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Eckalbar et al. The genetic basis of bat wing development
DOI:10.1038/bonekey.2016.79
Investigating how the bat’s genome is regulated as its forelimbs and hindlimbs develop at sequential embryonic stages should help us understand some of adaptations that give the bat the power of flight.
These adaptations include substantial forelimb specialization with extension of the second to fifth digit and reduced bone mineralization in the wing along the proximal-distal axis. Bats also have interdigit webbing, which is controlled by an unusual set of muscles not seen in other mammals.
More than 7,000 separate genes and many long noncoding RNAs were differentially expressed between the embryonic forelimb and hindlimb and across different developmental stages. Using comparative genomics, the authors discovered over 2,700 bat-accelerated regions. The most active included the genes cereblon (Crbn: a known target of the drug thalidomide) and leucine-rich repeat neuronal 1 (Lrrn1). A second highly active region encompassed Fgf2 and Spry1.
Many ribosomal protein genes were differentially regulated in the bat forelimb compared to hindlimb. Among the top ten canonical pathways identified, Fgf, Wnt and Bmp signaling are known to play an important role in human limb and bone development.
Editor’s comment: Unsurprisingly, the Bmp signaling pathway was involved in temporal activation of genes involved in bat wing development. This fits well with the roles this pathway plays in chondrogenesis, osteogenesis and apoptosis in humans. Notable also are the changes in expression of chondrogenic markers (Sox6, Aggrecan and Mmp9) and in Spry1, all of which are known to be involved in human muscle and tendon development.
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