Exome sequencing identified mutations in CASK and MYBPC3 as the cause of a complex dilated cardiomyopathy phenotype

Case Report: Identification of a novel CASK missense variant in a Chinese family with MICPCH

Mental retardation and microcephaly with pontine and cerebellar hypoplasia (MICPCH) is a rare genetic disorder that results in varying levels of pontocerebellar hypoplasia, microcephaly, and severe intellectual disabilities. Prior genetic analyses have identified the CASK gene as a driver of MICPCH. Herein, we analyzed a Chinese family with MICPCH. The index patient was an 8-year-old male. He and his 3-year-old brother suffered from microcephaly, pontocerebellar hypoplasia, serious mental retardation, ataxia, gait disorder, and inability to speak. Through a combination of whole-exome sequencing and subsequent Sanger sequencing, a novel X-linked missense mutation, c.1882G>C (p.D628H) in the CASK gene, was identified in two siblings, as well as their mother and grandmother, who exhibited mild mental retardation. Other family members with negative genetic testing were normal. In silico analyses indicated that this missense mutation was predicted to reduce CASK protein stability, disrupt the SRC homology 3 (SH3) domain, and abolish its function. In summary, we identified a novel missense variate in CASK associated with MICPCH. Our work facilitates the diagnosis of the disease in this family and broadens the gene variant spectrum of the CASK in MICPCH patients.

Microcephaly, disproportionate pontine, and cerebellar hypoplasia syndrome: Two novel mutations in the CASK gene were discovered in Chinese females

Microcephaly, disproportionate pontine and cerebellar hypoplasia (MICPCH) syndrome is a rare and genetic disorder, which is mainly caused by mutations in the CASK gene. We described four variations in the CASK gene in Chinese female patients with MICPCH, who presented with microcephaly, developmental delay, and motor disorder. The CASK mutations were identified using NGS (the next-generation sequencing), copy number variation sequencing. Two novel variations in the CASK gene were revealed including a frameshift mutation c.1000_1001insG (p.Asp334GlyfsTer32) and a nonsense mutation c.2110A > T (p.Lys704Ter). Two other aberrations were c.316C > T (p.Arg106Ter) and Xp11.4-p11.3 (41,700,001-44,660,000) × 1 loss. We provided clinical manifestations and neuroimaging findings of the four patients. The genetic variation spectrum of MICPCH caused by CASK was updated. Furthermore, we expounded on the molecular mechanism of the disease and noticed that it was not possible to relate the magnitude of the genetic alteration to a particular phenotype.

Novel CASK mutations in cases with syndromic microcephaly

Mutations in CASK cause a wide spectrum of phenotypes in humans ranging from mild X-linked intellectual disability to a severe microcephaly (MC) and pontocerebellar hypoplasia syndrome. Nevertheless, predicting pathogenicity and phenotypic consequences of novel CASK mutations through the exclusive consideration of genetic information and population-based data remains a challenge. Using whole exome sequencing, we identified four novel CASK mutations in individuals with syndromic MC. To understand the functional consequences of the different point mutations on the development of MC and cerebellar defects, we established a transient loss-of-function zebrafish model, and demonstrate recapitulation of relevant neuroanatomical phenotypes. Furthermore, we utilized in vivo complementation studies to demonstrate that the three point mutations confer a loss-of-function effect. This work endorses zebrafish as a tractable model to rapidly assess the effect of novel CASK variants on brain development.