A Zebrafish/Drosophila Dual System Model for Investigating Human Microcephaly.

Microcephaly presents in neurodevelopmental disorders with multiple aetiologies, including bi-allelic mutation in , a component of the biologically fundamental and conserved microtubule-nucleation complex, γ-TuRC. Elucidating underlying principles driving microcephaly requires clear phenotype recapitulation and assay reproducibility, areas where go-to experimental models fall short. We present an alternative simple vertebrate/invertebrate dual system to investigate fundamental -related processes driving human microcephaly and associated developmental traits. We show that antisense morpholino knockdown (KD) of the homolog, , recapitulates human -associated microcephaly. Co-injection of wild type mRNA pre-empts microcephaly in 55% of KD zebrafish larvae, confirming causality. Body shortening observed in morphants is also rescued. Mitotic marker (pH3) staining further reveals aberrantly accumulated dividing brain cells in microcephalic KD morphants, indicating that depletion disrupts normal mitosis and/or proliferation in zebrafish neural progenitor brain cells. double knockouts (KO) for homologs also develop microcephalic brains with general microsomia. Exacerbated linked developmental aberration versus single mutations strongly suggests interactive or coinciding gene functions. We infer that and affect brain size similarly to and recapitulate both microcephaly and microcephaly-associated developmental impact, validating the zebrafish/fly research model for human microcephaly. Given the conserved cross-phyla homolog function, the data also strongly support mitotic and/or proliferative disruption linked to aberrant microtubule nucleation in progenitor brain cells as key mechanistic defects for human microcephaly.