An evolutionarily conserved non-coding element in casein locus acts as transcriptional repressor

• By comparative genome analysis a 147 bp long ECR was identified in casein locus.
• In mammals, the ECR is adjacent to Odam, a gene in casein locus.
• The ECR is absent in non-mammalian vertebrates.
• The ECR is a transcriptional repressor element.
• We speculate that the ECR represses Odam expression in mammary gland during lactation.

In mammals, the casein locus consists of stretches of non-coding DNA, the functions of most of which are unknown. These regions are believed to harbour elements responsible for spatio-temporally regulated expression of genes in this locus and so far, only a few such elements have been identified. In this study, we report a novel regulatory element in the casein locus. Comparative analysis of genomic DNA sequences of casein loci from different mammals identified a 147 bp long evolutionarily conserved region (ECR) upstream of Odam, a gene in this locus. The ECR was found in close proximity of Odam gene in all the mammals examined. In-silico analysis predicted the ECR as a potential regulatory element. Functional analysis in different cell lines identified it as a unidirectional repressor element. From our findings we speculate that the ECR may be involved in the repression of the Odam expression in the mammary gland during lactation.