K25 (K25irs1), K26 (K25irs2), K27 (K25irs3), and K28 (K25irs4) represent the type I inner root sheath keratins of the human hair follicle

A comparative proteomic-based study identifies essential factors involved in hair follicle growth in inner Mongolia cashmere goats

Renowned for its invaluable undercoat, the cashmere goat is well known. The growth of cashmere fibre initiates when the relatively inactive telogen stage transitions to the anagen stage, which involves active proliferation. However, the molecular mechanisms responsible for this process are still unclear. Here, SWATH mass spectrometry (MS), a comparative proteomic analysis, was conducted to examine the proteomic alterations in Inner Mongolia cashmere goat skin samples at two different developmental stages (anagen and telogen). In total, 2414 proteins were detected, with 631 proteins showing differential regulation (503 upregulated proteins and 128 downregulated proteins). Bioinformatic analysis revealed that these proteins, which are differentially regulated, play crucial roles in the pathways associated with metabolism and fatty acids according to the GO and KEGG analyses. Furthermore, interactome analysis revealed that differentially regulated keratins have a crucial impact. The localization of KRT25, KRT71, and KRT82 using immunohistochemistry revealed that these proteins were expressed in the secondary hair follicles of cashmere goat skin. The keratin family plays an irreplaceable and important role in the process of hair follicle growth.

Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures

Reptiles, birds, mammals and amphibians, together forming the clade tetrapods, have a large diversity of cornified skin appendages, such as scales, feathers, hair and claws. The skin appendages consist of dead epithelial cells that are tightly packed with specific structural proteins. Here, we review the molecular diversity and expression patterns of major types of skin appendage proteins, namely keratin intermediate filament proteins, keratin-associated proteins (KRTAPs) and proteins encoded by genes of the epidermal differentiation complex (EDC), including corneous beta-proteins, also known as beta-keratins. We summarize the current knowledge about the components of skin appendages with a focus on keratins and EDC proteins that have recently been identified in reptiles and birds. We discuss gaps of knowledge and suggest directions of future research.

Effect of Skin Barrier on Atopic Dermatitis

The skin acts as the body's primary physical and immune barrier, maintaining the skin microbiome and providing a physical, chemical, and immune barrier. A disrupted skin barrier plays a critical role in the onset and advancement of inflammatory skin conditions such as atopic dermatitis (AD) and contact dermatitis. This narrative review outlines the relationship between AD and skin barrier function in preparation for the search for possible markers for the treatment of AD.

Proteomic Analysis of Crimped and Straight Wool in Chinese Tan Sheep

Crimped wool in Tan sheep gradually transitions to straight wool after 35 days (the er-mao stage), which reduces its commercial value. To investigate the changes in wool proteins during this stage, we performed comparative proteomic analysis of the straight and crimped wool using tandem mass tag (TMT)-based quantification. The mean fur curvature (MFC) of crimped wool was significantly greater than that of straight wool (p < 0.001). We identified 1218 proteins between the two types of wool, including 50 keratins (Ks) and 10 keratin-associated proteins (KAPs). There were 213 differentially expressed proteins, including 13 Ks and 4 KAPs. Crimped wool showed relatively high abundances of KAP24-1, K84, K32, K82, and intermediate filament rod domain-containing protein (IRDC), whereas straight wool had relatively high abundances of K6A, K27, K80, KAP16-1, KAP27-1, and trichohyalin (TCHH). The expression levels of KAP16-1, KAP24-1, and KAP27-1 were related to the ratio of paracortex, which may be associated with wool crimp formation. Additionally, high expressions of TCHH, K27, and K6A in the inner root sheath (IRS) were linked to fiber fineness in straight wool. These findings provide insight into the overall expression and distribution patterns of Ks and KAPs, offering opportunities to improve wool quality and enhance its economic potential in the textile industry.

Changing human hair fibre colour and shape from the follicle

INTRODUCTION

Natural hair curvature and colour are genetically determined human traits, that we intentionally change by applying thermal and chemical treatments to the fibre. Presently, those cosmetic methodologies act externally and their recurrent use is quite detrimental to hair fibre quality and even to our health.

OBJECTIVES

This work represents a disruptive concept to modify natural hair colour and curvature. We aim to model the fibre phenotype as it is actively produced in the follicle through the topical delivery of specific bioactive molecules to the scalp.

METHODS

Transcriptome differences between curly and straight hairs were identified by microarray. In scalp samples, the most variable transcripts were mapped by in situ hybridization. Then, by using appropriate cellular models, we screened a chemical library of 1200 generic drugs, searching for molecules that could lead to changes in either fibre colour or curvature. A pilot-scale, single-centre, investigator-initiated, prospective, blind, bilateral (split-scalp) placebo-controlled clinical study with the intervention of cosmetics was conducted to obtain a proof of concept (RNEC n.92938).

RESULTS

We found 85 genes transcribed significantly different between curly and straight hair, not previously associated with this human trait. Next, we mapped some of the most variable genes to the inner root sheath of follicles, reinforcing the role of this cell layer in fibre shape moulding. From the drug library screening, we selected 3 and 4 hits as modulators of melanin synthesis and gene transcription, respectively, to be further tested in 33 volunteers. The intentional specific hair change occurred: 8 of 14 volunteers exhibited colour changes, and 16 of 19 volunteers presented curvature modifications, by the end of the study.

CONCLUSION

The promising results obtained are the first step towards future cosmetics, complementary or alternative to current methodologies, taking hair styling to a new level: changing hair from the inside out.

Population structure and selection signal analysis of indigenous sheep from the southern edge of the Taklamakan Desert

Analyzing the genetic diversity and selection characteristics of sheep (Ovis aries) holds significant value in understanding their environmental adaptability, enhancing breeding efficiency, and achieving effective conservation and rational utilization of genetic resources. In this study, we utilized Illumina Ovine SNP 50 K BeadChip data from four indigenous sheep breeds from the southern margin of the Taklamakan Desert (Duolang sheep: n = 36, Hetian sheep: n = 74, Kunlun sheep: n = 27, Qira black sheep: n = 178) and three foreign meat sheep breeds (Poll Dorset sheep: n = 105, Suffolk sheep: n = 153, Texel sheep: n = 150) to investigate the population structure, genetic diversity, and genomic signals of positive selection within the indigenous sheep. According to the Principal component analysis (PCA), the Neighbor-Joining tree (NJ tree), and Admixture, we revealed distinct clustering patterns of these seven sheep breeds based on their geographical distribution. Then used Cross Population Extended Haplotype Homozygosity (XP-EHH), Fixation Index (FST), and Integrated Haplotype Score (iHS), we identified a collective set of 32 overlapping genes under positive selection across four indigenous sheep breeds. These genes are associated with wool follicle development and wool traits, desert environmental adaptability, disease resistance, reproduction, and high-altitude adaptability. This study reveals the population structure and genomic selection characteristics in the extreme desert environments of native sheep breeds from the southern edge of the Taklimakan Desert, providing new insights into the conservation and sustainable use of indigenous sheep genetic resources in extreme environments. Additionally, these findings offer valuable genetic resources for sheep and other mammals to adapt to global climate change.

Whole-exome sequencing reveals novel cancer genes and actionable targets in biliary tract cancers in primary sclerosing cholangitis

BACKGROUND

People with primary sclerosing cholangitis (PSC) have a 20% lifetime risk of biliary tract cancer (BTC). Using whole-exome sequencing, we characterized genomic alterations in tissue samples from BTC with underlying PSC.

METHODS

We extracted DNA from formalin-fixed, paraffin-embedded tumor and paired nontumor tissue from 52 resection or biopsy specimens from patients with PSC and BTC and performed whole-exome sequencing. Following copy number analysis, variant calling, and filtering, putative PSC-BTC-associated genes were assessed by pathway analyses and annotated to targeted cancer therapies.

RESULTS

We identified 53 candidate cancer genes with a total of 123 nonsynonymous alterations passing filtering thresholds in 2 or more samples. Of the identified genes, 19% had not previously been implicated in BTC, including CNGA3, KRT28, and EFCAB5. Another subset comprised genes previously implicated in hepato-pancreato-biliary cancer, such as ARID2, ELF3, and PTPRD. Finally, we identified a subset of genes implicated in a wide range of cancers such as the tumor suppressor genes TP53, CDKN2A, SMAD4, and RNF43 and the oncogenes KRAS, ERBB2, and BRAF. Focal copy number variations were found in 51.9% of the samples. Alterations in potential actionable genes, including ERBB2, MDM2, and FGFR3 were identified and alterations in the RTK/RAS (p = 0.036), TP53 (p = 0.04), and PI3K (p = 0.043) pathways were significantly associated with reduced overall survival.

CONCLUSIONS

In this exome-wide characterization of PSC-associated BTC, we delineated both PSC-specific and universal cancer genes. Our findings provide opportunities for a better understanding of the development of BTC in PSC and could be used as a platform to develop personalized treatment approaches.

Optimization of hair follicle spheroids for hair-on-a-chip

Currently, most models for hair follicle research have the limitation of not replicating some key features of the hair follicle microenvironment. To complement this, we transfected various factors for hair growth into dermal papilla cells (DPCs) by electroporation and cultured the spheroids with keratinocytes (KCs). We optimized the cell number and culture period for applying spheroids to hair-on-a-chip. Furthermore, we investigated the expression of hair growth factors in spheroids depending on the presence or absence of human umbilical vein endothelial cells (HUVECs) and transfection. In spheroids in which DPCs, KCs, and HUVECs were co-cultured for 21 days, the expression of lymphoid enhancer factor 1 (LEF1), T-cell factor 1 (TCF1), and keratin 25 (K25) in the center of the spheroid, the expression of keratin 17 (K17) on the outer surface of the spheroid, and the shape of hair extending outward from the spheroid surface were observed. From these results, it is expected that a hair-on-a-chip experiment in which short-term cultured TKH spheroids are injected into the dermis and co-cultured with KC will enable the production of full-thickness skin equivalents containing hair in vitro without transplantation into animals.

Whole-Genome Resequencing Reveals Selection Signal Related to Sheep Wool Fineness

Wool fineness affects the quality of wool, and some studies have identified about forty candidate genes that affect sheep wool fineness, but these genes often reveal only a certain proportion of the variation in wool thickness. We further explore additional genes associated with the fineness of sheep wool. Whole-genome resequencing of eight sheep breeds was performed to reveal selection signals associated with wool fineness, including four coarse wool and four fine/semi-fine wool sheep breeds. Multiple methods to reveal selection signals (Fst and θπ Ratio and XP-EHH) were applied for sheep wool fineness traits. In total, 269 and 319 genes were annotated in the fine wool (F vs. C) group and the coarse wool (C vs. F) group, such as LGR4, PIK3CA, and SEMA3C and NFIB, OPHN1, and THADA. In F vs. C, 269 genes were enriched in 15 significant GO Terms (p < 0.05) and 38 significant KEGG Pathways (p < 0.05), such as protein localization to plasma membrane (GO: 0072659) and Inositol phosphate metabolism (oas 00562). In C vs. F, 319 genes were enriched in 21 GO Terms (p < 0.05) and 16 KEGG Pathways (p < 0.05), such as negative regulation of focal adhesion assembly (GO: 0051895) and Axon guidance (oas 04360). Our study has uncovered genomic information pertaining to significant traits in sheep and has identified valuable candidate genes. This will pave the way for subsequent investigations into related traits.

Identification of the Key Genes Associated with Different Hair Types in the Inner Mongolia Cashmere Goat

The Inner Mongolia cashmere goat is an excellent local breed in China. According to the characteristics of wool quilts, the Inner Mongolia cashmere goat can be divided into three types: a long-hair type (hair length of >22 cm), a short-hair type (hair length of ≤13 cm), and an intermediate type (hair length of >13 cm and ≤22 cm). It is found that hair length has a certain reference value for the indirect selection of other important economic traits of cashmere. In order to explore the molecular mechanisms and related regulatory genes of the different hair types, a weighted gene coexpression network analysis (WGCNA) was carried out on the gene expression data and phenotypic data of 12-month-old Inner Mongolia cashmere goats with a long-hair type (LHG) and a short-hair type (SHG) to explore the coexpression modules related to different coat types and nine candidate genes, and detect the relative expression of key candidate genes. The results showed that the WGCNA divided these genes into 19 coexpression modules and found that there was a strong correlation between one module and different hair types. The expression trends of this module’s genes were different in the two hair types, with high expression in the LHG and low expression in the SHG. GO functions are mainly concentrated in cellular components, including intermediate filaments (GO:0005882), intermediate filament cytoskeletons (GO:0045111), and cytoskeletal parts (GO:0044430). The KEGG pathway is mainly enriched in arginine as well as proline metabolism (chx00330) and the MAPK signaling pathway (chx04010). The candidate genes of the different hair types, including the KRT39, KRT74, LOC100861184, LOC102177231, LOC102178767, LOC102179881, LOC106503203, LOC108638293, and LOC108638298 genes, were screened. Through qRT-PCR, it was found that there were significant differences in these candidate genes between the two hair types, and most of them had a significant positive correlation with hair length. It was preliminarily inferred that these candidate genes could regulate the different hair types of cashmere goats and provide molecular markers for hair growth.

LGR5 is a conserved marker of hair follicle stem cells in multiple species and is present early and throughout follicle morphogenesis

Hair follicle stem cells are key for driving growth and homeostasis of the hair follicle niche, have remarkable regenerative capacity throughout hair cycling, and display fate plasticity during cutaneous wound healing. Due to the need for a transgenic reporter, essentially all observations related to LGR5-expressing hair follicle stem cells have been generated using transgenic mice, which have significant differences in anatomy and physiology from the human. Using a transgenic pig model, a widely accepted model for human skin and human skin repair, we demonstrate that LGR5 is a marker of hair follicle stem cells across species in homeostasis and development. We also report the strong similarities and important differences in expression patterns, gene expression profiles, and developmental processes between species. This information is important for understanding the fundamental differences and similarities across species, and ultimately improving human hair follicle regeneration, cutaneous wound healing, and skin cancer treatment.

RNA-Seq reveals the functional specificity of epididymal caput, corpus, and cauda genes of cattleyak

The first filial generation of the cattleyaks demonstrates hybrid vigor; however, the male cattleyaks are infertile and restrict productivity and breeding. The discovery of genes in a segment-specific approach offers valuable information and understanding concerning fertility status, yet the biology of cattleyak epididymis is still progressing. Comparative transcriptome analysis was performed on segment pairs of cattleyak epididymis. The caput versus corpus epididymis provided the highest (57.8%) differentially expressed genes (DEGs), corpus versus cauda (25.1%) followed, whereas caput versus cauda pair (17.1%) had the least DEGs. The expression levels of genes coding EPHB6, TLR1, MUC20, MT3, INHBB, TRPV5, EI24, PAOX, KIF12, DEPDC5, and KRT25, which might have the potentials to regulate the homeostasis, innate immunity, differentiation, motility, transport, and sperm maturation-related function in epididymal cells, were downregulated in the distal segment of epididymis. Top enriched KEGG pathways included mTOR, axon guidance, and taste transduction signaling pathways. EIF4B, EPHB6, and TAS2R42 were enriched in the pathways, respectively. Identifying key, new, and unexplored DEGs among the epididymal segments and further analyzing them could boost cattleyak fertility by maximizing sperm quality from genetically better sires and also facilitate better understanding of the epididymal biology.

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.

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.

TMT-Based Quantitative Proteomic Analysis Reveals the Effect of Bone Marrow Derived Mesenchymal Stem Cell on Hair Follicle Regeneration

Hair loss (HL) is a common chronic problem of poorly defined etiology. Herein, we explored the functionality of bone marrow-derived mesenchymal stem cell (BMSC) and conditioned medium (MSC-CM) as regulators of hair follicle proliferation and regeneration, and the mechanistic basis for such activity. BMSC were cultured and identified in vitro through the induction of multilineage differentiation and the use of a CCK-8 kit. The dorsal skin of mice was then injected with BMSC and MSC-CM, and the impact of these injections on hair cycle transition and hair follicle stem cell (HFSC) proliferation was then evaluated via hematoxylin and eosin (H&E) staining and immunofluorescent (IF) staining. We then conducted a tandem mass tags (TMT)-based quantitative proteomic analysis of control mice and mice treated with BMSC or MSC-CM to identify differentially expressed proteins (DEPs) associated with these treatments. Parallel reaction monitoring (PRM) was utilized as a means of verifying our proteomic analysis results. Herein, we found that BMSC and MSC-CM injection resulted in the transition of telogen hair follicles to anagen hair follicles, and we observed the enhanced proliferation of HFSCs positive for Krt15 and Sox9. Our TMT analyses identified 1,060 and 770 DEPs (fold change＞1.2 or＜0.83 and p ＜ 0.05) when comparing the BMSC vs. control and MSC-CM vs. control groups, respectively. Subsequent PRM validation of 14 selected DEPs confirmed these findings, and led to the identification of Stmn1, Ncapd2, Krt25, and Ctps1 as hub DEPs in a protein-protein interaction network. Together, these data suggest that BMSC and MSC-CM treatment can promote the proliferation of HFSCs, thereby facilitating hair follicle regeneration. Our proteomics analyses further indicate that Krt25, Cpm, Stmn1, and Mb may play central roles in hair follicle transition in this context and may represent viable clinical targets for the treatment of HL.

Molecular Modeling of Pathogenic Mutations in the Keratin 1B Domain

Keratin intermediate filaments constitute the primary cytoskeletal component of epithelial cells. Numerous human disease phenotypes related to keratin mutation remain mechanistically elusive. Our recent crystal structures of the helix 1B heterotetramer from keratin 1/10 enabled further investigation of the effect of pathologic 1B domain mutations on keratin structure. We used our highest resolution keratin 1B structure as a template for homology-modeling the 1B heterotetramers of keratin 5/14 (associated with blistering skin disorders), keratin 8/18 (associated with liver disease), and keratin 74/28 (associated with hair disorder). Each structure was examined for the molecular alterations caused by incorporating pathogenic 1B keratin mutations. Structural modeling indicated keratin 1B mutations can harm the heterodimer interface (R265P^K5, L311R^K5, R211P^K14, I150V^K18), the tetramer interface (F231L^K1, F274S^K74), or higher-order interactions needed for mature filament formation (S233L^K1, L311R^K5, Q169E^K8, H128L^K18). The biochemical changes included altered hydrophobic and electrostatic interactions, and altered surface charge, hydrophobicity or contour. Together, these findings advance the genotype-structurotype-phenotype correlation for keratin-based human diseases.

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).

Regulation of keratin network dynamics by the mechanical properties of the environment in migrating cells

Keratin intermediate filaments provide mechanical resilience for epithelia. They are nevertheless highly dynamic and turn over continuously, even in sessile keratinocytes. The aim of this study was to characterize and understand how the dynamic behavior of the keratin cytoskeleton is integrated in migrating cells. By imaging human primary keratinocytes producing fluorescent reporters and by using standardized image analysis we detect inward-directed keratin flow with highest rates in the cell periphery. The keratin flow correlates with speed and trajectory of migration. Changes in fibronectin-coating density and substrate stiffness induces concordant changes in migration speed and keratin flow. When keratinocytes are pseudo-confined on stripes, migration speed and keratin flow are reduced affecting the latter disproportionately. The regulation of keratin flow is linked to the regulation of actin flow. Local speed and direction of keratin and actin flow are very similar in migrating keratinocytes with keratin flow lagging behind actin flow. Conversely, reduced actin flow in areas of high keratin density indicates an inhibitory function of keratins on actin dynamics. Together, we propose that keratins enhance persistence of migration by directing actin dynamics and that the interplay of keratin and actin dynamics is modulated by matrix adhesions.

Transcriptome Analysis of Improved Wool Production in Skin-Specific Transgenic Sheep Overexpressing Ovine β-Catenin

β-Catenin is an evolutionarily conserved molecule in the canonical Wnt signaling pathway, which controls decisive steps in embryogenesis and functions as a crucial effector in the development of hair follicles. However, the molecular mechanisms underlying wool production have not been fully elucidated. In this study, we investigated the effects of ovine β-catenin on wool follicles of transgenic sheep produced by pronuclear microinjection with a skin-specific promoter of human keratin14 (k14). Both polymerase chain reaction and Southern blot analysis showed that the sheep carried the ovine β-catenin gene and that the β-catenin gene could be stably inherited. To study the molecular responses to high expression of β-catenin, high-throughput RNA-seq technology was employed using three transgenic sheep and their wild-type siblings. These findings suggest that β-catenin normally plays an important role in wool follicle development by activating the downstream genes of the Wnt pathway and enhancing the expression of keratin protein genes and keratin-associated protein genes.

A novel KRT71 variant in curly-coated dogs

Curly fur is a common phenotype in many dog breeds, known to result from a missense variant (c.451C>T) in exon 2 of the keratin 71 (KRT71) gene. During screening for this variant across various breeds, we found that Curly Coated Retrievers (CCRs) fixed with the trait did not carry the known variant. By analysis of whole-genome sequencing data of one CCR we identified a novel genetic cause for curly fur. We found a novel structural variant in exon 7 of the KRT71 gene (c.1266_1273delinsACA) that was predicted to result in a frameshift and stop loss, therefore significantly affecting the structure of the protein, if translated. The variant was also found at lower frequencies in five other breeds, including Lagotto Romagnolo, Bichon Frise, Spanish Water Dog, Chesapeake Bay Retriever and Irish Terrier. One curly-coated Lagotto carried neither of the two KRT71 variants. These results identify a second variant for curly coat in KRT71 and suggest the existence of additional alleles. This study enables the development of an additional KRT71 gene test for breeders to understand and manage coat types.

Long noncoding RNA and gene expression analysis of melatonin-exposed Liaoning cashmere goat fibroblasts indicating cashmere growth

Cashmere produced from Liaoning cashmere goat is highly valuable. Melatonin is an important factor affecting cashmere growth and can regulate the growth cycle via effects on gene expression. Long noncoding RNAs (lncRNAs) regulate gene expression, but detailed studies of their effect on hair growth are lacking. To explore how lncRNA mediates the effects of melatonin on cashmere growth, we used RNA-Seq including a control condition (C) and three melatonin treatments (1.0 g/L 24 h (M1_24H), 0.2 g/L 24 h (M2_24H), 0.2 g/L 72 h (M2_72H)). M1_24H, M2_24H, and M2_72H had 32, 10, and 113 differentially expressed lncRNAs, respectively. Gene ontology (GO) and pathway analyses results showed that melatonin was most beneficial to cashmere growth at 0.2 g/L 72 h, and nuclear factor (NF)-κB signaling corresponding to an effect of LncRNA MTC was involved in hair follicle development. We found that melatonin upregulated XLOC_005914 lncRNA (LncRNA MTC). Proliferation increased in the 0.2 g/L 72 h condition and cells with high LncRNA MTC expression, but it was reduced in fibroblasts with knocked down LncRNA MTC expression. This is the first report that LncRNA MTC promotes fibroblast proliferation and regulates hair follicle development and cashmere growth by activating NF-κB signaling.

Msx2 Prevents Stratified Squamous Epithelium Formation in the Enamel Organ

Tooth enamel is manufactured by the inner enamel epithelium of the multilayered enamel organ. Msx2 loss-of-function mutation in a mouse model causes an abnormal accumulation of epithelial cells in the enamel organ, but the underlying mechanism by which Msx2 regulates amelogenesis is poorly understood. We therefore performed detailed histological and molecular analyses of Msx2 null mice. Msx2 null ameloblasts and stratum intermedium (SI) cells differentiated normally in the early stages of amelogenesis. However, during subsequent developmental stages, the outer enamel epithelium (OEE) became highly proliferative and transformed into a keratinized stratified squamous epithelium that ectopically expressed stratified squamous epithelium markers, including Heat shock protein 25, Loricrin, and Keratin 10. Moreover, expression of hair follicle-specific keratin genes such as Keratin 26 and Keratin 73 was upregulated in the enamel organ of Msx2 mutants. With the accumulation of keratin in the stellate reticulum (SR) region and subsequent odontogenic cyst formation, SI cells gradually lost the ability to differentiate, and the expression of Sox2 and Notch1 was downregulated, leading to ameloblast depolarization. As a consequence, the organization of the Msx2 mutant enamel organ became disturbed and enamel failed to form in the normal location. Instead, there was ectopic mineralization that likely occurred within the SR. In summary, we show that during amelogenesis, Msx2 executes a bipartite function, repressing the transformation of OEE into a keratinized stratified squamous epithelium while simultaneously promoting the development of a properly differentiated enamel organ competent for enamel formation.

An epistatic effect of KRT25 on SP6 is involved in curly coat in horses

Curly coat represents an extraordinary type of coat in horses, particularly seen in American Bashkir Curly Horses and Missouri Foxtrotters. In some horses with curly coat, a hypotrichosis of variable extent was observed, making the phenotype appear more complex. In our study, we aimed at investigating the genetic background of curly coat with and without hypotrichosis using high density bead chip genotype and next generation sequencing data. Genome-wide association analysis detected significant signals (p = 1.412 × 10⁻⁰⁵–1.102 × 10⁻⁰⁸) on horse chromosome 11 at 22–35 Mb. In this significantly associated region, six missense variants were filtered out from whole-genome sequencing data of three curly coated horses of which two variants within KRT25 and SP6 could explain all hair phenotypes. Horses heterozygous or homozygous only for KRT25 variant showed curly coat and hypotrichosis, whereas horses with SP6 variant only, exhibited curly coat without hypotrichosis. Horses with mutant alleles in both variants developed curly hair and hypotrichosis. Thus, mutant KRT25 allele is masking SP6 allele effect, indicative for epistasis of KRT25 variant over SP6 variant. In summary, genetic variants in two different genes, KRT25 and SP6, are responsible for curly hair. All horses with KRT25 variant are additionally hypotrichotic due to the KRT25 epistatic effect on SP6.

RNA-seq reveals transcriptome changes in goats following myostatin gene knockout

Myostatin (MSTN) is a powerful negative regulator of skeletal muscle mass in mammalian species that is primarily expressed in skeletal muscles, and mutations of its encoding gene can result in the double-muscling trait. In this study, the CRISPR/Cas9 technique was used to edit MSTN in Shaanbei Cashmere goats and generate knockout animals. RNA sequencing was used to determine and compare the transcriptome profiles of the muscles from three wild-type (WT) goats, three fibroblast growth factor 5 (FGF5) knockout goats (FGF5+/- group) and three goats with disrupted expression of both the FGF5 and MSTN genes (FM+/- group). The sequence reads were obtained using the Illumina HiSeq 2000 system and mapped to the Capra hircus reference genome using TopHat (v2.0.9). In total, 68.93, 62.04 and 66.26 million clean sequencing reads were obtained from the WT, FM+/- and FGF5+/- groups, respectively. There were 201 differentially expressed genes (DEGs) between the WT and FGF5+/- groups, with 86 down- and 115 up-regulated genes in the FGF5+/- group. Between the WT and FM+/- groups, 121 DEGs were identified, including 81 down- and 40 up-regulated genes in the FM+/- group. A total of 198 DEGs were detected between the FGF5+/- group and FM+/- group, with 128 down- and 70 up-regulated genes in the FM+/- group. At the transcriptome level, we found substantial changes in genes involved in fatty acid metabolism and the biosynthesis of unsaturated fatty acids, such as stearoyl-CoA dehydrogenase, 3-hydroxyacyl-CoA dehydratase 2, ELOVL fatty acid elongase 6 and fatty acid synthase, suggesting that the expression levels of these genes may be directly regulated by MSTN and that these genes are likely downstream targets of MSTN with potential roles in lipid metabolism in goats. Moreover, five randomly selected DEGs were further validated with qRT-PCR, and the results were consistent with the transcriptome analysis. The present study provides insight into the unique transcriptome profile of the MSTN knockout goat, which is a valuable resource for studying goat genomics.

Identification of genes and proteins associated with anagen wool growth

Identifying genes of major effect for wool growth would offer strategies for improving the quality and increasing the yield of fine wool. In this study, we employed the Agilent Sheep Gene Expression Microarray and proteomic technology to investigate the gene expression patterns of body side skin (more wool growing) in Aohan fine wool sheep (a Chinese indigenous breed) in comparison with groin skin (no wool growing) at the anagen stage of the wool follicle. A microarray study revealed that 4772 probes were differentially expressed, including 2071 upregulated and 2701 downregulated probes, in the comparisons of body side skin vs. groin skin (S/G). The microarray results were verified by means of quantitative PCR. A total of 1099 probes were assigned to unique genes/transcripts. The number of distinct genes/transcripts (annotated) was 926, of which 352 were upregulated and 574 were downregulated. In S/G, 13 genes were upregulated by more than 10 fold, whereas 60 genes were downregulated by more than 10 fold. Further analysis revealed that the majority of the genes possibly related to the wool growth could be assigned to categories including regulation of cell division, intermediate filament, cytoskeletal part and growth factor activity. Several potential gene families may participate in hair growth regulation, including fibroblast growth factors, transforming growth factor-β, WNTs, insulin-like growth factor, vascular endothelial growth factors and so on. Proteomic analysis also revealed 196 differentially expressed protein points, of which 121 were identified as single protein points.

Localisation of keratin K78 in the basal layer and first suprabasal layers of stratified epithelia completes expression catalogue of type II keratins and provides new insights into sequential keratin expression

Among the 26 human type II keratins, K78 is the only one that has not yet been explored with regard to its expression characteristics. Here, we show that, at both the transcriptional and translational levels, K78 is strongly expressed in the basal and parabasal cell layers with decreasing intensity in the lower suprabasal cells of keratinising and non-keratinising squamous epithelia and keratinocyte cultures. The same pattern has been detected at the transcriptional level in the corresponding mouse epithelia. Murine K78 protein, which contains an extraordinary large extension of its tail domain, which is unique among all known keratins, is not detectable by the antibody used. Concomitant studies in human epithelia have confirmed K78 co-expression with the classical basal keratins K5 and K14. Similarly, K78 co-expression with the differentiation-related type I keratins K10 (epidermis) and K13 (non-keratinising epithelia) occurs in the parabasal cell layer, whereas that of the corresponding type II keratins K1 (epidermis) and K4 (non-keratinising epithelia) unequivocally starts subsequent to the respective type I keratins. Our data concerning K78 expression modify the classical concept of keratin pair K5/K14 representing the basal compartment and keratin pairs K1/K10 or K4/K13 defining the differentiating compartment of stratified epithelia. Moreover, the K78 expression pattern and the decoupled K1/K10 and K4/K13 expression define the existence of a hitherto unperceived early differentiation stage in the parabasal layer characterized by K78/K10 or K78/K13 expression.

Autosomal Recessive Hypotrichosis with Woolly Hair Caused by a Mutation in the Keratin 25 Gene Expressed in Hair Follicles

Hypotrichosis is an abnormal condition characterized by decreased hair density and various defects in hair structure and growth patterns. In particular, in woolly hair, hypotrichosis is characterized by a tightly curled structure and abnormal growth. In this study, we present a detailed comparative examination of individuals affected by autosomal-recessive hypotrichosis (ARH), which distinguishes two types of ARH. Earlier, we demonstrated that exon 4 deletion in the lipase H gene caused an ARH (hypotrichosis 7; MIM: 604379) in populations of the Volga-Ural region of Russia. Screening for this mutation in all affected individuals revealed its presence only in the group with the hypotrichosis 7 phenotype. Other patients formed a separate group of woolly hair-associated ARH, with a homozygous missense mutation c.712G>T (p.Val238Leu) in a highly conserved position of type I keratin KRT25 (K25). Haplotype analysis indicated a founder effect. An expression study in the HaCaT cell line demonstrated a deleterious effect of the p.Val238Leu mutation on the formation of keratin intermediate filaments. Hence, we have identified a previously unreported missense mutation in the KRT25 gene causing ARH with woolly hair.

A homozygous missense variant in type I keratin KRT25 causes autosomal recessive woolly hair

BACKGROUND

Woolly hair (WH) is a hair abnormality that is primarily characterised by tightly curled hair with abnormal growth.

METHODS

In two unrelated consanguineous Pakistani families with non-syndromic autosomal recessive (AR) WH, homozygosity mapping and linkage analysis identified a locus within 17q21.1-q22, which contains the type I keratin gene cluster. A DNA sample from an affected individual from each family underwent exome sequencing.

RESULTS

A homozygous missense variant c.950T>C (p.(Leu317Pro)) within KRT25 segregated with ARWH in both families, and has a combined maximum two-point LOD score of 7.9 at ϴ=0. The KRT25 variant is predicted to result in disruption of the second α-helical rod domain and the entire protein structure, thus possibly interfering with heterodimerisation of K25 with type II keratins within the inner root sheath (IRS) of the hair follicle and the medulla of the hair shaft.

CONCLUSIONS

Our findings implicate a novel gene involved in human hair abnormality, and are consistent with the curled, fragile hair found in mice with Krt25 mutations, and further support the role of IRS-specific type I keratins in hair follicle development and maintenance of hair texture.

Proteomic analysis of differentially expressed skin proteins in iRhom2(Uncv) mice

A mouse homozygous for the spontaneous mutation uncovered (Uncv) has a hairless phenotype. A 309-bp non-frameshift deletion mutation in the N-terminal cytoplasmic domain of iRhom2 was identified in Uncv mice (iRhom2^Uncv) using target region sequencing. The detailed molecular basis for how the iRhom2 mutation causes the hairless phenotype observed in the homozygous iRhom2^Uncv mouse remains unknown. To identify differentially expressed proteins in the skin of wild-type and homozygous iRhom2^Uncv littermates at postnatal day 5, proteomic approaches, including two-dimensional gel electrophoresis and mass spectrometry were used. Twelve proteins were differentially expressed in the skin in a comparison between wild-type and homozygous iRhom2^Uncv mice. A selection of the proteomic results were tested and verified using qRT-PCR, western blot and immunohistochemistry. These data indicate that differentially expressed proteins, especially KRT73, MEMO1 and Coro-1, might participate in the mechanism by which iRhom2 regulates the development of murine skin. [BMB Reports 2015; 48(1): 19-24]

Utility of Scalp Hair Follicles as a Novel Source of Biomarker Genes for Psychiatric Illnesses

BACKGROUND

Identifying beneficial surrogate genetic markers in psychiatric disorders is crucial but challenging.

METHODS

Given that scalp hair follicles are easily accessible and, like the brain, are derived from the ectoderm, expressions of messenger RNA (mRNA) and microRNA in the organ were examined between schizophrenia (n for first/second = 52/42) and control subjects (n = 62/55) in two sets of cohort. Genes of significance were also analyzed using postmortem brains (n for case/control = 35/35 in Brodmann area 46, 20/20 in cornu ammonis 1) and induced pluripotent stem cells (n = 4/4) and pluripotent stem cell-derived neurospheres (n = 12/12) to see their role in the central nervous system. Expression levels of mRNA for autism (n for case/control = 18/24) were also examined using scalp hair follicles.

RESULTS

Among mRNA examined, FABP4 was downregulated in schizophrenia subjects by two independent sample sets. Receiver operating characteristic curve analysis determined that the sensitivity and specificity were 71.8% and 66.7%, respectively. FABP4 was expressed from the stage of neurosphere. Additionally, microarray-based microRNA analysis showed a trend of increased expression of hsa-miR-4449 (p = .0634) in hair follicles from schizophrenia. hsa-miR-4449 expression was increased in Brodmann area 46 from schizophrenia (p = .0007). Finally, we tested the expression of nine putative autism candidate genes in hair follicles and found decreased CNTNAP2 expression in the autism cohort.

CONCLUSIONS

Scalp hair follicles could be a beneficial genetic biomarker resource for brain diseases, and further studies of FABP4 are merited in schizophrenia pathogenesis.

Expression profiling reveals genes involved in the regulation of wool follicle bulb regression and regeneration in sheep

Wool is an important material in textile manufacturing. In order to investigate the intrinsic factors that regulate wool follicle cycling and wool fiber properties, Illumina sequencing was performed on wool follicle bulb samples from the middle anagen, catagen and late telogen/early anagen phases. In total, 13,898 genes were identified. KRTs and KRTAPs are the most highly expressed gene families in wool follicle bulb. In addition, 438 and 203 genes were identified to be differentially expressed in wool follicle bulb samples from the middle anagen phase compared to the catagen phase and the samples from the catagen phase compared to the late telogen/early anagen phase, respectively. Finally, our data revealed that two groups of genes presenting distinct expression patterns during the phase transformation may have important roles for wool follicle bulb regression and regeneration. In conclusion, our results demonstrated the gene expression patterns in the wool follicle bulb and add new data towards an understanding of the mechanisms involved in wool fiber growth in sheep.

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.

New facets of keratin K77: interspecies variations of expression and different intracellular location in embryonic and adult skin of humans and mice

The differential expression of keratins is central to the formation of various epithelia and their appendages. Structurally, the type II keratin K77 is closely related to K1, the prototypical type II keratin of the suprabasal epidermis. Here, we perform a developmental study on K77 expression in human and murine skin. In both species, K77 is expressed in the suprabasal fetal epidermis. While K77 appears after K1 in the human epidermis, the opposite is true for the murine tissue. This species-specific pattern of expression is also found in conventional and organotypic cultures of human and murine keratinocytes. Ultrastructure investigation shows that, in contrast to K77 intermediate filaments of mice, those of the human ortholog are not attached to desmosomes. After birth, K77 disappears without deleterious consequences from human epidermis while it is maintained in the adult mouse epidermis, where its presence has so far gone unnoticed. After targeted Krt1 gene deletion in mice, K77 is normally expressed but fails to functionally replace K1. Besides the epidermis, both human and mouse K77 are present in luminal duct cells of eccrine sweat glands. The demonstration of a K77 ortholog in platypus but not in non-mammalian vertebrates identifies K77 as an evolutionarily ancient component of the mammalian integument that has evolved different patterns of intracellular distribution and adult tissue expression in primates.

To the Root of the Curl: A Signature of a Recent Selective Sweep Identifies a Mutation That Defines the Cornish Rex Cat Breed

The cat (Felis silvestris catus) shows significant variation in pelage, morphological, and behavioral phenotypes amongst its over 40 domesticated breeds. The majority of the breed specific phenotypic presentations originated through artificial selection, especially on desired novel phenotypic characteristics that arose only a few hundred years ago. Variations in coat texture and color of hair often delineate breeds amongst domestic animals. Although the genetic basis of several feline coat colors and hair lengths are characterized, less is known about the genes influencing variation in coat growth and texture, especially rexoid – curly coated types. Cornish Rex is a cat breed defined by a fixed recessive curly coat trait. Genome-wide analyses for selection (d_i, Tajima’s D and nucleotide diversity) were performed in the Cornish Rex breed and in 11 phenotypically diverse breeds and two random bred populations. Approximately 63K SNPs were used in the analysis that aimed to localize the locus controlling the rexoid hair texture. A region with a strong signature of recent selective sweep was identified in the Cornish Rex breed on chromosome A1, as well as a consensus block of homozygosity that spans approximately 3 Mb. Inspection of the region for candidate genes led to the identification of the lysophosphatidic acid receptor 6 (LPAR6). A 4 bp deletion in exon 5, c.250_253_delTTTG, which induces a premature stop codon in the receptor, was identified via Sanger sequencing. The mutation is fixed in Cornish Rex, absent in all straight haired cats analyzed, and is also segregating in the German Rex breed. LPAR6 encodes a G protein-coupled receptor essential for maintaining the structural integrity of the hair shaft; and has mutations resulting in a wooly hair phenotype in humans.

A splice variant in KRT71 is associated with curly coat phenotype of Selkirk Rex cats

One of the salient features of the domestic cat is the aesthetics of its fur. The Selkirk Rex breed is defined by an autosomal dominant woolly rexoid hair (ADWH) abnormality that is characterized by tightly curled hair shafts. A genome-wide case - control association study was conducted using 9 curly coated Selkirk Rex and 29 controls, including straight-coated Selkirk Rex, British Shorthair and Persian, to localize the Selkirk autosomal dominant rexoid locus (SADRE). Although the control cats were from different breed lineages, they share recent breeding histories and were validated as controls by Bayesian clustering, multi-dimensional scaling and genomic inflation. A significant association was found on cat chromosome B4 (Praw = 2.87 × 10(-11)), and a unique haplotype spanning ~600 Kb was found in all the curly coated cats. Direct sequencing of four candidate genes revealed a splice site variant within the KRT71 gene associated with the hair abnormality in Selkirk Rex.

The Germinative Epithelium of Sheep Vibrissae and Wool Follicles has Extensive Proliferative Potential but is Dependent on the Dermal Papilla

AIM

To investigate the growth potential of keratinocytes derived from the germinative epithelium (GE) of ovine hair follicles. Stem cells from the outer root sheath (ORS) of hair follicles migrate to the GE in the lower follicle where they proliferate and differentiate to form the hair fiber. It has been suggested that the GE comprises transit-amplifying cells and that the duration of anagen is determined by their limited proliferative potential. However, we show here that keratinocytes derived from the GE of ovine follicles grow extensively in vitro, arguing against this hypothesis.

MATERIALS AND METHODS

Primary cultures of keratinocytes were initiated from microdissected GE tissue from ovine vibrissae and wool follicles. Clonal lines of keratinocytes were derived by limiting dilution. Their growth potential was determined by exhaustive serial passaging. Expression of differentiation markers was evaluated by real-time polymerase chain reaction.

RESULTS

Initiation of these cultures required that interaction between the GE and dermal papilla was maintained. However, the keratinocytes could subsequently be cloned and were grown as pure cell populations for 26-52 cell doublings. This proliferative potential is several orders of magnitude greater than required to maintain a single anagen phase. The keratinocytes were indistinguishable from ORS keratinocytes from the same follicles, expressing K14 while undifferentiated, and upregulating the epidermal and inner root sheath markers, loricrin and KRT27 on differentiation. Thus, these cells initially depend on papilla-derived signals to grow, but can revert to an ORS-like phenotype in vitro. Their extensive proliferative capacity shows that the GE is not an exclusively transit-amplifying cell population.

An in vivo screen of secreted proteins identifies adiponectin as a regulator of murine cutaneous wound healing

Skin wounds comprise a serious medical issue for which few pharmacological interventions are available. Moreover, the inflammatory, angiogenic, and proliferative facets of a typical response to a wound each have broader relevance in other pathological conditions. Here we describe a genomics-driven approach to identify secreted proteins that modulate wound healing in a mouse ear punch model. We show that adiponectin, when injected into the wound edge, accelerates wound healing. Notably, adiponectin injection causes upregulation of keratin gene transcripts within hours of treatment, and subsequently promotes collagen organization, formation of pilosebaceous units, and proliferation of cells in the basal epithelial cell layer and pilosebaceous units of healing tissue. The globular domain of adiponectin is sufficient to mediate accelerated dorsal skin wound closure, and the effects are lost in mice that are homozygous null for the adiponectin receptor 1 gene. These findings extend recent observations of a protective role of adiponectin in other tissue injury settings, suggest modulation of AdipoR1 for the clinical management of wounds, and demonstrate a new approach to the identification of regulators of a wound healing response.

Redefining the structure of the hair follicle by 3D clonal analysis

The hair follicle (HF) is a multi-tissue mini-organ that self-renews periodically. However, the cellular organisation of this much-studied model is not fully understood. The structures of the outer layer and of the bulb, which ensures HF growth, have not been completely established. To clarify these points, we have conducted in vivo clonal analyses with 3D imaging in mice. The upper two-thirds of the HF outer layer consists of two clonally unrelated groups of cells that exhibit different modes of growth. They correspond to the basal outer root sheath (ORS) and the companion layer (Cp). The basal ORS has an unusual anisotropic mode of growth from a suprabulbar zone, which we named the privileged proliferation zone. The Cp has a stem/transient-amplifying mode of growth and is shown to be an HF internal structure. Furthermore, we describe an additional element, the bulb outer layer, which is contiguous and shares markers (e.g. Lgr5) with the basal ORS but is formed by a separate lineage that belongs neither to the ORS nor Cp lineage. It represents a novel element with proximal cells that are contiguous with the germinative layer in the bulb. In reference to its shape and position we named it the lower proximal cup (LPC). These clonal hierarchies reveal a novel model of HF organisation and growth based on two major entities: the basal ORS and the LPC plus the seven internal layers.

Mutations in AEC syndrome skin reveal a role for p63 in basement membrane adhesion, skin barrier integrity and hair follicle biology

BACKGROUND

AEC (ankyloblepharon-ectodermal defects-clefting) syndrome is an autosomal dominant ectodermal dysplasia disorder caused by mutations in the transcription factor p63. Clinically, the skin is dry and often fragile; other features can include partial eyelid fusion (ankyloblepharon), hypodontia, orofacial clefting, sparse hair or alopecia, and nail dystrophy.

OBJECTIVES

To investigate how p63 gene mutations affect gene and protein expression in AEC syndrome skin.

METHODS

We performed microarray analysis on samples of intact and eroded AEC syndrome skin compared with control skin. Changes were verified by quantitative real-time reverse transcription-polymerase chain reaction and, for basal keratinocyte-associated genes, by immunohistochemistry and analysis of microdissected skin.

RESULTS

We identified significant upregulation of six genes and downregulation of 69 genes in AEC syndrome skin, with the main changes in genes implicated in epidermal adhesion, skin barrier formation and hair follicle biology. There was reduced expression of genes encoding the basement membrane proteins FRAS1 and collagen VII, as well as the skin barrier-associated small proline-rich proteins 1A and 4, late cornified envelope protein 5A, hornerin, and lipid transporters including ALOX15B. Reduced expression of the hair-associated keratins 25, 27, 31, 33B, 34, 35, 81 and 85 was also noted. We also confirmed similar alterations in gene expression for 26 of the 75 genes in eroded AEC scalp skin.

CONCLUSIONS

This study identifies specific changes in skin structural biology and signalling pathways that result from mutant p63 and provides new molecular insight into the AEC syndrome phenotype.

The post-apoptotic fate of RNAs identified through high-throughput sequencing of human hair

The hair of all mammals consists of terminally differentiated cells that undergo a specialized form of apoptosis called cornification. While DNA is destroyed during cornification, the extent to which RNA is lost is unknown. Here we find that multiple types of RNA are incompletely degraded after hair shaft formation in both mouse and human. Notably, mRNAs and short regulatory microRNAs (miRNAs) are stable in the hair as far as 10 cm from the scalp. To better characterize the post-apoptotic RNAs that escape degradation in the hair, we performed sequencing (RNA-seq) on RNA isolated from hair shafts pooled from several individuals. This hair shaft RNA library, which encompasses different hair types, genders, and populations, revealed 7,193 mRNAs, 449 miRNAs and thousands of unannotated transcripts that remain in the post-apoptotic hair. A comparison of the hair shaft RNA library to that of viable keratinocytes revealed surprisingly similar patterns of gene coverage and indicates that degradation of RNA is highly inefficient during apoptosis of hair lineages. The generation of a hair shaft RNA library could be used as months of accumulated transcriptional history useful for retrospective detection of disease, drug response and environmental exposure.

LPA-producing enzyme PA-PLA₁α regulates hair follicle development by modulating EGFR signalling

Recent genetic studies of human hair disorders have suggested a critical role of lysophosphatidic acid (LPA) signalling in hair follicle development, mediated by an LPA-producing enzyme, phosphatidic acid-selective phospholipase A(1)α (PA-PLA(1)α, also known as LIPH), and a recently identified LPA receptor, P2Y5 (also known as LPA(6)). However, the underlying molecular mechanism is unknown. Here, we show that epidermal growth factor receptor (EGFR) signalling underlies LPA-induced hair follicle development. PA-PLA(1)α-deficient mice generated in this study exhibited wavy hairs due to the aberrant formation of the inner root sheath (IRS) in hair follicles, which resembled mutant mice defective in tumour necrosis factor α converting enzyme (TACE), transforming growth factor α (TGFα) and EGFR. PA-PLA(1)α was co-localized with TACE, TGFα and tyrosine-phosphorylated EGFR in the IRS. In PA-PLA(1)α-deficient hair follicles, cleaved TGFα and tyrosine-phosphorylated EGFR, as well as LPA, were significantly reduced. LPA, P2Y5 agonists and recombinant PA-PLA(1)α enzyme induced P2Y5- and TACE-mediated ectodomain shedding of TGFα through G12/13 pathway and consequent EGFR transactivation in vitro. These data demonstrate that a PA-PLA(1)α-LPA-P2Y5 axis regulates differentiation and maturation of hair follicles via a TACE-TGFα-EGFR pathway, thus underscoring the physiological importance of LPA-induced EGFR transactivation.