Willing, Marcia

Abstract Calmodulin‐binding transcriptional activator 1 (CAMTA1) is highly expressed in the brain and plays a role in cell cycle regulation, cell differentiation, regulation of long‐term memory, and initial development, maturation, and survival of cerebellar neurons. The existence of human neurological phenotypes, including cerebellar dysfunction with variable cognitive and behavioral abnormalities (CECBA), associated with CAMTA1 variants, has further supported its role in brain functions. In this study, we phenotypically and molecularly characterize the largest cohort of individuals ( n = 26) with 23 novel CAMTA1 variants (frameshift‐7, nonsense‐6, splicing‐1, initiation codon‐1, missense‐5, and intragenic deletions‐3) and compare the findings with all previously reported cases (total = 53). We show that the most notable phenotypic findings are developmental delay/intellectual disability, unsteady or uncoordinated gait, hypotonia, behavioral problems, and eye abnormalities. In addition, there is a high incidence of dysarthria, dysgraphia, microcephaly, gastrointestinal abnormalities, sleep difficulties, and nonspecific brain MRI findings; a few of which have been under‐reported. More than one third of the variants in this cohort were inherited from an asymptomatic or mildly affected parent suggesting reduced penetrance and variable expressivity. Our cohort provides a comprehensive characterization of the spectrum of phenotypes and genotypes among individuals with CECBA and the large data will facilitate counseling and formulating management plans and surveillance recommendations for these individuals.

Germ line mutations in H3F3A and H3F3B cause a previously unidentified neurodevelopmental syndrome.