Meeting Abstract

144.2  Monday, Jan. 7  A novel transcriptional regulator, lbh, regulates cranial neural crest development and craniofacial evolution in East African cichlids POWDER, KE*; ALBERTSON, RC; Univ Massachusetts; Univ Massachusetts kepowder@bio.umass.edu

East African cichlids exhibit a rapid and extensive adaptive radiation. One major axis of their divergence is trophic specialization, which is reflected in their craniofacial skeleton. We previously identified a quantitative trait locus (QTL) that contributes to the mechanical advantage of closing the lower jaw (i.e. a functional tradeoff of force versus speed). This region includes the genes bone morphogenetic protein 4 (bmp4), expression of which is associated with more robust cichlid jaws and avian beaks, and limb bud and heart homolog (lbh), a poorly characterized transcriptional regulator. In order to further characterize this linkage, we re-sequenced the region in wild-caught cichlid populations. We identified two single nucleotide polymorphisms (SNPs) that are alternatively fixed in cichlids with differing feeding strategies and jaw morphologies. The first is located in a putative craniofacial enhancer for bmp4, and may mediate different expression levels of bmp4 previously identified in cichlids with differing jaw morphologies. The other alternately fixed SNP encodes a non-synonymous change in the largely unknown gene lbh that alters protein polarity. We observed lbh expression in cranial neural crest (CNC) cells, which give rise to the facial skeleton. Knock-down of Lbh in zebrafish results in aberrant CNC development and discrete facial defects including a severe reduction of the lower jaw precursor. These data suggest that the linked genes bmp4 and lbh may both contribute craniofacial evolution in cichlids, and offer lbh as a molecular inroad into the developmental processes that mediate this process.