Specific ectodermal enhancers control the expression of Hoxc genes in developing mammalian teguments [RNA-seq]
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ABSTRACT: Vertebrate Hox genes are key players in the establishment of structures during the development of the main body axis. Subsequently, they play important roles either in organizing secondary axial structures such as the appendages, or during homeostasis in postnatal stages and adulthood. Here we set up to analyze their elusive function in the ectodermal compartment, using the mouse limb bud as a model. We report that the HoxC gene cluster was globally co-opted to be transcribed in the distal limb ectoderm, where it is activated following the rule of temporal colinearity. These ectodermal cells subsequently produce various keratinized organs such as nails or claws. Accordingly, deletion of the HoxC cluster led to mice lacking nails (anonychia) and also hairs (alopecia), a condition stronger than the previously reported loss of function of Hoxc13, which is causative of the ectodermal dysplasia 9 (ECTD9) syndrome in human patients. We further identified, in mammals only, two ectodermal-specific enhancers located upstream the gene cluster, which act synergistically to regulate Hoxc genes in these ectodermal organs. Deletion of these enhancers alone or in combination revealed a strong quantitative component in the regulation of these genes in the ectoderm, suggesting that these two enhancers may have evolved along with mammals to provide the level of HOXC proteins necessary for the full development of hairs and nails.
Project description:Vertebrate Hox genes are key players in the establishment of structures during the development of the main body axis. Subsequently, they play important roles either in organizing secondary axial structures such as the appendages, or during homeostasis in postnatal stages and adulthood. Here we set up to analyze their elusive function in the ectodermal compartment, using the mouse limb bud as a model. We report that the HoxC gene cluster was globally co-opted to be transcribed in the distal limb ectoderm, where it is activated following the rule of temporal colinearity. These ectodermal cells subsequently produce various keratinized organs such as nails or claws. Accordingly, deletion of the HoxC cluster led to mice lacking nails (anonychia) and also hairs (alopecia), a condition stronger than the previously reported loss of function of Hoxc13, which is causative of the ectodermal dysplasia 9 (ECTD9) syndrome in human patients. We further identified, in mammals only, two ectodermal-specific enhancers located upstream the gene cluster, which act synergistically to regulate Hoxc genes in these ectodermal organs. Deletion of these enhancers alone or in combination revealed a strong quantitative component in the regulation of these genes in the ectoderm, suggesting that these two enhancers may have evolved along with mammals to provide the level of HOXC proteins necessary for the full development of hairs and nails.
Project description:The apical ectodermal ridge (AER) is a transient ectodermal population of cells that defines the dorso-ventral border of the developing limb bud. It functions as a major signaling centre that, through the secretion of various growth factors including FGF8, instructs the growth and patterning of the developing limb. We have identified that the AER expresses markers of cellular senescence and wanted to examine if there was any overlap with oncogene-induced senescence, an adult form of senescence induced in premalignant lesions. To achieve this, we microdissected the AER from embryonic day 11.5 mouse embryos. In addition, we collected the surface ectoderm from the proximal limb bud, that was not senescent and profiled both populations, to identify those genes that are enriched in the AER The AER was microdissected from embryonic day 11.5 mouse forelimb. Surface ectoderm from the posterior limb was used as a comparative control. Samples from 2-3 mice were pooled for each replicate, for 3-4 replicates.
Project description:The apical ectodermal ridge (AER) is a transient ectodermal population of cells that defines the dorso-ventral border of the developing limb bud. It functions as a major signaling centre that, through the secretion of various growth factors including FGF8, instructs the growth and patterning of the developing limb. We have identified that the AER expresses markers of cellular senescence and wanted to examine if there was any overlap with oncogene-induced senescence, an adult form of senescence induced in premalignant lesions. To achieve this, we microdissected the AER from embryonic day 11.5 mouse embryos. In addition, we collected the surface ectoderm from the proximal limb bud, that was not senescent and profiled both populations, to identify those genes that are enriched in the AER
Project description:Samples used for hybridization consisted of non-pooled (NP) RNA extracts from 8 groups in each of two time periods after drug administration: oil vehicle treated control embryonic limb bud mesoderm and ectoderm, phosphate buffered saline vehicle control embryonic limb bud mesoderm and ectoderm, acetazolamide treated embryonic limb bud mesoderm and ectoderm, and cadmium sulfate treated embryonic limb bud mesoderm and ectoderm. Forty-eight hybridization experiments were on non-pooled (NP) individual RNA extracts. Experiment Overall Design: Samples used for hybridization consisted of non-pooled (NP) RNA extracts from 8 groups in each of two time periods after drug administration: oil vehicle treated control embryonic limb bud mesoderm and ectoderm, phosphate buffered saline vehicle control embryonic limb bud mesoderm and ectoderm, acetazolamide treated embryonic limb bud mesoderm and ectoderm, and cadmium sulfate treated embryonic limb bud mesoderm and ectoderm. Forty-eight hybridization experiments were on non-pooled (NP) individual RNA extracts.
Project description:we report that regional expression of the Hoxc genes is regulated by antagonistic switch between repression and activation epigenetic modification. In freshly isolated dermal cells from P50 telogen Wt/Wt ear skin, no enrichment of H3K27ac was detected at Hoxc cluster, consistent with their lack of expression; in contrast, robust peaks of this marker are observed in 3’ region of the Hoxc cluster in dorsal skin dermal cells. Secondly we looked at H3K27 trimethylation (H3K27me3), a marker for polycomb-dependent gene repression, which antagonizes H3K27ac. Concomitantly, we found that H3K27me3 spread across the entire Hoxc cluster in adult ear skin dermal cells but was restricted to the 5’ region of the Hoxc cluster in adult dorsal skin dermal cells . In adult dorsal skin dermal cells, we found three occupied CTCF binding sites inside Hoxc cluster. The rostral CTCF binding site marks the discontinuity point of H3K27me3 modification at the intergenic region between Hoxc11 and Hoxc10 in dorsal skin dermal cells. This indicates the CTCF binding event within Hoxc cluster might forge a topological barrier that can insulate activation region from repression region and therefore lead to the region specific expression of the Hoxc cluster genes.To directly test whether there is ectopic interaction between Hoxc cluster and the active domain in proximal-TAD, we used circularized chromosome conformation capture (4C) with Hoxc4 as bait. In Wt/Koa ear skin dermal cells, there are clear ectopic interactions of Hoxc4 with the remaining active regulatory landscape in proximal-TAD; on the other hand, all of the interactions of Hoxc4 remained inside the distal-TAD with repressive domain in Wt/Wt ear skin.
Project description:we report that regional expression of the Hoxc genes is regulated by antagonistic switch between repression and activation epigenetic modification. In freshly isolated dermal cells from P50 telogen Wt/Wt ear skin, no enrichment of H3K27ac was detected at Hoxc cluster, consistent with their lack of expression; in contrast, robust peaks of this marker are observed in 3’ region of the Hoxc cluster in dorsal skin dermal cells. Secondly we looked at H3K27 trimethylation (H3K27me3), a marker for polycomb-dependent gene repression, which antagonizes H3K27ac. Concomitantly, we found that H3K27me3 spread across the entire Hoxc cluster in adult ear skin dermal cells but was restricted to the 5’ region of the Hoxc cluster in adult dorsal skin dermal cells . In adult dorsal skin dermal cells, we found three occupied CTCF binding sites inside Hoxc cluster. The rostral CTCF binding site marks the discontinuity point of H3K27me3 modification at the intergenic region between Hoxc11 and Hoxc10 in dorsal skin dermal cells. This indicates the CTCF binding event within Hoxc cluster might forge a topological barrier that can insulate activation region from repression region and therefore lead to the region specific expression of the Hoxc cluster genes.To directly test whether there is ectopic interaction between Hoxc cluster and the active domain in proximal-TAD, we used circularized chromosome conformation capture (4C) with Hoxc4 as bait. In Wt/Koa ear skin dermal cells, there are clear ectopic interactions of Hoxc4 with the remaining active regulatory landscape in proximal-TAD; on the other hand, all of the interactions of Hoxc4 remained inside the distal-TAD with repressive domain in Wt/Wt ear skin.
Project description:we report that regional expression of the Hoxc genes is regulated by antagonistic switch between repression and activation epigenetic modification. In freshly isolated dermal cells from P50 telogen Wt/Wt ear skin, no enrichment of H3K27ac was detected at Hoxc cluster, consistent with their lack of expression; in contrast, robust peaks of this marker are observed in 3’ region of the Hoxc cluster in dorsal skin dermal cells. Secondly we looked at H3K27 trimethylation (H3K27me3), a marker for polycomb-dependent gene repression, which antagonizes H3K27ac. Concomitantly, we found that H3K27me3 spread across the entire Hoxc cluster in adult ear skin dermal cells but was restricted to the 5’ region of the Hoxc cluster in adult dorsal skin dermal cells . In adult dorsal skin dermal cells, we found three occupied CTCF binding sites inside Hoxc cluster. The rostral CTCF binding site marks the discontinuity point of H3K27me3 modification at the intergenic region between Hoxc11 and Hoxc10 in dorsal skin dermal cells. This indicates the CTCF binding event within Hoxc cluster might forge a topological barrier that can insulate activation region from repression region and therefore lead to the region specific expression of the Hoxc cluster genes.To directly test whether there is ectopic interaction between Hoxc cluster and the active domain in proximal-TAD, we used circularized chromosome conformation capture (4C) with Hoxc4 as bait. In Wt/Koa ear skin dermal cells, there are clear ectopic interactions of Hoxc4 with the remaining active regulatory landscape in proximal-TAD; on the other hand, all of the interactions of Hoxc4 remained inside the distal-TAD with repressive domain in Wt/Wt ear skin.
Project description:The integument plays a critical role in functional adaptation, with macro-regional specification forming structures like beaks, combs, feathers, and scales, while micro-regional specification modifies skin appendage shapes. However, the molecular mechanisms remain largely unknown. Craniofacial integument displays dramatic diversity, exemplified by the Polish chicken (PC) with a homeotic transformation of comb-to-crest feathers, caused by a 195–base pair (bp) duplication in HoxC10 intron. Micro-C analyses show that HoxC-containing topologically associating domain (TAD) is normally closed in the scalp but open in the dorsal and tail regions, allowing multiple long-distance contacts. In the PC scalp, the TAD is open, resulting in high HoxC expression. CRISPR-Cas9 deletion of the 195-bp duplication reduces crest feather formation, and HoxC misexpression alters feather shapes. The 195-bp sequence is found only in Archelosauria (crocodilians and birds) and not in mammals. These findings suggest that higher-order regulation of the HoxC cluster modulates gene expression, driving the evolution of adaptive integumentary appendages in birds.
Project description:The integument plays a critical role in functional adaptation, with macro-regional specification forming structures like beaks, combs, feathers, and scales, while micro-regional specification modifies skin appendage shapes. However, the molecular mechanisms remain largely unknown. Craniofacial integument displays dramatic diversity, exemplified by the Polish chicken (PC) with a homeotic transformation of comb-to-crest feathers, caused by a 195–base pair (bp) duplication in HoxC10 intron. Micro-C analyses show that HoxC-containing topologically associating domain (TAD) is normally closed in the scalp but open in the dorsal and tail regions, allowing multiple long-distance contacts. In the PC scalp, the TAD is open, resulting in high HoxC expression. CRISPR-Cas9 deletion of the 195-bp duplication reduces crest feather formation, and HoxC misexpression alters feather shapes. The 195-bp sequence is found only in Archelosauria (crocodilians and birds) and not in mammals. These findings suggest that higher-order regulation of the HoxC cluster modulates gene expression, driving the evolution of adaptive integumentary appendages in birds.