Reciprocal requirements for EDA/EDAR/NF-kappaB and Wnt/beta-catenin signaling pathways in hair follicle induction

The development of hair follicles and nail

The hair follicle and nail unit develop and regenerate through epithelial-mesenchymal interactions. Here, we review some of the key signals and molecular interactions that regulate mammalian hair follicle and nail formation during embryonic development and how these interactions are reutilized to promote their regeneration during adult homeostasis and in response to skin wounding. Finally, we highlight the role of some of these signals in mediating human hair follicle and nail conditions.

Region-specific gene expression profiling of early mouse mandible uncovered SATB2 as a key molecule for teeth patterning

Mammalian dentition exhibits distinct heterodonty, with more simple teeth located in the anterior area of the jaw and more complex teeth situated posteriorly. While some region-specific differences in signalling have been described previously, here we performed a comprehensive analysis of gene expression at the early stages of odontogenesis to obtain complete knowledge of the signalling pathways involved in early jaw patterning. Gene expression was analysed separately on anterior and posterior areas of the lower jaw at two early stages (E11.5 and E12.5) of odontogenesis. Gene expression profiling revealed distinct region-specific expression patterns in mouse mandibles, including several known BMP and FGF signalling members and we also identified several new molecules exhibiting significant differences in expression along the anterior-posterior axis, which potentially can play the role during incisor and molar specification. Next, we followed one of the anterior molecules, SATB2, which was expressed not only in the anterior mesenchyme where incisor germs are initiated, however, we uncovered a distinct SATB2-positive region in the mesenchyme closely surrounding molars. Satb2-deficient animals demonstrated defective incisor development confirming a crucial role of SATB2 in formation of anterior teeth. On the other hand, ectopic tooth germs were observed in the molar area indicating differential effect of Satb2-deficiency in individual jaw regions. In conclusion, our data provide a rich source of fundamental information, which can be used to determine molecular regulation driving early embryonic jaw patterning and serve for a deeper understanding of molecular signalling directed towards incisor and molar development.

Skin Development and Disease: A Molecular Perspective

Skin, the largest organ in the human body, is a crucial protective barrier that plays essential roles in thermoregulation, sensation, and immune defence. This complex organ undergoes intricate processes of development. Skin development initiates during the embryonic stage, orchestrated by molecular cues that control epidermal specification, commitment, stratification, terminal differentiation, and appendage growth. Key signalling pathways are integral in coordinating the development of the epidermis, hair follicles, and sweat glands. The complex interplay among these pathways is vital for the appropriate formation and functionality of the skin. Disruptions in multiple molecular pathways can give rise to a spectrum of skin diseases, from congenital skin disorders to cancers. By delving into the molecular mechanisms implicated in developmental processes, as well as in the pathogenesis of diseases, this narrative review aims to present a comprehensive understanding of these aspects. Such knowledge paves the way for developing innovative targeted therapies and personalised treatment approaches for various skin conditions.

Dynamic duo: Cell-extracellular matrix interactions in hair follicle development and regeneration

Ectodermal organs, such as hair follicles, originate from simple epithelial and mesenchymal sheets through a complex developmental process driven by interactions between these cell types. This process involves dermal condensation, placode formation, bud morphogenesis, and organogenesis, and all of these processes require intricate interactions among various tissues. Recent research has emphasized the crucial role of reciprocal and dynamic interactions between cells and the extracellular matrix (ECM), referred to as the "dynamic duo", in the development of ectodermal organs. These interactions provide spatially and temporally changing biophysical and biochemical cues within tissues. Using the hair follicle as an example, this review highlights two types of cell-ECM adhesion units-focal adhesion-type and hemidesmosome-type adhesion units-that facilitate communication between epithelial and mesenchymal cells. This review further explores how these adhesion units, along with other cell-ECM interactions, evolve during hair follicle development and regeneration, underscoring their importance in guiding both developmental and regenerative processes.

Notum regulates the cusp and root patterns in mouse molar

Notum is a direct target of Wnt/β-catenin signaling and plays a crucial role as a Wnt inhibitor within a negative feedback loop. In the tooth, Notum is known to be expressed in odontoblasts, and severe dentin defects and irregular tooth roots have been reported in Notum-deficient mice. However, the precise expression pattern of Notum in early tooth development, and the role of Notum in crown and root patterns remain elusive. In the present study, we identified a novel Notum expression in primary enamel knot (EK), secondary EKs, and dental papilla during tooth development. Notum-deficient mice exhibited enlarged secondary EKs, resulting in broader cusp tips, altered cusp patterns, and reduced concavity in crown outline. These alterations in crown outline led to a reduction in cervical tongue length, thereby inducing root fusion in Notum-deficient mice. Overall, these results suggest that the secondary EK size, regulated by the Wnt/Notum negative feedback loop, has a significant impact on the patterns of crown and root during tooth morphogenesis.

Anatomy, development and regeneration of zebrafish elasmoid scales

Vertebrate skin appendages - particularly avian feathers and mammalian hairs, glands and teeth - are perennially useful systems for investigating fundamental mechanisms of development. The most common type of skin appendage in teleost fishes is the elasmoid scale, yet this structure has received much less attention than the skin appendages of tetrapods. Elasmoid scales are thin, overlapping plates of partially mineralized extracellular matrices, deposited in the skin in a hexagonal pattern by a specialized population of dermal cells in cooperation with the overlying epidermis. Recent years have seen rapid progress in our understanding of elasmoid scale development and regeneration, driven by the deployment of developmental genetics, live imaging and transcriptomics in larval and adult zebrafish. These findings are reviewed together with histological and ultrastructural approaches to understanding scale development and regeneration.

Stabilization of Epithelial β-Catenin Compromises Mammary Cell Fate Acquisition and Branching Morphogenesis

The Wnt/β-catenin pathway plays a critical role in cell fate specification, morphogenesis, and stem cell activation across diverse tissues, including the skin. In mammals, the embryonic surface epithelium gives rise to the epidermis as well as the associated appendages including hair follicles and mammary glands, both of which depend on epithelial Wnt/β-catenin activity for initiation of their development. Later on, Wnts are thought to enhance mammary gland growth and branching, whereas in hair follicles, they are essential for hair shaft formation. In this study, we report a strong downregulation of epithelial Wnt/β-catenin activity as the mammary bud progresses to branching. We show that forced activation of epithelial β-catenin severely compromises embryonic mammary gland branching. However, the phenotype of conditional Lef1-deficient embryos implies that a low level of Wnt/β-catenin activity is necessary for mammary cell survival. Transcriptomic profiling suggests that sustained high β-catenin activity leads to maintenance of mammary bud gene signature at the expense of outgrowth/branching gene signature. In addition, it leads to upregulation of epidermal differentiation genes. Strikingly, we find a partial switch to hair follicle fate early on upon stabilization of β-catenin, suggesting that the level of epithelial Wnt/β-catenin signaling activity may contribute to the choice between skin appendage identities.

Oxidative stress in hair follicle development and hair growth: Signalling pathways, intervening mechanisms and potential of natural antioxidants

Hair follicle development and hair growth are regulated by multiple factors and multiple signalling pathways. The hair follicle, as an important skin appendage, is the basis for hair growth, and it has the functions of safeguarding the body, perceiving the environment and regulating body temperature. Hair growth undergoes a regular hair cycle, including anagen, catagen and telogen. A small amount of physiological shedding of hair occurs under normal conditions, always in a dynamic equilibrium. Hair loss occurs when the skin or hair follicles are stimulated by oxidative stress, inflammation or hormonal disorders that disrupt the homeostasis of the hair follicles. Numerous researches have indicated that oxidative stress is an important factor causing hair loss. Here, we summarize the signalling pathways and intervention mechanisms by which oxidative stress affects hair follicle development and hair growth, discuss existing treatments for hair loss via the antioxidant pathway and provide our own insights. In addition, we collate antioxidant natural products promoting hair growth in recent years and discuss the limitations and perspectives of current hair loss prevention and treatment.

Integrating Single-Cell and Spatial Transcriptomics Reveals Heterogeneity of Early Pig Skin Development and a Subpopulation with Hair Placode Formation

The dermis and epidermis, crucial structural layers of the skin, encompass appendages, hair follicles (HFs), and intricate cellular heterogeneity. However, an integrated spatiotemporal transcriptomic atlas of embryonic skin has not yet been described and would be invaluable for studying skin-related diseases in humans. Here, single-cell and spatial transcriptomic analyses are performed on skin samples of normal and hairless fetal pigs across four developmental periods. The cross-species comparison of skin cells illustrated that the pig epidermis is more representative of the human epidermis than mice epidermis. Moreover, Phenome-wide association study analysis revealed that the conserved genes between pigs and humans are strongly associated with human skin-related diseases. In the epidermis, two lineage differentiation trajectories describe hair follicle (HF) morphogenesis and epidermal development. By comparing normal and hairless fetal pigs, it is found that the hair placode (Pc), the most characteristic initial structure in HFs, arises from progenitor-like OGN+/UCHL1+ cells. These progenitors appear earlier in development than the previously described early Pc cells and exhibit abnormal proliferation and migration during differentiation in hairless pigs. The study provides a valuable resource for in-depth insights into HF development, which may serve as a key reference atlas for studying human skin disease etiology using porcine models.

Modelling Human Hair Follicles-Lessons from Animal Models and Beyond

The hair follicle is a specialized appendage of the skin that is critical for multiple functions, including thermoregulation, immune surveillance, and sebum production. Mammals are born with a fixed number of hair follicles that develop embryonically. Postnatally, these hair follicles undergo regenerative cycles of regression and growth that recapitulate many of the embryonic signaling pathways. Furthermore, hair cycles have a direct impact on skin regeneration in homeostasis, cutaneous wound healing, and disease conditions such as alopecia. Here, we review the current knowledge of hair follicle formation during embryonic development and the post-natal hair cycle, with an emphasis on the molecular signaling pathways underlying these processes. We then discuss efforts to capitalize on the field's understanding of in vivo mechanisms to bioengineer hair follicles or hair-bearing skin in vitro and how such models may be further improved to develop strategies for hair regeneration.

Immune niches for hair follicle development and homeostasis

The hair follicle is a dynamic mini-organ that has specialized cycles and architectures with diverse cell types to form hairs. Previous studies for several decades have investigated morphogenesis and signaling pathways during embryonic development and adult hair cycles in both mouse and human skin. In particular, hair follicle stem cells and mesenchymal niches received major attention as key players, and their roles and interactions were heavily revealed. Although resident and circulating immune cells affect cellular function and interactions in the skin, research on immune cells has mainly received attention on diseases rather than development or homeostasis. Recently, many studies have suggested the functional roles of diverse immune cells as a niche for hair follicles. Here, we will review recent findings about immune niches for hair follicles and provide insight into mechanisms of hair growth and diseases.

Mechanical forces across compartments coordinate cell shape and fate transitions to generate tissue architecture

Morphogenesis and cell state transitions must be coordinated in time and space to produce a functional tissue. An excellent paradigm to understand the coupling of these processes is mammalian hair follicle development, which is initiated by the formation of an epithelial invagination-termed placode-that coincides with the emergence of a designated hair follicle stem cell population. The mechanisms directing the deformation of the epithelium, cell state transitions and physical compartmentalization of the placode are unknown. Here we identify a key role for coordinated mechanical forces stemming from contractile, proliferative and proteolytic activities across the epithelial and mesenchymal compartments in generating the placode structure. A ring of fibroblast cells gradually wraps around the placode cells to generate centripetal contractile forces, which, in collaboration with polarized epithelial myosin activity, promote elongation and local tissue thickening. These mechanical stresses further enhance compartmentalization of Sox9 expression to promote stem cell positioning. Subsequently, proteolytic remodelling locally softens the basement membrane to facilitate a release of pressure on the placode, enabling localized cell divisions, tissue fluidification and epithelial invagination into the underlying mesenchyme. Together, our experiments and modelling identify dynamic cell shape transformations and tissue-scale mechanical cooperation as key factors for orchestrating organ formation.

Compound heterozygous WNT10A missense variations exacerbated the tooth agenesis caused by hypohidrotic ectodermal dysplasia

BACKGROUND

The aim of this study was to analyse the differences in the phenotypes of missing teeth between a pair of brothers with hypohidrotic ectodermal dysplasia (HED) and to investigate the underlying mechanism by comparing the mutated gene loci between the brothers with whole-exome sequencing.

METHODS

The clinical data of the patients and their mother were collected, and genomic DNA was extracted from peripheral blood samples. By Whole-exome sequencing filtered for a minor allele frequency (MAF) ≤0.05 non-synonymous single-nucleotide variations and insertions/deletions variations in genes previously associated with tooth agenesis, and variations considered as potentially pathogenic were assessed by SIFT, Polyphen-2, CADD and ACMG. Sanger sequencing was performed to detect gene variations. The secondary and tertiary structures of the mutated proteins were predicted by PsiPred 4.0 and AlphaFold 2.

RESULTS

Both brothers were clinically diagnosed with HED, but the younger brother had more teeth than the elder brother. An EDA variation (c.878 T > G) was identified in both brothers. Additionally, compound heterozygous variations of WNT10A (c.511C > T and c.637G > A) were identified in the elder brother. Digenic variations in EDA (c.878 T > G) and WNT10A (c.511C > T and c.637G > A) in the same patient have not been reported previously. The secondary structure of the variant WNT10A protein showed changes in the number and position of α-helices and β-folds compared to the wild-type protein. The tertiary structure of the WNT10A variant and molecular simulation docking showed that the site and direction where WNT10A binds to FZD5 was changed.

CONCLUSIONS

Compound heterozygous WNT10A missense variations may exacerbate the number of missing teeth in HED caused by EDA variation.

Activation of wnt/β-catenin signaling pathway down regulated osteogenic differentiation of bone marrow-derived stem cells in an anhidrotic ectodermal dysplasia patient with EDA/EDAR/EDARADD mutation

Objective

To explore the mechanism by which the Wnt/β-catenin pathway induces osteogenic differentiation of bone marrow-derived stem cells (BMSCs) in anhidrotic ectodermal dysplasia (AED) with an Ectodysplasin A (EDA)/EDA receptor (EDAR)/EDARADD mutation.

Methods

An AED patient served as the AED group, whereas the other patients without AED were included in the normal group. Peripheral venous blood collected from the AED patient was subjected to whole-genome resequencing. BMSCs from the mandible of patients with AED and normal individuals were isolated and cultured in vitro. Cell proliferation assay was performed to compare the growth speed of BMSCs between the AED and normal groups. CHIR-99021, an activator of the Wnt/β-catenin pathway and XAV-939, an inhibitor, was used to manage BMSCs in an osteogenic environment in both groups. The expression of β-catenin was detected by quantitative polymerase chain reaction, while that of RUNX2 was detected by western blotting. Alizarin red was used for staining.

Results

A novel mutation (c.152T > A in EDA) and two known mutations (c.1109T > C in EDAR and c.27G > A in EDARADD) were identified. The growth rate in the normal group was higher than that in the AED group. In the normal group, the number and size of calcified nodes and the expression of RUNX-2 increased with CHIR-99021 treatment, which could be inhibited by XAV-939. In contrast, CHIR-99021 inhibited osteogenesis in the AED group and this effect was promoted by XAV-939.

Conclusion

Activation of the Wnt/β-catenin pathway downregulates osteogenesis of BMSCs in AED patients with EDA/EDAR/EDARADD gene mutations. Further investigation in more AED patients is required, given the wide range of mutations involved in AED.

Sweat gland development requires an eccrine dermal niche and couples two epidermal programs

Eccrine sweat glands are indispensable for human thermoregulation and, similar to other mammalian skin appendages, form from multipotent epidermal progenitors. Limited understanding of how epidermal progenitors specialize to form these vital organs has precluded therapeutic efforts toward their regeneration. Herein, we applied single-nucleus transcriptomics to compare the expression content of wild-type, eccrine-forming mouse skin to that of mice harboring a skin-specific disruption of Engrailed 1 (En1), a transcription factor that promotes eccrine gland formation in humans and mice. We identify two concurrent but disproportionate epidermal transcriptomes in the early eccrine anlagen: one that is shared with hair follicles and one that is En1 dependent and eccrine specific. We demonstrate that eccrine development requires the induction of a dermal niche proximal to each developing gland in humans and mice. Our study defines the signatures of eccrine identity and uncovers the eccrine dermal niche, setting the stage for targeted regeneration and comprehensive skin repair.

A Missense Mutation in the Collagen Triple Helix of EDA Is Associated with X-Linked Recessive Hypohidrotic Ectodermal Dysplasia in Fleckvieh Cattle

Mutations within the ectodysplasin A (EDA) gene have been associated with congenital hypotrichosis and anodontia (HAD/XHED) in humans, mice, dogs and cattle. We identified a three-generation family of Fleckvieh cattle with male calves exhibiting clinical and histopathological signs consistent with an X-linked recessive HAD (XHED). Whole genome and Sanger sequencing of cDNA showed a perfect association of the missense mutation g.85716041G>A (ss2019497443, rs1114816375) within the EDA gene with all three cases following an X-linked recessive inheritance, but normal EDAR and EDARADD. This mutation causes an exchange of glycine (G) with arginine (R) at amino acid position 227 (p.227G>R) in the second collagen triple helix repeat domain of EDA. The EDA variant was associated with a significant reduction and underdevelopment of hair follicles along with a reduced outgrowth of hairs, a complete loss of seromucous nasolabial and mucous tracheal and bronchial glands and a malformation of and reduction in number of teeth. Thermostability of EDA G227R was reduced, consistent with a relatively mild hair and tooth phenotype. However, incisors and canines were more severely affected in one of the calves, which correlated with the presence of a homozygous missense mutation of RNF111 (g.51306765T>G), a putative candidate gene possibly associated with tooth number in EDA-deficient Fleckvieh calves.

Identification of Potential miRNA-mRNA Regulatory Network Associated with Growth and Development of Hair Follicles in Forest Musk Deer

In this study, sRNA libraries and mRNA libraries of HFs of FMD were constructed and sequenced using an Illumina HiSeq 2500, and the expression profiles of miRNAs and genes in the HFs of FMD were obtained at the anagen and catagen stages. In total, 565 differentially expressed unigenes (DEGs) were identified, 90 of which were upregulated and 475 of which were downregulated. In the BP category of GO enrichment, the DEGs were enriched in the processes related to HF development and differentiation, including the hair cycle regulation and processes, HF development, skin epidermis development, regulation of HF development, skin development, the Wnt signaling pathway, and the BMP signaling pathway. Through KEGG analysis it was found that DEGs were significantly enriched in pathways associated with HF development and growth. A total of 186 differentially expressed miRNAs (DEmiRNAs) were screened (p < 0.05) in the HFs of FMD at the anagen stage vs. the catagen stage, 33 of which were upregulated and 153 of which were downregulated. Through DEmiRNA-mRNA association analysis, we found DEmiRNAs and target genes that mainly play regulatory roles in HF development and growth. The enrichment analysis of DEmiRNA target genes revealed similarities with the enrichment results of DEGs associated with HF development. Notably, both sets of genes were enriched in key pathways such as the Notch signaling pathway, melanogenesis, the cAMP signaling pathway, and cGMP-PKG. To validate our findings, we selected 11 DEGs and 11 DEmiRNAs for experimental verification using RT-qPCR. The results of the experimental validation were consistent with the RNA-Seq results.

EDARADD promotes colon cancer progression by suppressing E3 ligase Trim21-mediated ubiquitination and degradation of Snail

Tumor cell migration, specifically epithelial-mesenchymal transition (EMT), serves as a key contributor to treatment failure in colon cancer patients. However, the limited comprehension of its genetic and biological aspects presents challenges for its investigation. EDAR-associated death domain (EDARADD), an important TNFR superfamily member, is elevated in colon cancer. However, it remains unclear about the exact role of EDARADD in the progression of colon cancer metastasis. In this study, we initially demonstrated that both protein and mRNA levels of EDDARADD are elevated in colon cancer tissues and cells, associated with reduced overall survival. Furthermore, functional experiments demonstrated that EDARADD promotes colon cancer cell proliferation and participates in EMT both in vitro and vivo. Mechanistically, Co-IP verified EDARADD could stabilize Snail1 by interacting with E3 ubiquitin ligase Trim21 to inhibit ubiquitination of Snail1. Interestingly, RNA-seq and ubiquitination assay revealed EDARADD's dual downregulation of Trim21 expression at the translational level via Cul1-mediated ubiquitin degradation, and at the transcriptional level through PPARa regulation. Moreover, EDARADD activates NF-κB signaling and experiences feedback transcriptional regulation by p65. In conclusion, this study highlights the signal pathway of EDARADD-PPARa-Trim21-Snail1-EMT and a feedback regulation of NF-κB signaling on EDARADD, which indicated EDARADD as an emerging therapeutic target for colon cancer.

Identification of N6-Methyladenosine-Related Factors and the Prediction of the Regulatory Mechanism of Hair Follicle Development in Rex and Hycole Rabbits

Hair follicle development directly affects the development of the rabbit fur industry. The growth and development of a hair follicle is modified and regulated by many genes and mechanisms. M6A is an important RNA modification. However, there are few studies on the effects of the regulation of m6A on hair follicle growth and development. In this study, hematoxylin-eosin (HE) staining was used to explore the difference in hair follicle development between Rex rabbits and Hycole rabbits, and we performed m6A sequencing to identify the key genes with m6A modification in hair follicle growth. The results showed that the hair length, coarse hair percentage, primary hair follicle ratio, and skin thickness of Hycole rabbits were significantly higher than those of Rex rabbits. However, the proportion of secondary hair follicles in Hycole rabbits was significantly lower than that in Rex rabbits. In addition, we found five differential methylases, 20 differential genes, and 24 differential signaling pathways related to hair growth and development. The results of the Sankey diagram showed that 12 genes were related to 13 signal pathways. Finally, we found that five methylases regulated the development of hair follicles through differential genes/signal pathways. These findings laid a molecular foundation for the function of m6A modification in hair development.

Mesenchyme governs hair follicle induction

Tissue interactions are essential for guiding organ development and regeneration. Hair follicle formation relies on inductive signalling between two tissues, the embryonic surface epithelium and the adjacent mesenchyme. Although previous research has highlighted the hair-inducing potential of the mesenchymal component of the hair follicle - the dermal papilla and its precursor, the dermal condensate - the source and nature of the primary inductive signal before dermal condensate formation have remained elusive. Here, we performed epithelial-mesenchymal tissue recombination experiments using hair-forming back skin and glabrous plantar skin from mouse embryos to unveil that the back skin mesenchyme is inductive even before dermal condensate formation. Moreover, the naïve, unpatterned mesenchyme was sufficient to trigger hair follicle formation even in the oral epithelium. Building on previous knowledge, we explored the hair-inductive ability of the Wnt agonist R-spondin 1 and a Bmp receptor inhibitor in embryonic skin explants. Although R-spondin 1 instigated precocious placode-specific transcriptional responses, it was insufficient for hair follicle induction, either alone or in combination with Bmp receptor inhibition. Our findings pave the way for identifying the hair follicle-inducing cue.

Molecular and spatial landmarks of early mouse skin development

A wealth of specialized cell populations within the skin facilitates its hair-producing, protective, sensory, and thermoregulatory functions. How the vast cell-type diversity and tissue architecture develops is largely unexplored. Here, with single-cell transcriptomics, spatial cell-type assignment, and cell-lineage tracing, we deconstruct early embryonic mouse skin during the key transitions from seemingly uniform developmental precursor states to a multilayered, multilineage epithelium, and complex dermal identity. We identify the spatiotemporal emergence of hair-follicle-inducing, muscle-supportive, and fascia-forming fibroblasts. We also demonstrate the formation of the panniculus carnosus muscle (PCM), sprouting blood vessels without pericyte coverage, and the earliest residence of mast and dendritic immune cells in skin. Finally, we identify an unexpected epithelial heterogeneity within the early single-layered epidermis and a signaling-rich periderm layer. Overall, this cellular and molecular blueprint of early skin development-which can be explored at https://kasperlab.org/tools-establishes histological landmarks and highlights unprecedented dynamic interactions among skin cells.

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.

Extremely hair follicle density is associated with a significantly different cecal microbiota in rex rabbits

It has become increasingly clear that gut microbiota and skin are interconnected since the discovery of the 'gut-brain-skin' axis. Hair follicles (HFs) are skin microorganisms, but few studies have investigated their relationship to gut microbiota. Hence, we hypothesize that HFs have a close relationship with the gut, similarly to what was reported for the skin. Using rex rabbits as an animal model, one hundred healthy half-sibling rex rabbits were selected for the experiment, and 16 s rRNA gene sequencing was performed on the cecal microbiota of nine rabbits with the extremely high (HS) and low (LS) hair density (n = 9 per group) to determine differences between the composition and function of these communities. In comparison with the LS group, several alpha diversity index values were significantly lower in the HS group, although the higher variation in species composition in the HS group. Additionally, species diversity and abundance differed significantly in the cecum microbiota of HS and LS rabbits. Further, primary and secondary HF density was significantly correlated with the families Muribaculaceae and Bacteroidaceae, and genera Blautia, Bacteroides and Desulfovibrio. In particular, Muribaculaceae, Bacteroidaceae, Blautia and Bacteroides may support the development of HFs. Moreover, the expression of WNT4, WNT10a, WNT10b, CTNNB1 (β-catenin) and LEF1 in the skin was significantly higher in the HS group compared with the LS group. Altogether, the results of this study suggest that the extremely high density of HF in rabbits is associated with a significantly different microbiota diversity and community structure, and the Wnt/β-catenin signalling pathway was activated in the HS group. Thus, key bacteria may promote the development of HF.

Bioengineered skin organoids: from development to applications

Significant advancements have been made in recent years in the development of highly sophisticated skin organoids. Serving as three-dimensional models that mimic human skin, these organoids have evolved into complex structures and are increasingly recognized as effective alternatives to traditional culture models and human skin due to their ability to overcome the limitations of two-dimensional systems and ethical concerns. The inherent plasticity of skin organoids allows for their construction into physiological and pathological models, enabling the study of skin development and dynamic changes. This review provides an overview of the pivotal work in the progression from 3D layered epidermis to cyst-like skin organoids with appendages. Furthermore, it highlights the latest advancements in organoid construction facilitated by state-of-the-art engineering techniques, such as 3D printing and microfluidic devices. The review also summarizes and discusses the diverse applications of skin organoids in developmental biology, disease modelling, regenerative medicine, and personalized medicine, while considering their prospects and limitations.

Garlic Exosomes Promote Hair Growth Through the Wnt/β-catenin Pathway and Growth Factors

Background Exosomes are membrane-derived nanovesicles produced by cells and play an important role in intercellular communication. Objectives This study aimed to investigate the effects of garlic exosome (GE) on hair growth. Methods Forty-two Sprague-Dawley/Wistar albino rats were randomly divided into six groups: non-shaved control, shaved control, topical control, GE 2 mg, GE 4 mg, and topical GE. At the end of the experiment, the number of hair follicles, follicle diameter, and subcutaneous tissue thicknesses were measured histopathologically. The Wnt-1, β-catenin, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), transforming growth factor-β1 (TGF-β1), and collagen I levels were measured by the Western Blot method. Results The anagen follicle counts of the GE 2 mg, 4 mg, and topical GE groups were 66.57±15.49, 105.71±25.06, and 55.29±6.72, and were significantly higher than the control groups (p<0.01, p<0.001 and p<0.05, respectively). The follicle diameter of the GE 4 mg group was higher than the others (p<0.05). The Wnt-1, PDGF, VEGF, TGF-β1, and collagen I levels of all GE groups, and the β-catenin levels of the GE 4 mg and topical GE groups were significantly higher than the control groups (p<0.05). Conclusion GE induces hair growth in rats via the Wnt-1, β-catenin, VEGF, PDGF, and TGF-β1 signaling pathways.

Transcriptomic landscape of early hair follicle and epidermal development

Morphogenesis of ectodermal organs, such as hair, tooth, and mammary gland, starts with the formation of local epithelial thickenings, or placodes, but it remains to be determined how distinct cell types and differentiation programs are established during ontogeny. Here, we use bulk and single-cell transcriptomics and pseudotime modeling to address these questions in developing hair follicles and epidermis and produce a comprehensive transcriptomic profile of cellular populations in the hair placode and interplacodal epithelium. We report previously unknown cell populations and marker genes, including early suprabasal and genuine interfollicular basal markers, and propose the identity of suprabasal progenitors. By uncovering four different hair placode cell populations organized in three spatially distinct areas, with fine gene expression gradients between them, we posit early biases in cell fate establishment. This work is accompanied by a readily accessible online tool to stimulate further research on skin appendages and their progenitors.

Urotensin II promotes the proliferation and secretion of vascular endothelial growth factor in rat dermal papilla cells by activating the Wnt-β-catenin signaling pathway

Introduction. Urotensin II (U II) is a kind of active peptide with a variety of biological effects, such as promoting cell proliferation and endocrine effects. The aim of this study is to investigate the effect of urotensin II on the proliferation and secretion of vascular endothelial growth factor (VEGF) in cultured rat dermal papilla cells (DPCs), and to explore its molecular mechanism. Materials and Methods. We used the DPCs isolated from the thoracic aortas of Wistar-Kyoto rats to run the CCK8 and ELISA assay, RC-PCR and Western blotting techniques to identify the effect of Urotensin II on the proliferation and secretion of VEGF in DPCs, data were analyzed by one-way ANOVA or t-test. Results. U II can increase the mRNA expression of proliferation markers Ki67 and PCNA. In addition, the Wnt/β-catenin pathway was activated by U II, but Wnt inhibitor DKK1 reversed the effect of U II. Conclusions. U II promoted the proliferation and secretion of VEGF in rat DPCs through activation of the Wnt-β-catenin signaling pathway.

Altered hair root gene expression profiles highlight calcium signaling and lipid metabolism pathways to be associated with curly hair initiation and maintenance in Mangalitza pigs

Hair types have been under strong targeted selection in domestic animals for their impact on skin protection, thermoregulation and exterior morphology, and subsequent economic importance. In pigs, a very special hair phenotype was observed in Mangalitza, who expresses a thick coat of curly bristles and downy hair. Two breed-specific missense variants in TRPM2 and CYP4F3 were suggested to be associated with the Mangalitza pig's hair shape due to their role in hair follicle morphogenesis reported for human and mice. However, the mechanism behind this expression of a curly hair type is still unclear and needs to be explored. In our study, hair shafts were measured and investigated for the curvature of the hair in Mangalitza and crossbreeds in comparison to straight-coated pigs. For molecular studies, hair roots underwent RNA sequencing for a differential gene expression analysis using DESeq2. The output matrix of normalized counts was then used to construct weighted gene co-expression networks. The resulting hair root gene expression profiles highlighted 454 genes to be significantly differentially expressed for initiation of curly hair phenotype in newborn Mangalitza piglets versus post-initiation in later development. Furthermore, 2,554 genes showed a significant differential gene expression in curly hair in comparison to straight hair. Neither TRPM2 nor CYP4F3 were identified as differentially expressed. Incidence of the genes in weighted co-expression networks associated with TRPM2 and CYP4F3, and prominent interactions of subsequent proteins with lipids and calcium-related pathways suggested calcium signaling and/or lipid metabolism as essential players in the induction of the curly hair as well as an ionic calcium-dependency to be a prominent factor for the maintenance of this phenotype. Subsequently, our study highlights the complex interrelations and dependencies of mutant genes TRPM2 and CYP4F3 and associated gene expression patterns, allowing the initiation of curly hair type during the development of a piglet as well as the maintenance in adult individuals.

Of Turing and zebras: Turing diffusion inspires applications in nature and beyond: Turing diffusion inspires applications in nature and beyond

The Turing diffusion model emerges as an explanation for pattern formation in many species and across biological scales.

Combination of Transcriptomics and Proteomics Reveals Differentially Expressed Genes and Proteins in the Skin of EDAR Gene-Targeted and Wildtype Cashmere Goats

Cashmere goats play a pivotal role in the animal hair industry and are economically valuable. Cashmere is produced through the periodic growth of secondary hair follicles. To improve their yield of cashmere, the regulatory mechanisms of cashmere follicle growth and development need to be analysed. Therefore, in this study, EDAR gene-targeted cashmere goats were used as an animal model to observe the phenotypic characteristics of abnormal hair growth and development at the top of the head. Transcriptomic and proteomic techniques were used to screen for differentially expressed genes and proteins. In total, 732 differentially expressed genes were identified, including 395 upregulated and 337 downregulated genes. In addition, 140 differentially expressed proteins were identified, including 69 upregulated and 71 downregulated proteins. These results provide a research target for elucidating the mechanism through which EDAR regulates hair follicle growth in cashmere goats. It also enriches the available data on the regulatory network involved in hair follicle growth.

The developmental basis of fingerprint pattern formation and variation

Fingerprints are complex and individually unique patterns in the skin. Established prenatally, the molecular and cellular mechanisms that guide fingerprint ridge formation and their intricate arrangements are unknown. Here we show that fingerprint ridges are epithelial structures that undergo a truncated hair follicle developmental program and fail to recruit a mesenchymal condensate. Their spatial pattern is established by a Turing reaction-diffusion system, based on signaling between EDAR, WNT, and antagonistic BMP pathways. These signals resolve epithelial growth into bands of focalized proliferation under a precociously differentiated suprabasal layer. Ridge formation occurs as a set of waves spreading from variable initiation sites defined by the local signaling environments and anatomical intricacies of the digit, with the propagation and meeting of these waves determining the type of pattern that forms. Relying on a dynamic patterning system triggered at spatially distinct sites generates the characteristic types and unending variation of human fingerprint patterns.

Structural insights into pathogenic mechanism of hypohidrotic ectodermal dysplasia caused by ectodysplasin A variants

EDA is a tumor necrosis factor (TNF) family member, which functions together with its cognate receptor EDAR during ectodermal organ development. Mutations of EDA have long been known to cause X-linked hypohidrotic dysplasia in humans characterized by primary defects in teeth, hair and sweat glands. However, the structural information of EDA interaction with EDAR is lacking and the pathogenic mechanism of EDA variants is poorly understood. Here, we report the crystal structure of EDA C-terminal TNF homology domain bound to the N-terminal cysteine-rich domains of EDAR. Together with biochemical, cellular and mouse genetic studies, we show that different EDA mutations lead to varying degrees of ectodermal developmental defects in mice, which is consistent with the clinical observations on human patients. Our work extends the understanding of the EDA signaling mechanism, and provides important insights into the molecular pathogenesis of disease-causing EDA variants.

Advances in tooth agenesis and tooth regeneration

The lack of treatment options for congenital (0.1%) and partial (10%) tooth anomalies highlights the need to develop innovative strategies. Over two decades of dedicated research have led to breakthroughs in the treatment of congenital and acquired tooth loss. We revealed that by inactivating USAG-1, congenital tooth agenesis can be successfully ameliorated during early tooth development and that the inactivation promotes late-stage tooth morphogenesis in double knockout mice. Furthermore, Anti- USAG-1 antibody treatment in mice is effective in tooth regeneration and can be a breakthrough in treating tooth anomalies in humans. With approximately 0.1% of the population suffering from congenital tooth agenesis and 10% of children worldwide suffering from partial tooth loss, early diagnosis will improve outcomes and the quality of life of patients. Understanding the role of pathogenic USAG-1 variants, their interacting gene partners, and their protein functions will help develop critical biomarkers. Advances in next-generation sequencing, mass spectrometry, and imaging technologies will assist in developing companion and predictive biomarkers to help identify patients who will benefit from tooth regeneration.

Wound-Induced Hair Neogenesis: A Portal to the Development of New Therapies for Hair Loss and Wound Regeneration

Adult mammals retain the remarkable ability to regenerate hair follicles after wounding. Wound-induced hair neogenesis (WIHN) in many ways recapitulates embryogenesis. The origin of the stem cells that give rise to a nascent hair follicle after wounding and the role of mesenchymal cells and signaling pathways responsible for this regenerative phenomenon are slowly being elucidated. WIHN provides a potential therapeutic window for manipulating cell fate by the introduction of factors during the wound healing process to enhance hair follicle formation.

Association between Circulating Ectodysplasin A and Diabetic Kidney Disease

Background

Ectodysplasin A (EDA), a member of the TNF family, plays important roles in ectodermal development, while recent studies expanded its regulatory effects on insulin resistance and lipid metabolism. This study was the first time to investigate the correlation between circulating EDA and albuminuria in patients with T2DM.

Methods

A total of 189 T2DM and 59 healthy subjects were enrolled in the study. We analyzed the concentrations of EDA by ELISA. Plasma glucose, insulin, HbA1c, lipids, creatinine, BUN, and UACR were also measured. Insulin resistance and pancreatic cell function were assessed by HOMA.

Results

Circulating EDA concentration was significantly increased in T2DM patients and increased with the degree of albuminuria. EDA was positively correlated with age, FIns, HOMA-IR, HOMA-β, Scr, and UACR, and negatively correlated with eGFR. Linear stepwise regression showed that FIns, HOMA-β, and UACR were independent influencing factors of EDA. Logistic regression analysis showed that EDA was independently associated with the occurrence of albuminuria in T2DM. ROC curve showed that EDA had an area under the receiver operating curve of 0.701 [95%CI = (0.625 - 0.777), P < 0.001].

Conclusion

EDA is positively correlated with the degree of albuminuria in patients with T2DM and may be involved in the occurrence and progression of diabetic kidney disease (DKD).

Skin-on-a-chip strategies for human hair follicle regeneration

The number of hair loss patients increases every year, and hair loss treatment has several limitations, so research on hair is attracting attention recently. However, most current hair follicle research models are limited by their inability to replicate several key functions of the hair follicle microenvironment. To complement this, an in vitro culture system similar to the in vivo environment must be constructed. It is necessary to develop a hair-on-a-chip that implements a fully functional hair follicle model by reproducing the main characteristics of hair follicle morphogenesis and cycle. In this review, we summarize the gradation of hair follicle morphogenesis and the roles and mechanisms of molecular signals involved in the hair follicle cycle. In addition, we discuss research results of various in vitro organoid products and organ-on-a-chip-based hair follicle tissue chips for the treatment of alopecia and present future research and development directions.

Distinct fibroblast progenitor subpopulation expedites regenerative mucosal healing by immunomodulation

Injuries that heal by fibrosis can compromise organ function and increase patient morbidity. The oral mucosal barrier has a high regenerative capacity with minimal scarring, but the cellular mechanisms remain elusive. Here, we identify distinct postnatal paired-related homeobox-1+ (Prx1+) cells as a critical fibroblast subpopulation that expedites mucosal healing by facilitating early immune response. Using transplantation and genetic ablation model in mice, we show that oral mucosa enriched with Prx1+ cells heals faster than those that lack Prx1+ cells. Lineage tracing and scRNA-seq reveal that Prx1+ fibroblasts exhibit progenitor signatures in physiologic and injured conditions. Mechanistically, Prx1+ progenitors accelerate wound healing by differentiating into immunomodulatory SCA1+ fibroblasts, which prime macrophage recruitment through CCL2 as a key part of pro-wound healing response. Furthermore, human Prx1+ fibroblasts share similar gene and spatial profiles compared to their murine counterpart. Thus, our data suggest that Prx1+ fibroblasts may provide a valuable source in regenerative procedures for the treatment of corneal wounds and enteropathic fibrosis.

The Role of Ectodysplasin A on the Ocular Surface Homeostasis

Ectodysplasin A (EDA), a ligand of the TNF family, plays an important role in maintaining the homeostasis of the ocular surface. EDA is necessary for the development of the meibomian gland, the lacrimal gland, as well as the proliferation and barrier function of the corneal epithelium. The mutation of EDA can induce the destruction of the ocular surface resulting in keratopathy, abnormality of the meibomian gland and maturation of the lacrimal gland. Experimental animal studies showed that a prenatal ultrasound-guided intra-amniotic injection or postnatal intravenous administration of soluble recombinant EDA protein can efficiently prevent the development of ocular surface abnormalities in EDA mutant animals. Furthermore, local application of EDA could restore the damaged ocular surface to some extent. Hence, a recombinant EDA-based therapy may serve as a novel paradigm to treat ocular surface disorders, such as meibomian gland dysfunction and corneal epithelium abnormalities.

Single-cell chromatin landscapes of mouse skin development

The coat of mammals is produced by hair follicles, and hair follicle is an important and complex accessory organ of skin. As a complex physiological regulation process, hair follicle morphogenesis is regulated by a series of signal pathway factors, involves the interaction of multiple cell types and begins in the early embryonic stage. However, its transcriptional regulatory mechanism is unclear. We have therefore utilized single-cell ATAC sequencing to obtain the chromatin accessibility landscapes of 6,928, 6,961 and 7,374 high-quality cells from the dorsal skins of E13.5, E16.5 and P0 mice (Mus musculus), respectively. Based on marker gene activity clustering, we defined 6, 8 and 5 distinct cell types in E13.5, E16.5 and P0 stages, respectively. Furtherly, we integrated the fibroblasts and keratinocytes clusters, performed further analysis and re-clustered. The single cell map of the chromatin open area was drawn from each cell type and the mechanism of cell transcription regulation was explored. Collectively, our data provide a reference for deeply exploring the epigenetic regulation mechanism of mouse hair follicles development.

The origins of skin diversity: lessons from dermal fibroblasts

Skin is largely composed of an epidermis that overlies a supporting dermis. Recent advancements in our understanding of how diverse groups of dermal fibroblasts regulate epidermal and hair follicle growth and differentiation have been fueled by tools capable of resolving molecular heterogeneity at a single-cell level. Fibroblast heterogeneity can be traced back to their developmental origin before their segregation into spatially distinct fibroblast subtypes. The mechanisms that drive this lineage diversification during development are being unraveled, with studies showing that both large- and small-scale positional signals play important roles during dermal development. Here, we first delineate what is known about the origins of the dermis and the central role of Wnt/β-catenin signaling in its specification across anatomical locations. We then discuss how one of the first morphologically recognizable fibroblast subtypes, the hair follicle dermal condensate lineage, emerges. Leveraging the natural variation of skin and its appendages between species and between different anatomical locations, these collective studies have identified shared and divergent factors that contribute to the extraordinary diversity of skin.

Identification of key pathways and genes that regulate cashmere development in cashmere goats mediated by exogenous melatonin

The growth of secondary hair follicles in cashmere goats follows a seasonal cycle. Melatonin can regulate the cycle of cashmere growth. In this study, melatonin was implanted into live cashmere goats. After skin samples were collected, transcriptome sequencing and histological section observation were performed, and weighted gene co-expression network analysis (WGCNA) was used to identify key genes and establish an interaction network. A total of 14 co-expression modules were defined by WGCNA, and combined with previous analysis results, it was found that the blue module was related to the cycle of cashmere growth after melatonin implantation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the first initiation of exogenous melatonin-mediated cashmere development was related mainly to the signaling pathway regulating stem cell pluripotency and to the Hippo, TGF-beta and MAPK signaling pathways. Via combined differential gene expression analyses, 6 hub genes were identified: PDGFRA, WNT5A, PPP2R1A, BMPR2, BMPR1A, and SMAD1. This study provides a foundation for further research on the mechanism by which melatonin regulates cashmere growth.

Homeostases of epidermis and hair follicle, and development of basal cell carcinoma

Hedgehog signaling (Hh) plays a critical role in embryogenesis. On the other hand, its overactivity may cause basal cell carcinoma (BCC), the most common human cancer. Further, epidermal and hair follicle homeostases may have a key role in the development of BCC. This article describes the importance of different signaling pathways in the different stages of the two processes. The description of the homeostases brought up the importance of the Notch signaling along with the sonic hedgehog (Shh) and the Wnt pathways. Loss of the Notch signaling adversely affects the late stages of hair follicle formation and allows the bulge cells in the hair follicles to take the fate of the keratinocytes in the interfollicular epidermis. Further, the loss of Notch activity upregulates the Shh and Wnt activities, adversely affecting the homeostases. Notably, the Notch signaling is suppressed in BCC, and the peripheral BCC cells, which have low Notch activity, show drug resistance in comparison to the interior suprabasal BCC cells, which have high Notch activity.

WNT10A variants: following the pattern of inheritance in tooth agenesis and self-reported family history of cancer

OBJECTIVES

The aim of this study was the analysis of WNT10A variants in seven families of probands with various forms of tooth agenesis and self-reported family history of cancer.

MATERIALS AND METHODS

We enrolled 60 young subjects (aged 13 to 17) from the Czech Republic with various forms of tooth agenesis. Dental phenotypes were assessed using Planmeca ProMax 3D (Planmeca Oy, Finland) with Planmeca Romexis software (version 2.9.2) together with oral examinations. After screening PAX9, MSX1, EDA, EDAR, AXIN2 and WNT10A genes on the Illumina MiSeq platform (Illumina, USA), we further analyzed the evolutionarily highly conserved WNT10A gene by capillary sequencing in the seven families.

RESULTS

All the detected variants were heterozygous or compound heterozygous with various levels of phenotypic expression. The most severe phenotype (oligodontia) was found in a proband who was compound heterozygous for the previously identified WNT10A variant p.Phe228Ile and a newly discovered c.748G > A variant (p.Gly250Arg) of WNT10A. The newly identified variant causes substitution of hydrophobic glycine for hydrophilic arginine.

CONCLUSIONS

We suggest that the amino acid changes in otherwise highly conserved sequences significantly affect the dental phenotype. No relationship between the presence of WNT10A variants and a risk of cancer has been found.

CLINICAL RELEVANCE

Screening of PAX9, MSX1, EDA, EDAR, AXIN2 and WNT10A genes in hope to elucidate the pattern of inheritance in families.

A Study of Combined Genotype Effects of SHCBP1 on Wool Quality Traits in Chinese Merino

SHCBP1 (Shc SH2-domain binding protein 1) is a member of the Src and collagen homolog (Shc) protein family and is closely associated with multiple signaling pathways that play important roles during hair follicle induction, morphogenesis, and cycling. The purpose of this study was to investigate SHCBP1 gene expression, polymorphisms, and the association between SHCBP1 and wool quality traits in Chinese Merino sheep. The SHCBP1 gene was shown, by qPCR, to be ubiquitously expressed in sheep tissues and differentially expressed in the adult skin of Chinese Merino and Suffolk sheep. Four SNPs (termed SHCBP1SNPs 1-4) were identified by Sanger sequencing and were located in exon 2, intron 9, intron 12, and exon 13 of the sheep SHCBP1 gene, respectively. SHCBP1SNPs 3 and 4 (rs411176240 and rs160910635) were significantly associated with wool crimp (P < 0.05). The combined polymorphism (SHCBP1SNP3-SHCBP1SNP4) was significantly associated with wool crimp (P < 0.05). Bioinformatics analysis showed that the SNPs associated with wool crimp (SHCBP1SNPs 3 and 4) might affect the pre-mRNA splicing by creating binding sites for serine-arginine-rich proteins and that SHCBP1SNP4 might alter the SHCBP1 mRNA and protein secondary structure. Our results suggest that SHCBP1 influences wool crimp and SHCBP1SNPs 3 and 4 might be useful markers for marker-assisted selection and sheep breeding.

Wound healing, fibroblast heterogeneity, and fibrosis

Fibroblasts are highly dynamic cells that play a central role in tissue repair and fibrosis. However, the mechanisms by which they contribute to both physiologic and pathologic states of extracellular matrix deposition and remodeling are just starting to be understood. In this review article, we discuss the current state of knowledge in fibroblast biology and heterogeneity, with a primary focus on the role of fibroblasts in skin wound repair. We also consider emerging techniques in the field, which enable an increasingly nuanced and contextualized understanding of these complex systems, and evaluate limitations of existing methodologies and knowledge. Collectively, this review spotlights a diverse body of research examining an often-overlooked cell type-the fibroblast-and its critical functions in wound repair and beyond.

Hair Follicle Morphogenesis During Embryogenesis, Neogenesis, and Organogenesis

Hair follicles are mini organs that repeat the growth and regression cycle continuously. These dynamic changes are driven by the regulation of stem cells via their multiple niche components. To build the complex structure of hair follicles and surrounding niches, sophisticated morphogenesis is required during embryonic development. This review will explore how hair follicles are formed and maintained through dynamic cellular changes and diverse signaling pathways. In addition, comparison of differences in stem cells and surrounding niche components during embryogenesis, neogenesis, and organogenesis will provide a comprehensive understanding of mechanisms for hair follicle generation and insights into skin regeneration.

Evidence of selection in the ectodysplasin pathway among endangered aquatic mammals

Synopsis

The ectodysplasin pathway has been a target of evolution repeatedly. Genetic variation in the key genes of this pathway (EDA, EDAR, and EDARADD) results in a rich source of pleiotropic effects across ectodermally-derived structures, including teeth, hair, sweat glands, and mammary glands. In addition, a non-canonical Wnt pathway has a very similar functional role, making variation in the WNT10A gene also of evolutionary significance. The adaptation of mammals to aquatic environments has occurred independently in at least 4 orders, whose species occupy a wide geographic range (from equatorial to polar regions) and exhibit great phenotypic variation in ectodermally-derived structures, including the presence or absence of fur and extreme lactational strategies. The role of the ectodysplasin pathway in the adaptation to aquatic environments has been never explored in mammalian species. In the present study, we analyze the genetic variation in orthologous coding sequences from EDA, EDAR, EDARADD, and WNT10A genes together with ectodermally-derived phenotypic variation from 34 aquatic and non-aquatic mammalian species to assess signals of positive selection, gene-trait coevolution, and genetic convergence. Our study reveals strong evidence of positive selection in a proportion of coding sites in EDA and EDAR genes in 3 endangered aquatic mammals (the Hawaiian monk seal, the Yangtze finless porpoise, and the sea otter). We hypothesize functional implications potentially related to the adaptation to the low-latitude aquatic environment in the Hawaiian monk seal and the freshwater in the Yangtze finless porpoise. The signal in the sea otter is likely the result of an increased genetic drift after an intense bottleneck and reduction of genetic diversity. Besides positive selection, we have not detected robust signals of gene-trait coevolution or convergent amino acid shifts in the ectodysplasin pathway associated with shared phenotypic traits among aquatic mammals. This study provides new evidence of the evolutionary role of the ectodysplasin pathway and encourages further investigation, including functional studies, to fully resolve its relationship with mammalian aquatic adaptation.

Spanish

La vía de la ectodisplasina ha sido objeto de la evolución repetidamente. La variación genética en los principales genes de esta vía (EDA, EDAR y EDARADD) da como resultado una gran diversidad de efectos pleiotrópicos en las estructuras derivadas del ectodermo, incluidos los dientes, el cabello, las glándulas sudoríparas y las glándulas mamarias. Además, una vía wnt no canónica tiene un papel funcional muy similar, por lo que la variación en el gen WNT10A también tiene importancia evolutiva. La adaptación de los mamíferos a los entornes acuáticos se ha producido de forma independiente en al menos cuatro órdenes, cuyas especies ocupan un amplio rango geográfico (desde regiones ecuatoriales a polares) y presentan una gran variación fenotípica en las estructuras derivadas del ectodermo, incluyendo la presencia o ausencia de pelaje y estrategias de lactancia muy diferentes. El papel de la vía de la ectodisplasina en la adaptación a entornos acuáticos no se ha explorado nunca en especies de mamíferos. En este estudio, analizamos la variación genética en las secuencias codificantes ortólogas de los genes EDA, EDAR, EDARADD y WNT10A junto con la variación fenotípica derivada del ectodermo de 34 especies de mamíferos acuáticos y no acuáticos para evaluar señales de selección positiva, coevolución gen-rasgo y convergencia genética. Nuestro estudio revela señales de selección positiva en regiones de las secuencias codificantes de los genes EDA y EDAR en tres mamíferos acuáticos en peligro de extinción (la foca monje de Hawái, la marsopa lisa y la nutria marina). Estas señales podrían tener implicaciones funcionales potencialmente relacionadas con la adaptación al entorno acuático de baja latitud en la foca monje de Hawái y el agua dulce en la marsopa lisa. La señal en la nutria marina es probablemente el resultado de una mayor deriva genética tras un intenso un cuello de botella y una reducción de la diversidad genética. A parte de selección positiva, no hemos detectado señales sólidas de coevolución gen-rasgo o cambios convergentes de aminoácidos en la vía de la ectodisplasina asociados a rasgos fenotípicos compartidos entre mamíferos acuáticos. Este estudio proporciona nuevas evidencias del papel evolutivo de la vía de la ectodisplasina y quiere promover futuras investigaciones con estudios funcionales para acabar de resolver la relación de esta vía con la adaptación acuática de los mamíferos.

miR-29a-5p Inhibits Prenatal Hair Placode Formation Through Targeting EDAR by ceRNA Regulatory Network

Hair placode formation is an important stage of hair follicle morphogenesis and it is a complex process facilitated by non-coding RNAs. In this study, we conducted whole transcriptome sequencing analysis of skin, heart, liver, lung, and kidney tissues of day 41 (E41) normal and hairless pig embryos, and respectively detected 15, 8, and 515 skin-specific differentially expressed (DE) lncRNAs, miRNAs, and mRNAs. Furthermore, 18 competing endogenous RNA (ceRNA) networks were constructed. Following weighted gene co-expression network analysis (WGCNA) of stages E39, E41, E45, E52, and E60, between normal and hairless pig embryos, only two ceRNAs (lncRNA2162.1/miR-29a-5p/BMPR1b and lncRNA627.1/miR-29a-5p/EDAR) that showed period-specific differential expression in E41 skin were retained. Dual-luciferase reporter assays further indicated that EDAR was a direct, functioning target of miR-29a-5p and that no binding site was found in BMPR1b. Moreover, miR-29a-5p overexpression inhibited the mRNA and protein expression of EDAR while no significant differential expression of BMPR1b was detected. In addition, over-expressed lncRNA627.1 reduces the expression of miR-29a-5p and increase EDAR expression while inhibits lncRNA627.1 resulted in a opposite expression trend. Cell proliferation result demonstrated that lower expression of EDAR and lncRNA627.1 inhibited hair placode precursor cells (HPPCs) proliferation in a manner similar to that shown by over-expressed miR-29a-5p. This study identified that miR-29a-5p inhibited HPPCs proliferation via the suppression of EDAR expression in the EDA/EDAR signaling pathway, while lncRNA627.1 rescues EDAR expression. Our study provides a basis for a better understanding of the mechanisms underlying the ceRNA complex, miR29a-5p/EDAR/lncRNA627.1, that could regulate hair placode formation, which may help decipher diseases affecting human hair.

Decomposing a deterministic path to mesenchymal niche formation by two intersecting morphogen gradients

Organ formation requires integrating signals to coordinate proliferation, specify cell fates, and shape tissue. Tracing these events and signals remains a challenge, as intermediate states across many critical transitions are unresolvable over real time and space. Here, we designed a unique computational approach to decompose a non-linear differentiation process into key components to resolve the signals and cell behaviors that drive a rapid transition, using the hair follicle dermal condensate as a model. Combining scRNA sequencing with genetic perturbation, we reveal that proliferative Dkk1+ progenitors transiently amplify to become quiescent dermal condensate cells by the mere spatiotemporal patterning of Wnt/β-catenin and SHH signaling gradients. Together, they deterministically coordinate a rapid transition from proliferation to quiescence, cell fate specification, and morphogenesis. Moreover, genetically repatterning these gradients reproduces these events autonomously in "slow motion" across more intermediates that resolve the process. This analysis unravels two morphogen gradients that intersect to coordinate events of organogenesis.

Integrated Hair Follicle Profiles of microRNAs and mRNAs to Reveal the Pattern Formation of Hu Sheep Lambskin

Hair follicle development is closely associated with wool curvature. Current studies reveal the crucial role of microRNAs (miRNAs) in hair follicle growth and development. However, few studies are known regarding their role in wool curvature. To reveal the potential roles of miRNAs in Hu sheep lambskin with different patterns, a total of 37 differentially expressed (DE) miRNAs were identified in hair follicles between small waves (SM) and straight wool (ST) groups using RNA-seq. Through functional enrichment and miRNA-mRNA co-expression analysis, some key miRNAs (oar-miR-143, oar-miR-200b, oar-miR-10a, oar-miR-181a, oar-miR-10b, oar-miR-125b, etc.) and miRNA-mRNA pairs (miR-125b target CD34, miR-181a target FGF12, LMO3, miR-200b target ZNF536, etc.) were identified. Though direct or indirect ways affecting hair follicle development, these miRNAs and mRNAs may have possible effects on wool curvature, and this study thus provides valuable insight on potential pattern formation.