Cux2 acts as a critical regulator for neurogenesis in the olfactory epithelium of vertebrates

Abstract

Signaling pathways and transcription factors are crucial regulators of vertebrate neurogenesis, exerting their function in a spatial and temporal manner. Despite recent advances in our understanding of the molecular regulation of embryonic neurogenesis, little is known regarding how different signaling pathways interact to tightly regulate this process during the development of neuroepithelia. To address this, we have investigated the events lying upstream and downstream of a key neurogenic factor, the Cut-like homeodomain transcription factor-2 (Cux2), during embryonic neurogenesis in chick and mouse. By using the olfactory epithelium as a model for neurogenesis we have analyzed mouse embryos deficient in Cux2, as well as chick embryos exposed to Cux2 silencing (si) RNA or a Cux2 over-expression construct. We provide evidence that enhanced BMP activity increases Cux2 expression and suppresses olfactory neurogenesis in the chick olfactory epithelium. In addition, our results show that up-regulation of Cux2, either BMP-induced or ectopically over-expressed, reduce Delta1 expression and suppress proliferation. Interestingly, the loss of Cux2 activity, using mutant mice or siRNA in chick, also diminishes neurogenesis, Notch activity and cell proliferation in the olfactory epithelium. Our results suggest that controlled low levels of Cux2 activity are necessary for proper Notch signaling, maintenance of the proliferative pool and ongoing neurogenesis in the olfactory epithelium. Thus, we demonstrate a novel conserved mechanism in vertebrates in which levels of Cux2 activity play an important role for ongoing neurogenesis in the olfactory epithelium.

Neurogenin 3 mediates sex chromosome effects on the generation of sex differences in hypothalamic neuronal development

“…Cux2 (cut-like homeobox 2 gene) regulates fundamental aspects of late neuronal differentiation and controls intrinsic mechanisms of dendrite development, spine formation and synaptic function in layers II–III of the cortex (Cubelos et al, 2010). Cux2 has been identified as upstream and downstream target of Notch signaling (Iulianella et al, 2009; Wittmann et al, 2014) and Cux2 overexpression has been shown to inhibit Notch signaling in the olfactory epithelium (Wittmann et al, 2014). This is relevant for our findings, since Ngn3 transcription is negatively regulated by Notch signaling (Salama-Cohen et al, 2006).…”

Cux2 serves as a novel lineage marker of granule cell layer neurons from the rhombic lip in mouse and chick embryos

“…Previous overexpression studies in the chick have revealed an important role of Cux2 in neurogenesis, and have validated the use of the chick model for in ovo electroporations of Cux2 to determine gene function (Iulianella et al, 2008;Wittmann et al, 2014). Cux2pCIG and pCIG control vectors were prepared as previously described (Iulianella et al, 2008;Wittmann et al, 2014), and electroporated into the developing hindbrain of E2 chicks (HH stage 11-13; N ¼ 6 experimental vs. N ¼ 4 control). The embryos were allowed to develop until E9 (HH stage 35).…”

“…We recently identified a role for the homeodomain-containing factor, Cux2, in fate restriction of granule cell precursors in the hippocampus (Yamada et al, 2015). In the various regions in which it is expressed, Cux2 plays an important role in proliferation and differentiation of neural progenitors (Iulianella et al, 2008(Iulianella et al, , 2009Zimmer et al, 2004;Wittmann et al, 2014). Of interest, it has been argued that Cux2 activity in the developing cortex acts to restrict the fate of progenitors to upper layer pyramidal neurons, however, this remains controversial (Guo et al, 2013;Eckler et al, 2015).…”

Neural retina identity is specified by lens‐derived BMP signals

“…In situ RNA hybridization and immunohistochemistry were performed essentially as described previously (Wilkinson and Nieto, 1993;Wittmann et al, 2014). Probes and antibodies are described in the methods in the supplementary material.…”