Transcriptional Regulation of wnt1 and wnt10b by Evolutionarily Conserved CIS- Regulatory Regions

Abstract

This study assesses the importance of enhancers of wnt genes- wnt1 and wnt10b during midbrain hindbrain boundary formation in zebrafish. These cis-regulatory elements are hypothesized to regulate wnt1 and wnt10b transcription both spatially and temporally. A secreted signaling molecule is encoded by wnt1 that is first expressed in the presumptive midbrain region of the neural plate and is essential for midbrain and hindbrain development. An understanding of wnt regulation would, therefore, shed light on transcriptional mechanisms that underlay regional organization of the vertebrate CNS.

In mice it has been shown that certain non-coding regions work as enhancer elements and trigger the full wnt1 expression in the early murine embryo. These enhancers are proved to be both necessary and sufficient component of endogenous regulatory machinery of wnt1 expression. The wnt1 and wnt10b locus in fish shows many conserved non-coding regions. As compared to spotted gar (Lepisosteus oculatus), zebrafish underwent an additional round of whole-genome duplication but these cis-regulatory regions have still been conserved. That indicates they might be of key importance in regulating wnt1 and wnt10b during brain development. There is a possibility that these regions represent an evolutionarily conserved regulatory module controlling the wnt1 and wnt10b expression.

This project targets a comparative sequence analysis of non-coding regions from zebrafish and spotted gar to check their ability to activate reporter gene expression in zebrafish midbrain and midbrain-hindbrain boundary. Our goal is to understand the transcriptional regulation of wnt in detail. ECRs are critical in understanding the regulation of wnt genes around midbrain hindbrain boundary. Overall, this study helped us to better understand the role of wnt in anterior posterior patterning in vertebrates as wells as complex control of brain development.