Annotation of Rheb (Ras homolog enhanced in brain) and its Genomic Neighborhood in Two Species of Drosophila

Genome annotation of related species reveals the principles governing gene and genome evolution. In collaboration with Dr. Laura Reed and the Genomics Education Partnership, we aim to better understand how the positions of genes within well-characterized biological pathways influence the evolution of pathway genes and their regulatory regions. To better understand how genes and regulatory regions in the insulin signaling pathway evolve, annotation of the small GTPase Rheb was attempted in two species of Drosophila, Drosophila yakuba and Drosophila arizonae. Rheb is a Ras homolog that is enriched in the brain. The target gene Rheb was first observed in its genomic context in Drosophila melanogaster, our reference species. Genomic comparisons utilizing the UCSC genome browser, BLAST (Basic Local Alignment Search Tool) and the assumption of synteny revealed putative genomic neighborhoods for Rheb in previously unannotated species. A Rheb ortholog was identified in Drosophila yakuba, and a gene model was created with support from computational, conservation, and expression data. Surprisingly, the genes immediately adjacent to Rheb in Drosophila melanogaster occupy two different chromosomes in Drosophila arizonae, and the adjacent Rheb gene was absent from either location, implying significant genomic rearrangement in Drosophila arizonae as compared to Drosophila melanogaster