Effects of retinoic acid excess on expression of Hox‐2.9 and Krox‐20 and on morphological segmentation in the hindbrain of mouse embryos.

摘要: Mouse embryos were exposed to maternally administered RA on day 8.0 or 7 3/4 of development, i.e. at just before the differentiation cranial neural plate, and start segmentation. On 9.0, RA-treated had a shorter preotic hindbrain than controls clear rhombomeric segmentation was absent. These morphological effects correlated with alterations in spatiotemporal distribution patterns two genes, Hox-2.9 Krox-20, which are expressed otic specific crest cell populations. throughout region, instead being confined rhombomere 4. Krox-20 not rostral domain, its normal 3 domain The Hox-2.9/Krox-20 boundary ill-defined, patches alternating expression genes. In migrating cells, both abnormally extensive prolonged. Neural cells expressing remained close tube. Embryos 8 1/4 appeared be morphologically normal. We suggest that early events leading rhombomere-specific gene specifically vulnerable raised levels, may require levels lower those region somitic