Hairless plays a role in formation of inner root sheath via regulation of Dlx3 gene

Whole-transcriptome analysis reveals the profiles and roles of coding and non-coding RNAs during hair follicle cycling in Rex rabbits

BACKGROUND

Rex rabbit is famous for its silky and soft fur coat, a characteristic predominantly attributed to its hair follicles. Numerous studies have confirmed the crucial roles of mRNAs and non-coding RNAs (ncRNAs) in regulating key cellular processes such as cell proliferation, differentiation, apoptosis and immunity. However, their involvement in the regulation of the hair cycle in Rex rabbits remains unknown.

RESULTS

In this study, we identified the hair follicle stages of Rex rabbits aged 3 to 5.5 months. Skin samples collected at 4, 5 and 5.5 months, representing the morphological features of the anagen, catagen and telogen stage separately, were finally selected for whole-transcriptome analysis. 25,736 mRNA, 8280 lncRNA, 24,885 circRNA and 1138 miRNA transcripts were identified. 6027 differently expressed mRNAs (DEGs), 2381 differently expressed lncRNAs (DELs), 438 differently expressed circRNAs (DECs) and 167 differently expressed miRNAs (DEMs) were detected in the anagen vs. catagen (AvC) comparison. 4092 DEGs, 1540 DELs, 356 DECs and 141 DEMs were detected in the anagen vs. telogen (AvT) comparison. 2290 DEGs, 779 DELs, 249 DECs and 92 DEMs were detected in the catagen vs. telogen (CvT) comparison. DEGs were primarily enriched in GO items including plasma membrane, integral component of plasma membrane and extracellular space. KEGG enrichment analysis revealed that DEGs were mainly enriched in PI3K-Akt signaling pathway, cell cycle and Wnt signaling pathway (p < 0.05). KEGG analysis showed trans-acting genes of DELs were significantly enriched in Hippo signaling pathway, PI3K-Akt signaling pathway and Melanogenesis. Target genes of DEMs were mainly enriched in MAPK signaling pathway, Wnt signaling pathway, ECM-receptor interaction and Signaling pathways regulating pluripotency of stem cells. Based on the ceRNA mechanism, lncRNA/circRNA-miRNA-mRNA networks were constructed involving 9 DECs, 437 DELs, 50 DEMs and 416 DEGs.

CONCLUSIONS

Totally, this study provides comprehensive insights into the expression patterns of protein-coding genes and non-coding transcripts throughout the HF cycle, and enhancing the understanding of the regulatory mechanisms underlying mammalian hair fiber development.

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

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

Lef1 and Dlx3 May Facilitate the Maturation of Secondary Hair Follicles in the Skin of Gansu Alpine Merino

Lymphatic enhancer factor 1 (Lef1) and distal-less homeobox 3 (Dlx3) are the transcription factors involved in regulating hair follicle development in mice, goats, and other animals. Their deletion can lead to hair follicle deficiency. In this study, hematoxylin−eosin staining (HE), real-time quantitative PCR (RT-qPCR), immunohistochemistry, and immunofluorescence were used to analyze the expression, location, and biological functions of Lef1 and Dlx3 in the lateral skin of Gansu Alpine Merino aged 1, 30, 60, and 90 days. The results revealed that the number of hair follicles decreased with age and was significantly higher at 1 day than in the other three age groups (p < 0.05). The mRNA levels of Lef1 and Dlx3 in the skin of 30-day old Gansu Alpine Merino were significantly higher than those in the other three age groups (p < 0.05). Protein expression of Lef1 and Dlx3 was lowest at 1 day (p < 0.05) and peaked at 60 days. Lef1 and Dlx3 exhibited a high density and strong positive expression in the dermal papillae; additionally, Dlx3 exhibited a high density and strong positive expression in the inner and outer root sheaths. Collectively, Lef1 and Dlx3 may facilitate the maturation of secondary hair follicles, which is mainly achieved through the dermal papillae and inner and outer root sheaths.

Poly(rC) binding protein 2 acts as a negative regulator of IRES-mediated translation of Hr mRNA

During the hair follicle (HF) cycle, HR protein expression is not concordant with the presence of the Hr mRNA transcript, suggesting an elaborate regulation of Hr gene expression. Here we present evidence that the 5' untranslated region (UTR) of the Hr gene has internal ribosome entry site (IRES) activity and this activity is regulated by the binding of poly (rC) binding protein 2 (PCBP2) to Hr mRNA. Overexpression and knockdown of PCBP2 resulted in a decrease in Hr 5' UTR IRES activity and an increase in HR protein expression without changing mRNA levels. We also found that this regulation was disrupted in a mutant Hr 5' UTR that has a mutation responsible for Marie Unna hereditary hypotrichosis (MUHH) in both mice and humans. These findings suggest that Hr mRNA expression is regulated at the post-transcriptional level via IRES-mediated translation control through interaction with PCPB2, but not in MUHH.

Human Hairless Protein Roles in Skin/Hair and Emerging Connections to Brain and Other Cancers

The mammalian hairless protein (HR) is a 130 kDa nuclear transcription factor that is essential for proper skin and hair follicle function. Previous studies have focused on the role of HR in skin maintenance and hair cycling. However, the hairless gene (HR) is also expressed in brain and other tissues, where its role remains poorly understood. HR has been reported to contain functional domains that potentially serve in DNA binding, histone demethylation, nuclear translocation and protein-protein interactions. Indeed, HR has been shown to interact with and repress the action of the nuclear receptors for vitamin D and thyroid hormone as well as RAR-related orphan receptor alpha, possibly via recruitment of histone deacetylases. HR may also have important functions in non-skin tissues given that nearly 200 HR mutations have been identified in patients with various cancers, including prostate, breast, lung, melanoma, uterine, and glioma. This suggests that HR and/or mutants thereof have relevance to the growth and survival of cancer cells. For example, the reported intrinsic histone H3K9 demethylase activity of HR may activate dormant genes to contribute to carcinogenesis. Alternatively, the demonstrated ability of HR to interact with p53 and/or the p53 DNA response element to influence p53-regulated pathways may explain, at least in part, why many cancers express mutated HR proteins. In this review, we summarize the current knowledge of HR bioactions, how HR mutations may be contributing to alopecia as well as to cancer, and, finally, outline future directions in the study of this largely enigmatic nuclear protein. J. Cell. Biochem. 119: 69-80, 2018. © 2017 Wiley Periodicals, Inc.

The Mammalian Hairless Protein as a DNA Binding Phosphoprotein

The mammalian hairless (Hr) protein plays critical roles in skin and brain tissues, but how it interacts with DNA and partner protein is only now being defined. Our initial tests of four consensus response elements, revealed that rat Hr can specifically bind to a consensus p53 response element (p53RE), 5'-AGACATGCCTAGACATGCCT-3', but not to response elements for NF-κB, TCF4 or Sp1. We then employed ChIP assays which verified that human HR binds to a p53RE of the GADD45A gene in both HEK293 (embryonic kidney) and U87 (glioblastoma) cells. Further, HR was shown to interact directly with the p53 protein in a co-immunoprecipitation assay. Cotransfections with p53RE reporter gene constructs revealed that rat Hr can boost p53-mediated transactivation of a reporter gene linked to the GADD45A p53RE, but blunts p53-mediated transactivation when the reporter gene is linked to a p21 promoter fragment containing a p53RE, with implications for the regulation of these two cell cycle control genes. Finally, our investigations of HR phosphorylation revealed that rat Hr is a substrate for PKC, but not PKA, and that human HR is phosphorylated in intact U87 cells at Ser-416, located in a highly conserved region which partially fulfills the criteria of a PKC site. We propose that mammalian Hr is a phosphoprotein which can exert cross-talk with the p53 pathway with important implications for the regulation of cell proliferation and differentiation in tissues such as skin and brain where Hr is highly expressed. J. Cell. Biochem. 118: 341-350, 2017. © 2016 Wiley Periodicals, Inc.

Functional Characterization of a Single Nucleotide Polymorphism in the 3' Untranslated Region of Sheep DLX3 Gene

The Distal-less 3 (homeobox protein DLX-3), a transcription factor, is critical for the development of hair follicle and hair formation and regeneration. We previously identified and found that four SNPs (c. *118T>C, c. *228T>C, c. *688A>G and c. *1,038_1,039 insC) in 3' untranslated region (UTR) of sheep DLX3 were in high linkage disequilibrium with each other and significantly associated with wool crimp (P<0.05), however, the underlying mechanisms by which these SNPs affect the wool crimp remains unknown. In the present study, we performed association analysis between these four identified SNPs and DLX3 gene expression in sheep skin using quantitative real-time RT-PCR. The results showed that these SNPs were significantly associated with sheep skin DLX3 mRNA expression levels. Then, we constructed DLX3 3'UTR luciferase reporters and validated the association. The reporter assays showed that the three major haplotypes, derived from the four SNPs, had significantly different effects on luciferase reporter activity and the four SNPs also had significantly different allelic effects on the luciferase reporter activity (p < 0.05). Bioinformatics analysis showed that the SNP (c. *1,038_1,039 insC) was located within a potential miR-188 binding site of the 3'UTR of sheep DLX3 mRNA. This SNP may affect miR-188-mediated DLX3 gene expression and result in phenotypic variation. To test the hypothesis, we investigated the effects of miR-188 mimic and inhibitor on the activity of the DLX3 3'UTR luciferase reporter with different SNP alleles. The results showed that in both sheep fetal fibroblasts (SFFs) and human HaCaT cells, miR-188 mimic could significantly decrease the allele D (deletion) luciferase reporter activity (p < 0.05), but miR-188 inhibitor could increased the reporter activitiy. However, neither miR-188 mimc nor inhibitor could influence the allele I (insertion) reporter activity. In addition, transfection of miR-188 mimic dramatically decreased the endogenous expression of DLX3 in SFFs (p < 0.05). Taken together, we demonstrated that DLX3 is a target gene of miR-188 and the SNP (c. *1,038_1,039 insC) is a functional SNP, and affects miR-188-mediated gene regulation of sheep DLX3. Our finding may in part explain allelic difference in gene expression and wool crimp in our tested sheep population.

A polymorphism of the renin gene rs6682082 is associated with essential hypertension risk and blood pressure levels in Korean women

PURPOSE

The aim of the present study was to investigate associations between the renin gene (REN) and the risk of essential hypertension and blood pressure (BP) levels in Koreans.

MATERIALS AND METHODS

To outline the functional role of a single nucleotide polymorphism in the transcription of the REN gene, we conducted a case-control study of 1975 individuals: 646 hypertension (HT) patients and 1329 ethnically and age-matched normotensive subjects.

RESULTS

Logistic regression analysis indicated that the genotypes AA/AG were strongly associated with risk of HT (odds ratio, 1.493; 95% confidence interval, 1.069-2.086, p=0.018) in female subjects. The genotypes AA/AG also showed significant association with higher blood pressure levels, both systolic and diastolic, in postmenopausal HT women (p=0.003 and p=0.017, respectively). Analysis of the promoter containing rs6682082 revealed a 2.4±0.01-fold higher activity in the A variant promoter than the G variant promoter, suggesting that rs6682082 is itself a functional variant.

CONCLUSION

We suggest that the A allele of rs6682082 is a positive genetic marker for predisposition to essential hypertension and high BP in Korean women and may be mediated through the transcriptional activation of REN.

Increased expression of Dkk1 by HR is associated with alteration of hair cycle in hairpoor mice

BACKGROUND

Hairless (Hr), a transcriptional corepressor expressed mainly in the skin, regulates hair follicle (HF) morphogenesis and hair cycling. Recently, we reported a new Hr mutant mouse, "Hairpoor" (Hr(Hp)), that resembles the human hair disorder Marie Unna hereditary hypotrichosis (MUHH) in the heterozygous state. The Wnt/β-catenin signaling pathway is critical for homeostasis in various adult tissues including skin and HFs. One of the Wnt inhibitors, Dickkopf (Dkk), inhibits hair growth during the hair cycle as a catagen inducer of apoptosis, resulting in HF reductions.

OBJECTIVE

To investigate regulation of Dkk1 by HR and its effect on hair formation.

METHODS

The relative expression of Dkk1 in (+)/Hr(HP) and Hr(Hp)/Hr(Hp) mice during the hair cycle was investigated using real time PCR and Western blot analysis. Immunohistochemistry was performed in order to confirm abnormal expression of Dkk1 in HFs of (+)/Hr(HP) and Hr(Hp)/Hr(Hp) mice. To determine whether Dkk1 expression was also regulated by HR in vitro, an Hr-transient transfection experiment was performed. Alteration of the hair cycle in Hr(HP) heterozygous mice was identified by determination of the hair cycle and measurement of HF length.

RESULTS

Dkk1 expression was increased in the skin of (+)/Hr(HP) and Hr(Hp)/Hr(Hp) mice, as well as in Hr-overexpressing mouse keratinocytes. Additionally, an earlier entrance of HFs into catagen and shortened HF length in (+)/Hr(HP) mice compared to wild-type mice was observed.

CONCLUSION

Study results suggested that up-regulation of Dkk1 by HR contributed to abnormal development of HFs and failure in regeneration of HFs in Hr(Hp)/Hr(Hp) mice. These findings also indicated that alteration of the hair cycle in (+)/Hr(HP) mice was related to the up-regulation of Dkk1 by HR.

Hairless is a histone H3K9 demethylase

The hairless (HR) protein contains a Jumonji C (JmjC) domain that is conserved among a family of proteins with histone demethylase (HDM) activity. To test whether HR possesses HDM activity, we performed a series of in vitro demethylation assays, which demonstrated that HR can demethylate monomethylated or dimethylated histone H3 lysine 9 (H3K9me1 or me2). Moreover, ectopic expression of wild-type HR, but not JmjC-mutant HR, led to pronounced demethylation of H3K9 in cultured human HeLa cells. We also show that two missense mutations in HR, which we and others described in patients with atrichia with papular lesions, abolished the demethylase activity of HR, demonstrating the role of HR demethylase activity in human disease. By ChIP-Seq analysis, we identified multiple new HR target genes, many of which play important roles in epidermal development, neural function, and transcriptional regulation, consistent with the predicted biological functions of HR. Our findings demonstrate for the first time that HR is a H3K9 demethylase that regulates epidermal homeostasis via direct control of its target genes.

CtBP1 overexpression in keratinocytes perturbs skin homeostasis

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

Hairless down-regulates expression of Msx2 and its related target genes in hair follicles

BACKGROUND

Hairless (HR), a transcriptional cofactor, plays important roles in hair follicle (HF) morphogenesis and cycling. Recently, we reported the new Hr mutant mouse called "Hairpoor" (Hr(Hp)) that causes HR overexpression through translational de-repression. The Msh homeobox 2 (Msx2) is a homolog of the Drosophila muscle segment homeobox (msh) gene, which expressed in the hair bulb, including in the germinal matrix, and its expression spreads into the upper region of the HF including the hair cortex.

OBJECTIVE

Although Msx2 is regarded as an important gene in hair cycle control and hair shaft differentiation, the regulation of Msx2 expression is not well-known.

METHODS

Using realtime polymerase chain reaction (PCR) and western blot, we investigated the relationship between HR and Msx2 in the Hr(Hp)/Hr(Hp) mouse during the HF morphogenesis. Immunohistochemistry was performed to compare the pattern of expression of MSX2 in Hr(Hp)/Hr(Hp) mouse skin with that in wild-type skin. Msx2 mRNA expression and promoter activity was estimated using a transient expression system to see whether HR down-regulates Msx2 expression in vitro. We also investigated whether downregulation of MSX2 by HR also affects the MSX2 regulatory pathway in the Hr(Hp)/Hr(Hp) mouse and in an in vitro system.

RESULTS

We found that the expression of Msx2 was down-regulated by HR, which in turn down-regulated expression of Foxn1 and Lef1, MSX2 target genes, in vivo as well as in vitro.

CONCLUSION

Our results show that HR regulates expression of genes in the MSX2 regulatory pathway, which explains abnormal HF formation in Hr(Hp)/Hr(Hp) skin.

Craniofacial variations in the tricho-dento-osseous syndrome

Tricho-dento-osseous (TDO) syndrome is an autosomal dominant trait characterized by curly kinky hair at birth, enamel hypoplasia, taurodontism, thickening of cortical bones and variable expression of craniofacial morphology. Genetic studies have identified a 4-bp deletion in the DLX3 gene that is associated with TDO; however, phenotypic characterization and classification of TDO remains unclear in the literature. This study compares the craniofacial variations between 53 TDO-affected subjects and 34 unaffected family members. Standardized cephalograms were obtained and digitized. Cephalometric measurements were analyzed using a general linear model with family as a random effect. Numerous craniofacial measurements from both groups showed marked variability. TDO-affected subjects showed a Class III skeletal pattern (smaller SNA and ANB angles), longer mandibular corpus length (GoGn) and shorter ramus height (p < 0.05).