KATNAL2 dysfunction impairs microtubule dynamics and contributes to syndromic neurodevelopmental disease.

Katanins are microtubule-severing ATPases. Dysfunction of katanin subunits has been implicated in impaired neurogenesis, morphogenesis, and neuronal migration. Although heterozygous variants in KATNAL2 (katanin-like 2), a known autism-spectrum disorder (ASD) risk gene, have been reported in patients with ASD or other neurodevelopmental disorders (NDD), the underlying cellular mechanisms remain incompletely defined. Whole-exome sequencing (WES) identified a homozygous missense variant in KATNAL2 (NM_001387690.1:c.1390T>C; p.(Ser464Pro)) in a pediatric patient presenting with severe global developmental delay, intellectual disability, infantile-onset epilepsy, and autistic features, extending the phenotypic spectrum beyond prior autism-focused associations. To elucidate the cellular mechanisms underlying KATNAL2 dysfunction, we established induced pluripotent stem cells (iPSCs) from patient fibroblasts and differentiated them into neural progenitor cells (NPCs) for quantitative immunofluorescence analyses of microtubule organization, microtubule regulatory proteins, and transcriptome profiling. In parallel, we generated CRISPR/Cas9 katnal2 zebrafish crispants and assessed body patterning and axonal projections using the transgenic nbt:dsRed line. Patient iPSC-derived NPCs showed impaired interphase microtubule network organization with increased angular standard deviation in directionality and mitotic/cytokinetic abnormalities, including abnormal positioning of the microtubule-rich cytokinetic midbody region. In vivo, CRISPR/Cas9 katnal2 zebrafish crispants showed abnormal body patterning together with disorganized motor neuron and posterior lateral line nerve axonal projections. Together, these findings support KATNAL2 as a regulator of microtubule network organization and mitotic progression in human NPCs. Our data from patient-derived NPCs and a zebrafish model provide functional evidence linking the p.(Ser464Pro) variant to an expanded syndromic neurodevelopmental phenotype.