RNA methyltransferase SPOUT1/CENP-32 links mitotic spindle organization with the neurodevelopmental disorder SpADMiSS

Abstract

SUMMARYSPOUT1/CENP-32encodes a putative SPOUT RNA methyltransferase previously identified as a mitotic chromosome associated protein. SPOUT1/CENP-32 depletion leads to centrosome detachment from the spindle poles and chromosome misalignment. Aided by gene matching platforms, we identified 24 individuals with neurodevelopmental delays from 18 families with bi-allelic variants inSPOUT1/CENP-32detected by exome/genome sequencing. Zebrafishspout1/cenp-32mutants showed reduction in larval head size with concomitant apoptosis likely associated with altered cell cycle progression.In vivocomplementation assays in zebrafish indicated thatSPOUT1/CENP-32missense variants identified in humans are pathogenic. Crystal structure analysis of SPOUT1/CENP-32 revealed that most disease-associated missense variants mapped to the catalytic domain. Additionally, SPOUT1/CENP-32 recurrent missense variants had reduced methyltransferase activityin vitroand compromised centrosome tethering to the spindle poles in human cells. Thus,SPOUT1/CENP-32pathogenic variants cause an autosomal recessive neurodevelopmental disorder: SpADMiSS (SPOUT1Associated Development delay Microcephaly Seizures Short stature) underpinned by mitotic spindle organization defects and consequent chromosome segregation errors.