Cilia defects upon loss of WDR4 are linked to proteasomal hyperactivity and ubiquitin shortage.
Martin D BurkhalterTom StiffLars D MaerzTeresa Casar TenaHeike WieseJulian GerhardsSteffen A SailerLinh Anna Trúc VuMax Duong PhuCornelia DonowMarius AlupeiSebastian IbenMarco GrothSebastian WieseJoseph A ChurchPenelope A JeggoMelanie PhilippPublished in: Cell death & disease (2024)
The WD repeat-containing protein 4 (WDR4) has repeatedly been associated with primary microcephaly, a condition of impaired brain and skull growth. Often, faulty centrosomes cause microcephaly, yet aberrant cilia may also be involved. Here, we show using a combination of approaches in human fibroblasts, zebrafish embryos and patient-derived cells that WDR4 facilitates cilium formation. Molecularly, we associated WDR4 loss-of-function with increased protein synthesis and concomitant upregulation of proteasomal activity, while ubiquitin precursor pools are reduced. Inhibition of proteasomal activity as well as supplementation with free ubiquitin restored normal ciliogenesis. Proteasome inhibition ameliorated microcephaly phenotypes. Thus, we propose that WDR4 loss-of-function impairs head growth and neurogenesis via aberrant cilia formation, initially caused by disturbed protein and ubiquitin homeostasis.