Hair follicle-specific keratins and their diseases

Hair Growth-Promoting Effect of Hydrangea serrata (Thunb.) Ser. Extract and Its Active Component Hydrangenol: In Vitro and In Vivo Study

With the escalating prevalence of hair loss, the demand for effective hair loss treatment has surged. This study evaluated the effects of hot water extract of Hydrangea serrata (Thunb.) Ser. leaf (WHS) on hair growth, employing cell cultures, mice, and human skin organoid models. Both WHS and hydrangenol were found to enhance 5α-reductase inhibitory activity. WHS and hydrangenol have been shown to stimulate dermal papilla cell (DPC) growth, potentially through factors like keratinocyte growth factor (KGF), fibroblast growth factor 10 (FGF10), and transforming growth factor-β1 (TGF-β1). They also elevated the expression levels of keratin genes (K31 and K85) and the ceramide synthase (CerS3) gene, crucial clinical indicators of hair health. Furthermore, they exhibited notable anti-inflammatory and anti-androgenic properties by reducing the levels of tumor necrosis factor-α (TNF-α) and androgen signaling molecules, including androgen receptor (AR) and dickkopf-1 (DKK-1) gene expression. Oral administration of WHS to C57BL/6 mice for 3 weeks confirmed its hair growth-promoting effects, improving hair growth parameters and gene expression without significant changes in hair weight. Additionally, in a human skin organoid model, WHS was found to stimulate hair formation and augment the expression of follicle markers. These findings position WHS as a promising nutraceutical for promoting hair health, as evidenced by its efficacy in both in vitro and in vivo models.

The formulation and in vitro evaluation of WS Biotin, a novel encapsulated form of D-Biotin with improved water solubility for hair and skin treatment applications

OBJECTIVE

To develop and evaluate the efficacy of WS Biotin, a novel water-soluble form of D-Biotin, for cosmetic use.

METHODS

A new encapsulated form of D-Biotin was developed with the purpose of improving the water solubility of biotin. This novel form of encapsulated biotin was characterized by its physicochemical properties: particle size, D-Biotin content and solubility in water. Also, proliferation and gene expression in vitro tests in cell culture were performed to evaluate its effectiveness in promoting hair growth, an ELISA test was conducted for hair keratinization and skin lightening property was tested by analysing the intracellular melanin content.

RESULTS

The developed WS Biotin microcapsules exhibit a particle size range of 2-30 μm with D-Biotin content of ~50% (w/w). The water solubility of WS Biotin was found to be 20-fold greater than free biotin. The obtained in vitro results indicated that WS Biotin enhances the expression of hair-related keratins in hair follicle keratinocytes, as well as the expression of hair growth-promoting genes in dermal papilla cells. Moreover, the melanin content in UVA-exposed epidermal melanocytes was reduced upon exposure to WS Biotin.

CONCLUSION

In this work, a novel form of encapsulated biotin, WS Biotin, was developed in order to improve the water solubility of free biotin and was found to be effective for cosmetic use in both hair and skin applications.

Regulatory T cells in skin mediate immune privilege of the hair follicle stem cell niche

Immune tolerance is maintained in lymphoid organs (LOs). Despite the presence of complex immune cell networks in non-LOs, it is unknown whether self-tolerance is maintained in these tissues. We developed a technique to restrict genetic recombination to regulatory T cells (Tregs) only in skin. Selective depletion of skin Tregs resulted in T cell-mediated inflammation of hair follicles (HFs). Suppression did not rely on CTLA-4, but instead on high-affinity interleukin-2 (IL-2) receptor expression by skin Tregs, functioning exclusively in a cell-extrinsic manner. In a novel model of HF stem cell (HFSC)-driven autoimmunity, we reveal that skin Tregs immunologically protect the HFSC niche. Finally, we used spatial transcriptomics to identify aberrant IL-2 signaling at stromal-HF interfaces in a rare form of human alopecia characterized by HFSC destruction and alopecia areata. Collectively, these results reveal the fundamental biology of Tregs in skin uncoupled from the systemic pool and elucidate a mechanism of self-tolerance.

Spatial transcriptomics of a giant pilomatricoma

Pilomatricomas (PMs) are common benign adnexal tumors that show a predilection for the head and neck region and are characterized at the molecular level by activating mutations in the beta-catenin (CTNNB1) gene. Giant PMs are a rare histopathological variant, according to the World Health Organization, which are defined by a size greater than 4 cm and are reported to show upregulation of yes-associated protein compared to PMs of typical 1-3 cm size. We describe the case of a 67-year-old man with an 8 cm giant PM involving his temporal scalp, whose PM we characterized by 10X spatial gene expression analysis. This revealed five total transcriptomic clusters, including four distinct clusters within the giant PM, each with a unique transcriptional pattern of hair follicle-related factors, keratin gene expression, and beta-catenin pathway activity.

Spatial transcriptomic profiling reveals the pathophysiology of early-stage hidradenitis suppurativa

We investigated the role of the epithelium of nodules in Hurley stage I hidradenitis suppurativa (HS) by using spatial transcriptomics to analyse the profiles of epithelial cells and dermal-infiltrating immune cells. Compared with epidermal cysts, genes related to bacterial response, inflammatory mediators and neutrophil degranulation pathways were upregulated in the epithelial cells of early-stage HS nodules. Our analysis of dermal-infiltrating immune cells surrounding the epithelium of nodules revealed significantly elevated levels of B-cell-related genes. Similarly to the sinus tract formation observed in moderate-to-severe HS, we propose that the production of inflammatory mediators in early-stage HS may involve the activation of keratinocytes and their interaction with dermal-infiltrating immune cells.

Recent advances in the genetics of alopecia areata

Alopecia areata (AA) is a common autoimmune-mediated hair loss disorder in humans with an estimated lifetime risk of approximately 2 %. Episodes of hair loss usually begin with isolated hairless patches that may progress to complete hair loss over the entire body. A familial occurrence of AA is well established, with recurrence risks of about 6-8 % in first-degree relatives. AA is a multifactorial disorder involving both environmental and genetic risk factors. Previous research has identified 14 susceptibility loci, most of which implicate genes involved in the immune response. The following review presents a summary of the latest findings from genome-wide association, sequencing and gene expression studies of AA, as well as their contribution to the recent therapeutic developments.

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.

DNA and protein analyses of hair in forensic genetics

Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.

DNA dioxygenases Tet2/3 regulate gene promoter accessibility and chromatin topology in lineage-specific loci to control epithelial differentiation

Execution of lineage-specific differentiation programs requires tight coordination between many regulators including Ten-eleven translocation (TET) family enzymes, catalyzing 5-methylcytosine oxidation in DNA. Here, by using Keratin 14-Cre-driven ablation of Tet genes in skin epithelial cells, we demonstrate that ablation of Tet2/Tet3 results in marked alterations of hair shape and length followed by hair loss. We show that, through DNA demethylation, Tet2/Tet3 control chromatin accessibility and Dlx3 binding and promoter activity of the Krt25 and Krt28 genes regulating hair shape, as well as regulate interactions between the Krt28 gene promoter and distal enhancer. Moreover, Tet2/Tet3 also control three-dimensional chromatin topology in Keratin type I/II gene loci via DNA methylation-independent mechanisms. These data demonstrate the essential roles for Tet2/3 in establishment of lineage-specific gene expression program and control of Dlx3/Krt25/Krt28 axis in hair follicle epithelial cells and implicate modulation of DNA methylation as a novel approach for hair growth control.

Investigating the morphology and genetics of scalp and facial hair characteristics for phenotype prediction

Microscopic traits and ultrastructure of hair such as cross-sectional shape, pigmentation, curvature, and internal structure help determine the level of variations between and across human populations. Apart from cosmetics and anthropological applications, such as determining species, somatic origin (body area), and biogeographic ancestry, the evidential value of hair has increased with rapid progression in the area of forensic DNA phenotyping (FDP). Individuals differ in the features of their scalp hair (greying, shape, colour, balding, thickness, and density) and facial hair (eyebrow thickness, monobrow, and beard thickness) features. Scalp and facial hair characteristics are genetically controlled and lead to visible inter-individual variations within and among populations of various ethnic origins. Hence, these characteristics can be exploited and made more inclusive in FDP, thereby leading to more comprehensive, accurate, and robust prediction models for forensic purposes. The present article focuses on understanding the genetics of scalp and facial hair characteristics with the goal to develop a more inclusive approach to better understand hair biology by integrating hair microscopy with genetics for genotype-phenotype correlation research.

Talquetamab, a T-Cell-Redirecting GPRC5D Bispecific Antibody for Multiple Myeloma

BACKGROUND

G protein-coupled receptor, family C, group 5, member D (GPRC5D) is an orphan receptor expressed in malignant plasma cells. Talquetamab, a bispecific antibody against CD3 and GPRC5D, redirects T cells to mediate killing of GPRC5D-expressing myeloma cells.

METHODS

In a phase 1 study, we evaluated talquetamab administered intravenously weekly or every other week (in doses from 0.5 to 180 μg per kilogram of body weight) or subcutaneously weekly, every other week, or monthly (5 to 1600 μg per kilogram) in patients who had heavily pretreated relapsed or refractory multiple myeloma that had progressed with established therapies (a median of six previous lines of therapy) or who could not receive these therapies without unacceptable side effects. The primary end points - the frequency and type of dose-limiting toxic effects (study part 1 only), adverse events, and laboratory abnormalities - were assessed in order to select the recommended doses for a phase 2 study.

RESULTS

At the data-cutoff date, 232 patients had received talquetamab (102 intravenously and 130 subcutaneously). At the two subcutaneous doses recommended for a phase 2 study (405 μg per kilogram weekly [30 patients] and 800 μg per kilogram every other week [44 patients]), common adverse events were cytokine release syndrome (in 77% and 80% of the patients, respectively), skin-related events (in 67% and 70%), and dysgeusia (in 63% and 57%); all but one cytokine release syndrome event were of grade 1 or 2. One dose-limiting toxic effect of grade 3 rash was reported in a patient who had received talquetamab at the 800-μg dose level. At median follow-ups of 11.7 months (in patients who had received talquetamab at the 405-μg dose level) and 4.2 months (in those who had received it at the 800-μg dose level), the percentages of patients with a response were 70% (95% confidence interval [CI], 51 to 85) and 64% (95% CI, 48 to 78), respectively. The median duration of response was 10.2 months and 7.8 months, respectively.

CONCLUSIONS

Cytokine release syndrome, skin-related events, and dysgeusia were common with talquetamab treatment but were primarily low-grade. Talquetamab induced a substantial response among patients with heavily pretreated relapsed or refractory multiple myeloma. (Funded by Janssen Research and Development; MonumenTAL-1 ClinicalTrials.gov number, NCT03399799.).

The Mechanisms of Fur Development and Color Formation in American Mink Revealed Using Comparative Transcriptomics

American mink fur is an important economic product, but the molecular mechanisms underlying its color formation and fur development remain unclear. We used RNA-seq to analyze the skin transcriptomes of young and adult mink with two different hair colors. The mink comprised black adults (AB), white adults (AW), black juveniles (TB), and white juveniles (TW) (three each). Through pair comparison and cross-screening among different subgroups, we found that 13 KRTAP genes and five signaling pathways (the JAK-STAT signaling pathway (cfa04630), signaling pathways regulating pluripotency of stem cells (cfa04550), ECM-receptor interaction (cfa04512), focal adhesion (cfa04510), and the Ras signaling pathway (cfa04014)) were related to mink fur development. We also found that members of a tyrosinase family (TYR, TYRP1, and TYRP2) are involved in mink hair color formation. The expression levels of TYR were higher in young black mink than in young white mink, but this phenomenon was not observed in adult mink. Our study found significant differences in adult and juvenile mink skin transcriptomes, which may shed light on the mechanisms of mink fur development. At the same time, the skin transcriptomes of black and white mink also showed differences, with the results varying by age, suggesting that the genes regulating hair color are active in early development rather than in adulthood. The results of this study provide molecular support in breeding for mink coat color and improving fur quality.

Non-invasive human skin transcriptome analysis using mRNA in skin surface lipids

Non-invasive acquisition of mRNA data from the skin can be extremely useful for understanding skin physiology and diseases. Inspired by the holocrine process, in which the sebaceous glands secrete cell contents into the sebum, we focused on the possible presence of mRNAs in skin surface lipids (SSLs). We found that measurable levels of human mRNAs exist in SSLs, where the sebum protects them from degradation by RNases. The AmpliSeq transcriptome analysis was modified to measure SSL-RNA levels, and our results revealed that the SSL-RNAs predominantly comprised mRNAs derived from sebaceous glands, the epidermis, and hair follicles. Analysis of SSL-RNAs non-invasively collected from patients with atopic dermatitis revealed increased expression of inflammation-related genes and decreased expression of terminal differentiation-related genes, consistent with the results of previous reports. Further, we found that lipid synthesis-related genes were downregulated in the sebaceous glands of patients with atopic dermatitis. These results indicate that the analysis of SSL-RNAs is a promising strategy to understand the pathophysiology of skin diseases.

Inoue et al develop a non-invasive method of analyzing human skin mRNA using RNA in skin surface lipids collected with oil-blotting films. The authors outline the validation of this methodology and describe an application to determine transcriptome in skin surface lipids in patients with atopic dermatitis versus healthy skin.

Single-Cell Transcriptomics Reveals the Molecular Anatomy of Sheep Hair Follicle Heterogeneity and Wool Curvature

Wool is the critical textile raw material which is produced by the hair follicle of sheep. Therefore, it has important implications to investigate the molecular mechanism governing hair follicle development. Due to high cellular heterogeneity as well as the insufficient cellular, molecular, and spatial characterization of hair follicles on sheep, the molecular mechanisms involved in hair follicle development and wool curvature of sheep remains largely unknown. Single-cell RNA sequencing (scRNA-seq) technologies have made it possible to comprehensively dissect the cellular composition of complex skin tissues and unveil the differentiation and spatial signatures of epidermal and hair follicle development. However, such studies are lacking so far in sheep. Here, single-cell suspensions from the curly wool and straight wool lambskins were prepared for unbiased scRNA-seq. Based on UAMP dimension reduction analysis, we identified 19 distinct cell populations from 15,830 single-cell transcriptomes and characterized their cellular identity according to specific gene expression profiles. Furthermore, novel marker gene was applied in identifying dermal papilla cells isolated in vitro. By using pseudotime ordering analysis, we constructed the matrix cell lineage differentiation trajectory and revealed the dynamic gene expression profiles of matrix progenitors' commitment to the hair shaft and inner root sheath (IRS) cells. Meanwhile, intercellular communication between mesenchymal and epithelial cells was inferred based on CellChat and the prior knowledge of ligand–receptor pairs. As a result, strong intercellular communication and associated signaling pathways were revealed. Besides, to clarify the molecular mechanism of wool curvature, differentially expressed genes in specific cells between straight wool and curly wool were identified and analyzed. Our findings here provided an unbiased and systematic view of the molecular anatomy of sheep hair follicle comprising 19 clusters; revealed the differentiation, spatial signatures, and intercellular communication underlying sheep hair follicle development; and at the same time revealed the potential molecular mechanism of wool curvature, which will give important new insights into the biology of the sheep hair follicle and has implications for sheep breeding.

Essential Role of STAT3 Signaling in Hair Follicle Homeostasis

Dominant-negative mutations associated with signal transducer and activator of transcription 3 (STAT3) signaling, which controls epithelial proliferation in various tissues, lead to atopic dermatitis in hyper IgE syndrome. This dermatitis is thought to be attributed to defects in STAT3 signaling in type 17 helper T cell　specification. However, the role of STAT3 signaling in skin epithelial cells remains unclear. We found that STAT3 signaling in keratinocytes is required to maintain skin homeostasis by negatively controlling the expression of hair follicle-specific keratin genes. These expression patterns correlated with the onset of dermatitis, which was observed in specific pathogen-free conditions but not in germ-free conditions, suggesting the involvement of Toll-like receptor-mediated inflammatory responses. Thus, our study suggests that STAT3-dependent gene expression in keratinocytes plays a critical role in maintaining the homeostasis of skin, which is constantly exposed to microorganisms.

An integrated scalp and blood biomarker approach suggests the systemic nature of alopecia areata

BACKGROUND

Alopecia areata (AA) is characterized by immune dysregulation in both scalp and blood, but a large-scale approach establishing biomarkers of AA incorporating both scalp tissue and serum compartments is lacking. We aimed to characterize the transcriptomic signature of AA lesional and nonlesional scalp compared to healthy scalp and determine its relationship with the blood proteome in the same individuals, with comparative correlations to clinical AA disease severity.

METHODS

We evaluated lesional and nonlesional scalp tissues and serum from patients with moderate-to-severe AA (n = 18) and healthy individuals (n = 8). We assessed 33,118 genes in AA scalp tissue using RNAseq transcriptomic evaluation and 340 inflammatory proteins in serum using OLINK high-throughput proteomics. Univariate and multivariate approaches were used to correlate disease biomarkers with Severity of Alopecia Tool (SALT).

RESULTS

A total of 608 inflammatory genes were differentially expressed in lesional AA scalp (fold change/FCH>1.5, false discovery rate/FDR<0.05) including Th1 (IFNG/IL12B/CXCL11), Th2 (IL13/CCL18), and T-cell activation-related (ICOS) products. Th1/Th2-related markers were significantly correlated with AA clinical severity in lesional/nonlesional tissue, while keratins (KRT35/KRT83/KRT81) were significantly downregulated in lesional compared to healthy scalp (p < .05). Expression of cardiovascular/atherosclerosis-related markers (MMP9/CCL2/IL1RL1/IL33R/ST2/AGER) in lesional scalp correlated with their corresponding serum expression (p < .05). AA scalp demonstrated significantly greater biomarker dysregulation compared to blood. An integrated multivariate approach combining scalp and serum biomarkers improved correlations with disease severity/SALT.

CONCLUSION

This study contributes a unique understanding of the phenotype of moderate-to-severe AA with an integrated scalp and serum biomarker model suggesting the systemic nature of the disease, advocating for the need for immune-based systemic treatment.

Syndecan-1 shedding by meprin β impairs keratinocyte adhesion and differentiation in hyperkeratosis

Dysregulation of proteolytic enzymes has huge impact on epidermal homeostasis, which can result in severe pathological conditions such as fibrosis or Netherton syndrome. The metalloprotease meprin β was found to be upregulated in hyperproliferative skin diseases. AP-1 transcription factor complex has been reported to induce Mep1b expression. Since AP-1 and its subunit fos-related antigen 2 (fra-2) are associated with the onset and progression of psoriasis, we wanted to investigate if this could partially be attributed to increased meprin β activity. Here, we demonstrate that fra-2 transgenic mice show increased meprin β expression and proteolytic activity in the epidermis. To avoid influence by other fra-2 regulated genes, we additionally generated a mouse model that enabled tamoxifen-inducible expression of meprin β under the Krt5-promotor to mimic the pathological condition. Interestingly, induced meprin β expression in the epidermis resulted in hyperkeratosis, hair loss and mottled pigmentation of the skin. Employing N-terminomics revealed syndecan-1 as a substrate of meprin β in skin. Shedding of syndecan-1 at the cell surface caused delayed calcium-induced differentiation and impaired adhesion of keratinocytes, which was blocked by the meprin β inhibitor fetuin-B.

Human iPS Cell-Derived Cell Aggregates Exhibited Dermal Papilla Cell Properties in in vitro Three-Dimensional Assemblage Mimicking Hair Follicle Structures

Current approaches for human hair follicle (HF) regeneration mostly adopt cell-autonomous tissue reassembly in a permissive murine intracorporeal environment. This, together with the limitation in human-derived trichogenic starting materials, potentially hinders the bioengineering of human HF structures, especially for the drug discovery and treatment of hair loss disorders. In this study, we attempted to reproduce the anatomical relationship between an epithelial main body and the dermal papilla (DP) within HF in vitro by three-dimensionally assembling columnarly molded human keratinocytes (KCs) and the aggregates of DP cells and evaluated how HF characteristics were reproduced in the constructs. The replaceability of human-induced pluripotent stem cell (hiPSC)-derived DP substitutes was assessed using the aforementioned reconstruction assay. Human DP cell aggregates were embedded into Matrigel as a cluster. Subsequently, highly condensed human KCs were cylindrically injected onto DP spheroids. After 2-week culture, the structures visually mimicking HFs were obtained. KC-DP constructs partially reproduced HF microanatomy and demonstrated differential keratin (KRT) expression pattern in HFs: KRT14 in the outermost part and KRT13, KRT17, and KRT40, respectively, in the inner portion of the main body. KC-DP constructs tended to upregulate HF-related genes, KRT25, KRT33A, KRT82, WNT5A, and LEF1. Next, DP substitutes were prepared by exposing hiPSC-derived mesenchymal cells to retinoic acid and subsequently to WNT, BMP, and FGF signal activators, followed by cell aggregation. The resultant hiPSC-derived DP substitutes (iDPs) were combined with KCs in the invented assay. KC-iDP constructs morphologically resemble KC-DP constructs and analogously mimicked KRT expression pattern in HF. iDP in the constructs expressed DP-related markers, such as vimentin and versican. Intriguingly, KC-iDP constructs more intensely expressed KRT33A, KRT82, and LEF1, which were stepwisely upregulated by the addition of WNT ligand and the mixture of WNT, SHH, and EDA signaling activators, supporting the idea that iDP exhibited biological properties analogous to DP cell aggregates in the constructs in vitro. These preliminary findings suggested the possibility of regenerating DP equivalents with in vitro hair-inductive capacity using hiPSC-derived cell composites, which potentially reduce the necessity of human tissue-derived trichogenic cell subset and eventually allow xeno-free bioengineering of human HFs.

Rescuing key native traits in cultured dermal papilla cells for human hair regeneration

Introduction

The dermal papilla (DP) represents the major regulatory entity within the hair follicle (HF), inducing hair formation and growth through reciprocal interactions with epithelial cells. However, human DP cells rapidly lose their hair inductive ability when cultured in an epithelium-deficient environment.

Objectives

To determine if the conditioned medium collected from interfollicular keratinocytes (KCs-CM) is capable of improving DP cell native properties and inductive phenotype.

Methods

DP cells were cultured with KCs-CM both in 2D and 3D culture conditions (spheroids). Further, the hair-inductive capacity of DP cells precultured with KCs-CM was tested in a hair reconstitution assay, after co-grafting with human keratinocytes in nude mice.

Results

We demonstrate that KCs-CM contributes to restore the inductivity of cultured human DP cells in a more effective mode than the conventional 3D-cultures. This is supported by the higher active alkaline phosphatase (ALP) levels in DP cells, the improved self-aggregative capacity and the reduced expression of α-SMA and the V1-isoform of versican. Moreover, DP cells cultured with KCs-CM displayed a secretome profile (VEGF, BMP2, TGF- β1, IL-6) that matches the one observed during anagen. KCs-CM also enhanced DP cell proliferation, while preventing cells to undergo morphological changes characteristic of high passage cells. In opposition, the amount of collagenous and non-collagenous proteins deposited by DP cells was lower in the presence of KCs-CM. The improvement in ALP activity was maintained in 3D spheroidal cultures, even after KCs-CM retrieval, being superior to the effect of the gold-standard culture conditions. Moreover, DP cells cultured with KCs-CM and grafted with human keratinocytes supported the formation of HF- and sebaceous gland-like structures in mice.

Conclusion

The proposed strategy encourages future cell-based strategies for HF regeneration not only in the context of hair-associated disorders, but also in the management of wounds to aid in restoring critical skin regulatory appendages.

De novo filament formation by human hair keratins K85 and K35 follows a filament development pattern distinct from cytokeratin filament networks

In human hair follicles, the hair‐forming cells express 16 hair keratin genes depending on the differentiation stages. K85 and K35 are the first hair keratins expressed in cortical cells at the early stage of the differentiation. Two types of mutations in the gene encoding K85 are associated with ectodermal dysplasia of hair and nail type. Here, we transfected cultured SW‐13 cells with human K85 and K35 genes and characterized filament formation. The K85–K35 pair formed short filaments in the cytoplasm, which gradually elongated and became thicker and entangled around the nucleus, indicating that K85–K35 promotes lateral association of short intermediate filaments (IFs) into bundles but cannot form IF networks in the cytoplasm. Of the K85 mutations related to ectodermal dysplasia of hair and nail type, a two‐nucleotide (C¹⁴⁴⁸T¹⁴⁴⁹) deletion (delCT) in the protein tail domain of K85 interfered with the K85–K35 filament formation and gave only aggregates, whereas a missense mutation (233A>G) that replaces Arg⁷⁸ with His (R78H) in the head domain of K85 did not interfere with the filament formation. Transfection of cultured MCF‐7 cells with all the hair keratin gene combinations, K85–K35, K85(R78H)–K35 and K85(delCT)–K35, as well as the individual hair keratin genes, formed well‐developed cytoplasmic IF networks, probably by incorporating into the endogenous cytokeratin IF networks. Thus, the unique de novo assembly properties of the K85–K35 pair might play a key role in the early stage of hair formation.

CCL13 is upregulated in alopecia areata lesions and is correlated with disease severity

Alopecia areata (AA) is a multi-factors disease characterized by non-scarring hair loss. AA could be classified into three main clinical phenotypes including patchy type AA (AAP), alopecia totalis (AT) and alopecia universalis (AU) based on the severity and areas of hair loss. Recent studies suggested immunological factor was critical in AA, but the precise aetiology and pathogenesis of AA still need exploration. In the work, we screened two gene expression profiles (GSE45512 and GSE68801) from Gene Expression Omnibus (GEO). Based on the two data sets, 10 upregulated genes and 107 downregulated genes in AA skin biopsies were identified. CCL13, as one of the remarkably upregulated genes, was found to have potential biological functions in aberrant immune response of AA according to the GO and KEGG analyses. The PPI network showed CCL13 was associated with multiple immune-related genes. The expression of CCL13 was increased depending on the severity of disease in AA patients. Cytotoxic lymphocytes, T cells and myeloid dendritic cells accumulated remarkably in scalp tissue depending on the severity of AA, and CCL13 was significantly correlated to cytotoxic lymphocytes, T cells and myeloid dendritic cells in AA patients. Our RT-PCR and ELISA results found CCL13 was upregulated in skin biopsy and serum of AA patients, and the immunohistochemistry (IHC) detection showed CCL13 was expressed by both the hair follicle epithelium and infiltrating immune cells. In conclusion, the upregulated of CCL13 and subsequent immune cell infiltration was related to AA, which could be a promising target for diagnosis and therapy in AA patients.

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.

The microfollicle: a model of the human hair follicle for in vitro studies

Access to complex in vitro models that recapitulate the unique markers and cell-cell interactions of the hair follicle is rather limited. Creation of scalable, affordable, and relevant in vitro systems which can provide predictive screens of cosmetic ingredients and therapeutic actives for hair health would be highly valued. In this study, we explore the features of the microfollicle, a human hair follicle organoid model based on the spatio-temporally defined co-culture of primary cells. The microfollicle provides a 3D differentiation platform for outer root sheath keratinocytes, dermal papilla fibroblasts, and melanocytes, via epidermal-mesenchymal-neuroectodermal cross-talk. For assay applications, microfollicle cultures were adapted to 96-well plates suitable for medium-throughput testing up to 21 days, and characterized for their spatial and lineage markers. The microfollicles showed hair-specific keratin expression in both early and late stages of cultivation. The gene expression profile of microfollicles was also compared with human clinical biopsy samples in response to the benchmark hair-growth compound, minoxidil. The gene expression changes in microfollicles showed up to 75% overlap with the corresponding gene expression signature observed in the clinical study. Based on our results, the cultivation of the microfollicle appears to be a practical tool for generating testable insights for hair follicle development and offers a complex model for pre-clinical substance testing.

ERK1/2 Pathway Is Involved in the Enhancement of Fatty Acids from Phaeodactylum tricornutum Extract (PTE) on Hair Follicle Cell Proliferation

Extractions from Phaeodactylum tricornutum have been widely studied and evaluated to various biological effects. The aim of this study was to investigate the promotional effect of P. tricornutum extract (PTE) on the ERK1/2 signaling pathway involved in hair follicle cell proliferation. In order to illuminate the enhancement of PTE on hair growth by promoting proliferation of hair follicle cells, the activities of human hair follicle outer root sheath cell (HFORSC), human hair follicle germinal matrix cells (HFGMC), and hair epithelial melanocytes (HEM) were observed under PET treatment. Levels of keratins, PKCζ, ERK1/2, and p38 MAPK in hair follicle cells were determined by Western blotting to illustrate the mechanisms of PTE effects on hair growth. Analyzed by GC-MS, the main polyunsaturated fatty acids which were 9.43% of total fatty acids in PTE were linolenic acid, linoleic acid, eicosapentaenoic acid, and docosahexaenoic acid. Melanin content and tyrosinase activity in HEM were measured. The results showed that PTE exhibited remarkable enhancement on cell proliferation. Melanin production was inhibited by PTE treatment, while keratin-14, keratin-15, and keratin-17 levels on hair follicle cells were elevated at different concentrations. The promotions of ERK1/2 and p38 MAPK levels indicated that the ERK1/2 signaling pathway is involved in the proliferation of hair follicle cells. These results are the evidence that PTE potentially deserves further study as a new natural candidate for hair care applications.

Alopecia areata susceptibility variant in MHC region impacts expressions of genes contributing to hair keratinization and is involved in hair loss

Background

Alopecia areata (AA) is considered a highly heritable, T-cell-mediated autoimmune disease of the hair follicle. However, no convincing susceptibility gene has yet been pinpointed in the major histocompatibility complex (MHC), a genome region known to be associated with AA as compared to other regions.

Methods

We engineered mice carrying AA risk allele identified by haplotype sequencing for the MHC region using allele-specific genome editing with the CRISPR/Cas9 system. Finally, we performed functional evaluations in the mice and AA patients with and without the risk allele.

Findings

We identified a variant (rs142986308, p.Arg587Trp) in the coiled-coil alpha-helical rod protein 1 (CCHCR1) gene as the only non-synonymous variant in the AA risk haplotype. Furthermore, mice engineered to carry the risk allele displayed a hair loss phenotype. Transcriptomics further identified CCHCR1 as a novel component interacting with hair cortex keratin in hair shafts. Both, these alopecic mice and AA patients with the risk allele displayed morphologically impaired hair and comparable differential expression of hair-related genes, including hair keratin and keratin-associated proteins (KRTAPs).

Interpretation

Our results implicate CCHCR1 with the risk allele in a previously unidentified subtype of AA based on aberrant keratinization in addition to autoimmune events.

Funding

This work was supported by JSPS KAKENHI (JP16K10177) and the NIHR UCLH Biomedical Research center (BRC84/CN/SB/5984).

Keratin 86 is up-regulated in the uterus during implantation, induced by oestradiol

Background

Uterine receptivity is one of the determinants of embryo implantation, which is responsible for pregnancy success. Aberrant embryo implantation due to disrupted uterine receptivity is usually found in ovarian hyperstimulation induced hyperoestrogen patients.

Results

This study identified keratin 86 (KRT86), a fibrous structural protein, which was upregulated in uterine endometrium during peri-implantation. Using a hyperoestrogen mouse model established in a previous study, we found abnormal oestradiol (E2) levels during pre-implantation could trigger high expression of Krt86 in the uterine epithelium. In an ovariectomised mouse model, combining oestrogen receptors ERα and ERβ knockout mice models, uterine Krt86 was found to be up-regulated after E2 treatment, mediated by nuclear ERα. Furthermore, we found progesterone (P4) could ameliorate Krt86 expression, induced by abnormal E2.

Conclusions

These results revealed the dynamic expression and regulation of Krt86, especially in hyperoestrogen treated mice, indicating it might act as a marker for non-receptive uterus.

Induction of Hair Keratins Expression by an Annurca Apple-Based Nutraceutical Formulation in Human Follicular Cells

Hair disorders may considerably impact the social and psychological well-being of an individual. Recent advances in the understanding the biology of hair have encouraged the research and development of novel and safer natural hair growth agents. In this context, we have previously demonstrated—at both preclinical and clinical level—that an Annurca apple-based dietary supplement (AMS), acting as a nutraceutical, is endowed with an intense hair-inductive activity (trichogenicity), at once increasing hair tropism and keratin content. Herein, in the framework of preclinical investigations, new experiments in primary human models of follicular keratinocytes and dermal papilla cells have been performed to give an insight around AMS biological effects on specific hair keratins expression. As well as confirming the biocompatibility and the antioxidant proprieties of our nutraceutical formulation, we have proven an engagement of trichokeratins production underlying its biological effects on human follicular cells. Annurca apples are particularly rich in oligomeric procyanidins, natural polyphenols belonging to the broader class of bioflavonoids believed to exert many beneficial health effects. To our knowledge, none of the current available remedies for hair loss has hitherto shown to stimulate the production of hair keratins so clearly.

Ubiquitously Expressed Proteins and Restricted Phenotypes: Exploring Cell-Specific Sensitivities to Impaired tRNA Charging

Aminoacyl-tRNA synthetases (ARS) are ubiquitously expressed, essential enzymes that charge tRNA with cognate amino acids. Variants in genes encoding ARS enzymes lead to myriad human inherited diseases. First, missense alleles cause dominant peripheral neuropathy. Second, missense, nonsense, and frameshift alleles cause recessive multisystem disorders that differentially affect tissues depending on which ARS is mutated. A preponderance of evidence has shown that both phenotypic classes are associated with loss-of-function alleles, suggesting that tRNA charging plays a central role in disease pathogenesis. However, it is currently unclear how perturbation in the function of these ubiquitously expressed enzymes leads to tissue-specific or tissue-predominant phenotypes. Here, we review our current understanding of ARS-associated disease phenotypes and discuss potential explanations for the observed tissue specificity.

Human basal cell carcinoma: the induction of anagen hair follicle differentiation

BACKGROUND

Consistent with cancer stem cell driven pattern of growth, human basal cell carcinomas (BCCs) demonstrate differentiation along hair follicle (HF) lineages.

AIM

To define the pattern of differentiation and therapeutic targets that promote BCC differentiation and therefore BCC cancer stem cell exhaustion.

METHODS

An alkaline phosphatase substrate kit was used to determine dermal papilla cells within the BCC stroma. Autonomous HF cycle-dependent gene expression was identified by analysis of the human homologues of a murine gene set (total 2289 genes) that is differentially expressed in hair cycle phases. The findings were validated by quantitative real-time PCR and immunofluorescence, as well as in vitro transforming growth factor (TGF)-β2 stimulation of BCC cancer stem cell colonies.

RESULTS

As in the HF, keratin expression in the inner root sheath and matrix in BCC correlated with proliferative index and was tightly regulated, despite the absence of dermal papilla cells. Cross-species microarray analysis comparing human BCC and murine synchronous HF growth cycle datasets revealed 74% concordance with telogen differentiation compared with anagen (23%, P < 0.01) and catagen (49%; P < 0.01). Incomplete anagen differentiation within BCC was characterized by reduced expression of the anagen master regulator DLX3 (-5.5-fold), and increased expression of telogen-associated genes: AEBP1 (2.2-fold), DEFB8 (35.3-fold), MMP3 (106.0-fold) and MMP12 (12.9-fold). Restoration of dermal papilla signals by in vitro addition of TGF-β2 enhanced anagen differentiation.

CONCLUSION

Our findings show that BCC cells differentiate along HF lineages and may be susceptible to exogenous HF cycle modulators.

Hair Growth Promoting Effect of 4HGF Encapsulated with PGA Nanoparticles (PGA-4HGF) by β-Catenin Activation and Its Related Cell Cycle Molecules

Poly-γ-glutamic acid (γ-PGA)-based nanoparticles draw remarkable attention as drug delivery agents due to their controlled release characteristics, low toxicity, and biocompatibility. 4HGF is an herbal mixture of Phellinus linteus grown on germinated brown rice, Cordyceps militaris grown on germinated soybeans, Polygonum multiflorum, Ficus carica, and Cocos nucifera oil. Here, we encapsulated 4HGF within PGA-based hydrogel nanoparticles, prepared by simple ionic gelation with chitosan, to facilitate its penetration into hair follicles (HFs). In this study, we report the hair promoting activity of 4HGF encapsulated with PGA nanoparticles (PGA-4HGF) and their mechanism, compared to 4HGF alone. The average size of spherical nanoparticles was ~400 nm in diameter. Continuous release of PGA-4HGF was observed in a simulated physiological condition. As expected, PGA-4HGF treatment increased hair length, induced earlier anagen initiation, and elongated the duration of the anagen phase in C57BL/6N mice, compared with free 4HGF treatment. PGA-4HGF significantly increased dermal papilla cell proliferation and induced cell cycle progression. PGA-4HGF also significantly increased the total amount of β-catenin protein expression, a stimulator of the anagen phase, through induction of cyclinD1 and CDK4 protein levels, compared to free 4HGF treatment. Our findings underscore the potential of PGA nanocapsules to efficiently deliver 4HGF into HFs, hence promoting hair-growth. Therefore, PGA-4HGF nanoparticles may be promising therapeutic agents for hair growth disorders.

Porcine keratin 75 in developing enamel

OBJECTIVE

To provide in vivo biochemical evidence for the isolation, identification, and characterization of porcine keratin 75 (K75) in developing enamel.

METHODS

Immunolocalization of K75 was observed in mandibles from mice at postnatal days 5 and 11. K75 gene expression was analyzed by quantitative reverse transcription-polymerase chain reaction using enamel organ epithelium (EOE) of incisors from pigs at 5 months of age. Enamel protein was extracted and isolated from both immature and mature enamel of second molars from 5-month-old pigs, and the K75 antibody-positive fraction was analyzed by liquid chromatography-mass spectrometry (LC-MS/MS). In vitro protease digestion of K75-antibody-positive fraction was carried out using porcine kallikrein 4 (pKLK4) or recombinant human enamelysin (rhMMP20) and their degradation patterns were characterized by both SDS-PAGE and western blotting.

RESULTS

Specific immunostaining for K75 was restricted to the layers of stratum intermedium and the enamel side of ameloblasts in mice at postnatal day 5, and to the papillary layer at postnatal day 11. Porcine K75 was expressed throughout enamel formation, but its transcript levels were significantly higher in the transition EOE than in the secretory- and maturation-stage EOE. Porcine K75 was extracted from the neutral soluble fraction from both immature and mature enamel. It was identified by LC-MS/MS analysis, and was found not to be degraded by either pKLK4 or rhMMP20.

CONCLUSION

We propose that K75 is present in the developing enamel and undergoes different processing/degradation compared to other enamel proteins.

DOX-Conjugated keratin nanoparticles for pH-Sensitive drug delivery

Keratin is a good candidate for drug carrier due to its good biocompatibility, low immunogenicity, redox responsiveness, and abundant renewable sources. Herein, doxorubicin (DOX) was first conjugated with keratin through a pH-sensitive hydrazone linkage, and then prepared into particulate drug carrier via desolvation method. The size, morphology, and surface potential of keratin-DOX nanoparticles (KDNPs) were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The drug release results showed that KDNPs performed an excellent pH-sensitive behavior under acidic tumor microenvironment. Cytotoxicity assay by MTT confirmed that KDNPs exhibited the enhanced cytotoxicity against A549 cells. Furthermore, KDNPs had higher therapeutic efficiency in vivo than free DOX. Hemolysis assay indicated that KDNPs was blood compatible. All the results identified that KDNPs are well suited as an ideal drug carrier.

Hair Proteome Variation at Different Body Locations on Genetically Variant Peptide Detection for Protein-Based Human Identification

Human hair contains minimal intact nuclear DNA for human identification in forensic and archaeological applications. In contrast, proteins offer a pathway to exploit hair evidence for human identification owing to their persistence, abundance, and derivation from DNA. Individualizing single nucleotide polymorphisms (SNPs) are often conserved as single amino acid polymorphisms in genetically variant peptides (GVPs). Detection of GVP markers in the hair proteome via high-resolution tandem mass spectrometry permits inference of SNPs with known statistical probabilities. To adopt this approach for forensic investigations, hair proteomic variation and its effects on GVP identification must first be characterized. This research aimed to assess variation in single-inch head, arm, and pubic hair, and discover body location-invariant GVP markers to distinguish individuals. Comparison of protein profiles revealed greater body location-specific variation in keratin-associated proteins and intracellular proteins, allowing body location differentiation. However, robust GVP markers derive primarily from keratins that do not exhibit body location-specific differential expression, supporting GVP identification independence from hair proteomic variation at the various body locations. Further, pairwise comparisons of GVP profiles with 8 SNPs demonstrated greatest interindividual variation and high intraindividual consistency, enabling similar differentiative potential of individuals using single hairs irrespective of body location origin.

Selection signatures in four German warmblood horse breeds: Tracing breeding history in the modern sport horse

The study of selection signatures helps to find genomic regions that have been under selective pressure and might host genes or variants that modulate important phenotypes. Such knowledge improves our understanding of how breeding programmes have shaped the genomes of livestock. In this study, 942 stallions were included from four, exemplarily chosen, German warmblood breeds with divergent historical and recent selection focus and different crossbreeding policies: Trakehner (N = 44), Holsteiner (N = 358), Hanoverian (N = 319) and Oldenburger (N = 221). Those breeds are nowadays bred for athletic performance and aptitude for show-jumping, dressage or eventing, with a particular focus of Holsteiner on the first discipline. Blood samples were collected during the health exams of the stallion preselections before licensing and were genotyped with the Illumina EquineSNP50 BeadChip. Autosomal markers were used for a multi-method search for signals of positive selection. Analyses within and across breeds were conducted by using the integrated Haplotype Score (iHS), cross-population Extended Haplotype Homozygosity (xpEHH) and Runs of Homozygosity (ROH). Oldenburger and Hanoverian showed very similar iHS signatures, but breed specificities were detected on multiple chromosomes with the xpEHH. The Trakehner clustered as a distinct group in a principal component analysis and also showed the highest number of ROHs, which reflects their historical bottleneck. Beside breed specific differences, we found shared selection signals in an across breed iHS analysis on chromosomes 1, 4 and 7. After investigation of these iHS signals and shared ROH for potential functional candidate genes and affected pathways including enrichment analyses, we suggest that genes affecting muscle functionality (TPM1, TMOD2-3, MYO5A, MYO5C), energy metabolism and growth (AEBP1, RALGAPA2, IGFBP1, IGFBP3-4), embryonic development (HOXB-complex) and fertility (THEGL, ZPBP1-2, TEX14, ZP1, SUN3 and CFAP61) have been targeted by selection in all breeds. Our findings also indicate selection pressure on KITLG, which is well-documented for influencing pigmentation.

Health improvement of human hair and their reshaping using recombinant keratin K31

•

We expressed in E. coli, refolded and purified keratin K31, which is known to be a major protein degraded and eluted in hair damage.

•

Analysis of the recombinant protein by MALDI-TOF, CD spectroscopy and molecular modelling showed its similarity to the native protein.

•

Marked improvements in thickness, strength and smoothness on application of this protein on damaged hair has been shown for the first time.

Hair, being one of the most important components of the beauty care processes, attracts the use of a variety of hair treating cosmetics. Conventional hair treating cosmetics are not satisfactory for one reason or the other. Commercially used keratins are isolated from wool or chicken feathers. As these lack complete sequence identity with human hair keratin, are likely to be less efficient than the human hair keratin. K31, a type I acidic keratin, is a major protein of human hair keratin complex and it is essential for maintaining the hair tensile strength. In this study keratin K31 (46 kDa) gene was expressed in Escherichia coli at a level of approximately 35% of the total cell proteins. The protein, however, was expressed as insoluble inclusion bodies. The expressed protein was refolded and purified by FPLC using an anion-exchange column. The CD analysis results showed that the K31 was properly refolded. MALDI-TOF mass spectroscopy showed the characteristics expected for human K31 keratin. The refolded and partially purified K31 protein, when applied on chemically damaged hairs, increased the diameter of the hair up to 49%. The mechanical strength of the bleached hair increased by almost 2 fold after a single treatment of K31. The protein also straightened curly hair efficiently on a single treatment for one hour. Application of K31 resulted in marked improvements in smoothness, diameter and mechanical strength of the damaged hair.

Three Streams for the Mechanism of Hair Graying

Hair graying is an obvious sign of human aging. Although graying has been investigated extensively, the mechanism remains unclear. Here, we reviewed previous studies on the mechanism of graying and seek to offer some new insights. The traditional view is that hair graying is caused by exhaustion of the pigmentary potential of the melanocytes of hair bulbs. Melanocyte dysfunction may be attributable to the effects of toxic reactive oxygen species on melanocyte nuclei and mitochondria. A recent study suggests that bulge melanocyte stem cells (MSCs) are the key cells in play. Graying may be caused by defective MSC self-maintenance, not by any deficiency in bulbar melanocytes. Our previous study suggested that graying may be principally attributable to active hair growth. Active hair growth may produce oxidative or genotoxic stress in hair bulge. These internal stress may cause eventually depletion of MSC in the hair follicles. Taken together, hair graying may be caused by MSC depletion by genotoxic stress in the hair bulge. Hair graying may also be sometimes caused by dysfunction of the melanocytes by oxidative stress in the hair bulb. In addition, hair graying may be attributable to MSC depletion by active hair growth.

Mutational analysis of epidermal and hyperproliferative type I keratins in mild and moderate psoriasis vulgaris patients: a possible role in the pathogenesis of psoriasis along with disease severity

Background

Mutations in keratin proteins have been vastly associated with a wide array of genodermatoses; however, mutations of keratins in psoriasis have not been fully investigated. The main aim of the current research was to identify the mutation in K14, K10, K16, and K17 genes in two stages of psoriasis patients.

Methods

Ninety-six psoriatic skin biopsies were collected. mRNA transcript of K14, K10, K16, and K17 was prepared, amplified, and sequenced. Sanger sequences of all keratins were further validated for mutational analysis using Mutation Surveyor and Alamut Visual. Then, in silico analysis of protein stability and protein and gene expression of all keratins was performed and validated.

Results

Out of 44 mutations, about 75% of keratins are highly pathogenic and deleterious. Remaining 25% mutations are less pathogenic and tolerated in nature. In these 33 deleterious mutations were immensely found to decrease keratin protein stability. We also found a correlation between keratin and Psoriasis Area and Severity Index score which added that alteration in keratin gene in skin causes severity of psoriasis.

Conclusions

We strongly concluded that acanthosis and abnormal terminal differentiation was mainly due to the mutation in epidermal keratins. In turn, disease severity and relapsing of psoriasis are mainly due to the mutation of hyperproliferative keratins. These novel keratin mutations in psoriatic epidermis might be one of the causative factors for psoriasis.

Electronic supplementary material

The online version of this article (10.1186/s40246-018-0158-2) contains supplementary material, which is available to authorized users.

Phylogeny of dermatophytes with genomic character evaluation of clinically distinct Trichophyton rubrum and T. violaceum

Trichophyton rubrum and T. violaceum are prevalent agents of human dermatophyte infections, the former being found on glabrous skin and nail, while the latter is confined to the scalp. The two species are phenotypically different but are highly similar phylogenetically. The taxonomy of dermatophytes is currently being reconsidered on the basis of molecular phylogeny. Molecular species definitions do not always coincide with existing concepts which are guided by ecological and clinical principles. In this article, we aim to bring phylogenetic and ecological data together in an attempt to develop new species concepts for anthropophilic dermatophytes. Focus is on the T. rubrum complex with analysis of rDNA ITS supplemented with LSU, TUB2, TEF3 and ribosomal protein L10 gene sequences. In order to explore genomic differences between T. rubrum and T. violaceum, one representative for both species was whole genome sequenced. Draft sequences were compared with currently available dermatophyte genomes. Potential virulence factors of adhesins and secreted proteases were predicted and compared phylogenetically. General phylogeny showed clear gaps between geophilic species of Arthroderma, but multilocus distances between species were often very small in the derived anthropophilic and zoophilic genus Trichophyton. Significant genome conservation between T. rubrum and T. violaceum was observed, with a high similarity at the nucleic acid level of 99.38 % identity. Trichophyton violaceum contains more paralogs than T. rubrum. About 30 adhesion genes were predicted among dermatophytes. Seventeen adhesins were common between T. rubrum and T. violaceum, while four were specific for the former and eight for the latter. Phylogenetic analysis of secreted proteases reveals considerable expansion and conservation among the analyzed species. Multilocus phylogeny and genome comparison of T. rubrum and T. violaceum underlined their close affinity. The possibility that they represent a single species exhibiting different phenotypes due to different localizations on the human body is discussed.

Studies on the Proteome of Human Hair - Identification of Histones and Deamidated Keratins

Human hair is laminar-fibrous tissue and an evolutionarily old keratinization product of follicle trichocytes. Studies on the hair proteome can give new insights into hair function and lead to the development of novel biomarkers for hair in health and disease. Human hair proteins were extracted by detergent and detergent-free techniques. We adopted a shotgun proteomics approach, which demonstrated a large extractability and variety of hair proteins after detergent extraction. We found an enrichment of keratin, keratin-associated proteins (KAPs), and intermediate filament proteins, which were part of protein networks associated with response to stress, innate immunity, epidermis development, and the hair cycle. Our analysis also revealed a significant deamidation of keratin type I and II, and KAPs. The hair shafts were found to contain several types of histones, which are well known to exert antimicrobial activity. Analysis of the hair proteome, particularly its composition, protein abundances, deamidated hair proteins, and modification sites, may offer a novel approach to explore potential biomarkers of hair health quality, hair diseases, and aging.

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.

Structural Hierarchy of Trichocyte Keratin Intermediate Filaments

Although trichocyte keratins (hair, wool, quill, claw) have been studied since the 1930s it is only over the last 30 years or so that major advances have been made in our understanding of the complex structural hierarchy of the filamentous component of this important filament-matrix composite. A variety of techniques, including amino acid sequence analysis, computer modelling, X-ray fibre diffraction and protein crystallography, various forms of electron microscopy, and crosslinking methods have now combined to reveal much of the structural detail. The heterodimeric structure of the keratin molecule is clear, as are the highly-specific modes by which these molecules aggregate to form functionally viable IF. The observation that hair keratin can adopt not one but two structurally-distinct conformations, one formed in the living cells at the base of the hair follicle in a reducing environment and the second in the fully differentiated hair in dead cells in an oxidized state, was unexpected but has major implications for the mechanism of hair growth. Insights have also been made into the mechanism of the uppermost level of hair superstructure, relating to the assembly of the IF in the paracortical and orthocortical macrofibrils.

A curated catalog of canine and equine keratin genes

Keratins represent a large protein family with essential structural and functional roles in epithelial cells of skin, hair follicles, and other organs. During evolution the genes encoding keratins have undergone multiple rounds of duplication and humans have two clusters with a total of 55 functional keratin genes in their genomes. Due to the high similarity between different keratin paralogs and species-specific differences in gene content, the currently available keratin gene annotation in species with draft genome assemblies such as dog and horse is still imperfect. We compared the National Center for Biotechnology Information (NCBI) (dog annotation release 103, horse annotation release 101) and Ensembl (release 87) gene predictions for the canine and equine keratin gene clusters to RNA-seq data that were generated from adult skin of five dogs and two horses and from adult hair follicle tissue of one dog. Taking into consideration the knowledge on the conserved exon/intron structure of keratin genes, we annotated 61 putatively functional keratin genes in both the dog and horse, respectively. Subsequently, curators in the RefSeq group at NCBI reviewed their annotation of keratin genes in the dog and horse genomes (Annotation Release 104 and Annotation Release 102, respectively) and updated annotation and gene nomenclature of several keratin genes. The updates are now available in the NCBI Gene database (https://www.ncbi.nlm.nih.gov/gene).

Comparative genomics analyses of alpha-keratins reveal insights into evolutionary adaptation of marine mammals

Background

Diversity of hair in marine mammals was suggested as an evolutionary innovation to adapt aquatic environment, yet its genetic basis remained poorly explored. We scanned α-keratin genes, one major structural components of hair, in 16 genomes of mammalian species, including seven cetaceans, two pinnipeds, polar bear, manatee and five terrestrial species.

Results

Extensive gene loss and high pseudogenization rate of α-keratin genes were identified in cetaceans when compared to terrestrial artiodactylans (average number of α-keratins 37.29 vs. 58.33; pseudogenization rate 29.89% vs. 8.00%), especially of hair follicle-specific keratin genes (average pseudogenization rate in cetaceans of 43.88% relative to 3.80% artiodactylian average). Compared to toothed whale, the much more number of intact functional α-keratin genes was examined in the baleen whale that had specific keratinized baleen. In contrast, the number of keratin genes in pinnipeds, polar bear and manatee were comparable to those of their respective terrestrial relatives. Additionally, four keratin genes (K39, K9, K42, and K74) were found to be pseudogenes or lost uniquely in cetaceans and manatees.

Conclusions

Species-specific evolution of α-keratin gene family identified in the marine mammals might be responsible for their different hair characteristics. Increased gene loss and pseudogenization rate identified in cetacean lineages was likely to contribute to hair-less phenotype to adaptation for complete aquatic environment. However, the fully aquatic manatee still remained the comparable number of intact genes to its terrestrial relative, probably due to its perioral bristles and bristle-like hairs on the oral disk. By contrast, similar evolution pattern of α-keratin gene repertoire in the pinnipeds, polar bear and their terrestrial relatives was likely due to abundant hair to keep warm when they went ashore. Interestingly, some keratin genes were exclusively lost in cetaceans and manatees, likely as a result of convergent hair-loss phenotype to inhabit completely aquatic environment in both groups.

Electronic supplementary material

The online version of this article (doi:10.1186/s12983-017-0225-x) contains supplementary material, which is available to authorized users.

Derivation of marker gene signatures from human skin and their use in the interpretation of the transcriptional changes associated with dermatological disorders

Numerous studies have explored the altered transcriptional landscape associated with skin diseases to understand the nature of these disorders. However, data interpretation represents a significant challenge due to a lack of good maker sets for many of the specialized cell types that make up this tissue, whose composition may fundamentally alter during disease. Here we have sought to derive expression signatures that define the various cell types and structures that make up human skin, and demonstrate how they can be used to aid the interpretation of transcriptomic data derived from this organ. Two large normal skin transcriptomic datasets were identified, one RNA-seq (n = 578), the other microarray (n = 165), quality controlled and subjected separately to network-based analyses to identify clusters of robustly co-expressed genes. The biological significance of these clusters was then assigned using a combination of bioinformatics analyses, literature, and expert review. After cross comparison between analyses, 20 gene signatures were defined. These included expression signatures for hair follicles, glands (sebaceous, sweat, apocrine), keratinocytes, melanocytes, endothelia, muscle, adipocytes, immune cells, and a number of pathway systems. Collectively, we have named this resource SkinSig. SkinSig was then used in the analysis of transcriptomic datasets for 18 skin conditions, providing in-context interpretation of these data. For instance, conventional analysis has shown there to be a decrease in keratinization and fatty metabolism with age; we more accurately define these changes to be due to loss of hair follicles and sebaceous glands. SkinSig also highlighted the over-/under-representation of various cell types in skin diseases, reflecting an influx in immune cells in inflammatory disorders and a relative reduction in other cell types. Overall, our analyses demonstrate the value of this new resource in defining the functional profile of skin cell types and appendages, and in improving the interpretation of disease data. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.