Functional conservation between rodents and chicken of regulatory sequences driving skeletal muscle gene expression in transgenic chickens

We have observed that a conserved downstream MLC enhancer is present in the chicken MLC locus. We found that the rat MLC1/3 regulatory elements were transcriptionally active in chick skeletal muscle primary cultures. We observed that a single copy lentiviral insert containing this regulatory cassette was able to drive expression of a lacZ reporter gene in the fast-fibres of skeletal muscle in chicken in three independent transgenic chicken lines in a pattern similar to the endogenous MLC locus. Reporter gene expression in cardiac muscle tissues was not observed for any of these lines.From these results we conclude that skeletal expression from this regulatory module is conserved in a genomic context between rodents and chickens. This transgenic module will be useful in future investigations of muscle development in avian species.The development of an organism entails the precise expression of lineage and tissue-specific gene products in a temporally-regulated manner during embryogenesis. The information for a cell to respond to external signals by differentiating down a particular developmental pathway is 'hardwired' into the regulatory regions surrounding these developmentally regulated genes [reviewed in [1]]. These conserved regulatory regions or modules drive spatial gene expression patterns in the forming tissues of the developing organism. Changes in the cis-regulatory elements of regulatory modules are hypothesized to be the predominant mechanism behind evolutionary changes in pattern formation [2].Many expression modules have been shown to be functionally conserved in vertebrate species. For example, regulatory regions from several hox genes from fish and chicken are capable of driving some aspects of the spatial expression patterns of the paralogous murine gene in transgenic mice [3-6]. Examples of conserved regulatory modules have been shown for the processes of neurogenesis [7-9], limb morphogenesis [10] and haematopoiesis [11,12], amongst many other exam