Foxi3 Deficiency Compromises Hair Follicle Stem Cell Specification and Activation

Knockdown of miR-361-5p promotes the induced activation of SHF-stem cells through FOXM1 mediated Wnt/β-catenin pathway in cashmere goats

The inducing activation event of secondary hair follicle (SHF)-stem cells is considered a key biological process in the SHF regeneration, and the morphogenesis of cashmere fiber in cashmere goats. The miR-361-5p was essentially implicated in the induced activation of SHF-stem cells of cashmere goats, but its functional mechanisms are unclear. Here, we confirmed miR-361-5p was significantly downregulated in anagen SHF bugle of cashmere goats compared with that at telogen, and miR-361-5p expression was significantly lower in SHF-stem cells after activation than its counterpart before activation. Further, we found that miR-361-5p could negatively regulate the induced activation event of SHF-stem cells in cashmere goats. Mechanistically, through dual-luciferase reporter assays, miR-361-5p specifically bound with FOXM1 mRNA in SHF-stem cells of cashmere goats and negatively regulated the expression of FOXM1 gene. Also, through overexpression/knockdown analysis of FOXM1 gene, our results indicated that FOXM1 upregulated the expression of Wnt/β-catenin pathway related genes in SHF-stem cells. Moreover, based on TOP/FOP-flash Wnt report assays, the knockdown of miR-361-5p promotes the Wnt/β-catenin pathway activation through upregulating the FOXM1 expression in SHF-stem cells. Finally, we demonstrated that miR-361-5p negatively regulated the induced activation of SHF-stem cells through FOXM1 mediated Wnt/β-catenin pathway in cashmere goats.

ASH2L mediates epidermal differentiation and hair follicle morphogenesis via H3K4me3 modification

The processes of epidermal development in mammals are regulated by complex molecular mechanisms, such as histone modifications. Histone H3 lysine K4 (H3K4) methylation mediated by COMPASS methyltransferase is associated with gene activation, but its effect on epidermal lineage development remains unclear. Therefore, we constructed a mouse model of specific ASH2L (COMPASS methyltransferase core subunit) deletion in epidermal progenitor cells and investigated its effect on the development of mouse epidermal lineage. Furthermore, downstream target genes regulated by H3K4me3 were screened using RNA-sequencing combined with Cleavage Under Targets and Tagmentation (CUT&Tag) sequencing. Deletion of ASH2L in epidermal progenitor cells caused thinning of the suprabasal layer of the epidermis and delayed hair follicle morphogenesis in newborn mice. These phenotypes may be related to the reduced proliferative capacity of epidermal and hair follicle progenitor cells. ASH2L depletion may also lead to depletion of the epidermal stem cell pools in late mouse development. Finally, genes related to hair follicle development (Shh, Edar and Fzd6), Notch signaling pathway (Notch2, Notch3, Hes5 and Nrarp) and ΔNp63 were identified as downstream target genes regulated by H3K4me3. Collectively, ASH2L-dependent H3K4me3 modification served as an upstream epigenetic regulator in epidermal differentiation and hair follicle morphogenesis in mice.

The Biology and Genomics of Human Hair Follicles: A Focus on Androgenetic Alopecia

Androgenetic alopecia is a highly prevalent condition mainly affecting men. This complex trait is related to aging and genetics; however, multiple other factors, for example, lifestyle, are also involved. Despite its prevalence, the underlying biology of androgenetic alopecia remains elusive, and thus advances in its treatment have been hindered. Herein, we review the functional anatomy of hair follicles and the cell signaling events that play a role in follicle cycling. We also discuss the pathology of androgenetic alopecia and the known molecular mechanisms underlying this condition. Additionally, we describe studies comparing the transcriptional differences in hair follicles between balding and non-balding scalp regions. Given the genetic contribution, we also discuss the most significant risk variants found to be associated with androgenetic alopecia. A more comprehensive understanding of this pathology may be generated through using multi-omics approaches.

Deciphering the molecular mechanisms of stem cell dynamics in hair follicle regeneration

Hair follicles, which are connected to sebaceous glands in the skin, undergo cyclic periods of regeneration, degeneration, and rest throughout adult life in mammals. The crucial function of hair follicle stem cells is to maintain these hair growth cycles. Another vital aspect is the activity of melanocyte stem cells, which differentiate into melanin-producing melanocytes, contributing to skin and hair pigmentation. Sebaceous gland stem cells also have a pivotal role in maintaining the skin barrier by regenerating mature sebocytes. These stem cells are maintained in a specialized microenvironment or niche and are regulated by internal and external signals, determining their dynamic behaviors in homeostasis and hair follicle regeneration. The activity of these stem cells is tightly controlled by various factors secreted by the niche components around the hair follicles, as well as immune-mediated damage signals, aging, metabolic status, and stress. In this study, we review these diverse stem cell regulatory and related molecular mechanisms of hair regeneration and disease conditions. Molecular insights would provide new perspectives on the disease mechanisms as well as hair and skin disorder treatment.

Foxi3GFP and Foxi3CreER mice allow identification and lineage labeling of pharyngeal arch ectoderm and endoderm, and tooth and hair placodes

BACKGROUND

FOXI3 is a forkhead family transcription factor that is expressed in the progenitors of craniofacial placodes, epidermal placodes, and the ectoderm and endoderm of the pharyngeal arch region. Loss of Foxi3 in mice and pathogenic Foxi3 variants in dogs and humans cause a variety of craniofacial defects including absence of the inner ear, severe truncations of the jaw, loss or reduction in external and middle ear structures, and defects in teeth and hair.

RESULTS

To allow for the identification, isolation, and lineage tracing of Foxi3-expressing cells in developing mice, we targeted the Foxi3 locus to create Foxi3GFP and Foxi3CreER mice. We show that Foxi3GFP mice faithfully recapitulate the expression pattern of Foxi3 mRNA at all ages examined, and Foxi3CreER mice can trace the derivatives of pharyngeal arch ectoderm and endoderm, the pharyngeal pouches and clefts that separate each arch, and the derivatives of hair and tooth placodes.

CONCLUSIONS

Foxi3GFP and Foxi3CreER mice are new tools that will be of use in identifying and manipulating pharyngeal arch ectoderm and endoderm and hair and tooth placodes.

Nanotechnology-based techniques for hair follicle regeneration

The hair follicle (HF) is a multicellular complex structure of the skin that contains a reservoir of multipotent stem cells. Traditional hair repair methods such as drug therapies, hair transplantation, and stem cell therapy have limitations. Advances in nanotechnology offer new approaches for HF regeneration, including controlled drug release and HF-specific targeting. Until recently, embryogenesis was thought to be the only mechanism for forming hair follicles. However, in recent years, the phenomenon of wound-induced hair neogenesis (WIHN) or de novo HF regeneration has gained attention as it can occur under certain conditions in wound beds. This review covers HF-specific targeting strategies, with particular emphasis on currently used nanotechnology-based strategies for both hair loss-related diseases and HF regeneration. HF regeneration is discussed in several modalities: modulation of the hair cycle, stimulation of progenitor cells and signaling pathways, tissue engineering, WIHN, and gene therapy. The HF has been identified as an ideal target for nanotechnology-based strategies for hair regeneration. However, some regulatory challenges may delay the development of HF regeneration nanotechnology based-strategies, which will be lastly discussed.

Canine noninflammatory alopecia: An approach to its classification and a diagnostic aid

Noninflammatory alopecia is common in dogs and is a frequent cause to consult a veterinarian. It is also a common reason to take biopsies. Noninflammatory alopecia can be attributed to a decreased formation or cytodifferentiation of the hair follicle or the hair shaft in utero, resulting in congenital alopecia. Congenital alopecia often has a hereditary cause, and examples of such disorders are ectodermal dysplasias associated with gene variants of the ectodysplasin A gene. Noninflammatory alopecia may also be caused by impaired postnatal regeneration of hair follicles or shafts. Such disorders may have a clear breed predilection, and alopecia starts early in life. A hereditary background is suspected in those cases but has not been proven. They are referred to as follicular dysplasia although some of these disorders present histologically like a hair cycle disturbance. Late-onset alopecia is usually acquired and may be associated with endocrinopathies. Other possible causes are impaired vascular perfusion or stress. As the hair follicle has limited possible responses to altered regulation, and histopathology may change during the course of a disease, a detailed clinical history, thorough clinical examination including blood work, appropriate biopsy site selection, and detailed histological findings need to be combined to achieve a final diagnosis. This review aims to provide an overview about the known noninflammatory alopecic disorders in dogs. As the pathogenesis of most disorders is unknown, some statements are based on comparative aspects or reflect the authors' opinion.

Expression of FOXO3 in the skin follicles of goose embryos during embryonic development

1. The Forkhead box O3 (FOXO3) transcription factor is a crucial regulator in controlling cell metabolism, proliferation, apoptosis, migration and response to oxidative stress. However, FOXO3 has not previously been studied much in the embryonic skin follicles of geese.2. This study used Zhedong white geese (Anser cygnoides), Jilin white geese (Anser cygnoides) and Hungarian white geese (Anser anser). The feather follicle structure in the dorsal skin during embryonic stages was examined with haematoxylin and eosin (HE) and Pollak staining. The FOXO3 protein content in the embryonic dorsal skin from feather follicles was detected using western blotting and quantitative real-time PCR.3. The mRNA expression level of FOXO3 in the dorsal skin of Jilin white geese was highly expressed on embryonic day 23 (E23; P < 0.01), while mRNA expression of FOXO3 was highly expressed in the feather follicle of Hungarian white geese at E28 (P < 0.01). The expression of FOXO3 protein mainly concentrated in the early embryonic phase among these goose breeds (P < 0.05). This suggested that FOXO3 plays a crucial role in the development and growth of embryonic dorsal skin of feather follicles. The location of the FOXO3 protein was determined using the IHC technique, which further verified the effect of FOXO3 in the dorsal skin for feather follicles during embryogenesis.4. The study demonstrated the differential expression and localisation of the FOXO3 gene among different goose species. It was speculated that the gene could potentially improve goose feather follicle development and feather-related traits and provide a basis for further understanding of FOXO3 function in the dorsal tissue of goose embryos.

FOXI3 pathogenic variants cause one form of craniofacial microsomia

Craniofacial microsomia (CFM; also known as Goldenhar syndrome), is a craniofacial developmental disorder of variable expressivity and severity with a recognizable set of abnormalities. These birth defects are associated with structures derived from the first and second pharyngeal arches, can occur unilaterally and include ear dysplasia, microtia, preauricular tags and pits, facial asymmetry and other malformations. The inheritance pattern is controversial, and the molecular etiology of this syndrome is largely unknown. A total of 670 patients belonging to unrelated pedigrees with European and Chinese ancestry with CFM, are investigated. We identify 18 likely pathogenic variants in 21 probands (3.1%) in FOXI3. Biochemical experiments on transcriptional activity and subcellular localization of the likely pathogenic FOXI3 variants, and knock-in mouse studies strongly support the involvement of FOXI3 in CFM. Our findings indicate autosomal dominant inheritance with reduced penetrance, and/or autosomal recessive inheritance. The phenotypic expression of the FOXI3 variants is variable. The penetrance of the likely pathogenic variants in the seemingly dominant form is reduced, since a considerable number of such variants in affected individuals were inherited from non-affected parents. Here we provide suggestive evidence that common variation in the FOXI3 allele in trans with the pathogenic variant could modify the phenotypic severity and accounts for the incomplete penetrance.

N6-Methyladenosine modification (m6A) of circRNA-ZNF638 contributes to the induced activation of SHF stem cells through miR-361-5p/Wnt5a axis in cashmere goats

OBJECTIVE

The objective of this study was to investigate the effects of N6-Methyladenosine modification-circRNA-zinc finger protein 638 (m6A-circRNA-ZNF638) on the induced activation of secondary hair follicle (SHF) stem cells with its potential mechanisms in cashmere goats.

METHODS

The m6A modification of ZNF638 was analyzed using methylation immunoprecipitation with real-time quantitative polymerase chain reaction technique in SHF stem cells. The effects of circRNA-ZNF638 on the induced activation of SHF stem cells in m6A dependence were evaluated through the overexpression of circRNA-ZNF638/its m6Adeficient mutants in circRNA-ZNF638 knockdown SHF stem cells. The competitive binding of miR-361-5p to circRNA-ZNF638/Wnt5a 3'- untranslated region was analyzed through Dual-luciferase reporter assay.

RESULTS

The m6A-circRNA-ZNF638 had significantly higher transcription at anagen SHF bulge of cashmere goats compared with that at telogen, as well as it positively regulated the induced activation of SHF-stem cells in cashmere goats. Mechanismly, m6A-circRNA-ZNF638 sponged miR-361-5p to heighten the transcriptional expression of Wnt5a gene in SHFstem cells. We further demonstrated that the internal m6A modification within circRNAZNF638 is required for mediating the miR-361-5p/Wnt5a pathway to regulate the induced activation of SHF stem cells through an introducing of m6A-deficient mutant of circRNAZNF638.

CONCLUSION

The circRNA-ZNF638 contributes the proper induced activation of SHF-stem cells in cashmere goats in m6A-dependent manner through miR-361-5p/Wnt5a axis.

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.

Aging of hair follicle stem cells and their niches

Hair follicles in the skin undergo cyclic rounds of regeneration, degeneration, and rest throughout life. Stem cells residing in hair follicles play a pivotal role in maintaining tissue homeostasis and hair growth cycles. Research on hair follicle aging and age-related hair loss has demonstrated that a decline in hair follicle stem cell (HFSC) activity with aging can decrease the regeneration capacity of hair follicles. This review summarizes our understanding of how age-associated HFSC intrinsic and extrinsic mechanisms can induce HFSC aging and hair loss. In addition, we discuss approaches developed to attenuate ageassociated changes in HFSCs and their niches, thereby promoting hair regrowth. [BMB Reports 2023; 56(1): 2-9].

Aging of hair follicle stem cells and their niches

Hair follicles in the skin undergo cyclic rounds of regeneration, degeneration, and rest throughout life. Stem cells residing in hair follicles play a pivotal role in maintaining tissue homeostasis and hair growth cycles. Research on hair follicle aging and age-related hair loss has demonstrated that a decline in hair follicle stem cell (HFSC) activity with aging can decrease the regeneration capacity of hair follicles. This review summarizes our understanding of how age-associated HFSC intrinsic and extrinsic mechanisms can induce HFSC aging and hair loss. In addition, we discuss approaches developed to attenuate ageassociated changes in HFSCs and their niches, thereby promoting hair regrowth. [BMB Reports 2023; 56(1): 2-9].

Foxp1 and Foxp4 deletion causes the loss of follicle stem cell niche and cyclic hair shedding by inducing inner bulge cell apoptosis

Quiescent hair follicle stem cells (HFSCs) reside in specialized bulge niche where they undergo activation and differentiation upon sensing niche-dependent signals during hair follicle (HF) homeostasis and wound repair. The underlying mechanism of HFSCs and bulge niche maintenance is poorly understood. Our previous study has reported that a transcription factor, forkhead box P1 (Foxp1), functions to maintain the quiescence of HFSCs. Here, we further discovered that forkhead box P4 (Foxp4), a close family member of Foxp1, had similar expression profiles in various components of HFs and formed a complex with Foxp1 in vitro and in vivo. The HF-specific deficiency of Foxp4 resulted in the precocious activation of HFSCs during hair cycles. In contrast to single Foxp1 or Foxp4 conditional knockout (cKO) mice, Foxp1/4 double cKO exerted an additive effect in the spectrum and severity of phenotypes in HFSC activation, hair cycling acceleration and hair loss, coupled with remarkable downregulation of fibroblast growth factor 18 (Fgf18) and bone morphogenetic protein 6 (Bmp6) expression in bulge cells. In addition, the double KO of Foxp1/4 induced the apoptosis of K6-positive (K6+) inner bulge cells, a well-established stem cell (SC) niche, thus resulting in the destruction of the bulge SC niche and recurrent hair loss. Our investigation reveals the synergistic role of Foxp1/4 in sustaining K6+ niche cells for the quiescence of HFSCs.

The Evaluation of FGFR1, FGFR2 and FOXO1 in Orofacial Cleft Tissue

Although cleft lip with or without cleft palate (CL/P) is one of the most common congenital anomalies worldwide, the morphopathogenesis of non-syndromic orofacial clefts is still unclear. Many candidate genes have been proposed to play a causal role; however, only a few have been confirmed, leaving many still to be assessed. Taking into account the significance of FGFR1, FGFR2 and FOXO1 in embryogenesis, the aim of this work was to detect and compare the three candidate genes in cleft-affected lip and palatine tissue. Ten soft tissue samples were taken during cheiloplasty and veloplasty. The signals of the candidate genes were visualized using chromogenic in situ hybridization and analyzed using a semi-quantitative method. No statistically important difference in the distribution of FGFR1, FGFR2 and FOXO1 between neither the patients’ lip and vomer mucosa nor the control group was observed. Statistically significant very strong and strong correlations were found between genes in the lip and palatine tissue. The expression of FGFR1, FGFR2 and FOXO1 in cleft-affected lip and palatine tissue seems to be highly individual. Numerous intercorrelations between the genes do not exclude their role in the possible complex morphopathogenesis of orofacial clefts.

CircRNA-0100 positively regulates the differentiation of cashmere goat SHF-SCs into hair follicle lineage via sequestering miR-153-3p to heighten the KLF5 expression

Abstract. Circular RNAs (circRNAs) have stable structures, being a covalently closed loop without 5′ and 3′ free ends. They can function as “miRNA sponges” in regulating the expression of their target genes. It was thought that circRNAs are involved in the development of the secondary hair follicle (SHF) in cashmere goats. In our previous investigation, a new circRNA named circRNA-0100 was identified from the SHF of cashmere goats, but its function is unknown. In this work, we found that circRNA-0100 exhibited significantly higher expression at anagen SHF bulge than its counterpart at telogen in cashmere goats. Based on the use of both overexpression and siRNA interference assays, our data indicated that circRNA-0100 promoted the differentiation of cashmere goat SHF stem cells (SHF-SCs) into hair follicle lineage, which was evaluated by analyzing the transcriptional level changes of six indicator genes in SHF-SCs of cashmere goats. Using the RNA pull-down technique, we showed that circRNA-0100 served as “molecular sponges” of miR-153-3p in SHF-SCs. Through the use of dual-luciferase reporter assays, our data indicated that circRNA-0100 positively regulated the transcriptional expression of the KLF5 gene via the miR-153-3p-mediated pathway. Ultimately, we showed that circRNA-0100 promoted the differentiation of SHF-SCs into hair lineage, which might be achieved via sequestering miR-153-3p to heighten the KLF5 expression in SHF-SCs of cashmere goats. Our results provide novel scientific evidence for revealing the potential molecular regulatory mechanisms on the differentiation of SHF-SCs into hair lineage in cashmere goats.

A systematic summary of survival and death signalling during the life of hair follicle stem cells

Hair follicle stem cells (HFSCs) are among the most widely available resources and most frequently approved model systems used for studying adult stem cells. HFSCs are particularly useful because of their self-renewal and differentiation properties. Additionally, the cyclic growth of hair follicles is driven by HFSCs. There are high expectations for the use of HFSCs as favourable systems for studying the molecular mechanisms that contribute to HFSC identification and can be applied to hair loss therapy, such as the activation or regeneration of hair follicles, and to the generation of hair using a tissue-engineering strategy. A variety of molecules are involved in the networks that critically regulate the fate of HFSCs, such as factors in hair follicle growth and development (in the Wnt pathway, Sonic hedgehog pathway, Notch pathway, and BMP pathway), and that suppress apoptotic cues (the apoptosis pathway). Here, we review the life cycle, biomarkers and functions of HFSCs, concluding with a summary of the signalling pathways involved in HFSC fate for promoting better understanding of the pathophysiological changes in the HFSC niche. Importantly, we highlight the potential mechanisms underlying the therapeutic targets involved in pathways associated with the treatment of hair loss and other disorders of skin and hair, including alopecia, skin cancer, skin inflammation, and skin wound healing.

Stem cell-intrinsic mechanisms regulating adult hair follicle homeostasis

Adult hair follicle stem cells (HFSCs) undergo dynamic and periodic molecular changes in their cellular states throughout the hair homeostatic cycle. These states are tightly regulated by cell-intrinsic mechanisms and by extrinsic signals from the microenvironment. HFSCs are essential not only for fuelling hair growth, but also for skin wound healing. Increasing evidence suggests an important role of HFSCs in organizing multiple skin components around the hair follicle, thus functioning as an organizing centre during adult skin homeostasis. Here, we focus on recent findings on cell-intrinsic mechanisms of HFSC homeostasis, which include transcription factors, histone modifications, DNA regulatory elements, non-coding RNAs, cell metabolism, cell polarity and post-transcriptional mRNA processing. Several transcription factors are now known to participate in well-known signalling pathways that control hair follicle homeostasis, as well as in super-enhancer activities to modulate HFSC and progenitor lineage progression. Interestingly, HFSCs have been shown to secrete molecules that are important in guiding the organization of several skin components around the hair follicle, including nerves, arrector pili muscle and vasculature. Finally, we discuss recent technological advances in the field such as single-cell RNA sequencing and live imaging, which revealed HFSC and progenitor heterogeneity and brought new light to understanding crosstalking between HFSCs and the microenvironment. The field is well on its way to generate a comprehensive map of molecular interactions that should serve as a solid theoretical platform for application in hair and skin disease and ageing.

T-Cell Immunodeficiencies With Congenital Alterations of Thymic Development: Genes Implicated and Differential Immunological and Clinical Features

Combined Immunodeficiencies (CID) are rare congenital disorders characterized by defective T-cell development that may be associated with B- and NK-cell deficiency. They are usually due to alterations in genes expressed in hematopoietic precursors but in few cases, they are caused by impaired thymic development. Athymia was classically associated with DiGeorge Syndrome due to TBX1 gene haploinsufficiency. Other genes, implicated in thymic organogenesis include FOXN1, associated with Nude SCID syndrome, PAX1, associated with Otofaciocervical Syndrome type 2, and CHD7, one of the genes implicated in CHARGE syndrome. More recently, chromosome 2p11.2 microdeletion, causing FOXI3 haploinsufficiency, has been identified in 5 families with impaired thymus development. In this review, we will summarize the main genetic, clinical, and immunological features related to the abovementioned gene mutations. We will also focus on different therapeutic approaches to treat SCID in these patients.

Werewolf, There Wolf: Variants in Hairless Associated with Hypotrichia and Roaning in the Lykoi Cat Breed

A variety of cat breeds have been developed via novelty selection on aesthetic, dermatological traits, such as coat colors and fur types. A recently developed breed, the lykoi (a.k.a. werewolf cat), was bred from cats with a sparse hair coat with roaning, implying full color and all white hairs. The lykoi phenotype is a form of hypotrichia, presenting as a significant reduction in the average numbers of follicles per hair follicle group as compared to domestic shorthair cats, a mild to severe perifollicular to mural lymphocytic infiltration in 77% of observed hair follicle groups, and the follicles are often miniaturized, dilated, and dysplastic. Whole genome sequencing was conducted on a single lykoi cat that was a cross between two independently ascertained lineages. Comparison to the 99 Lives dataset of 194 non-lykoi cats suggested two variants in the cat homolog for Hairless (HR) (HR lysine demethylase and nuclear receptor corepressor) as candidate causal gene variants. The lykoi cat was a compound heterozygote for two loss of function variants in HR, an exon 3 c.1255_1256dupGT (chrB1:36040783), which should produce a stop codon at amino acid 420 (p.Gln420Serfs*100) and, an exon 18 c.3389insGACA (chrB1:36051555), which should produce a stop codon at amino acid position 1130 (p.Ser1130Argfs*29). Ascertainment of 14 additional cats from founder lineages from Canada, France and different areas of the USA identified four additional loss of function HR variants likely causing the highly similar phenotypic hair coat across the diverse cats. The novel variants in HR for cat hypotrichia can now be established between minor differences in the phenotypic presentations.

Characterization and functional analysis of SIAH1 during skin and hair follicle development in the angora rabbit (Oryctolagus cuniculus)

BACKGROUND

Seven in absentia homolog 1 (SIAH1) is an E3 ubiquitin ligase containing a RING-finger domain and a key regulator of normal development. Skin and hair follicle development is a complex and special process of morphogenesis involving multiple signaling pathways. SIAH1 is enriched in the Wnt signaling pathway and potentially related to hair follicle cycle and skin development. This study aims to provide evidence for the role of SIAH1 in skin and hair development.

RESULTS

Full-length cloning and analysis of SIAH1 was conducted to better understand its function. Phylogenetically, the sequence of SIAH1 in the rabbit shares the greatest homology with Home sapiens, Pongo abelii and Mus mulatta. Based on the rabbit hair follicle synchronization model, we found that the expression level of SIAH1 in the regressive period of the rabbit hair cycle is significantly lower than in the active growth and rest periods. In addition, the mRNA expression levels of skin and hair follicle development-related genes changed significantly when SIAH1 was overexpressed and silenced. After SIAH1 overexpression, the expression levels of WNT2, LEF1 and FGF2 decreased, and those of SFRP2 and DKK1 increased (P < 0.05). After interference of SIAH1, the expression levels of WNT2, LEF1 and FGF2 increased (P < 0.05), and SFRP2 and DKK1 decreased.

CONCLUSIONS

SIAH1 can affect skin and hair follicle development and exert an inhibitory effect. These results could provide foundamental insights into the role of SIAH1 as a target gene in rabbit skin and hair follicle development.

Recurrent microdeletions at chromosome 2p11.2 are associated with thymic hypoplasia and features resembling DiGeorge syndrome

BACKGROUND

Thymic hypoplasia/aplasia occurs as a part of DiGeorge syndrome, which has several known genetic causes, and with loss-of-function mutations in forkhead box N1 (FOXN1).

OBJECTIVE

We sought to determine the cause of selective T-cell lymphopenia with inverted kappa/lambda ratio in several kindreds.

METHODS

Patients were identified through newborn screening for severe combined immunodeficiency using the T-cell receptor excision circle assay. Those found to have selective T-cell lymphopenia underwent testing with chromosomal microarray analysis. Three-week-old mice heterozygous for a loss-of-function mutation in forkhead box I3 (FOXI3), a candidate gene within the common deleted region found in patients, were compared with wild-type littermates. Assessments included body and organ weights, flow cytometric analysis of thymocytes and splenocytes, and histologic/transcriptomic analyses of thymic tissue.

RESULTS

Five kindreds with similar immunophenotypes that included selective T-cell lymphopenia had overlapping microdeletions at chromosome 2p11.2 that spanned FOXI3 and, in most cases, the immunoglobulin kappa light chain locus. Studies in a mouse knockout strain for FOXI3 revealed smaller body weights and relatively lower thymus weights in heterozygous compared with wild-type animals. Histology and flow cytometry on spleens and thymi from 3-week-old pups for T- and B-cell subsets and epithelial cells did not show any significant qualitative or quantitative differences. Transcriptomic analysis of thymic RNA revealed divergence in global transcriptomic signatures, and Ingenuity Pathway Analysis revealed predicted dysfunction in epithelial adherens junctions.

CONCLUSIONS

Microdeletions at chromosome 2p11.2 are associated with T-cell lymphopenia and probable thymic hypoplasia in human subjects, and haploinsufficiency for FOXI3, a candidate gene within the deleted region, is the likely underlying cause.

Systematic Analysis of Non-coding RNAs Involved in the Angora Rabbit (Oryctolagus cuniculus) Hair Follicle Cycle by RNA Sequencing

The hair follicle (HF) cycle is a complicated and dynamic process in mammals, associated with various signaling pathways and gene expression patterns. Non-coding RNAs (ncRNAs) are RNA molecules that are not translated into proteins but are involved in the regulation of various cellular and biological processes. This study explored the relationship between ncRNAs and the HF cycle by developing a synchronization model in Angora rabbits. Transcriptome analysis was performed to investigate ncRNAs and mRNAs associated with the various stages of the HF cycle. One hundred and eleven long non-coding RNAs (lncRNAs), 247 circular RNAs (circRNAs), 97 microRNAs (miRNAs), and 1,168 mRNAs were differentially expressed during the three HF growth stages. Quantitative real-time PCR was used to validate the ncRNA transcriptome analysis results. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses provided information on the possible roles of ncRNAs and mRNAs during the HF cycle. In addition, lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA ceRNA networks were constructed to investigate the underlying relationships between ncRNAs and mRNAs. LNC_002919 and novel_circ_0026326 were found to act as ceRNAs and participated in the regulation of the HF cycle as miR-320-3p sponges. This research comprehensively identified candidate regulatory ncRNAs during the HF cycle by transcriptome analysis, highlighting the possible association between ncRNAs and the regulation of hair growth. This study provides a basis for systematic further research and new insights on the regulation of the HF cycle.

A frameshift insertion in SGK3 leads to recessive hairlessness in Scottish Deerhounds: a candidate gene for human alopecia conditions

Hairlessness is a breed-specific feature selected for in some dog breeds but a rare abnormality in some others such as Scottish Deerhounds (SD). In SDs, the affected puppies are born with sparse hair but lose it within the first 2 months leaving the dogs completely hairless. The previous studies have implicated variants in FOXI3 and SGK3 in hairlessness; however, the known variants do not explain hairlessness in all breeds such as SDs. We investigated the genetic cause in 66 SDs, including a litter with two hairless dogs. We utilized a combined approach of genome-wide homozygosity mapping and whole-genome sequencing of a hairless SD followed by recessive filtering according to a recessive model against 340 control genomes. Only two homozygous-coding variants were discovered in the homozygosity regions, including a 1-bp insertion in exon 2 of SGK3. This results in a predicted frameshift and very early truncation (49/490 amino acids) of the SGK3 protein. Additional screening of the recessive variant demonstrated a full segregation with the hairlessness and a 12% carrier frequency in the SD breed. The variant was not found in the related Irish Wolfhound breed. This study identifies the second hairless variant in the SGK3 gene in dogs and further highlights its role as a candidate gene for androgen-independent hair loss or alopecia in human.

A Review of FOXI3 Regulation of Development and Possible Roles in Cancer Progression and Metastasis

Development and cancer share a variety of functional traits such as EMT, cell migration, angiogenesis, and tissue remodeling. In addition, many cellular signaling pathways are noted to coordinate developmental processes and facilitate aspects of tumor progression. The Forkhead box superfamily of transcription factors consists of a highly conserved DNA binding domain, which binds to specific DNA sequences and play significant roles during adult tissue homoeostasis and embryogenesis including development, differentiation, metabolism, proliferation, apoptosis, migration, and invasion. Interestingly, various studies have implicated the role of key Fox family members such as FOXP, FOXO, and FOXA during cancer initiation and metastases. FOXI3, a member of the Forkhead family affects embryogenesis, development, and bone remodeling; however, no studies have reported a role in cancer. In this review, we summarize the role of FOXI3 in embryogenesis and bone development and discuss its potential involvement in cancer progression with a focus on the bone metastasis. Moreover, we hypothesize possible mechanisms underlying the role of FOXI3 in the development of solid tumor bone metastasis.

Transcriptome Reveals Long Non-coding RNAs and mRNAs Involved in Primary Wool Follicle Induction in Carpet Sheep Fetal Skin

Murine primary hair follicle induction is driven by the communication between the mesenchyme and epithelium and mostly governed by signaling pathways including wingless-related integration site (WNT), ectodysplasin A receptor (EDAR), bone morphogenetic protein (BMP), and fibroblast growth factor (FGF), as observed in genetically modified mouse models. Sheep skin may serve as a valuable system for hair research owing to the co-existence of sweat glands with wool follicles in trunk skin and asynchronized wool follicle growth pattern similar to that of human head hair follicles. However, the mechanisms underlying wool follicle development remain largely unknown. To understand how long non-coding RNAs (lncRNAs) and mRNAs function in primary wool follicle induction in carpet wool sheep, we conducted high-throughput RNA sequencing and revealed globally altered lncRNAs (36 upregulated and 26 downregulated), mRNAs (228 elevated and 225 decreased), and 80 differentially expressed novel transcripts. Several key signals in WNT (WNT2B and WNT16), BMP (BMP3, BMP4, and BMP7), EDAR (EDAR and EDARADD), and FGF (FGFR2 and FGF20) pathways, and a series of lncRNAs, including XLOC_539599, XLOC_556463, XLOC_015081, XLOC_1285606, XLOC_297809, and XLOC_764219, were shown to be potentially important for primary wool follicle induction. GO and KEGG analyses of differentially expressed mRNAs and potential targets of altered lncRNAs were both significantly enriched in morphogenesis biological processes and transforming growth factor-β, Hedgehog, and PI3K-Akt signaling, as well as focal adhesion and extracellular matrix-receptor interactions. The prediction of mRNA-mRNA and lncRNA-mRNA interaction networks further revealed transcripts potentially involved in primary wool follicle induction. The expression patterns of mRNAs and lncRNAs of interest were validated by qRT-PCR. The localization of XLOC_297809 and XLOC_764219 both in placodes and dermal condensations was detected by in situ hybridization, indicating important roles of lncRNAs in primary wool follicle induction and skin development. This is the first report elucidating the gene network of lncRNAs and mRNAs associated with primary wool follicle early development in carpet wool sheep and will shed new light on selective wool sheep breeding.

TGF-β Family Signaling in Epithelial Differentiation and Epithelial-Mesenchymal Transition

Epithelia exist in the animal body since the onset of embryonic development; they generate tissue barriers and specify organs and glands. Through epithelial-mesenchymal transitions (EMTs), epithelia generate mesenchymal cells that form new tissues and promote healing or disease manifestation when epithelial homeostasis is challenged physiologically or pathologically. Transforming growth factor-βs (TGF-βs), activins, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs) have been implicated in the regulation of epithelial differentiation. These TGF-β family ligands are expressed and secreted at sites where the epithelium interacts with the mesenchyme and provide paracrine queues from the mesenchyme to the neighboring epithelium, helping the specification of differentiated epithelial cell types within an organ. TGF-β ligands signal via Smads and cooperating kinase pathways and control the expression or activities of key transcription factors that promote either epithelial differentiation or mesenchymal transitions. In this review, we discuss evidence that illustrates how TGF-β family ligands contribute to epithelial differentiation and induce mesenchymal transitions, by focusing on the embryonic ectoderm and tissues that form the external mammalian body lining.

The bald and the beautiful: hairlessness in domestic dog breeds

An extraordinary amount of genomic variation is contained within the chromosomes of domestic dogs, manifesting as dramatic differences in morphology, behaviour and disease susceptibility. Morphology, in particular, has been a topic of enormous interest as biologists struggle to understand the small window of dog domestication from wolves, and the division of dogs into pure breeding, closed populations termed breeds. Many traits related to morphology, including body size, leg length and skull shape, have been under selection as part of the standard descriptions for the nearly 400 breeds recognized worldwide. Just as important, however, are the minor traits that have undergone selection by fanciers and breeders to define dogs of a particular appearance, such as tail length, ear position, back arch and variation in fur (pelage) growth patterns. In this paper, we both review and present new data for traits associated with pelage including fur length, curl, growth, shedding and even the presence or absence of fur. Finally, we report the discovery of a new gene associated with the absence of coat in the American Hairless Terrier breed.This article is part of the themed issue 'Evo-devo in the genomics era, and the origins of morphological diversity'.

Computational derivation of a molecular framework for hair follicle biology from disease genes

Knowledge about genetic drivers of disease increases the efficiency of interpreting patient DNA sequence and helps to identify and prioritize biological points of intervention. Discoveries of genes with single mutations exerting substantial phenotypic impact reliably provide new biological insight, although such approaches tend to generate knowledge that is disjointed from the complexity of biological systems governed by elaborate networks. Here we sought to facilitate diagnostic sequencing for hair disorders and assess the underlying biology by compiling an archive of 684 genes discovered in studies of monogenic disorders and identifying molecular annotations enriched by them. To demonstrate utility for this dataset, we performed two data driven analyses. First, we extracted and analyzed data implicating enriched signaling pathways and identified previously unrecognized contributions from Hippo signaling. Second, we performed hierarchical clustering on the entire dataset to investigate the underlying causal structure of hair disorders. We identified 35 gene clusters representing genetically derived biological modules that provide a foundation for the development of a new disease taxonomy grounded in biology, rather than clinical presentations alone. This Resource will be useful for diagnostic sequencing in patients with diseases affecting the hair follicle, improved characterization of hair follicle biology, and methods development in precision medicine.

A comparison of transcriptomic patterns measured in the skin of Chinese fine and coarse wool sheep breeds

We characterised wool traits, and skin gene expression profiles of fine wool Super Merino (SM) and coarse wool Small Tail Han (STH) sheep. SM sheep had a significantly higher total density of wool follicles, heavier fleeces, finer fibre diameter, and increased crimp frequency, staple length and wool grease (lanolin) production. We found 435 genes were expressed at significantly different levels in the skin of the two breeds (127 genes more highly in SM and 308 genes more highly in STH sheep). Classification of the genes more highly expressed in SM sheep revealed numerous lipid metabolic genes as well as genes encoding keratins, keratin-associated proteins, and wool follicle stem cell markers. In contrast, mammalian epidermal development complex genes and other genes associated with skin cornification and muscle function were more highly expressed in STH sheep. Genes identified in this study may be further evaluated for inclusion in breeding programs, or as targets for therapeutic or genetic interventions, aimed at altering wool quality or yield. Expression of the lipid metabolic genes in the skin of sheep may be used as a novel trait with the potential to alter the content or properties of lanolin or the fleece.

Epithelial Markers aSMA, Krt14, and Krt19 Unveil Elements of Murine Lacrimal Gland Morphogenesis and Maturation

As an element of the lacrimal apparatus, the lacrimal gland (LG) produces the aqueous part of the tear film, which protects the eye surface. Therefore, a defective LG can lead to serious eyesight impairment. Up to now, little is known about LG morphogenesis and subsequent maturation. In this study, we delineated elements of the cellular and molecular events involved in LG formation by using three epithelial markers, namely aSMA, Krt14, and Krt19. While aSMA marked a restricted epithelial population of the terminal end buds (TEBs) in the forming LG, Krt14 was found in the whole embryonic LG epithelial basal cell layer. Interestingly, Krt19 specifically labeled the presumptive ductal domain and subsequently, the luminal cell layer. By combining these markers, the Fucci reporter mouse strain and genetic fate mapping of the Krt14+ population, we demonstrated that LG epithelium expansion is fuelled by a patterned cell proliferation, and to a lesser extent by epithelial reorganization and possible mesenchymal-to-epithelial transition. We pointed out that this epithelial reorganization, which is associated with apoptosis, regulated the lumen formation. Finally, we showed that the inhibition of Notch signaling prevented the ductal identity from setting, and led to a LG covered by ectopic TEBs. Taken together our results bring a deeper understanding on LG morphogenesis, epithelial domain identity, and organ expansion.

Multiple-trait QTL mapping and genomic prediction for wool traits in sheep

BACKGROUND

The application of genomic selection to sheep breeding could lead to substantial increases in profitability of wool production due to the availability of accurate breeding values from single nucleotide polymorphism (SNP) data. Several key traits determine the value of wool and influence a sheep's susceptibility to fleece rot and fly strike. Our aim was to predict genomic estimated breeding values (GEBV) and to compare three methods of combining information across traits to map polymorphisms that affect these traits.

METHODS

GEBV for 5726 Merino and Merino crossbred sheep were calculated using BayesR and genomic best linear unbiased prediction (GBLUP) with real and imputed 510,174 SNPs for 22 traits (at yearling and adult ages) including wool production and quality, and breech conformation traits that are associated with susceptibility to fly strike. Accuracies of these GEBV were assessed using fivefold cross-validation. We also devised and compared three approximate multi-trait analyses to map pleiotropic quantitative trait loci (QTL): a multi-trait genome-wide association study and two multi-trait methods that use the output from BayesR analyses. One BayesR method used local GEBV for each trait, while the other used the posterior probabilities that a SNP had an effect on each trait.

RESULTS

BayesR and GBLUP resulted in similar average GEBV accuracies across traits (~0.22). BayesR accuracies were highest for wool yield and fibre diameter (>0.40) and lowest for skin quality and dag score (<0.10). Generally, accuracy was higher for traits with larger reference populations and higher heritability. In total, the three multi-trait analyses identified 206 putative QTL, of which 20 were common to the three analyses. The two BayesR multi-trait approaches mapped QTL in a more defined manner than the multi-trait GWAS. We identified genes with known effects on hair growth (i.e. FGF5, STAT3, KRT86, and ALX4) near SNPs with pleiotropic effects on wool traits.

CONCLUSIONS

The mean accuracy of genomic prediction across wool traits was around 0.22. The three multi-trait analyses identified 206 putative QTL across the ovine genome. Detailed phenotypic information helped to identify likely candidate genes.

Expression of fox-related genes in the skin follicles of Inner Mongolia cashmere goat

Objective

This study investigated the expression of genes in cashmere goats at different periods of their fetal development.

Methods

Bioinformatics analysis was used to evaluate data obtained by transcriptome sequencing of fetus skin samples collected from Inner Mongolia cashmere goats on days 45, 55, and 65 of fetal age.

Results

We found that FoxN1, FoxE1, and FoxI3 genes of the Fox gene family were probably involved in the growth and development of the follicle and the formation of hair, which is consistent with previous findings. Real-time quantitative polymerase chain reaction detecting system and Western blot analysis were employed to study the relative differentially expressed genes FoxN1, FoxE1, and FoxI3 in the body skin of cashmere goat fetuses and adult individuals.

Conclusion

This study provided new fundamental information for further investigation of the genes related to follicle development and exploration of their roles in hair follicle initiation, growth, and development.