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Abstract

The identification of candidate regulatory elements is based on the assumption that noncoding regions conserved across organisms are functionally important. Those elements can be identified via genomic sequence alignments and other computational methods. During my bachelor’s degree, I functionally analysed a region located in the 3’UTR of the Sonic Hedgehog (Shh) gene which is highly conserved among teleosts, but also in chicken (Gallus gallus), mouse (Mus musculus) and human (Homo sapiens). It has been previously shown that the injection of the Shh 3’UTR conserved region from various teleosts in zebrafish (Danio rerio) directs EGFP expression in different tissues. To check whether the chicken and mouse Shh 3’UTR conserved regions also represent functional elements and to identify the tissue where they direct expression, I have injected them in zebrafish embryos using the co-injection approach. I found that the conserved non-coding sequence from mouse induces an expression of EGFP in muscle tissue in 24hrs old zebrafish embryo. Through sequential injections of different parts of this region, I was able to show that a 248bp segment was responsible for this expression. Within this sequence I identified a binding site for the Mef2a transcription factor. This Mef2a site is most likely involved in inducing the EGFP expression in the muscle tissue. In addition, I have shown that the homologous elements from mouse and chicken induce EGFP expression in melanocytes and in the nervous system after 48hrs. So far no possible transcription factor binding site responsible for this expression pattern could be identified.