Microcephaly-associated genes asp and Sas4 influence chromatin organization and nuclear lamina structure in Drosophila melanogaster.

Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder characterized by reduced brain size and intellectual disability. Mutations in over 30 genes, nearly half linked to centrosome biogenesis or microtubule (MT) dynamics, highlight spindle defects in disease aetiology, yet these alone do not fully explain MCPH. Here we show that the Drosophila orthologs of ASPM/MCPH5 (asp) and CENPJ/MCPH6 (Sas4) contribute to safeguard nuclear architecture and chromatin organization during brain development. Loss of either gene perturbs MT organization and centromere clustering, leading to reduced Lamin and HP1α levels and deformed nuclear lamina. Mutants also display a global reduction in heterochromatin-associated histone marks, H3K9me2/3 and H3K27me3, along with an increase in the euchromatin-associated mark H3K4me3 and elevated DNA damage with delayed repair. Notably, inhibiting demethylases with Methylstat restores H3K9me3 and nuclear morphology. These findings suggest a novel role for centrosome proteins in regulating chromatin organization, providing new insights into the mechanisms underlying MCPH pathogenesis.