The molecular regulation of Hox genes during animal development. (360G-Wellcome-098410_Z_12_Z)

Q1. What are your research questions? How do gene regulatory programmes emerge from genomic information, and how does differential gene activity lead to distinct patterns of cellular differentiation are key open questions in modern Biology. The Hox genes provide an excellent system to investigate both these problems. They encode a family of evolutionary conserved transcription factors whose differential expression along head-to-tail triggers distinct programmes of cell differentiation along t he body axis1. Understanding the molecular mechanisms underlying Hox gene activity is thus crucial to decipher their secret ability to take cell populations into different developmental routes: a feature that hits the core question of how gene expression relates to the biology of cell function. In this proposal I investigate the impact of RNA regulation on Hox gene expression and function during development. Most previous work in Hox regulation focused on transcriptional control; in contrast, I study the effects of mRNA processing and microRNA (miRNA) regulation two emerging areas in gene regulation on Hox expression and developmental functions during the formation of the central nervous system (CNS). The work is firmly rooted in my strong molecular and developmental background and close understanding of the Hox system2-9 and tackles a series of novel and important questions including: The role of RNA regulation in the molecular processes underlying cellular diversity in the CNS T he cellular signals and molecular mechanisms controlling RNA regulation during development The role of RNA regulation on the expression and function of vertebrate Hox genes Previous work and the rationale underlying my new questions Prompted by recent demonstrations of the pervasive influence of post-transcriptional regulation on gene expression10,11 my laboratory has begun to study the effects of mRNA processing and microRNA (miRNA) regulation on Hox gene function in Drosophila. Our work demonstrated that several Hox transcripts undergo mRNA processing by alternative splicing and alternative polyadenylation (APA) and that these processes affect Hox gene expression and function in various developmental contexts6-9. Notably, we observed that longer Hox mRNAs (including more miRNA targets) are preferentially expressed in the CNS (Fig. 1) and that miRNA mutations affect Hox expression in the CNS but not in other tissues9. In this proposal I take my work on Hox regulation into the co ntext of CNS development because the mechanisms that lead to cellular diversity and specificity are still poorly understood within this tissue. The work will investigate whether the complexity of RNA regulation in the CNS is linked to the diversity in cell types in this tissue. The CNS offers an excellent experimental system with a stereotypical array of cells engaging in a variety of differentiation patterns tractable by established molecular/genetic markers. My proposal also uses the Hox syste m to investigate the problem of the molecular basis of APA regulation in vivo and exploits the evolutionary conservation of the Hox genes taking my work from the fly into mouse cells, and ultimately (in collaboration with Robb Krumlauf) to the study of Hox regulation in mouse embryos