Abstract

What’s in a Wing? Transcriptome analysis of bat limb development

Bats, the only mammals capable of powered flight, have highly specialized limbs. The ‘hand-wing’ of the bat has elongated metacarpals and phalanges (digits II to V) that support and control an expansive interdigital membrane during flight. In contrast to this, the short, free, clawed digits of the foot are morphologically similar to the bat’s free thumb. We used a novel cross-species microarray approach to identify differentially expressed (DE) genes between the bat fore- and hindlimb at developmental Carollia stages (CS) 16 and CS17 , and between the bat (CS17) and mouse (E13.5) forelimb. Small but robust groups of DE genes were identified. These included a long non-coding (lnc) transcript of Meis2, and the limb patterning gene Hoxd11 which were significantly over-expressed in the bat forelimb. These results have been validated using qRT-PCR and the expression pattern of these and associated genes examined using ‘in situ’ hybridisation on series of developmental stages in both bat and mouse. The results suggest that Meis2 and lncMeis2 may play a role in maintaining the expansive interdigital membrane of the bat wing while the 5’ Hoxd genes may be involved in the specifying the skeletal length of both the bat fore and hindlimb.