Characterization of Pin1 function in zebrafish development

Abstract

Zebrafish Pin1 was expressed maternally and in a ubiquitous manner early in development, but by 48 hpf it was restricted to the brain and neuromasts. Co-immunoprecipitation assays in cell lines showed that zPin1 could interact with neuroD in a phosphorylation dependent manner. Morpholino knockdown of zPin1 led to delay in development. Accounting for the delay, neuroD expression was significantly diminished in the hindbrain of morphants by 48 hpf equivalent. Morphants of ET4 and ET20 embryos also displayed defects in neuromasts formation. It has been shown that specification of hair cells in neuromasts is neuroD dependent but ngn1 independent. Using siRNA Pin1 knockdown 293T cells and Pin1 knockout MEFs cells, we showed that neuroD protein was degraded more rapidly in the absence of Pin1. NeuroD stability was restored when Pin1 was over-expressed. This is the first study to demonstrate functional regulation of a bHLH factor by Pin1 in neuronal specification.