Activin family members in the developing chick retina: expression patterns, protein distribution, and in vitro...

We have investigated whether the activin family of growth factors is involved in the regulation of retinal cell differentiation. Immunocytochemistry and in situ hybridization have shown that activin/inhibin subunits alpha, betaA, and betaB; receptors II and IIB; follistatin; and a follistatin-like gene are expressed in different regions of the chick embryo retina in developmentally regulated patterns. When tested in dissociated retinal cultures, activin did not appear to affect cell survival or proliferation, but it exerted marked inhibitory effects on the differentiation of photoreceptors, while stimulating the differentiation of nonphotoreceptor neurons; both effects were concentration-dependent and follistatin-sensitive. The results are consistent with the possibility that activin family members play significant roles in the regulation of retinal development.