Morphogenetic study of the eyelids in NC-eob mice fetuses with an open-eyelid malformation at birth

The NC-eob mice are mutants having open eyelids at birth with complete penetrance. Detailed scanning electron microscopy and light microscopy for study of the eyelid development of NC-eob embryos/fetuses were performed at days 13 to 17 of gestation and compared with normal NC mice, with the aim of investigating the etiopathogenesis of the open eyelids at birth. No difference was observed between NC and NC-eob embryos by scanning electron microscopy and histologic examination at days 13 and 14 of gestation. At day 15 the epithelium at the tip of the eyelids had 2 to 3 layers, and clumps of round periderm cells appeared on the outer surface of the margin of the lids in NC and NC-eob embryos. However, these clumps in NC-eob embryos were not as remarkable in number and in size compared with NC embryos. At day 16 the eyelids of NC fetuses extended over the cornea and began to fuse. The epithelium at the tip of the eyelids consisted of 4 to 5 layers with the following elongated area. The surface of the tip of the elongated epithelium was covered with a large number of round periderm cells. In NC-eob fetuses the epithelium remained stationary at 2 to 3 layers. Only a small number of round cells were noted at the tip of the eyelids, and fusion did not occur. At day 17, although the upper and lower eyelids of NC fetuses were entirely fused, no change occurred in NC-eob fetuses, either in the periderm or in the epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)