Project description:During tetrapod limb development, the HOXA13 and HOXD13 transcription factors are critical for the emergence and organization of the autopods, the most distal aspect where digits will develop. Since previous work had suggested that the Dbx2 gene is a target of these factors, we set up to analyze in detail this potential regulatory interaction. We used a chromatin conformation capture approach (4Cseq) to characterize the regulatory domain and interactions of the transcription factor Dbx2 and of its neighboring genes Nell2 and Ano6 in distal and/ or proximal forelimbs of E12 mouse embryos. In particular, we analyzed their interaction with distal limb specific regulatory elements (DLE1 and DLE2) by the analysis of H2K27ac coverages (Beccari et al 2016) and Hoxa13/Hoxd13 binding (Sheth R et al 2016). We report that Dbx2, Nell2 and Ano6 are expressed in distal limb buds and are controlled by the same enhancers located close to Dbx2. As the Nell2 and Ano6 genes are localized into two different topologically associating domains (TADs) flanking the Dbx2 locus, we conclude that these enhancers can overcome TAD boundaries in either direction, to co-regulate a set of genes located in distinct chromatin domains.
Project description:During tetrapod limb development, the HOXA13 and HOXD13 transcription factors are critical for the emergence and organization of the autopods, the most distal aspect where digits will develop. Since previous work had suggested that the Dbx2 gene is a target of these factors, we set up to analyze in detail this potential regulatory interaction. We used a chromatin conformation capture approach (4Cseq) to characterize the regulatory domain and interactions of the transcription factor Dbx2 and of its neighboring genes Nell2 and Ano6 in distal and/ or proximal forelimbs of E12 mouse embryos. In particular, we analyzed their interaction with distal limb specific regulatory elements (DLE1 and DLE2) by the analysis of H2K27ac coverages (Beccari et al 2016) and Hoxa13/Hoxd13 binding (Sheth R et al 2016). We report that Dbx2, Nell2 and Ano6 are expressed in distal limb buds and are controlled by the same enhancers located close to Dbx2. As the Nell2 and Ano6 genes are localized into two different topologically associating domains (TADs) flanking the Dbx2 locus, we conclude that these enhancers can overcome TAD boundaries in either direction, to co-regulate a set of genes located in distinct chromatin domains.
Project description:During tetrapod limb development, the HOXA13 and HOXD13 transcription factors are critical for the emergence and organization of the autopods, the most distal aspect where digits will develop. Since previous work had suggested that the Dbx2 gene is a target of these factors, we set up to analyze in detail this potential regulatory interaction. We used a chromatin conformation capture approach (4Cseq) to characterize the regulatory domain and interactions of the transcription factor Dbx2 and of its neighboring genes Nell2 and Ano6 in distal and/ or proximal forelimbs of E12 mouse embryos. In particular, we analyzed their interaction with distal limb specific regulatory elements (DLE1 and DLE2) by the analysis of H2K27ac coverages (Beccari et al 2016) and Hoxa13/Hoxd13 binding (Sheth R et al 2016). We report that Dbx2, Nell2 and Ano6 are expressed in distal limb buds and are controlled by the same enhancers located close to Dbx2. As the Nell2 and Ano6 genes are localized into two different topologically associating domains (TADs) flanking the Dbx2 locus, we conclude that these enhancers can overcome TAD boundaries in either direction, to co-regulate a set of genes located in distinct chromatin domains.
Project description:BackgroundDuring tetrapod limb development, the HOXA13 and HOXD13 transcription factors are critical for the emergence and organization of the autopod, the most distal aspect where digits will develop. Since previous work had suggested that the Dbx2 gene is a target of these factors, we set up to analyze in detail this potential regulatory interaction.ResultsWe show that HOX13 proteins bind to mammalian-specific sequences at the vicinity of the Dbx2 locus that have enhancer activity in developing digits. However, the functional inactivation of the DBX2 protein did not elicit any particular phenotype related to Hox genes inactivation in digits, suggesting either redundant or compensatory mechanisms. We report that the neighboring Nell2 and Ano6 genes are also expressed in distal limb buds and are in part controlled by the same Dbx2 enhancers despite being localized into two different topologically associating domains (TADs) flanking the Dbx2 locus.ConclusionsWe conclude that Hoxa13 and Hoxd genes cooperatively activate Dbx2 expression in developing digits through binding to mammalian specific regulatory sequences in the Dbx2 neighborhood. Furthermore, these enhancers can overcome TAD boundaries in either direction to co-regulate a set of genes located in distinct chromatin domains.
Project description:The expression of some genes depends on large, adjacent regions of the genome that contain multiple enhancers. These regulatory landscapes frequently align with Topologically Associating Domains (TADs), where they integrate the function of multiple similar enhancers to produce a global, TAD-specific regulation. We asked if an individual enhancer could overcome the influence of one of these landscapes, to drive gene transcription. To test this, we transferred an enhancer from its native location, into a nearby TAD with a related yet different functional specificity. We used the biphasic regulation of Hoxd genes during limb development as a paradigm. These genes are first activated in proximal limb cells by enhancers located in one TAD, which is then silenced when the neighboring TAD activates its enhancers in distal limb cells. We transferred a distal limb enhancer into the proximal limb TAD and found that its new context suppresses its normal distal specificity, even though it is bound by HOX13 transcription factors, which are responsible for the distal activity. This activity can be rescued only when a large portion of the surrounding environment is removed. These results indicate that, at least in some cases, the functioning of enhancer elements is subordinated to the host chromatin context, which can exert a dominant control over its activity.