Expression pattern of the melanopsin-like (cOpn4m) and VA opsin-like genes in the developing chicken retina and neural tissues

We examined the expression pattern of melanopsin-like (cOpn4m) and VA opsin-like (cVAL) genes during chicken development. Two types of cOpn4m transcripts, distinct in their carboxyl terminals were found, as is the case for the chicken melanopsin (cOpn4) reported previously. The expression of cOpn4m was restricted to the developing retina, specifically to a subset of developing amacrine cells from embryonic day 10. VA opsin is one of the non-canonical opsins, reported to exist in fish so far. In this study, an aberrant type of VA opsin-like (cVAL) cDNA was isolated from chicken embryonic neural tissues. The expression of cVAL was observed in the ventral region of the developing brain and neural tube; however, specific signals for cVAL could not be detected in the developing retina. These results indicate that the additional melanopsin in avian identifies a subset of developing amacrine cells in the retina and that the aberrant transcript of the VA opsin-like gene are present during neural tube development in the chicken.