Transcriptome in developing caeca

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. Transcriptional activity at the HoxD locus in developing caeca at E13.5 Overall design: Transcriptional activity at the HoxD locus in developing caeca at E13.5