Genome binding/occupancy profiling by high throughput sequencing
Summary
Regulation of high-density loci harboring genes with different cell-specificities remains a puzzle. Here we investigate a locus that evolved through gene duplication and contains eight genes and 20 candidate regulatory elements, including one super-enhancer. Five genes (Csn1s1, Csn2, Csn1s2a, Csn1s2b, Csn3) are expressed in mammary glands and account for 50% of mRNAs during lactation, two (Prr27, Fdcsp) are salivary-specific and one (Odam) has dual specificity. We probed the function of 12 candidate control elements, individually and in combination, in the mouse genome. The super-enhancer is essential for the expression of Csn3, Odam and Fdcsp but largely dispensable for Csn1s1, Csn2 and Csn1s2a. Csn3 activation also requires its own local enhancer. Synergism between local enhancers and cytokine-responsive promoter elements facilitated the 10,000-fold activation of Csn2 during pregnancy. Our work identifies regulatory complexity of a multigene locus with an ancestral super-enhancer active in mammary and salivary tissue and local enhancers and promoter elements.
Overall design
ChIP-seq for TFs and histone markers in the mammary tissues of wild type and mutant female mice for regulatory elements in the casein locus at virgin, day six of pregnancy (p6) and day one of lactation (L1). ChIP-seq for TFs and histone markers in the salivary tissues of wild type and mutant male mice.
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