Fine-tuning of fgf8a expression through alternative polyadenylation has a selective impact on Fgf-associated developmental processes.

The formation of distinct 3'UTRs through alternative polyadenylation is a mechanism of gene expression regulation that has been implicated in many physiological and pathological processes. However, its functions in the context of vertebrate embryonic development have been largely unaddressed, in particular with a gene-specific focus. Here we show that the most abundant 3'UTR for the zebrafish fgf8a gene in the developing embryo mediates a strong translational repression, when compared to a more sparsely used alternative 3'UTR, which supports a higher translational efficiency. By inducing a shift in the selection efficiency of the associated polyadenylation sites, we show a temporally and spatially specific impact of fgf8a 3'UTR usage on embryogenesis, in particular at late stages during sensory system development. In addition, we identified a previously undescribed role for Fgf signalling in the initial stages of superficial retinal vascularization. These results reveal a critical functional importance of gene-specific alternative 3'UTRs in vertebrate embryonic development.