Evolutionary conserved sequence elements with embryonic enhancer activity in the vicinity of the mammalian Sox8 gene

The transcription factor Sox8 is widely and dynamically expressed during embryonic development similar to its close relatives Sox9 and Sox10. Whereas gene-regulatory sequences have been identified in the vicinity of the Sox9 and Sox10 genes, no such sequences are known for Sox8. Here we used sequence conservation between mammals and birds to identify seven regions near the Sox8 gene as potential enhancers. Of these sequences, three indeed functioned as Sox8-specific enhancers in transgenic embryos. They were all localized in the upstream region of the Sox8 gene and distal to the promoter which by itself failed to drive significant transgene expression during embryogenesis. Tissues in which at least one of the three enhancers was active and that are known to express Sox8, included facial mesenchyme, the first branchial arch, peripheral nervous system and other neural crest derivatives as well as central nervous system, eye and limb. Other prominent sites of embryonic Sox8 expression were, however, not covered by the three enhancers arguing that additional enhancers exist that may be not conserved in their sequence between mammals and birds or located outside the 220 kb genomic interval analyzed in this study.