Single cell RNAseq of human nail unit defines RSPO4 onychofibroblasts and SPINK6 nail epithelium
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ABSTRACT: Here, we studied transcriptome profiles of human nail units from polydactly samples. Single cell RNAseq with 11,541 cells from 4 extra digits revealed nail-specific mesenchymal and epithelial cell populations
Project description:Research on human nail tissue has been limited by the restricted access to fresh specimen. Here, we studied transcriptome profiles of human nail units using polydactyly specimens. Single-cell RNAseq with 11,541 cells from 4 extra digits revealed nail-specific mesenchymal and epithelial cell populations, characterized by RSPO4 (major gene in congenital anonychia) and SPINK6, respectively. In situ RNA hybridization demonstrated the localization of RSPO4, MSX1 and WIF1 in onychofibroblasts suggesting the activation of WNT signaling. BMP-5 was also expressed in onychofibroblasts implicating the contribution of BMP signaling. SPINK6 expression distinguished the nail-specific keratinocytes from epidermal keratinocytes. RSPO4+ onychofibroblasts were distributed at close proximity with LGR6+ nail matrix, leading to WNT/β-catenin activation. In addition, we demonstrated RSPO4 was overexpressed in the fibroblasts of onychomatricoma and LGR6 was highly expressed at the basal layer of the overlying epithelial component, suggesting that onychofibroblasts may play an important role in the pathogenesis of onychomatricoma.
Project description:Nails protect the soft tissue of the tips of digits in humans. In birds and mammals the equivalent claws are used for purposes including capturing prey, digging, climbing, fighting and maintaining dexterity and balance. The molecular mechanism of nail (and claw) development is largely unknown, but we have recently identified a Wnt receptor gene, Frizzled6 (Fzd6), as mutated in a human autosomal-recessive nail dysplasia. To investigate the action of Fzd6 in claw development at the molecular level, we compared gene expression profiles of digit tips of wild-type and Fzd6-/- mice, and show that Fzd6 regulates the transcription of a striking number of epidermal differentiation-related genes. Sixty-three genes encoding keratins, keratin associated proteins, and transglutaminases and their substrates were significantly down-regulated in the knockout mice. Among them, four hard keratins, Krt86, Krt81, Krt34 and Krt31; two epithelial keratins, Krt6a and Krt6b; and transglutaminase1 were known to be expressed in nails and involved in nail abnormality when dysregulated. Immunohistochemical studies revealed decreased expression of Krt86, Krt6b and involucrin in the epidermal portion of the claw field in the knockout embryos. We further show that Dkk4, a Wnt antagonist, was significantly down-regulated in Fzd6-/- mice along with Wnt, Bmp and Hh family genes; and Dkk4 transgenic mice showed a subtly but appreciably modified claw phenotype. Thus, Fzd6-mediated Wnt signaling likely regulates the overall differentiation process of nail/claw formation. Heterozygous Fzd6+/- mice (kindly provided by Dr. J. Nathans) were crossed to generate Fzd6+/-, Fzd6-/- and wild-type offspring. Timed matings were set up to harvest embryos at E14.5, E16.5 and E18.5. The morning after mating was designated as E0.5. Tails and the digital tips from forelimbs of three wild-type and Fzd6-/- mice from each embryonic time-point were excised, immediately frozen on dry ice, and stored at 80 C freezer until use. Genotyping was done as described previously (15). RNA was extracted using Trizol Reagent (Life technologies). RNA from dissected forelimbs from each embryo of the three time-points was used for microarray analysis.
Project description:Mammalian digit-tip can regenerate upon amputation1-3, like amphibians. It is unknown why this capacity is limited to the area associated with the nail3-5. Here, we show that nail stem cells (NSCs) reside in the Wnt-suppressed proximal nail matrix and that the mechanisms governing NSC differentiation are directly coupled with their ability of orchestrating digit regeneration. Early nail progenitors located distal to the NCS region undergo Wnt-dependent differentiation into nail. Upon amputation, this Wnt activation is required for nail regeneration and also for attracting nerves that promote mesenchymal blastema growth, leading to regeneration of the entire digit. Amputations proximal to the Wnt-active nail progenitors result in failure to regenerate nail/digit. Nevertheless, β-catenin stabilization in the NSC region induced their regeneration. These results establish a link between NCS differentiation and digit regeneration, suggesting a utility of the NSCs in developing novel treatments for amputees. Nail matrix cells were harvested from proximal and distal matrix region by microdissection and processed to RNA extraction and hybridization on Affymetrix microarrays. We analyzed two proximal and two distal matrix cells.
Project description:Nails protect the soft tissue of the tips of digits in humans. In birds and mammals the equivalent claws are used for purposes including capturing prey, digging, climbing, fighting and maintaining dexterity and balance. The molecular mechanism of nail (and claw) development is largely unknown, but we have recently identified a Wnt receptor gene, Frizzled6 (Fzd6), as mutated in a human autosomal-recessive nail dysplasia. To investigate the action of Fzd6 in claw development at the molecular level, we compared gene expression profiles of digit tips of wild-type and Fzd6-/- mice, and show that Fzd6 regulates the transcription of a striking number of epidermal differentiation-related genes. Sixty-three genes encoding keratins, keratin associated proteins, and transglutaminases and their substrates were significantly down-regulated in the knockout mice. Among them, four hard keratins, Krt86, Krt81, Krt34 and Krt31; two epithelial keratins, Krt6a and Krt6b; and transglutaminase1 were known to be expressed in nails and involved in nail abnormality when dysregulated. Immunohistochemical studies revealed decreased expression of Krt86, Krt6b and involucrin in the epidermal portion of the claw field in the knockout embryos. We further show that Dkk4, a Wnt antagonist, was significantly down-regulated in Fzd6-/- mice along with Wnt, Bmp and Hh family genes; and Dkk4 transgenic mice showed a subtly but appreciably modified claw phenotype. Thus, Fzd6-mediated Wnt signaling likely regulates the overall differentiation process of nail/claw formation.
Project description:The mechanisms governing nail stem cell (NSC) differentiation are coupled directly with their ability to orchestrate digit regeneration. Recently, onychofibroblasts (OFs), specialized mesenchymal cells residing beneath the nail matrix in the dermis, have emerged as potential regulators of nail differentiation. However, due to limited sample sources, the cellular properties and transcriptome information of OFs remain largely unexplored. In this study, we isolated human OFs and characterized their mesenchymal stem cell-like phenotypes. To delineate the molecular features of human OFs, we conducted mRNA-seq analysis on three samples of OFs and control fibroblasts from human nail units. Our analysis identified 294 genes that were upregulated in OFs compared to surrounding fibroblasts. Through integrated analysis with scRNA-seq data from human nail units, we confirmed that BMP4, secreted by OFs, is a pivotal signal involved in mesenchymal-epithelial interactions and nail development. Furthermore, we demonstrated that BMP4 derived from OFs mediates the in vitro differentiation of NSCs using a co-culture model. Gene set enrichment analysis highlighted the involvement of the TGF-beta pathway in the differentiation of nail epithelial cells. Consequently, we validated the effect of exogenous BMP4 on the activation of the SMAD-dependent pathway and NSC differentiation, along with the rescue effect of BMP receptor inhibition. Taken together, transcriptome analysis reveals the differentiation-inducing influence of OFs on human NSCs, with the BMP4/BMPR/SMADs signaling pathway playing a key role in this process. These findings establish a connection between the dermal microenvironment and NSC differentiation, suggesting that OFs, in conjunction with NSCs, may hold promise for the development of novel therapies targeting nail and digit defects, even severe limb amputation.
Project description:Mammalian digit-tip can regenerate upon amputation1-3, like amphibians. It is unknown why this capacity is limited to the area associated with the nail3-5. Here, we show that nail stem cells (NSCs) reside in the Wnt-suppressed proximal nail matrix and that the mechanisms governing NSC differentiation are directly coupled with their ability of orchestrating digit regeneration. Early nail progenitors located distal to the NCS region undergo Wnt-dependent differentiation into nail. Upon amputation, this Wnt activation is required for nail regeneration and also for attracting nerves that promote mesenchymal blastema growth, leading to regeneration of the entire digit. Amputations proximal to the Wnt-active nail progenitors result in failure to regenerate nail/digit. Nevertheless, β-catenin stabilization in the NSC region induced their regeneration. These results establish a link between NCS differentiation and digit regeneration, suggesting a utility of the NSCs in developing novel treatments for amputees.
Project description:Mammalian digit tip regeneration is linked to the presence of nail tissue, but a nail-explicit model is missing. Here, we report that nail-less double-ventral digits of ΔLARM1/2 mutants that lack limb-specific Lmx1b enhancers, fail to regenerate. To separate the nail’s effect from the lack of DV polarity, we also interrogate double-dorsal double-nail digits and show that they regenerate. Thus, DV polarity is not a prerequisite for regeneration and the nail requirement is supported. Transcriptomic comparison between wild-type and non-regenerative ΔLARM1/2 mutant blastemas reveals differential up-regulation of vascularization and connective tissue functional signatures in wild-type versus upregulation of inflammation in the mutant. These results, together with the finding of Lmx1b expression in the postnatal dorsal dermis underneath the nail and uniformly in the regenerative blastema opens the possibility of additional Lmx1b roles in the progression of digit tip regeneration, in addition to the indirect effect of mediating the formation of the nail.
Project description:Here, we have asked why the nail base is essential for mammalian digit tip regeneration, focusing on the inductive nail mesenchyme. We identify a transcriptional signature for these cells that includes Lmx1b, and show that the Lmx1b-expressing nail mesenchyme is essential for blastema formation. We use a combination of Lmx1bCreERT2-based lineage tracing and single cell transcriptional analyses to show that the nail mesenchyme contributes cells for two pro-regenerative mechanisms. One group of cells maintains their identity and regenerates the new nail mesenchyme. A second group contributes specifically to the dorsal blastema, loses their nail mesenchyme phenotype, acquires a blastema transcriptional state that is highly similar to blastema cells of other origins and ultimately contributes to regeneration of the dorsal but not ventral dermis and bone. Thus, the regenerative necessity for an intact nail base is explained, at least part by a requirement for the inductive nail mesenchyme.
Project description:We report the genome wide occupancy of p65, H3K4Me3, H3K27Ac and p300 in MCF7-NAIL-WT and MCF7-NAIL-ΔNFκB cells stimulated with TNF alpha for 0min, 45min and 90 min.