SPATIOTEMPORAL EXPRESSION OF CD15 IN THE DEVELOPING CHICK RETINA

The spatiotemporal distribution pattern of the carbohydrate epitope CD 15 was examined in the developing chick retina. CD15 expression appear ed for the first time at E13 in the INL and GCL. The developmental pro file of the INL, from E13 to E16, showed increasing numbers of stratif ied amacrine cells, whereas diffuse amacrine subtypes appeared later, beginning at E15. Smaller populations of bipolar cells were seen at E1 7. Three types of CD15-positive ganglion cells could be differentiated by E15. A gradient in the appearance of identified immunoreactive ama crine cells extended from the dorsotemporal to the ventral and nasal r etina. The adult-like pattern of CD15 expression did not become establ ished until E19. Adult-like densities of immunoreactive cells were rea ched toward the end of the embryonic period between E18 in the dorsote mporal and ventral retina, and E19 in the dorsonasal retina. In the ad ult-like retina, labelled cells became particularly numerous at its gr eatest circumference, and were most densely packed in the dorsotempora l retinal quadrant. From E16 to P5, three membrane-bound, CD15-positiv e glycoproteins of 20, 32 and 34 kDa were identified by Western blots. The time course in the appearance of the membrane-associated CD15 rec ognition molecule on differentiating amacrine, bipolar and ganglion ce lls is correlated to the establishment of synaptic contacts.