J. LETELIER ET AL.
In a study published last month (March 19) in Nature Genetics, scientists found a single genetic enhancer, named ZRS, critical for normal dorsal fin development in Japanese rice fish (Oryzias latipes). In ancient organisms, dorsal fins are the first limbs seen in the fossil record, indicating they were the first to evolve. When the enhancers were deleted in mice, the rodents also developed abnormal limbs, meaning the pathways that evolved in ancient fins have been conserved across all vertebrates.
J. Letelier et al., “A conserved Shh cis-regulatory module highlights a common developmental origin of unpaired and paired fins,” Nature Genetics, doi:10.1038/s41588-018-0080-5, 2018.