Early identification of retinal subtypes in the developing, pre-laminated chick retina using the transcription factors Prox1, Lim1, Ap2a, Pax6, Isl1, Isl2, Lim3 and Chx10

In this study, antibodies toward the transcription factors Prox1, Lim1, Ap2a, Pax6, Isl1, Isl2, Lim3 and Chx10 were used to identify and distinguish between developing cell types in the pre-laminated chick retina. The spatio-temporal expression patterns were analysed from embryonic day 3 (E3) to E9, thus covering a time-span from the onset of retinal cell-fate determination to when retinal laminas can be distinguished. Most transcription factors were found at early stages of development, enabling us to trace various precursor cell populations throughout the lamination process. With time, each transcription factor expression became restricted to distinct laminas or sub-laminas of the maturing retina. These early emerging patterns were compared and found to be consistent with those of the hatched chick retina, where the outer nuclear layer label for Lim3, Isl1 and Isl2. In the inner nuclear layer, horizontal cells labeled for Prox1, Lim1, Isl1, Ap2a and Pax6, bipolar cell labeled for Lim3, Isl1 and Chx10 and amacrine cells labeled for Ap2a, Isl1 and Pax6. The ganglion cell layer labeled for Isl1, Pax6 and Isl2. The immunolabeling patterns of Lim3 and Isl2 have not previously been described in detail.