Molecular biology - mRNA vaccine

At Maimi , I studied molecular basis underlying wing development in red flour beetle, Tribolium castaneum, using well studied wing regulatory network in fruit fly, Drosophila melanogaster as a paradigm. A vital difference between wings of Drosophila and Tribolium involves fore/hind-wing differentiation, attributed to function of hox protein Ultrabithorax (Ubx), a conserved developmental gene.This question of differential regulation by Hox gene Ultrabithorax in these two different species is being addressed by taking advantage of the recently established genomics techniques like Chip seq, RNA seq , along with classical Genetics and molecular biology tools. Results obtained from this study will provide valuable insights into contribution of Ubx / Hox proteins in morphological diversity in a non Drosophilid insect .

Hox genes encode transcription factors, which play important roles in giving a unique identity to each segment and thereby set up diversified morphogenesis along the anterior posterior axis. In Drosophila, genes of the Bithorax complex (Ultrabithorax (Ubx), abdominal-A (abd-A) and Abdominal-B (Abd-B), perform a common function of promoting abdominal identity. Ubx and AbdA are closely related proteins, displaying a high degree of sequence conservation within the homeodomain (HD), and sharing domains outside the HD. These similarities may provide the molecular basis for common function. In contrast, AbdB has a very divergent HD, and lacks any sequence conservation with Ubx or AbdA outside the HD, evident by absence of Hexapeptide and UbdA motifs, which recruit Hox cofactor extradenticle (exd) in Ubx and possibly in adb-A. While most of the focus has so far been to unravel the mechanisms distinguishing the activity of structurally similar Hox proteins, we decided to address how different proteins attain similar function, an issue so far less investigated. Studies involving the role played by Abd-B in specification of abdominal denticles and repression of the limb promoting gene Distalless, we found that distinct genetic requirement and molecular mechanisms underlie the same biological function.

Summary of main findings from the work at CCMB:Growth and patterning during Drosophila wing development are mediated by signaling from its dorso-ventral (D/V) organizer. Wingless is expressed in the D/V boundary and functions as a morphogen to activate target genes at a distance. Wingless pathway and thereby D/V signaling is negatively regulated by the homeotic gene Ultrabithorax (Ubx) to mediate haltere development. In an enhancer-trap screen to identify genes that show differential expression between wing and haltere discs, we identified CG32062, which codes for a RNA-binding protein. In wing discs, CG32062 is expressed only in non-D/V cells. CG32062 expression in non-D/V cells is dependent on Notch-mediated signaling from the D/V boundary. However, CG32062 expression is independent of Wingless function, thus providing evidence for a second long-range signaling mechanism of the D/V organizer. In haltere discs, CG32062 is negatively regulated by Ubx. The non-cell autonomous nature of Ubx-mediated repression of CG32062 expression suggests that the novel component of D/V signaling is also negatively regulated during haltere specification.