Figure 6

Summary and working model for  cxcr5  expression and function in unlesioned and lesioned adult zebrafish telencephalons. In unlesioned adult zebrafish telencephalons, cxcr5 is expressed in proliferating and non-proliferating radial glial cells (RGCs), as well as neurons in the periventricular region. After a lesion, proliferating cxcr5-positive RGCs and cxcr5-positive periventricular neurons increase in number. cxcr5 expression is strongest at the ventricular surface and weakens towards the deeper layers of parenchyma. Based on the transgenic misexpression of the dominant negative and the full-length variants of cxcr5 gene in the ventricular zone cells, we propose that cxcr5 is a permissive cue for proliferative competency of the RGCs. cxcr5 is sufficient to enhance proliferation of RGCs not before but after injury, possibly due to additional injury-induced factors required in combination with cxcr5 to enhance cell proliferation. Based on the expression of cxcr5 in differentiating neurons and long-term neurogenesis experiments upon transgenic misexpression, we suggest that cxcr5 is also required for differentiation of RGCs to neurons. Since cxcr5 is also expressed in neurons, it might have other roles in neurons, such as migration, which are yet to be identified.