Cacci, E. | Search bioRxiv

bioRxiv2023

Dbx2, an aging-related homeobox gene, inhibits the proliferation of adult neural progenitors

The subventricular zone (SVZ) of the adult mouse brain contains quiescent neural stem cells, which can be activated (aNSCs) to generate transit amplifying progenitors (TAPs), neuroblasts (NBs) and newborn neurons. Neurogenesis declines during aging, as the aged SVZ niche causes transcriptomic changes that promote NSC quiescence and decrease proliferating neural/stem progenitor cells (NSPCs). The transcription factors mediating these changes, however, remain unclear. We previously found that the homeobox gene Dbx2 is upregulated in aged SVZ NSPCs and inhibits NSPC culture growth. Here, we report that Dbx2 is repressed by Epidermal Growth Factor Receptor signaling, which promotes NSPC proliferation and decreases in the aged SVZ. We show that Dbx2 inhibits NSPC proliferation by hindering the G2/M transition and elucidate the transcriptomic networks modulated by Dbx2, highlighting its role in the downregulation of the cell cycle molecular pathways. Accordingly, Dbx2 function is negatively correlated with the transcriptional signatures of proliferative NSPCs (aNSCs, TAPs and early NBs). These results point to Dbx2 as a molecular node relaying the anti-neurogenic input of the aged niche to the NSPC transcriptome.

developmental biology↗

bioRxiv2020

Cul3 regulates cytoskeleton protein homeostasis and cell migration during a critical window of brain development

De novo loss of function mutations in the ubiquitin ligase-encoding gene Cullin3 (CUL3) lead to autism spectrum disorder (ASD). Here, we used Cul3 mouse models to evaluate the consequences of Cul3 mutations in vivo. Our results show that Cul3 haploinsufficient mice exhibit deficits in motor coordination as well as ASD-relevant social and cognitive impairments. Cul3 mutant brain displays cortical lamination abnormalities due to defective neuronal migration and reduced numbers of excitatory and inhibitory neurons. In line with the observed abnormal columnar organization, Cul3 haploinsufficiency is associated with decreased spontaneous excitatory and inhibitory activity in the cortex. At the molecular level, employing a quantitative proteomic approach, we show that Cul3 regulates cytoskeletal and adhesion protein abundance in mouse embryos. Abnormal regulation of cytoskeletal proteins in Cul3 mutant neuronal cells results in atypical organization of the actin mesh at the cell leading edge, likely causing the observed migration deficits. In contrast to these important functions early in development, Cul3 deficiency appears less relevant at adult stages. In fact, induction of Cul3 haploinsufficiency in adult mice does not result in the behavioral defects observed in constitutive Cul3 haploinsufficient animals. Taken together, our data indicate that Cul3 has a critical role in the regulation of cytoskeletal proteins and neuronal migration and that ASD-associated defects and behavioral abnormalities are primarily due to Cul3 functions at early developmental stages.

neuroscience↗