Search

PPP3CA encodes the catalytic subunit of calcineurin, a calcium-calmodulin-regulated serine-threonine phosphatase. Loss-of-function (LoF) variants in the catalytic domain have been associated with epilepsy, while gain-of-function (GoF) variants in the auto-inhibitory domain cause multiple congenital abnormalities. We herein report five new patients with de novo PPP3CA variants. Interestingly, the two frameshift variants in this study and the six truncating variants reported previously are all located within a 26-amino acid region in the regulatory domain (RD). Patients with a truncating variant had more severe earlier onset seizures compared to patients with a LoF missense variant, while autism spectrum disorder was a more frequent feature in the latter. Expression studies of a truncating variant showed apparent RNA expression from the mutant allele, but no detectable mutant protein. Our data suggest that PPP3CA truncating variants clustered in the RD, causing more severe early-onset refractory epilepsy and representing a type of variants distinct from LoF or GoF missense variants., (© 2021 John Wiley & Sons A/S . Published by John Wiley & Sons Ltd.)

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., (Copyright © 2020 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

KIF21B is a kinesin protein that promotes intracellular transport and controls microtubule dynamics. We report three missense variants and one duplication in KIF21B in individuals with neurodevelopmental disorders associated with brain malformations, including corpus callosum agenesis (ACC) and microcephaly. We demonstrate, in vivo, that the expression of KIF21B missense variants specifically recapitulates patients' neurodevelopmental abnormalities, including microcephaly and reduced intra- and inter-hemispheric connectivity. We establish that missense KIF21B variants impede neuronal migration through attenuation of kinesin autoinhibition leading to aberrant KIF21B motility activity. We also show that the ACC-related KIF21B variant independently perturbs axonal growth and ipsilateral axon branching through two distinct mechanisms, both leading to deregulation of canonical kinesin motor activity. The duplication introduces a premature termination codon leading to nonsense-mediated mRNA decay. Although we demonstrate that Kif21b haploinsufficiency leads to an impaired neuronal positioning, the duplication variant might not be pathogenic. Altogether, our data indicate that impaired KIF21B autoregulation and function play a critical role in the pathogenicity of human neurodevelopmental disorder.

Autosomal recessive COX4I1 deficiency has been previously reported in a single individual with a homozygous pathogenic variant in COX4I1, who presented with short stature, poor weight gain, dysmorphic features, and features of Fanconi anemia. COX4I1 encodes subunit 4, isoform 1 of cytochrome c oxidase. Cytochrome c oxidase is a respiratory chain enzyme that plays an important role in mitochondrial electron transport and reduces molecular oxygen to water leading to the formation of ATP. Defective production of cytochrome c oxidase leads to a variable phenotypic spectrum ranging from isolated myopathy to Leigh syndrome. Here, we describe two siblings, born to consanguineous parents, who presented with encephalopathy, developmental regression, hypotonia, pathognomonic brain imaging findings resembling Leigh-syndrome, and a novel homozygous variant on COX4I1, expanding the known clinical phenotype associated with pathogenic variants in COX4I1., (© 2019 Wiley Periodicals, Inc.)

Pathogenic variants in CHD2 (chromodomain helicase DNA-binding protein 2) have been reported in neurodevelopmental disorders with a broad spectrum of phenotypic variability, ranging from mild intellectual disability to atonic-myoclonic epilepsy. However, given the paucity of reported cases the extent of this phenotypic spectrum is currently unknown. Furthermore, all confirmed pathogenic CHD2 variants reported to date have been de novo, preventing the study of intrafamilial phenotypic heterogeneity and creating ambiguity regarding recurrence risk, penetrance, and expressivity. Here, we report the first known case of an inherited pathogenic CHD2 variant in affected mother and daughter. This case demonstrates intrafamilial phenotypic heterogeneity and confirms potential heritability of CHD2-related neurodevelopmental disorders., (© 2018 Wiley Periodicals, Inc.)

Background: Mutations in the BRCA1 and BRCA2 genes are associated with increased risk of breast, ovarian, and several other cancers. The purpose of the present study was to evaluate the incidence of cancer in first- and second-degree relatives of BRCA mutation carriers compared with the general population., Materials and Methods: A total of 1,086 pedigrees of BRCA mutation carriers was obtained from a prospectively maintained, internal review board-approved study of persons referred for clinical genetic counseling at the University of Texas MD Anderson Cancer Center. We identified 9,032 first- and second-degree relatives from 784 pedigrees that had demonstrated a clear indication of parental origin of mutation. Standardized incidence ratios (SIRs) were used to compare the observed incidence of 20 primary cancer sites to the expected incidence of each cancer based on the calculated risk estimates according to each subject's age, sex, and ethnicity., Results: BRCA1 families had increased SIRs for breast and ovarian cancer (p < .001) and decreased SIRs for kidney, lung, prostate, and thyroid cancer and non-Hodgkin's lymphoma (p < .001). BRCA2 families had increased SIRs for breast, ovarian, and pancreatic cancer (p < .001) and decreased SIRs for kidney, lung, thyroid, and uterine cancer and non-Hodgkin's lymphoma (p < .0025). Analysis of only first-degree relatives (n = 4,099) identified no decreased SIRs and agreed with the increased SIRs observed in the overall study population., Conclusion: We have confirmed previous reports of an association between breast, ovarian, and pancreatic cancers with BRCA mutations. Additional research to quantify the relative risks of these cancers for BRCA mutation carriers can help tailor recommendations for risk reduction and enhance genetic counseling., Implications for Practice: BRCA gene mutations have been well described to carry an increased risk of both breast and ovarian cancer. However, the implications and risks of other cancers continues to be investigated. Evaluating the risks for other cancers further is key in identifying and managing risk reduction strategies., (©AlphaMed Press.)