Role of <i>Wdr45b</i> in maintaining neural autophagy and cognitive function

Macroautophagy/autophagy functions as a quality control mechanism by degrading misfolded proteins and damaged organelles and plays an essential role in maintaining neural homeostasis. The phosphoinositide phosphatidylinositol-3-phosphate (PtdIns3P) effector Atg18 is essential for autophagosome formation in yeast. Mammalian cells contain four Atg18 homologs, belonging to two subclasses, WIPI1 (WD repeat domain, phosphoinositide interacting 1), WIPI2 and WDR45B/WIPI3 (WD repeat domain 45B), WDR45/WIPI4. The role of <i>Wdr45b</i> in autophagy and in neural homeostasis, however, remains unknown. Recent human genetic studies have revealed a potential causative role of <i>WDR45B</i> in intellectual disability. Here we demonstrated that mice deficient in <i>Wdr45b</i> exhibit motor deficits and learning and memory defects. Histological analysis reveals that <i>wdr45b</i> knockout (KO) mice exhibit a large number of swollen axons and show cerebellar atrophy. SQSTM1- and ubiquitin-positive aggregates, which are autophagy substrates, accumulate in various brain regions in <i>wdr45b</i> KO mice. Double KO mice, <i>wdr45b</i> and <i>wdr45</i>, die within one day after birth and exhibit more severe autophagy defects than either of the single KO mice, suggesting that these two genes act cooperatively in autophagy. Our studies demonstrated that WDR45B is critical for neural homeostasis in mice. The <i>wdr45b</i> KO mice provide a model to study the pathogenesis of intellectual disability. <b>Abbreviations</b>: ACSF: artificial cerebrospinal fluid; AMC: aminomethylcoumarin; BPAN: beta-propeller protein-associated neurodegeneration; CALB1: calbindin 1; CNS: central nervous system; DCN: deep cerebellar nuclei; fEPSP: field excitatory postsynaptic potential; IC: internal capsule; ID: intellectual disability; ISH: <i>in situ</i> hybridization; KO: knockout; LTP: long-term potentiation; MBP: myelin basic protein; MGP: medial globus pallidus; PtdIns3P: phosphoinositide phosphatidylinositol-3-phosphate; WDR45B: WD repeat domain 45B; WIPI1: WD repeat domain, phosphoinositide interacting 1; WT: wild type.