Involvement of numb in vertebrate retinal development: Evidence for multiple roles of numb in neural differentiation and maturation

Abstract

Cell fate specification is regulated in part by lateral inhibition mediated by Notch signaling. Notch signaling is negatively regulated by Numb, an intrinsic factor that regulates cellular competence. In this study we have examined the involvement of Numb in retinal development, which has been shown to be influenced by Notch signaling. In the developing retina, Numb is asymmetrically distributed towards the ventricular and vitreal poles of different cells. Asymmetric localization is evident not only in mitotic cells but in postmitotic ganglion cells as well, suggesting that the subcellular distribution of Numb may play a role after cells have exited the cell cycle. This is supported by the expression of Numb in terminally differentiated neurons in the adult retina. Although Numb is an intrinsic factor, it is observed that its subcellular distribution is influenced by epigenetic cues such that a higher proportion of cells cultured at high density express Numb asymmetrically. A correlation is observed between asymmetric localization and cellular competence; cells in which Numb is asymmetric differentiate more readily in culture than those that express Numb symmetrically. We have identified alternative splice variants in the developing and adult retina that correspond to isoforms that have been shown to regulate proliferation and differentiation. The dynamic temporal expression patterns of alternative splice variants and isoforms suggest that Numb may influence proliferation and differentiation of retinal progenitors during neurogenesis and maturation of postmitotic neurons. Together, these results demonstrate the complex role of the distribution of Numb within progenitors and postmitotic neurons.

Global Profiling and Molecular Characterization of Alternative Splicing Events Misregulated in Lung Cancer

“…1B), the function of which is unknown. However, it has been reported that increased levels of PRR L NUMB isoforms can promote proliferation of embryo-derived cell lines whereas the expression of these isoforms declines following differentiation (1,18,19,52,58). These findings, coupled with our results supporting a specific role for NUMB exon 9-included/ PRR L isoforms in increased cell proliferation, suggest that increased levels of exon 9 inclusion in NUMB may function to promote cell proliferation both during development and during tumorigenesis.…”

The orientation of cell division influences cell-fate choice in the developing mammalian retina

“…We (Cayouette et al, 2001) and others (Dooley et al, 2003) previously provided evidence that Numb is asymmetrically distributed on the apical side of the rat retinal neuroepithelium. However, a recent paper raised the possibility that the anti-Numb monoclonal antibody (Transduction Lab) used in these two studies recognizes another protein, called Mortalin, which has the same molecular weight as Numb (Rivolta and Holey, 2002).…”

SWI/SNF Chromatin Remodeling ATPase Brm Regulates the Differentiation of Early Retinal Stem Cells/Progenitors by Influencing Brn3b Expression and Notch Signaling

“…Northern Analysis-Northern analysis was carried out to detect rBrm transcripts as described previously (39). Briefly, ϳ2 g of poly(A) RNA, isolated from adult retina, was electrophoresed on a 1.2% formaldehyde gel and transferred to Nytran Plus.…”

“…Western Blot Analysis-Western blot analysis was done as described previously (39). Samples from co-immunoprecipitation or protein isolated from siRNA-transfected retinas were electroblotted onto polyvinylidene difluoride membranes, following electrophoresis.…”