HOXC13 is involved in the regulation of human hair keratin gene expression

Differential requirement of the transcription factor HOXC13 for the stable maintenance of human papillomavirus genome among high-risk genotypes

The viral genome of the high-risk human papillomavirus (HPV), the causative agent of cervical cancer, is stably maintained as extrachromosomal episomes that establish persistent infection. We previously identified homeobox-transcription factor HOXC13 as an important host protein mediating the short-term retention of the HPV16 and HPV18 genomes in normal human immortalized keratinocytes (NIKS). Here, we used CRISPR-Cas9 technology to construct HOXC13 knockout (KO) NIKS cells to determine whether HOXC13 is required for the long-term maintenance of high-risk HPV genomes. HPV16, HPV18, HPV52, and HPV58 whole genomes were transfected into HOXC13 KO cells, and the copy number of viral genomes per cell was monitored over cell passages. Copy numbers of HPV16, HPV52, and HPV58 genomes decreased continuously in HOXC13 KO cells, whereas HPV18 genomes remained stable throughout passages. Thus, HOXC13 is critical for the stable maintenance of the viral genomes of HPV16, HPV52, and HPV58, but not HPV18.

Evolutionary origin of Hoxc13-dependent skin appendages in amphibians

Cornified skin appendages, such as hair and nails, are major evolutionary innovations of terrestrial vertebrates. Human hair and nails consist largely of special intermediate filament proteins, known as hair keratins, which are expressed under the control of the transcription factor Hoxc13. Here, we show that the cornified claws of Xenopus frogs contain homologs of hair keratins and the genes encoding these keratins are flanked by promoters in which binding sites of Hoxc13 are conserved. Furthermore, these keratins and Hoxc13 are co-expressed in the claw-forming epithelium of frog toe tips. Upon deletion of hoxc13, the expression of hair keratin homologs is abolished and the development of cornified claws is abrogated in X. tropicalis. These results indicate that Hoxc13-dependent expression of hair keratin homologs evolved already in stem tetrapods, presumably as a mechanism for protecting toe tips, and that this ancestral genetic program was coopted to the growth of hair in mammals.

ChIP-Seq analysis reveals PRKACB as a target gene of HOXC13 involved in rabbit hair follicle development

Dermal papilla cells (DPCs) are key regulators of hair follicle (HF) development and growth, which not only regulate HF growth and cycling but play a role in the pathogenesis of hair loss. The transcription factor Homeobox C13 (HOXC13) can modulate the growth and development of HFs. Nevertheless, the specific genes and pathways regulated by HOXC13 in DPCs have yet to be determined. Thus, to gain a better understanding of genomic binding sites involved in HOXC13-regulated HF development, chromatin immunoprecipitation followed by high throughput sequencing (ChIP-Seq) was performed on rabbit DPCs with pcDNA3.1-3 × Flag-HOXC13 overexpression. A complete set of 9670 enrichment peaks was acquired by applying HOXC13-Flag ChIP. Subsequently, the peak sequence was annotated to the rabbit genome, revealing that 6.1 % of the peaks were identified within in the promoter region. Thereafter, five annotated genes were verified using RT-qPCR. The peak-associated genes were mainly enriched in signaling pathways related to HF development, such as MAPK and PI3K-Akt. Furthermore, by using a dual-luciferase reporter assay, we found that HOXC13 can target the protein kinase cAMP‑dependent catalytic β (PRKACB) promoter region (-1596 ∼ -1107 bp) and inhibit its transcription, which was consistent with data obtained from ChIP-seq analysis. Overexpression of PRKACB gene significantly modulated the expression of BCL2, WNT2, LEF1, and SFRP2 genes related to HF development as determined by RT-qPCR (P < 0.01, P < 0.05). The CCK-8 and flow cytometry assays showed that PRKACB significantly inhibited the proliferation of DPCs and promoted apoptosis (P < 0.01). In conclusion, our research revealed that PRKACB has the potential to serve as a novel target gene of HOXC13, contributing to the regulation of the proliferation and apoptosis of DPCs. The process of identifying global target genes can contribute to the understanding of the intricate pathways that HOXC13 regulates in the growth of HFs.

Genetic insights into fiber quality, coat color and adaptation in Changthangi and Muzzafarnagri sheep: A comparative skin transcriptome analysis

Changthangi sheep, which inhabit the high-altitude regions of Ladakh, are known for their fine fiber production and are characterized by grey skin and either black or white coats. In contrast, Muzzafarnagri sheep from the plains of Uttar Pradesh produce coarse wool and have white skin and coats. We conducted comparative global gene expression profiling on four biological replicates of skin from each breed. Notably, our analysis identified 149 up-regulated genes and 2,139 down-regulated genes in Changthangi sheep compared to Muzzafarnagri sheep, with a p-adjusted value (padj) of ≤0.05 and a Log2 fold change of ≥1.5. Gene Ontology analysis of the up-regulated genes revealed an enrichment of terms related to melanin biosynthesis and developmental pigmentation. Additionally, enriched KEGG pathways included tyrosine metabolism and metabolic pathways. Among the melanogenesis-related genes that exhibited higher expression in Changthangi sheep were TYR, TYRP1, DCT, SLC45A2, PMEL, MLANA, and OCA2. These findings confirm melanin's role in both the animals' black coat color and UV protection at high-altitude. Furthermore, we observed more pronounced expression of genes related to fiber quality, namely KRTAP6, KRTAP7, KRTAP13, and KRTAP2, in the fine wool-producing sheep from Ladakh. The results of the RNA sequencing were validated using real-time PCR on 10 genes governing fiber quality and coat color, with ACTB and PPIB serving as reference genes. In conclusion, our comparative skin transcriptome analysis of Changthangi and Muzzafarnagri sheep sheds light on the genetic differences associated with distinct phenotypic traits and environmental adaptability, offering valuable insights into the underlying mechanisms.

Integrated single-cell chromatin and transcriptomic analyses of human scalp identify gene-regulatory programs and critical cell types for hair and skin diseases

Genome-wide association studies have identified many loci associated with hair and skin disease, but identification of causal variants requires deciphering of gene-regulatory networks in relevant cell types. We generated matched single-cell chromatin profiles and transcriptomes from scalp tissue from healthy controls and patients with alopecia areata, identifying diverse cell types of the hair follicle niche. By interrogating these datasets at multiple levels of cellular resolution, we infer 50-100% more enhancer-gene links than previous approaches and show that aggregate enhancer accessibility for highly regulated genes predicts expression. We use these gene-regulatory maps to prioritize cell types, genes and causal variants implicated in the pathobiology of androgenetic alopecia (AGA), eczema and other complex traits. AGA genome-wide association studies signals are enriched in dermal papilla regulatory regions, supporting the role of these cells as drivers of AGA pathogenesis. Finally, we train machine learning models to nominate single-nucleotide polymorphisms that affect gene expression through disruption of transcription factor binding, predicting candidate functional single-nucleotide polymorphism for AGA and eczema.

A Kaleidoscope of Keratin Gene Expression and the Mosaic of Its Regulatory Mechanisms

Keratins are a family of intermediate filament-forming proteins highly specific to epithelial cells. A combination of expressed keratin genes is a defining property of the epithelium belonging to a certain type, organ/tissue, cell differentiation potential, and at normal or pathological conditions. In a variety of processes such as differentiation and maturation, as well as during acute or chronic injury and malignant transformation, keratin expression undergoes switching: an initial keratin profile changes accordingly to changed cell functions and location within a tissue as well as other parameters of cellular phenotype and physiology. Tight control of keratin expression implies the presence of complex regulatory landscapes within the keratin gene loci. Here, we highlight patterns of keratin expression in different biological conditions and summarize disparate data on mechanisms controlling keratin expression at the level of genomic regulatory elements, transcription factors (TFs), and chromatin spatial structure.

CHAC1 as a novel biomarker for distinguishing alopecia from other dermatological diseases and determining its severity

Alopecia Areata (AA) is characterised by an autoimmune response to hair follicles (HFs) and its exact pathobiology remains unclear. The current study aims to look into the molecular changes in the skin of AA patients as well as the potential underlying molecular mechanisms of AA in order to identify potential candidates for early detection and treatment of AA. We applied Weighted Gene Co-expression Network Analysis (WGCNA) to identify key modules, hub genes, and mRNA-miRNA regulatory networks associated with AA. Furthermore, Chi2 as a machine-learning algorithm was used to compute the gene importance in AA. Finally, drug-target construction revealed the potential of repositioning drugs for the treatment of AA. Our analysis using four AA data sets established a network strongly correlated to AA pathogenicity based on GZMA, OXCT2, HOXC13, KRT40, COMP, CHAC1, and KRT83 hub genes. Interestingly, machine learning introduced these genes as important in AA pathogenicity. Besides that, using another ten data sets, we showed that CHAC1 could clearly distinguish AA from similar clinical phenotypes, such as scarring alopecia due to psoriasis. Also, two FDA-approved drug candidates and 30 experimentally validated miRNAs were identified that affected the co-expression network. Using transcriptome analysis, suggested CHAC1 as a potential diagnostic predictor to diagnose AA.

miR-129-5p Participates in Hair Follicle Growth by Targeting HOXC13 in Rabbit

Mammalian hair formation is critically determined by the growth of hair follicles (HF). MiRNAs are crucial in the periodic development of hair follicles; they maintain epidermal homeostasis by targeting genes and influencing the activity of signaling pathways and related regulators. Our study discovered miR-129-5p to be overexpressed in the skin of Angora rabbits during catagen, and was negatively correlated with HOXC13 expression (Pearson’s R = −0.313, p < 0.05). The dual-Luciferase reporter gene detection system and Western blotting confirmed that miR-129-5p targeted HOXC13. In addition, miR-129-5p overexpression was found to significantly inhibit the expression of hair follicle development-related genes (HFDRGs), such as BCL2, WNT2, CCND1, and LEF1 (p < 0.01), and promoted the expression of SFRP2, TGF-β1, and FGF2 (p < 0.01), which was the same as the knockdown of HOXC13. In contrast, the knockout of miR-129-5p was the opposite, and it demonstrated similar results to the overexpression of HOXC13. CCK8 and flow cytometry demonstrated that miR-129-5p mimics significantly promoted the apoptosis of dermal papilla cells (DPCs) and inhibited proliferation (p < 0.01), while the inhibitor was found to reduce the apoptosis of DPCs and promote proliferation (p < 0.01). These results showed that miR-129-5p can participate in the periodic development of HF by targeting HOXC13, and it can induce apoptosis and inhibit proliferation of DPCs. These results will help to understand the role and mechanism of miR-129-5p in the periodic development of HF, and will provide support for subsequent studies, not only providing a theoretical basis for genetically improving the quality of hair in animals in the future, but also a new theory and method for diagnosing and treating hair loss in humans.

Update of recent findings in genetic hair disorders

Genetic hair disorders, although unusual, are not very rare, and dermatologists often have opportunities to see patients. Significant advances in molecular genetics have led to identifying many causative genes for genetic hair disorders, including the recently identified causative genes, such as LSS and C3ORF52. Many patients have been detected with autosomal recessive woolly hair/hypotrichosis in the Japanese population caused by founder mutations in the LIPH gene. Additionally, many patients with genetic hair disorders caused by other genes have been reported in East Asia including Japan. Understanding genetic hair disorders is essential for dermatologists, and the findings obtained from analyzing these diseases will contribute to revealing the mechanisms of hair follicle morphogenesis and development in humans.

Naked (N) mutant mice carry a nonsense mutation in the homeobox of Hoxc13

Loss of function mutations in HOXC13 have been associated with Ectodermal Dysplasia-9, Hair/Nail Type (ECTD9) in consanguineous families, characterized by sparse to complete absence of hair and nail dystrophy. Here we characterize the spontaneous mouse mutation Naked (N) as a terminal truncation in the Hoxc13 (homeobox C13) gene. Similar to previous reports for homozygous Hoxc13 knock-out (KO) mice, homozygous N/N mice exhibit generalized alopecia with abnormal nails and a short lifespan. However, in contrast to Hoxc13 heterozygous KO mice, N/+ mice show generalized or partial alopecia, associated with loss of hair fibres, along with normal lifespan and fertility. Our data point to a lack of nonsense-mediated Hoxc13 transcript decay and the presence of the truncated mutant protein in N/N and N/+ hair follicles, thus suggesting a dominant-negative mutation. To our knowledge, this is the first report of a semi-dominant and potentially dominant-negative mutation affecting Hoxc13/HOXC13. Furthermore, recreating the N mutant allele in mice using CRISPR/Cas9-mediated genome editing resulted in the same spectrum of deficiencies as those associated with the spontaneous Naked mutation, thus confirming that N is indeed a Hoxc13 mutant allele. Considering the low viability of the Hoxc13 KO mice, the Naked mutation provides an attractive new model for studying ECTD9 disease mechanisms.

Alopecia in Harlequin mutant mice is associated with reduced AIF protein levels and expression of retroviral elements

We investigated the contribution of apoptosis-inducing factor (AIF), a key regulator of mitochondrial biogenesis, in supporting hair growth. We report that pelage abnormalities developed during hair follicle (HF) morphogenesis in Harlequin (Hq) mutant mice. Fragility of the hair cortex was associated with decreased expression of genes encoding structural hair proteins, though key transcriptional regulators of HF development were expressed at normal levels. Notably, Aifm1 (R200 del) knockin males and Aifm1(R200 del)/Hq females showed minor hair defects, despite substantially reduced AIF levels. Furthermore, we cloned the integrated ecotropic provirus of the Aifm1Hq allele. We found that its overexpression in wild-type keratinocyte cell lines led to down-regulation of HF-specific Krt84 and Krtap3-3 genes without altering Aifm1 or epidermal Krt5 expression. Together, our findings imply that pelage paucity in Hq mutant mice is mechanistically linked to severe AIF deficiency and is associated with the expression of retroviral elements that might potentially influence the transcriptional regulation of structural hair proteins.

Mammalian-specific ectodermal enhancers control the expression of Hoxc genes in developing nails and hair follicles

Vertebrate Hox genes are critical for 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 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), a condition stronger than the previously reported loss of function of Hoxc13, which is the causative gene of the ectodermal dysplasia 9 (ECTD9) in human patients. We further identified two mammalian-specific ectodermal enhancers located upstream of the HoxC gene cluster, which together regulate Hoxc gene expression in the hair and nail ectodermal organs. Deletion of these regulatory elements alone or in combination revealed a strong quantitative component in the regulation of Hoxc genes in the ectoderm, suggesting that these two enhancers may have evolved along with the mammalian taxon to provide the level of HOXC proteins necessary for the full development of hair and nail.

Transcriptome Profiling and Differential Gene Expression in Canine Microdissected Anagen and Telogen Hair Follicles and Interfollicular Epidermis

The transcriptome profile and differential gene expression in telogen and late anagen microdissected hair follicles and the interfollicular epidermis of healthy dogs was investigated by using RNAseq. The genes with the highest expression levels in each group were identified and genes known from studies in other species to be associated with structure and function of hair follicles and epidermis were evaluated. Transcriptome profiling revealed that late anagen follicles expressed mainly keratins and telogen follicles expressed GSN and KRT15. The interfollicular epidermis expressed predominately genes encoding for proteins associated with differentiation. All sample groups express genes encoding for proteins involved in cellular growth and signal transduction. The expression pattern of skin-associated genes in dogs is similar to humans. Differences in expression compared to mice and humans include BMP2 expression mainly in telogen and high KRT17 expression in the interfollicular epidermis of dogs. Our data provide the basis for the investigation of the structure and function of canine skin or skin disease and support the use of dogs as a model for human cutaneous disease by assigning gene expression to specific tissue states.

Integrative Analysis of Methylome and Transcriptome Reveals the Regulatory Mechanisms of Hair Follicle Morphogenesis in Cashmere Goat

Studies in humans and mice have revealed that hair follicle morphogenesis relies on tightly coordinated ectodermal–mesodermal interactions, involving multiple signals and regulatory factors. DNA methylation and long non-coding RNA (lncRNA) play a critical role in early embryonic skin development by controlling gene expression. Acting as an indirect regulator, lncRNA could recruit DNA methyltransferases to specific genomic sites to methylate DNA. However, the molecular regulation mechanisms underlying hair follicle morphogenesis is unclear in cashmere goat. In this study, RNA-seq and whole-genome bisulfite sequencing (WGBS) in embryonic day 65 (E 65) and E 120 skin tissues of cashmere goat were used to reveal this complex regulatory process. The RNA-seq, qRT-PCR, and immunohistochemistry results showed that Wnt signaling played an important role in both hair follicle induction and differentiation stage; transcriptional factors (TFs), including HOXC13, SOX9, SOX21, JUNB, LHX2, VDR, and GATA3, participated in hair follicle differentiation via specific expression at E 120. Subsequently, the combination of WGBS and RNA-seq analysis showed that the expression of some hair follicle differentiation genes and TF genes were negatively correlated with the DNA methylation level generally. A portion of hair follicle differentiation genes were methylated and repressed in the hair follicle induction stage but were subsequently demethylated and expressed during the hair follicle differentiation stage, suggesting that DNA methylation plays an important role in hair morphogenesis by regulating associated gene expression. Furthermore, 45 upregulated and 147 downregulated lncRNAs in E 120 compared with E 65 were identified by lncRNA mapping, and then the potential differentially expressed lncRNAs associated with DNA methylation on the target gene were revealed. In conclusion, critical signals and genes were revealed during hair follicle morphogenesis in the cashmere goat. In this process, DNA methylation was lower in the hair follicle differentiation compared with the hair follicle induction stage and may play an important role in hair morphogenesis by regulating associated gene expression. Furthermore, potential lncRNAs associated with DNA methylation on target genes were delineated. This study enriches the regulatory network and molecular mechanisms on hair morphogenesis.

Skin transcriptome profiling of Changthangi goats highlights the relevance of genes involved in Pashmina production

Pashmina, the world's finest natural fiber is derived from secondary hair follicles of Changthangi goats which are domesticated in Ladakh region of Jammu and Kashmir by nomadic pastoralists. Complex epithelial-mesenchymal interactions involving numerous signal molecules and signaling pathways govern hair follicle morphogenesis and mitosis across different species. The present study involved transcriptome profiling of skin from fiber type Changthangi goats and meat type Barbari goats to unravel gene networks and metabolic pathways that might contribute to Pashmina development. In Changthangi goats, 525 genes were expressed at significantly higher levels and 54 at significantly lower levels with fold change >2 (p_adj < 0.05). Functional annotation and enrichment analysis identified significantly enriched pathways to be formation of the cornified envelope, keratinization and developmental biology. Expression of genes for keratins (KRTs) and keratin-associated proteins (KRTAPs) was observed to be much higher in Changthangi goats. A host of transcriptional regulator genes for hair follicle keratin synthesis such as GPRC5D, PADI3, HOXC13, FOXN1, LEF1 and ELF5 showed higher transcript abundance in Pashmina producing goats. Positive regulation of Wnt signaling pathway and negative regulation of Oncostatin M signaling pathway may be speculated to be important contributors to hair follicle development and hair shaft differentiation in Changthangi goats.

Beta-caryophyllene enhances wound healing through multiple routes

Beta-caryophyllene is an odoriferous bicyclic sesquiterpene found in various herbs and spices. Recently, it was found that beta-caryophyllene is a ligand of the cannabinoid receptor 2 (CB2). Activation of CB2 will decrease pain, a major signal for inflammatory responses. We hypothesized that beta-caryophyllene can affect wound healing by decreasing inflammation. Here we show that cutaneous wounds of mice treated with beta-caryophyllene had enhanced re-epithelialization. The treated tissue showed increased cell proliferation and cells treated with beta-caryophyllene showed enhanced cell migration, suggesting that the higher re-epithelialization is due to enhanced cell proliferation and cell migration. The treated tissues also had up-regulated gene expression for hair follicle bulge stem cells. Olfactory receptors were not involved in the enhanced wound healing. Transient Receptor Potential channel genes were up-regulated in the injured skin exposed to beta-caryophyllene. Interestingly, there were sex differences in the impact of beta- caryophyllene as only the injured skin of female mice had enhanced re-epithelialization after exposure to beta-caryophyllene. Our study suggests that chemical compounds included in essential oils have the capability to improve wound healing, an effect generated by synergetic impacts of multiple pathways.

Genomic and transcriptomic insights into molecular basis of sexually dimorphic nuptial spines in Leptobrachium leishanense

Sexually dimorphic (SD) traits are important in sexual selection and species survival, yet the molecular basis remains elusive, especially in amphibians where SD traits have evolved repeatedly. We focus on the Leishan moustache toad (Leptobrachium leishanense), in which males develop nuptial spines on their maxillary skin. Here we report a 3.5 Gb genome assembly with a contig N50 of 1.93 Mb. We find a specific expansion of the intermediate filament gene family including numerous keratin genes. Within these genes, a cluster of duplicated hair keratin genes exhibits male-biased and maxillary skin-specific expression, suggesting a role in developing nuptial spines. We identify a module of coexpressed genes significantly associated with spine formation. In addition, we find several hormones likely to be involved in regulating spine development. This study not only presents a high-quality anuran genome but also provides a reference for studying skin-derived SD traits in amphibians.

The basis of sexual dimorphism in non-model species may be elusive, in part due to a lack of genomic and molecular resources. Here, Li et al. report a high-quality anuran genome and reveal candidate genes and pathways associated with shaping sexually dimorphic nuptial spines in a moustache toad.

The homeobox transcription factor HOXC13 upregulates human papillomavirus E1 gene expression and contributes to viral genome maintenance

Human papillomavirus (HPV) infects the basal cells of epithelia and maintains its genome stably as episomes. However, the mechanisms of viral genome maintenance are not fully understood. Here, using normal human immortalized keratinocytes (NIKS), we identified the homeobox transcription factor HOXC13 as a critical host factor for retaining the copy number of HPV genomes in the cell. HOXC13 knockdown in NIKS significantly decreased mRNA levels of the E1 gene, which encodes a DNA helicase required for HPV genome replication, accompanied by a reduction of the viral genome copy number. Chromatin immunoprecipitation assays revealed HOXC13 binding to the long control region that regulates E1 expression. These results indicate that HOXC13 plays invaluable roles in maintaining HPV persistent infection through E1 gene upregulation.

Paralogous HOX13 Genes in Human Cancers

Hox genes (HOX in humans), an evolutionary preserved gene family, are key determinants of embryonic development and cell memory gene program. Hox genes are organized in four clusters on four chromosomal loci aligned in 13 paralogous groups based on sequence homology (Hox gene network). During development Hox genes are transcribed, according to the rule of “spatio-temporal collinearity”, with early regulators of anterior body regions located at the 3’ end of each Hox cluster and the later regulators of posterior body regions placed at the distal 5’ end. The onset of 3’ Hox gene activation is determined by Wingless-type MMTV integration site family (Wnt) signaling, whereas 5’ Hox activation is due to paralogous group 13 genes, which act as posterior-inhibitors of more anterior Hox proteins (posterior prevalence). Deregulation of HOX genes is associated with developmental abnormalities and different human diseases. Paralogous HOX13 genes (HOX A13, HOX B13, HOX C13 and HOX D13) also play a relevant role in tumor development and progression. In this review, we will discuss the role of paralogous HOX13 genes regarding their regulatory mechanisms during carcinogenesis and tumor progression and their use as biomarkers for cancer diagnosis and treatment.

The inconsistent regulation of HOXC13 on different keratins and the regulation mechanism on HOXC13 in cashmere goat (Capra hircus)

Background

During hair growth, cortical cells emerging from the proliferative follicle bulb rapidly undergo a differentiation program and synthesize large amounts of hair keratin proteins. In this process, HOXC13 is one critical regulatory factor, proved by the hair defects in HOXC13 mutant mice and HOXC13 mutant patients. However, inconsistent conclusions were drawn from previous researches regarding the regulation of HOXC13 on different keratins. Whether HOXC13 has extensive and unified regulatory role on these numerous keratins is unclear.

Results

In this study, firstly, RNA-seq was performed to reveal the molecular mechanism of cashmere cycle including anagen and telogen. Subsequently, combining the sequencing with qRT-PCR and immunofluorescent staining results, we found that HOXC13 showed similar expression pattern with a large proportion of keratins except for KRT1 and KRT2, which were higher in anagen compared with telogen. Then, the regulatory role of HOXC13 on different keratins was investigated using dual-luciferase reporter system and keratin promoter-GFP system by overexpressing HOXC13 in HEK 293 T cells and dermal papilla cells. Our results demonstrated that HOXC13 up-regulated the promoter activity of KRT84 and KRT38, while down-regulated the promoter activity of KRT1 and KRT2, which suggested HOXC13 had an ambivalent effect on the promoters of different KRTs. Furtherly, the regulation on HOXC13 itself was investigated. At transcriptional level, the binding sites of HOXC13 and LEF1 were found in the promoter of HOXC13. Then, through transfecting corresponding overexpression vector and dual-luciferase reporter system into dermal papilla cells, the negative-feedback regulation of HOXC13 itself and positive regulation of LEF1 on HOXC13 promoter were revealed. In addition, melatonin could significantly increase the promoter activity of HOXC13 under the concentration of 10 μM and 25 μM by adding exogenous melatonin into dermal papilla cells. At post-transcriptional level, we investigated whether chi-miR-200a could target HOXC13 through dual-luciferase reporter system. At epigenetic level, we investigated the methylation level of HOXC13 promoter at different stages including anagen, telogen and 60d of embryonic period. As a result, miR-200a and methylation were not regulatory factors of HOXC13. Interestingly, we found two SNPs (c.812A > G and c.929A > C) in the homeodomain of HOXC13 that could deprive the regulatory function of HOXC13 on keratins without changing its protein expression.

Conclusion

HOXC13 had an inconsistent effect on the promoters of different keratins. Two SNPs (c.812A > G and c.929A > C) in the homeodomain of HOXC13 deprived its function on keratin regulation. Besides, the negative-feedback regulation by HOXC13 itself and positive regulation by LEF1 and melatonin on HOXC13 promoter were revealed. This study will enrich the function of HOXC13 on keratin regulation and contribute to understand the mechanism of hair follicle differentiation.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5011-4) contains supplementary material, which is available to authorized users.

Evolution of Trichocyte Keratins

The evolution of keratins was closely linked to the evolution of epithelia and epithelial appendages such as hair. The characterization of keratins in model species and recent comparative genomics studies have led to a comprehensive scenario for the evolution of keratins including the following key events. The primordial keratin gene originated as a member of the ancient gene family encoding intermediate filament proteins. Gene duplication and changes in the exon-intron structure led to the origin of type I and type II keratins which evolved further by nucleotide sequence modifications that affected both the amino acid sequences of the encoded proteins and the gene expression patterns. The diversification of keratins facilitated the emergence of new and epithelium type-specific properties of the cytoskeleton. In a common ancestor of reptiles, birds, and mammals, a rise in the number of cysteine residues facilitated extensive disulfide bond-mediated cross-linking of keratins in claws. Subsequently, these cysteine-rich keratins were co-opted for an additional function in epidermal follicular structures that evolved into hair, one of the key events in the evolution of mammals. Further diversification of keratins occurred during the evolution of the complex multi-layered organisation of hair follicles. Thus, together with the evolution of other structural proteins, epithelial patterning mechanisms, and development programmes, the evolution of keratins underlied the evolution of the mammalian integument.

Study of gene expression alteration in male androgenetic alopecia: evidence of predominant molecular signalling pathways

BACKGROUND

Male androgenetic alopecia (AGA) is the most common form of hair loss in men. It is characterized by a distinct pattern of progressive hair loss starting from the frontal area and the vertex of the scalp. Although several genetic risk loci have been identified, relevant genes for AGA remain to be defined.

OBJECTIVES

To identify biomarkers associated with AGA.

METHODS

Molecular biomarkers associated with premature AGA were identified through gene expression analysis using cDNA generated from scalp vertex biopsies of hairless or bald men with premature AGA, and healthy volunteers.

RESULTS

This monocentric study reveals that genes encoding mast cell granule enzymes, inflammatory mediators and immunoglobulin-associated immune mediators were significantly overexpressed in AGA. In contrast, underexpressed genes appear to be associated with the Wnt/β-catenin and bone morphogenic protein/transforming growth factor-β signalling pathways. Although involvement of these pathways in hair follicle regeneration is well described, functional interpretation of the transcriptomic data highlights different events that account for their inhibition. In particular, one of these events depends on the dysregulated expression of proopiomelanocortin, as confirmed by polymerase chain reaction and immunohistochemistry. In addition, lower expression of CYP27B1 in patients with AGA supports the notion that changes in vitamin D metabolism contributes to hair loss.

CONCLUSIONS

This study provides compelling evidence for distinct molecular events contributing to alopecia that may pave the way for new therapeutic approaches.

Integrated analysis of coding genes and non-coding RNAs during hair follicle cycle of cashmere goat (Capra hircus)

Background

Cashmere growth is a seasonal and cyclic phenomenon under the control of photoperiod and multiple stimulatory and inhibitory signals. Beyond relevant coding genes, microRNA (miRNA) and long non coding RNA (lncRNA) play an indispensable role in hair follicle (HF) development and skin homeostasis. Furthermore, the influence of lncRNA upon miRNA function is also rapidly emerging. However, little is known about miRNAs, lncRNAs and their functions as well as their interactions on cashmere development and cycling.

Result

Here, based on lncRNA and miRNA high-throughput sequencing and bioinformatics analysis, we have identified 1108 lncRNAs and 541 miRNAs in cashmere goat skin during anagen and telogen. Compared with telogen, 1388 coding genes, 41 lncRNAs and 15 miRNAs were upregulated, while 1104 coding genes, 157 lncRNAs and 8 miRNAs were downregulated in anagen (adjusted P-value ≤0.05 and relative fold-change ≥2). Subsequently, we investigated the impact of lncRNAs on their target genes in cis and trans, indicating that these lncRNAs are functionally conserved during HF development and cycling. Furthermore, miRNA-mRNA and miRNA-lncRNA interaction were identified through the bioinformatics algorithm miRanda, then the ceRNA networks, miR-221-5p-lnc_000679-WNT3, miR-34a-lnc_000181-GATA3 and miR-214-3p-lnc_000344-SMAD3, were constructed under defined rules, to illustrate their roles in cashmere goat HF biology.

Conclusion

The present study provides a resource for lncRNA, miRNA and mRNA studies in cashmere cycling and development. We also demonstrate potential ceRNA regulatory networks in cashmere goat HF cycling for the first time. It expands our knowledge about lncRNA and miRNA biology as well as contributes to the annotation of the goat genome.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4145-0) contains supplementary material, which is available to authorized users.

Chromosomal Alterations and Gene Expression Changes Associated with the Progression of Leukoplakia to Advanced Gingivobuccal Cancer

We present an integrative genome-wide analysis that can be used to predict the risk of progression from leukoplakia to oral squamous cell carcinoma (OSCC) arising in the gingivobuccal complex (GBC). We find that the genomic and transcriptomic profiles of leukoplakia resemble those observed in later stages of OSCC and that several changes are associated with this progression, including amplification of 8q24.3, deletion of 8p23.2, and dysregulation of DERL3, EIF5A2, ECT2, HOXC9, HOXC13, MAL, MFAP5 and NELL2. Comparing copy number profiles of primary tumors with and without lymph-node metastasis, we identify alterations associated with metastasis, including amplifications of 3p26.3, 8q24.21, 11q22.1, 11q22.3 and deletion of 8p23.2. Integrative analysis reveals several biomarkers that have never or rarely been reported in previous OSCC studies, including amplifications of 1p36.33 (attributable to MXRA8), 3q26.31 (EIF5A2), 9p24.1 (CD274), and 12q13.2 (HOXC9 and HOXC13). Additionally, we find that amplifications of 1p36.33 and 11q22.1 are strongly correlated with poor clinical outcome. Overall, our findings delineate genomic changes that can be used in treatment management for patients with potentially malignant leukoplakia and OSCC patients with higher risk of lymph-node metastasis.

A Novel Homozygous Missense Mutation in HOXC13 Leads to Autosomal Recessive Pure Hair and Nail Ectodermal Dysplasia

Pure hair and nail ectodermal dysplasia (PHNED) is a rare disorder that presents with hypotrichosis and nail dystrophy while sparing other ectodermal structures such as teeth and sweat glands. We describe a homozygous novel missense mutation in the HOXC13 gene that resulted in autosomal recessive PHNED in a Hispanic child. The mutation c.812A>G (p.Gln271Arg) is located within the DNA-binding domain of the HOXC13 gene, cosegregates within the family, and is predicted to be maximally damaging. This is the first reported case of a missense HOXC13 mutation resulting in PHNED and the first reported case of PHNED identified in a North American family. Our findings illustrate the critical role of HOXC13 in human hair and nail development.

Gata6 promotes hair follicle progenitor cell renewal by genome maintenance during proliferation

Cell proliferation is essential to rapid tissue growth and repair, but can result in replication-associated genome damage. Here, we implicate the transcription factor Gata6 in adult mouse hair follicle regeneration where it controls the renewal of rapidly proliferating epithelial (matrix) progenitors and hence the extent of production of terminally differentiated lineages. We find that Gata6 protects against DNA damage associated with proliferation, thus preventing cell cycle arrest and apoptosis. Furthermore, we show that in vivo Gata6 stimulates EDA-receptor signaling adaptor Edaradd level and NF-κB pathway activation, known to be important for DNA damage repair and stress response in general and for hair follicle growth in particular. In cultured keratinocytes, Edaradd rescues DNA damage, cell survival, and proliferation of Gata6 knockout cells and restores MCM10 expression. Our data add to recent evidence in embryonic stem and neural progenitor cells, suggesting a model whereby developmentally regulated transcription factors protect from DNA damage associated with proliferation at key stages of rapid tissue growth. Our data may add to understanding why Gata6 is a frequent target of amplification in cancers.

Genetics of syndromic and non-syndromic hereditary nail disorders

The nail is a unique epithelial skin appendage made up of a fully keratinized nail plate. The nail can be affected in several systemic illnesses, dermatological diseases, and inherited nail disorders. Nail dystrophies can present as isolated disorders or as a part of syndromes. Substantial progress has been achieved in the management and diagnosis of nail diseases; however, not much is known about the underlying molecular controls of nail growth. The homeostasis and development of the nail appendage depend on the intricate interactions between the epidermis and underlying mesenchyme, and comprise different signaling pathways such as the WNT signaling pathway. Digit-tip regeneration in mice and humans has been a known fact for the past six decades; however, only recently the underlying biological mechanisms by which the nail organ achieves digit regeneration have been elucidated. Moreover, significant progress has been made in identifying nail stem cells and localizing stem cell niches in the nail unit. More fascinating, however, is the role they play in orchestrating the processes that lead to the regeneration of the digit. Further elucidating the role of nail stem cells and the signaling pathways driving epithelial-mesenchymal interactions in the nail unit might contribute to the development of novel therapeutic tools for amputees.

Comparative Transcriptome Analysis of Fetal Skin Reveals Key Genes Related to Hair Follicle Morphogenesis in Cashmere Goats

Cashmere goat skin contains two types of hair follicles (HF): primary hair follicles (PHF) and secondary hair follicles (SHF). Although multiple genetic determinants associated with HF formation have been identified, the molecules that determine the independent morphogenesis of HF in cashmere goats remain elusive. The growth and development of SHF directly influence the quantity and quality of cashmere production. Here, we report the transcriptome profiling analysis of nine skin samples from cashmere goats using 60- and 120-day-old embryos (E60 and E120, respectively), as well as newborns (NB), through RNA-sequencing (RNA-seq). HF morphological changes indicated that PHF were initiated at E60, with maturation from E120, while differentiation of SHF was identified at E120 until formation of cashmere occurred after birth (NB). The RNA-sequencing analysis generated over 20.6 million clean reads from each mRNA library. The number of differentially expressed genes (DEGs) in E60 vs. E120, E120 vs. NB, and E60 vs. NB were 1,024, 0 and 1,801, respectively, indicating that no significant differences were found at transcriptomic levels between E120 and NB. Key genes including B4GALT4, TNC, a-integrin, and FGFR1, were up-regulated and expressed in HF initiation from E60 to E120, while regulatory genes such as GPRC5D, PAD3, HOXC13, PRR9, VSIG8, LRRC15, LHX2, MSX-2, and FOXN1 were up-regulated and expressed in HF keratinisation and hair shaft differentiation from E120 and NB to E60. Several genes belonging to the KRT and KRTAP gene families were detected throughout the three HF developmental stages. The transcriptional trajectory analyses of all DEGs indicated that immune privilege, glycosaminoglycan biosynthesis, extracellular matrix receptor interaction, and growth factor receptors all played dominant roles in the epithelial-mesenchymal interface and HF formation. We found that the Wnt, transforming growth factor-beta/bone morphogenetic protein, and Notch family members played vital roles in HF differentiation and maturation. The DEGs we found could be attributed to the generation and development of HF, and thus will be critically important for improving the quantity and quality of fleece production in animals for fibres.

Hoxc13 is a crucial regulator of murine hair cycle

Hair follicles undergo cyclical growth and regression during postnatal life. Hair regression is an apoptosis-driven process strictly controlled by micro- and macro-environmental signals. However, how these signals are controlled remains largely unknown. Hoxc13, a member of the Hox gene family, is reported to play an important role in hair follicle differentiation. In the present study, we observed that Hoxc13 was highly expressed in the outer root sheath, matrix, medulla and inner root sheath of hair follicles in a hair cycle-dependent manner. We therefore investigated the role of Hoxc13 in hair follicle cycling. Injection of ShRNA (ShHoxc13) to suppress Hoxc13 in early anagen promoted premature catagen entry, shown by significantly decreased hair length and hair bulb size, increased percentage of catagen hair follicles, hair cycle score and TUNEL+ cells and inhibited proliferation. In contrast, local injection of recombinant Hoxc13 polypeptide (rhHoxc13) during the late anagen phase prolonged the anagen phase. Additionally, rhHoxc13 injections during the telogen phase significantly promoted hair growth and induced the anagen progression. At the molecular level, the expression of phosphorylated smad2 (p-smad2), a key factor of active TGF-β1 signaling, was up-regulated in the ShHoxc13-treated hair follicles and down-regulated in rhHoxc13-treated hair follicles, suggesting that Hoxc13 might block anagen-catagen transition by inhibiting the TGF-β1 signaling. Taken together, our data strongly suggest that Hoxc13 is a novel and crucial regulator of the hair cycle. This might also provide an understanding of the mechanism of the 'hair cycle clock' and the development of alopecia treatments.

Dysregulated expression of sterol O-acyltransferase 1 (Soat1) in the hair shaft of Hoxc13 null mice

The cholesterol-metabolizing enzyme sterol O-acetyltransferase (SOAT1) is implicated in an increasing number of biological and pathological processes in a number of organ systems, including the differentiation of the hair shaft. While the functional and regulatory mechanisms underlying these diverse functional roles remain poorly understood, the compartment of the hair shaft known as medulla, affected by mutations in Soat1, may serve as a suitable model for defining some of these mechanisms. A comparative analysis of mRNA and protein expression patterns of Soat1/SOAT1 and the transcriptional regulator Hoxc13/HOXC13 in postnatal skin of FVB/NTac mice indicated co-expression in the most proximal cells of the differentiating medulla. This finding combined with the significant downregulation of Soat1 expression in postnatal skin of both Hoxc13 gene-targeted and transgenic mice based on previously reported DNA microarray results suggests a potential regulatory relationship between the two genes. Non-detectable SOAT1 expression in the defective hair follicle medulla of Hoxc13(tm1Mrc) mice and evidence for binding of HOXC13 to the Soat1 upstream control region obtained by ChIP assay suggests that Soat1 is a downstream regulatory target for HOXC13 during medulla differentiation.

Post-transcriptional Regulation of Keratinocyte Progenitor Cell Expansion, Differentiation and Hair Follicle Regression by miR-22

Hair follicles (HF) undergo precisely regulated recurrent cycles of growth, cessation, and rest. The transitions from anagen (growth), to catagen (regression), to telogen (rest) involve a physiological involution of the HF. This process is likely coordinated by a variety of mechanisms including apoptosis and loss of growth factor signaling. However, the precise molecular mechanisms underlying follicle involution after hair keratinocyte differentiation and hair shaft assembly remain poorly understood. Here we demonstrate that a highly conserved microRNA, miR-22 is markedly upregulated during catagen and peaks in telogen. Using gain- and loss-of-function approaches in vivo, we find that miR-22 overexpression leads to hair loss by promoting anagen-to-catagen transition of the HF, and that deletion of miR-22 delays entry to catagen and accelerates the transition from telogen to anagen. Ectopic activation of miR-22 results in hair loss due to the repression a hair keratinocyte differentiation program and keratinocyte progenitor expansion, as well as promotion of apoptosis. At the molecular level, we demonstrate that miR-22 directly represses numerous transcription factors upstream of phenotypic keratin genes, including Dlx3, Foxn1, and Hoxc13. We conclude that miR-22 is a critical post-transcriptional regulator of the hair cycle and may represent a novel target for therapeutic modulation of hair growth.

Expression of human skin-specific genes defined by transcriptomics and antibody-based profiling

To increase our understanding of skin, it is important to define the molecular constituents of the cell types and epidermal layers that signify normal skin. We have combined a genome-wide transcriptomics analysis, using deep sequencing of mRNA from skin biopsies, with immunohistochemistry-based protein profiling to characterize the landscape of gene and protein expression in normal human skin. The transcriptomics and protein expression data of skin were compared to 26 (RNA) and 44 (protein) other normal tissue types. All 20,050 putative protein-coding genes were classified into categories based on patterns of expression. We found that 417 genes showed elevated expression in skin, with 106 genes expressed at least five-fold higher than that in other tissues. The 106 genes categorized as skin enriched encoded for well-known proteins involved in epidermal differentiation and proteins with unknown functions and expression patterns in skin, including the C1orf68 protein, which showed the highest relative enrichment in skin. In conclusion, we have applied a genome-wide analysis to identify the human skin-specific proteome and map the precise localization of the corresponding proteins in different compartments of the skin, to facilitate further functional studies to explore the molecular repertoire of normal skin and to identify biomarkers related to various skin diseases.

A guide for building biological pathways along with two case studies: hair and breast development

Genomic information is being underlined in the format of biological pathways. Building these biological pathways is an ongoing demand and benefits from methods for extracting information from biomedical literature with the aid of text-mining tools. Here we hopefully guide you in the attempt of building a customized pathway or chart representation of a system. Our manual is based on a group of software designed to look at biointeractions in a set of abstracts retrieved from PubMed. However, they aim to support the work of someone with biological background, who does not need to be an expert on the subject and will play the role of manual curator while designing the representation of the system, the pathway. We therefore illustrate with two challenging case studies: hair and breast development. They were chosen for focusing on recent acquisitions of human evolution. We produced sub-pathways for each study, representing different phases of development. Differently from most charts present in current databases, we present detailed descriptions, which will additionally guide PESCADOR users along the process. The implementation as a web interface makes PESCADOR a unique tool for guiding the user along the biointeractions, which will constitute a novel pathway.

Expression analysis of KAP9.2 and Hoxc13 genes during different cashmere growth stages by qRT-PCR method

Keratin-associated protein 9.2 (KAP9.2) and Homeobox C13 (Hoxc13) genes were chosen to study because of their biological functions involving hair formation. KAP9.2 gene belongs to the ultra high sulfur KAPs, which is important for hair formation and may have association with cashmere. Hoxc13 takes part in the formation of cashmere keratin and maintaining the normal structure of follicle. It has been reported that Hoxc13 gene exists binding site of KP and KAP genes at its promoter regions in mouse. So the expression of KAP9.2 and Hoxc13 genes was detected at anagen stage vs telogen stage by qRT-PCR. The data showed that KAP9.2 and Hoxc13 gene had similar expression trend at different stages, which indicated that there was interaction between them. KAP9.2 and Hoxc13 gene had lower expression level in anagen than that of in telogen of cashmere growth. In anagen, KAP9.2 and Hoxc13 expressed lower in high cashmere yield individuals than that of in low cashmere yield ones. In telogen, the result was reverse. The study would provide the evidence of involvement of KAP9.2 and Hoxc13 in hair periodic growth.

Autosomal recessive transmission of a rare KRT74 variant causes hair and nail ectodermal dysplasia: allelism with dominant woolly hair/hypotrichosis

Pure hair and nail ectodermal dysplasia (PHNED) comprises a heterogeneous group of rare heritable disorders characterized by brittle hair, hypotrichosis, onychodystrophy and micronychia. Autosomal recessive (AR) PHNED has previously been associated with mutations in either KRT85 or HOXC13 on chromosome 12p11.1-q14.3. We investigated a consanguineous Pakistani family with AR PHNED linked to the keratin gene cluster on 12p11.1 but without detectable mutations in KRT85 and HOXC13. Whole exome sequencing of affected individuals revealed homozygosity for a rare c.821T>C variant (p.Phe274Ser) in the KRT74 gene that segregates AR PHNED in the family. The transition alters the highly conserved Phe274 residue in the coil 1B domain required for long-range dimerization of keratins, suggesting that the mutation compromises the stability of intermediate filaments. Immunohistochemical (IHC) analyses confirmed a strong keratin-74 expression in the nail matrix, the nail bed and the hyponychium of mouse distal digits, as well as in normal human hair follicles. Furthermore, hair follicles and epidermis of an affected family member stained negative for Keratin-74 suggesting a loss of function mechanism mediated by the Phe274Ser substitution. Our observations show for the first time that homozygosity for a KRT74 missense variant may be associated with AR PHNED. Heterozygous KRT74 mutations have previously been associated with autosomal dominant woolly hair/hypotrichosis simplex (ADWH). Thus, our findings expand the phenotypic spectrum associated with KRT74 mutations and imply that a subtype of AR PHNED is allelic with ADWH.

Hair curvature: a natural dialectic and review

Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways, and others, can explain many alternatives and specific variations of hair bending phenotypes. Mechanisms for hair papilla budding or its division by bisection or fission can explain MPC formation. Epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) transitions, acting in collaboration with epithelial-mesenchymal communications are also considered as mechanisms affecting hair growth and its bending and twisting. These may be treated as sub-mechanisms of an overall development from neural-crest stem cell (NCSC) lineages to differentiated hair follicle (HF) cell types, thus providing a unified framework for hair growth and development.

CtBP1 overexpression in keratinocytes perturbs skin homeostasis

Carboxyl-terminal binding protein-1 (CtBP1) is a transcriptional co-repressor with multiple in vitro targets, but its in vivo functions are largely unknown. We generated keratinocyte-specific CtBP1 transgenic mice with a keratin 5 promoter (K5.CtBP1) to probe the pathological roles of CtBP1. At transgene expression levels comparable with endogenous CtBP1 in acute skin wounds, K5.CtBP1 epidermis displayed hyperproliferation, loss of E-cadherin, and failed terminal differentiation. Known CtBP1 target genes associated with these processes, e.g., p21, Brca1, and E-cadherin were down-regulated in K5.CtBP1 skin. Surprisingly, K5.CtBP1 pups also exhibited a hair loss phenotype. We found that expression of the Distal-less 3 (Dlx3), a critical regulator of hair follicle differentiation and cycling, was decreased in K5.CtBP1 mice. Molecular studies revealed that CtBP1 directly suppressed Dlx3 transcription. Consistently, K5.CtBP1 mice displayed abnormal hair follicles with decreased expression of Dlx3 downstream targets Gata3, Hoxc13, and hair keratins. In sum, this first CtBP1 transgenic model provides in vivo evidence for certain CtBP1 functions predicted from in vitro studies, reveals to our knowledge previously unreported functions and transcriptional activities of CtBP1 in the context of epithelial-mesenchymal interplay, and suggest CtBP1 has a pathogenesis role in hair follicle morphogenesis and differentiation.

A homozygous frameshift mutation in the HOXC13 gene underlies pure hair and nail ectodermal dysplasia in a Syrian family

Pure hair and nail ectodermal dysplasia (PHNED) is a rare genetic disorder characterized by hypotrichosis or complete alopecia, as well as nail dystrophy. Mutations in the type II hair keratin gene KRT85 and the HOXC13 gene on chromosome 12q have recently been identified in families with autosomal-recessive PHNED. In the present study, we have analyzed a consanguineous Syrian family with an affected girl having complete alopecia and nail dystrophy since birth. The family clearly showed linkage to chromosome 12q13.13-12q14.3, which excluded the KRT85 gene. Sequencing of another candidate gene HOXC13 within the linkage interval identified a homozygous frameshift mutation (c.355delC; p.Leu119Trpfs*20). Expression studies in cultured cells revealed that the mutant HOXC13 protein mislocalized within the cytoplasm, and failed to upregulate the promoter activities of its target genes. Our results strongly suggest crucial roles of the HOXC13 gene in the development of hair and nails in humans.

Loss-of-function mutations in HOXC13 cause pure hair and nail ectodermal dysplasia

Pure hair and nail ectodermal dysplasia (PHNED) is a congenital condition characterized by hypotrichosis and nail dystrophy. Autosomal-recessive PHNED has previously been mapped to chromosomal region 12q12-q14.1, which contains the type II hair keratin and HOXC clusters. Hoxc13-null mice are known to develop hair and nail defects very similar to those seen in human PHNED. We performed whole-exome sequencing in a consanguineous Chinese family affected by PHNED and identified a homozygous nonsense mutation (c.390C>A [p.Tyr130(∗)]) in HOXC13 in all affected individuals. In an additional affected female from a consanguineous Afghan family, we found a 27.6 kb homozygous microdeletion involving the first exon of HOXC13. We examined HOXC13 expression in scalp specimen obtained from the index individual of the Chinese family and detected dramatically reduced mRNA levels in skin tissue and nearly absent protein staining in hair follicles, suggesting a mechanism of nonsense-mediated mRNA decay. We also observed markedly decreased expression of four HOXC13 target genes in the specimen. Taken together, our results demonstrate that loss-of-function mutations in HOXC13 cause autosomal-recessive PHNED and further highlight the importance of HOXC13 in hair and nail development.

Alopecia in a viable phospholipase C delta 1 and phospholipase C delta 3 double mutant

BACKGROUND

Inositol 1,4,5trisphosphate (IP(3)) and diacylglycerol (DAG) are important intracellular signalling molecules in various tissues. They are generated by the phospholipase C family of enzymes, of which phospholipase C delta (PLCD) forms one class. Studies with functional inactivation of Plcd isozyme encoding genes in mice have revealed that loss of both Plcd1 and Plcd3 causes early embryonic death. Inactivation of Plcd1 alone causes loss of hair (alopecia), whereas inactivation of Plcd3 alone has no apparent phenotypic effect. To investigate a possible synergy of Plcd1 and Plcd3 in postnatal mice, novel mutations of these genes compatible with life after birth need to be found.

METHODOLOGY/PRINCIPAL FINDINGS

We characterise a novel mouse mutant with a spontaneously arisen mutation in Plcd3 (Plcd3(mNab)) that resulted from the insertion of an intracisternal A particle (IAP) into intron 2 of the Plcd3 gene. This mutation leads to the predominant expression of a truncated PLCD3 protein lacking the N-terminal PH domain. C3H mice that carry one or two mutant Plcd3(mNab) alleles are phenotypically normal. However, the presence of one Plcd3(mNab) allele exacerbates the alopecia caused by the loss of functional Plcd1 in Del(9)olt1Pas mutant mice with respect to the number of hair follicles affected and the body region involved. Mice double homozygous for both the Del(9)olt1Pas and the Plcd3(mNab) mutations survive for several weeks and exhibit total alopecia associated with fragile hair shafts showing altered expression of some structural genes and shortened phases of proliferation in hair follicle matrix cells.

CONCLUSIONS/SIGNIFICANCE

The Plcd3(mNab) mutation is a novel hypomorphic mutation of Plcd3. Our investigations suggest that Plcd1 and Plcd3 have synergistic effects on the murine hair follicle in specific regions of the body surface.

Increased HOX C13 expression in metastatic melanoma progression

BACKGROUND

The process of malignant transformation, progression and metastasis of melanoma is not completely understood. Recently, the microarray technology has been used to survey transcriptional differences that might provide insight into the metastatic process, but the validation of changing gene expression during metastatic transition period is poorly investigated. A large body of literature has been produced on the role of the HOX genes network in tumour evolution, suggesting the involvement of HOX genes in several types of human cancers. Deregulated paralogous group 13 HOX genes expression has been detected in melanoma, cervical cancer and odonthogenic tumors. Among these, Hox C13 is also involved in the expression control of the human keratin genes hHa5 and hHa2, and recently it was identified as a member of human DNA replication complexes.

METHODS

In this study, to investigate HOX C13 expression in melanoma progression, we have compared its expression pattern between naevi, primary melanoma and metastasis. In addition HOXC13 profile pattern of expression has been evaluated in melanoma cell lines.

RESULTS

Our results show the strong and progressive HOX C13 overexpression in metastatic melanoma tissues and cytological samples compared to nevi and primary melanoma tissues and cells.

CONCLUSIONS

The data presentated in the paper suggest a possible role of HOX C13 in metastatic melanoma switch.

Deregulated HOX genes in ameloblastomas are located in physical contiguity to keratin genes

The expression of the HOX gene network in mid-stage human tooth development mostly concerns the epithelial tooth germ compartment and involves the C and D HOX loci. To further dissect the HOX gene implication with tooth epithelium differentiation we compared the expression of the whole HOX network in human ameloblastomas, as paradigm of epithelial odontogenic tumors, with tooth germs. We identified two ameloblastoma molecular types with respectively low and high number of active HOX C genes. The highly expressing HOX C gene ameloblastomas were characterized by a strong keratinized phenotype. Locus C HOX genes are located on chromosome 12q13-15 in physical contiguity with one of the two keratin gene clusters included in the human genome. The most posterior HOX C gene, HOX C13, is capable to interact with hair keratin genes located on the other keratin gene cluster in physical contiguity with the HOX B locus on chromosome 17q21-22. Inside the HOX C locus, a 2.2 kb ncRNA (HOTAIR) able to repress transcription, in cis, along the entire HOX C locus and, in trans, at the posterior region of the HOX D locus has recently been identified. Interestingly both loci are deregulated in ameloblastomas. Our finding support an important role of the HOX network in characterizing the epithelial tooth compartment. Furthermore, the physical contiguity between locus C HOX and keratin genes in normal tooth epithelium and their deregulation in the neoplastic counterparts suggest they may act on the same mechanism potentially involved with epithelial tumorigenesis.

The nude mutant gene Foxn1 is a HOXC13 regulatory target during hair follicle and nail differentiation

Among the Hox genes, homeobox C13 (Hoxc13) has been shown to be essential for proper hair shaft differentiation, as Hoxc13 gene-targeted (Hoxc13(tm1Mrc)) mice completely lack external hair. Because of the remarkable overt phenotypic parallels to the Foxn1(nu) (nude) mutant mice, we sought to determine whether Hoxc13 and forkhead box N1 (Foxn1) might act in a common pathway of hair follicle (HF) differentiation. We show that the alopecia exhibited by both the Hoxc13(tm1Mrc) and Foxn1(nu) mice is because of strikingly similar defects in hair shaft differentiation and that both mutants suffer from a severe nail dystrophy. These phenotypic similarities are consistent with the extensive overlap between Hoxc13 and Foxn1 expression patterns in the HF and the nail matrix. Furthermore, DNA microarray analysis of skin from Hoxc13(tm1Mrc) mice identified Foxn1 as significantly downregulated along with numerous hair keratin genes. This Foxn1 downregulation apparently reflects the loss of direct transcriptional control by HOXC13 as indicated by our results obtained through co-transfection and chromatin immunoprecipitation (ChIP) assays. As presented in the discussion, these data support a regulatory model of keratinocyte differentiation in which HOXC13-dependent activation of Foxn1 is part of a regulatory cascade controlling the expression of terminal differentiation markers.

[Hoxc13 and the development of hair follicle]

Hoxc13 belongs to the Abd-B class of Hox gene family, which participated in the hair follicle formation and hair growth regulation process. The structural protein of hair KP (keratin) and KAP (keratin-associated protein) expression is under regulation of Hoxc13, and then changes the characteristics of hair by regulating the composition of these two types of hair proteins and maintaining the normal morphology of hair follicle. In this review, we summarized that the relationship between the expression level of Hoxc13 and hair follicle development/hair growth and the mechanisim under the controling of Hoxc13 and relevant genes.