Developmental expression of Xenopus short-chain dehydrogenase/reductase 3.

During early embryonic development, the retinoic acid signaling pathway coordinates with other signaling pathways to regulate body axis patterning and organogenesis. The production of retinoic acid requires two enzymatic reactions, the first of which is the oxidization of vitamin A (all-trans-retinol) to all-trans -retinal, mediated in part by the short-chain dehydrogenase/reductase. Through DNA microarrays, we have identified a gene in Xenopus laevis which shares a high sequence similarity to human short-chain dehydrogenase/reductase member 3. We therefore annotated the gene Xenopus short-chain dehydrogenase/reductase 3 (dhrs3). Expression of dhrs3 was detected by whole mount in situ hybridization in the dorsal blastopore lip and axial mesoderm region in gastrula embryos. During neurulation, dhrs3 transcripts were found in the notochord and neural ectoderm. Strong expression of dhrs3 was mainly detected in the brain, spinal cord and pronephros region in tailbud and tadpole stages. Temporal expression tested by RT-PCR indicated that dhrs3 was activated at the onset of gastrulation, and remained highly expressed at later stages of embryonic development. The distinct and highly regulated spatial and temporal expression of dhrs3 highlights the complexity of retinoic acid regulation.