Gene expression and protein localization of calmodulin-dependent phosphodiesterase during ontogenesis of chick retina

Calmodulin-dependent phosphodiesterase (PDE1) is a key enzyme in cyclic nucleotides metabolism. We studied its gene expression and protein localization during retinal development in chick embryos. Western blot and densitometric analysis demonstrated that the expression of the three isoforms changed during development. PDE1A was highly expressed at the early stages and decreased as development proceeded. PDE1B expression remained relatively low and constant over time. PDE1C showed a prominent increase (13-fold) between embryonic day (E) 7 and E13, followed by a moderate increase between E13 and postnatal day (P) 1. The presence of the enzyme in the different retinal locations was strongly modulated by development. PDE1A immunostaining was first detected at the ganglion cell level (E7), then in the outer retina (E15-E21). At P5, the immunostaining was confined in the optic fiber layer. Isoform C immunolocalization followed the same inner-outer pattern as isoform A. At 5 days posthatching (P5), the immunoreactivity was restricted, as well as for the isoform A, in the optic fiber layer. The isoform B immunolabelling was low and evenly distributed across the retina at all stages. The different developmental profiles of PDE1A, PDE1B, and PDE1C induced a temporal modulation in cyclic nucleotides concentration, suggesting specific roles of this enzyme in the morphofunctional development of retinal circuitry.