p35 Promotes the Differentiation of Amacrine Cell Subtype in the Zebrafish Retina Under the Regulation of egr1

Background:Early growth response 1 (egr1) is a transcription factor (TF) for controlling the differentiation of Parvalbumin (Parv) -expressing amacrine cells (ACs) in zebrafish. However, the downstream factors of this process have not been identified. The purpose of this study was to investigate the role of p35, a neuronal-specific activator of cyclin-dependent kinase 5 (Cdk5) and a known in vitro target of egr1, in the differentiation of these ACs. Results: In the p35-knockdown retinas, Parv+ but not islet1+ ACs were specifically reduced. This phenotype was highly similar to that in the Egr1-knockdown retinas. Furthermore, p35 expression was reduced in the Egr1-knockdown retinas, particularly in the AC region; while egr1 was only modestly reduced in this region in the p35-knockdown retinas. Conclusions:p35 likely acts downstream of egr1 to control the differentiation of Parv+ ACs. Developmental Dynamics 243:315-323, 2014. (c) 2013 Wiley Periodicals, Inc.