, COMT rs4680) were obtained from 106 current heroin users. Subjects completed an array of DD choices during two imagined conditions: heroin satiation and withdrawal. Rewards were expressed as $10 heroin bag units, with maximum delayed amount of 30 bags. Delays progressively increased from 3 to 96 hours. RESULTS: DRD1 rs686 (A/A, n = 25; G/A, n = 56; G/G, n = 25) was linearly related to the difference in heroin DD (area under the curve; AUC) between the heroin satiation and withdrawal conditions; specifically, G/G homozygotes had a significantly smaller (satiation minus withdrawal) AUC difference score had higher drug-use impulsivity questionnaire scores, relative to A/A homozygotes, with G/A intermediate. DRD3 and COMT variants were not associated with these DD and impulsivity outcomes. CONCLUSION: DRD1 rs686 modulated the difference in heroin DD score between pharmacological states and was associated with drug-use impulsivity. These data support a role of DRD1 in opioid DD and impulsive behaviors.

GLI1 inactivation is associated with developmental phenotypes overlapping with Ellis-van Creveld syndrome.

GLI1, GLI2 and GLI3 form a family of transcription factors which regulate development by mediating the action of Hedgehog (Hh) morphogens. Accordingly, inactivating variants in GLI2 and GLI3 are found in several developmental disorders. In contrast, loss-of-function mutations in GLI1 have remained elusive, maintaining enigmatic the role of this gene in the human embryo. We describe eight patients from three independent families having biallelic truncating variants in GLI1 and developmental defects overlapping with Ellis-van Creveld syndrome (EvC), a disease caused by diminished Hh signaling. Two families had mutations in the last exon of the gene and a third family was identified with an N-terminal stop gain variant predicted to be degraded by the NMD-pathway. Analysis of fibroblasts from one of the patients with homozygous C-terminal truncation of GLI1 demonstrated that the corresponding mutant GLI1 protein is fabricated by patient cells and becomes upregulated in response to Hh signaling. However, the transcriptional activity of the truncated GLI1 factor was found to be severely impaired by cell culture and in vivo assays, indicating that the balance between GLI repressors and activators is altered in affected subjects. Consistent with this, reduced expression of the GLI target PTCH1 was observed in patient fibroblasts after chemical induction of the Hh pathway. We conclude that GLI1 inactivation is associated with a phenotypic spectrum extending from isolated postaxial polydactyly to an EvC-like condition.

Targeted exome analysis identifies the genetic basis of disease in over 50% of patients with a wide range of ataxia-related phenotypes.

PURPOSE: To examine the impact of a targeted exome approach for the molecular diagnosis of patients nationwide with a wide range of ataxia-related phenotypes. METHODS: One hundred and seventy patients with ataxia of unknown etiology referred from clinics throughout the United States and Canada were studied using a targeted exome approach. Patients ranged in age from 2 to 88 years. Analysis was focused on 441 curated genes associated with ataxia and ataxia-like conditions. RESULTS: Pathogenic and suspected diagnostic variants were identified in 88 of the 170 patients, providing a positive molecular diagnostic rate of 52%. Forty-six different genes were implicated, with the six most commonly mutated genes being SPG7, SYNE1, ADCK3, CACNA1A, ATP1A3, and SPTBN2, which accounted for >40% of the positive cases. In many cases a diagnosis was provided for conditions that were not suspected and resulted in the broadening of the clinical spectrum of several conditions. CONCLUSION: Exome sequencing with targeted analysis provides a high-yield approach for the genetic diagnosis of ataxia-related conditions. This is the largest targeted exome study performed to date in patients with ataxia and ataxia-like conditions and represents patients with a wide range of ataxia phenotypes typically encountered in neurology and genetics clinics.

Mutations in VPS13D lead to a new recessive ataxia with spasticity and mitochondrial defects.

OBJECTIVE: To identify novel causes of recessive ataxias, including spinocerebellar ataxia with saccadic intrusions, spastic ataxias, and spastic paraplegia. METHODS: In an international collaboration, we independently performed exome sequencing in 7 families with recessive ataxia and/or spastic paraplegia. To evaluate the role of VPS13D mutations, we evaluated a Drosophila knockout model and investigated mitochondrial function in patient-derived fibroblast cultures. RESULTS: Exome sequencing identified compound heterozygous mutations in VPS13D on chromosome 1p36 in all 7 families. This included a large family with 5 affected siblings with spinocerebellar ataxia with saccadic intrusions (SCASI), or spinocerebellar ataxia, recessive, type 4 (SCAR4). Linkage to chromosome 1p36 was found in this family with a logarithm of odds score of 3.1. The phenotypic spectrum in our 12 patients was broad. Although most presented with ataxia, additional or predominant spasticity was present in 5 patients. Disease onset ranged from infancy to 39 years, and symptoms were slowly progressive and included loss of independent ambulation in 5. All but 2 patients carried a loss-of-function (nonsense or splice site) mutation on one and a missense mutation on the other allele. Knockdown or removal of Vps13D in Drosophila neurons led to changes in mitochondrial morphology and impairment in mitochondrial distribution along axons. Patient fibroblasts showed altered morphology and functionality including reduced energy production. INTERPRETATION: Our study demonstrates that compound heterozygous mutations in VPS13D cause movement disorders along the ataxia-spasticity spectrum, making VPS13D the fourth VPS13 paralog involved in neurological disorders. Ann Neurol 2018.

Oxytocin Genotype Moderates the Impact of Social Support on Psychiatric Distress in Alcohol-Dependent Patients.

AIMS: The social environment strongly influences individual mental health. Individuals with strong social support systems tend to experience higher levels of well-being, lower levels of psychological distress and exhibit fewer psychiatric symptoms. However, there is a significant degree of individual variability as to the extent to which social support is beneficial to overall mental health. From a neurobiological perspective, it is suggested that the social hormone, oxytocin, may moderate the favorable effects of social interaction. To explore this possibility, we evaluated oxytocin genotype, social support and psychological health in a group of individuals diagnosed with DSM-IV alcohol dependence. METHODS: The associations between OXT genotype, social support and psychological health were analyzed in data from 269 adults diagnosed with DSM-IV alcohol dependence (25% female) admitted into residential treatment programs and outpatient centers in Warsaw, Poland. RESULTS: In line with past observations, we noted that psychiatric distress scores were negatively correlated with social support. Extending these observations, we uncovered a significant moderating effect of OXT genotype (rs2740210) on the relationship between social support and psychiatric distress. While G carriers displayed the predicted negative relationship between social support and psychiatric distress, T homozygotes failed to exhibit such a relationship. CONCLUSION: Genetically driven variation in oxytocin system functioning may influence the degree to which the beneficial effects of social support are felt in this population. These results have direct clinical relevance as enhancing social engagement to improve mental health may prove to be a less effective strategy in some patients owing to intrinsic factors. SHORT SUMMARY: The associations between oxytocin genotype, social support, and psychological health were analyzed in data from 269 adults diagnosed with DSM-IV alcohol dependence. A significant moderating effect of OXT genotype (rs2740210) on the relationship between social support and psychiatric distress was detected.

Pathways to Youth Behavior: The Role of Genetic, Neural, and Behavioral Markers.

Neural and temperamental mechanisms through which a genetic risk marker in the γ-amino butyric acid α2 receptor subunit (GABRA2) impacts adolescent functioning were investigated. Participants (N = 80; 29 female) completed an emotional word task during functional magnetic resonance imaging. Behavioral control, negative emotionality, and resiliency temperament constructs were assessed. Externalizing and internalizing problems were the outcomes. Those with the GABRA2 minor allele had reduced activation to positive words in the angular gyrus, middle temporal gyrus, and cerebellum, and to negative words in frontal, parietal, and occipital cortices. Reduced activation in the angular gyrus predicted greater negative emotionality and, in turn, elevated externalizing problems. Reduced activation in the inferior parietal cortex predicted greater resiliency and, in turn, low externalizing problems.

Beyond risk: Prospective effects of GABA Receptor Subunit Alpha-2 (GABRA2) × Positive Peer Involvement on adolescent behavior.

Research on Gene × Environment interactions typically focuses on maladaptive contexts and outcomes. However, the same genetic factors may also impact susceptibility to positive social contexts, leading to adaptive behavior. This paper examines whether the GABA receptor subunit alpha-2 (GABRA2) single nucleotide polymorphism rs279858 moderates the influence of positive peer affiliation on externalizing behavior and various forms of competence. Regions of significance were calculated to determine whether the form of the interaction supported differential susceptibility (increased sensitivity to both low and high positive peer affiliation) or vantage sensitivity (increased sensitivity to high positive peer affiliation). It was hypothesized that those carrying the homozygous minor allele (GG) would be more susceptible to peer effects. A sample (n = 300) of primarily male (69.7%) and White (93.0%) adolescents from the Michigan Longitudinal Study was assessed from ages 12 to 17. There was evidence for prospective Gene × Environment interactions in three of the four models. At low levels of positive peer involvement, those with the GG genotype were rated as having fewer adaptive outcomes, while at high levels they were rated as having greater adaptive outcomes. This supports differential susceptibility. Conceptualizing GABRA2 variants as purely risk factors may be inaccurate. Genetic differences in susceptibility to adaptive environmental exposures warrants further investigation.

Susceptibility effects of GABA receptor subunit alpha-2 (GABRA2) variants and parental monitoring on externalizing behavior trajectories: Risk and protection conveyed by the minor allele.

Understanding factors increasing susceptibility to social contexts and predicting psychopathology can help identify targets for prevention. Persistently high externalizing behavior in adolescence is predictive of psychopathology in adulthood. Parental monitoring predicts low externalizing behavior, yet youth likely vary in the degree to which they are affected by parents. Genetic variants of GABA receptor subunit alpha-2 (GABRA2) may increase susceptibility to parental monitoring, thus impacting externalizing trajectories. We had several objectives: (a) to determine whether GABRA2 (rs279827, rs279826, rs279858) moderates the relationship between a component of parental monitoring, parental knowledge, and externalizing trajectories; (b) to test the form of this interaction to assess whether GABRA2 variants reflect risk (diathesis-stress) or susceptibility (differential susceptibility) factors; and (c) to clarify GABRA2 associations on the development of problem behavior. This prospective study (N = 504) identified three externalizing trajectory classes (i.e., low, decreasing, and high) across adolescence. A GABRA2 × Parental Monitoring effect on class membership was observed, such that A-carriers were largely unaffected by parental monitoring, whereas class membership for those with the GG genotype was affected by parental monitoring. Findings support differential susceptibility in GABRA2.

Indirect effect of corticotropin-releasing hormone receptor 1 gene variation on negative emotionality and alcohol use via right ventrolateral prefrontal cortex.

Variations in the corticotropin-releasing hormone receptor 1 (CRHR1) gene have been found to interact with stress in modulating excessive alcohol consumption. However, the neural mechanisms through which CRHR1 influences this risk in humans is largely unknown. This study examined the influence of an intronic CRHR1 gene variant, rs110402, on brain responses to negative emotional words, negative emotional traits, and alcohol use in adolescents and young adults at high risk for alcoholism. Childhood stress was investigated as a potential moderator. Using functional magnetic resonance imaging, we found that a region in the right ventrolateral prefrontal cortex (rVLPFC) was more engaged during negative emotional word processing in G homozygotes than in A allele carriers (p(FWE corrected) < 0.01, N = 77). Moreover, an indirect effect of genotype on negative emotionality via rVLPFC activation (p < 0.05, N = 69) was observed, which was further moderated by childhood stress (p < 0.05, N = 63). Specifically, with low childhood stress, G homozygotes exhibited lower levels of negative emotionality associated with greater rVLPFC activation, suggesting that the rVLPFC is involved in reappraisal that neutralizes negative emotional responses. In addition, we found that genotype indirectly modulated excessive alcohol consumption (p < 0.05, N = 69). Specifically, G homozygotes showed greater rVLPFC activation and had lower levels of negative emotionality, which were associated with fewer binge-drinking days and fewer alcohol related problems. This work provides support for a model in which CRHR1 gene variation modulates the risk of problem drinking via an internalizing/negative affect pathway involving rVLPFC and reappraisal of negative emotion.

Dominant mutation of CCDC78 in a unique congenital myopathy with prominent internal nuclei and atypical cores.

Congenital myopathies are clinically and genetically heterogeneous diseases that typically present in childhood with hypotonia and weakness and are most commonly defined by changes observed in muscle biopsy. Approximately 40% of congenital myopathies are currently genetically unresolved. We identified a family with dominantly inherited congenital myopathy characterized by distal weakness and biopsy changes that included core-like areas and increased internalized nuclei. To identify the causative genetic abnormality in this family, we performed linkage analysis followed by whole-exome capture and next-generation sequencing. A splice-acceptor variant in previously uncharacterized CCDC78 was detected in affected individuals and absent in unaffected family members and > 10,000 controls. This variant alters RNA-transcript processing and results in a 222 bp in-frame insertion. CCDC78 is expressed in skeletal muscle, enriched in the perinuclear region and the triad, and found in intracellular aggregates in patient muscle. Modeling of the CCDC78 mutation in zebrafish resulted in changes mirroring the human disease that included altered motor function and abnormal muscle ultrastructure. Using a combination of linkage analysis, next-generation sequencing, and modeling in the zebrafish, we have identified a CCDC78 mutation associated with a unique myopathy with prominent internal nuclei and atypical cores.