Chromatin landscape at the HoxD locus in developing caeca (ChIP-chip)

Hox genes are required for the development of the intestinal caecum, a major organ of species eating plants. We have analysed the transcriptional regulation of Hoxd genes in caecal buds and show that they are controlled by a series of enhancers located in a gene desert telomeric to the HoxD cluster. The start site of two neighboring and opposite long non-coding RNAs, Hotdog and Twin of Hotdog, specifically transcribed in the caecum, contacts the expressed Hoxd genes in the framework of a topological domain, a large domain of interactions, which ensures a robust transcription of these genes during caecum budding. We show that hedgehogs have kept this regulatory potential despite the absence of caecum, suggesting that these enhancers are used in other developmental situations. In this context, we discuss some striking similarities between the caecum and the limb buds, suggesting the implementation of a common budding tool-kit. Distribution of histone marks and RNA Pol2 at the HoxD locus in caeca at E13.5, Array data were quantile normalized within ChIP/input replicate groups and scaled to medial feature intensity of 100 using TAS software (Affymetrix). For each genomic position, a data set was generated consisting of all (PM-MM) pairs mapping within a sliding window of 250 bp. For each tissue, two independent ChIP-chip experiments were performed with all mentionned antibodies.