PgmNr D1465: Characterization of a grainyhead neuroblast enhancer.

Authors:
Thomas Brody; Alexander Kuzin; Svetlana Smith; Ward Odenwald; Neural Cell-Fate Determinants Section


Institutes
NINDS/NIH, Bethesda, MD.


Keyword: enhancers

Abstract:

Analysis of cis-regulatory sequences using comparative genomics reveals that enhancers consist of clusters of conserved sequence blocks (CSBs) that are made up of unique and repeat sequence elements; both often consist of identifiable motifs corresponding to binding sites of known transcription factors. Our goal has been to address aspects of enhancer structure, including the basis for spatial and temporal regulation of gene expression and the functions of the large number of CSBs in neural enhancers. We have identified a late temporal network enhancer of grainyhead. The enhancer, grh-15  contains two separable activities, one that drives expression in the brain and another in the ventral cord.  We have systematically truncated, rearranged and mutated each of the nine CSBs present in the brain-specific portion of grh-15, expressed in a ~12 embryonic brain neuroblasts and in ~15 larval neuroblasts and their lineages. While our results indicate that information regulating enhancer expression is carried in a highly redundant fashion, individual CSBs convey expression in subsets of larval lineages. We also show that the grh enhancer is co-expressed within a subset of cells that express the temporal determinants Cas and Pdm, that it marks a subset of both type I and type II neuroblasts and their lineages in the larval brain, and that it is expressed in only some of the Grh+ lineages. These studies highlight the advantages of using evolutionary conservation as a guide to the analysis of cis-regulatory sequences.



Flybase Genetic Index:
1. FlyBase gene symbol: grh; FBgn: FBgn0259211
2. FlyBase gene symbol: cas; FBgn: FBgn0004878
3. FlyBase gene symbol: nub; FBgn: FBgn0085424