Most pathogenic tubulin variants arise de novo in sporadic patients, causing severe brain malformations and significant neurodevelopmental impairment. The resulting reproductive disadvantage typically prevents these mutations from being transmitted to offspring. While a few variants are inherited from somatic or gonadal mosaic parents, vertical transmission of constitutional variants remains rare, though increasingly documented. Here, we report the father-to-daughter transmission of a novel constitutional TUBB variant [NM_178014.4:c.991C>T; p.(Leu331Phe)]. Both individuals presented with intellectual disability and a malformation of cortical development (MCD). To validate the pathogenicity of this variant, we performed functional and immunofluorescence assays in vitro on patient-derived fibroblast cultures. These experiments supported the involvement of the variant in significantly impairing cell motility, altering cytoskeleton organization, and affecting cellular morphology. Our findings from this family, alongside literature review of constitutional and mosaic tubulinopathies, suggest that pathogenic germline TUBB variants can occasionally be inherited. Transmission is facilitated by the relatively mild clinical anatomoclinical phenotype. When a pathogenic TUBB variant is identified in an index patient, comprehensive parental clinical, neuroradiological, and genetic evaluation is crucial to accurately assess reproductive risk.
E. Cellini, D. Mei, Mara Cavallin et al.· American Journal of Medical...· 0 citations
We report a unique clinical case of a male child presenting with a blended phenotype characterized by intellectual disability, seizures, periventricular nodular heterotopia (PVNH), congenital central hypothyroidism, and multiorgan malformations. Exome sequencing (ES) identified three rare variants: a de novo frameshift variant in SETD5 (g.3-9441593 ;NM_001080517.3:c.812dup; p.(Leu271PhefsTer42)), a de novo missense variant in the WW domain of NEDD4L (NM_015277.6:c.1525C > T; p.(Arg529Cys)), and a maternally inherited nonsense variant in TBL1X (X-9711651-C-T) (NM_005647.4:c.1480C > T; p.(Arg494Ter)). While the likely pathogenic SETD5 and TBL1X variants are consistent with the neurodevelopmental delay and central hypothyroidism respectively, the NEDD4L variant of uncertain significance (VUS) represents a plausible candidate for the PVNH. To our knowledge, this is the first report of such a unique overlap, highlighting the importance of considering multilocus genomic variation in heterogeneous neurodevelopmental presentations.
M. Cassone, A. Moschella, D. Mei et al.· Gene· 0 citations
A patient with cerebellar atrophy, ataxia, and global developmental delay is described, and trio exome sequencing identified compound heterozygous variants in the final subunit EXOSC6.
Khondakar Sayef Ahammed, Renzo Guerrini, Milo B. Fasken et al.· medRxiv· 0 citations