Regional specific differentiation of integumentary organs: SATB2 is involved in α- and β-keratin gene cluster switching in the chicken
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ABSTRACT: Animals develop skin regional specificities to best adapt to their environments. Birds are excellent models in which to study the epigenetic mechanisms that facilitate these adaptions. Patients suffering from SATB2 mutations exhibit multiple defects including ectodermal dysplasia-like changes. The preferential expression of SATB2, a chromatin regulator, in feather-forming compared to scale-forming regions, suggests it functions in regional specification of chicken skin appendages by acting on either differentiation or morphogenesis. Retrovirus mediated SATB2 misexpression in developing feathers, beaks, and claws causes epidermal differentiation abnormalities (e.g. knobs, plaques) with few organ morphology alterations. Chicken β-keratins are encoded in 5 sub-clusters (Claw, Feather, Feather-like, Scale, and Keratinocyte) on Chromosome 25 and a large Feather keratin cluster on Chromosome 27. Type I and II α-keratin clusters are located on Chromosomes 27 and 33, respectively. Transcriptome analyses showed these keratins 1) are often tuned up or down collectively as a sub-cluster, and 2) these changes occur in a temporo-spatial specific manner. This cluster-level suppression is also seen in MMPs on Chromosome 1. SATB2 alters gene expression changes of most other transcripts without this cluster-level switching. These results suggest an organizing role of SATB2 in cluster-level gene co-regulation during skin regional specification.
Project description:Regional specification is critical for skin development, regeneration and evolution. The contribution of epigenetics in this process remains unknown. Here using avian epidermis we find two major strategies regulate β-keratin gene clusters. 1) Over the body, macro-regional specificities (scales, feathers, claws, etc) established by typical enhancers control five sub-clusters located within the epidermal differentiation complex on chromosome 25; 2) Within a feather, micro-regional specificities are orchestrated by temporo-spatial chromatin looping of the feather β-keratin gene cluster on chromosome 27. Analyses suggest a 3-factor model for regional specification: competence factors (e.g., AP1) make chromatin accessible, regional specifiers (e.g., Zic1) target specific genome regions, and chromatin organizers (e.g., CTCF, SATB2) establish looping configurations. Gene perturbations disrupt morphogenesis and histo-differentiation. This chicken skin paradigm advances our understanding of how regulation of big gene clusters can set up a two-dimensional body surface map.
Project description:Epithelial appendages are the product of epithelial – mesenchymal interactions. Tissue recombination experiments showed that in general, the dermis determines the phenotype of the epithelial appendage. Chicken dorsal skin epithelium interacts with its underlying mesenchyme to form feathers beginning at E7 (H&H stage 31), while metatarsal scale epithelium interacts with its mesenchyme to form scales beginning at E9 (H&H stage 35) which stabilize around E12 (H&H stage 38). We sought to evaluate the molecular differences of tissues with different competence and inductive abilities to form feathers and scales. Chicken embryos were selected to obtain competent E7 and non-competent at E9 feather forming skin from dorsal. The competent E9 and non-competent E11 meta-tarsal scale forming skin from metatarsal were selected for examing the differences in regional specificity. Epithelium and mesenchyme from each skin were prepared separately. Samples were prepared for RNA extraction and hybridization on Affymetrix microarrays. We gathered 8 sets of samples for the analysis: undifferentiated E7 feather skin epithelium (E7fe) and mesenchyme (E7fm); differentiated E9 feather skin epithelium (E9fe) and mesenchyme (E9fm); undifferentiated E9 scale skin epithelium (E9se) and mesenchyme (E9sm); and differentiated E11 scale skin epithelium (E11se) and mesenchyme (E11sm)
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.
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:Feather evolution enabled feathered dinosaurs and early Mesozoic birds to venture into new ecological niches. Studying how feathers and scales are specified provides insight into how a new organ evolves. We use genome-wide analyses to identify feather-associated genes and test their feather-forming ability by expressing them in chicken and alligator scales. Intermediate morphotypes revealed five cardinal morphogenetic events: localized growth zone, follicle invagination, branching, feather keratin differentiation and dermal papilla formation. In contrast to molecules known to induce feathers on scales (retinoic acid, beta-catenin), we identify novel scale-feather converters (Sox2, Zic1, Grem1, Spry2, Sox18) which induce only one or several of the five regulatory modules. Some morphotypes resemble filamentous appendages found in feathered dinosaur fossils, while others demonstrate some characteristics of modern feathers. We propose that at least five morpho-regulatory modules were used to diversify ancient reptile scales. The regulatory combination and hierarchical integration led to extant feather forms.
Project description:Feather evolution enabled feathered dinosaurs and early Mesozoic birds to venture into new ecological niches. Studying how feathers and scales are specified provides insight into how a new organ evolves. We use genome-wide analyses to identify feather-associated genes and test their feather-forming ability by expressing them in chicken and alligator scales. Intermediate morphotypes revealed five cardinal morphogenetic events: localized growth zone, follicle invagination, branching, feather keratin differentiation and dermal papilla formation. In contrast to molecules known to induce feathers on scales (retinoic acid, beta-catenin), we identify novel scale-feather converters (Sox2, Zic1, Grem1, Spry2, Sox18) which induce only one or several of the five regulatory modules. Some morphotypes resemble filamentous appendages found in feathered dinosaur fossils, while others demonstrate some characteristics of modern feathers. We propose that at least five morpho-regulatory modules were used to diversify ancient reptile scales. The regulatory combination and hierarchical integration led to extant feather forms.
Project description:Feather evolution enabled feathered dinosaurs and early Mesozoic birds to venture into new ecological niches. Studying how feathers and scales are specified provides insight into how a new organ evolves. We use genome-wide analyses to identify feather-associated genes and test their feather-forming ability by expressing them in chicken and alligator scales. Intermediate morphotypes revealed five cardinal morphogenetic events: localized growth zone, follicle invagination, branching, feather keratin differentiation and dermal papilla formation. In contrast to molecules known to induce feathers on scales (retinoic acid, beta-catenin), we identify novel scale-feather converters (Sox2, Zic1, Grem1, Spry2, Sox18) which induce only one or several of the five regulatory modules. Some morphotypes resemble filamentous appendages found in feathered dinosaur fossils, while others demonstrate some characteristics of modern feathers. We propose that at least five morpho-regulatory modules were used to diversify ancient reptile scales. The regulatory combination and hierarchical integration led to extant feather forms.
Project description:The epidermal barrier protects the body against mechanical injury, infection and dehydration. The respective contribution of type I and type II keratins which form the major cytoskeleton in epidermal keratinocytes in barrier formation and stress protection is incompletely understood. Here, we reveal a novel mechanism by which keratins control anti-oxidant responses through barrier-dependent and cell-autonomous mechanisms. Mice lacking the entire type I (KtyI) or type II (KtyII) keratin gene clusters suffer from distinct prenatal barrier defects. Comparative transcriptome profiling identifies essential cornified envelope components and reveals strong upregulation of the bZIP transcription factor Nrf2 in situ. Isolated keratinocytes from both strains of mice show elevated mitochondrial oxygen consumption and Nrf2 activity, decreased upon keratin re-expression. We propose a model in which keratins control mitochondria-derived oxidative stress via Nrf2 activation. Our findings reveal major contributions of keratins to chronic inflammation and autoimmune disorders. Total RNA obtained from E18.5 embryo back skin from typeI and II keratin knockout compared with respective wild type.
Project description:Regional specific differentiation of integumentary organs: SATB2 is involved in α- and β-keratin gene cluster switching in the chicken