Genetic hair and nail disorders

Oral Mucosa and Nails in Genodermatoses: A Diagnostic Challenge

Genodermatoses represent a group of uncommon, hereditary, single-gene skin disorders, characterized by multisystem involvement, heterogeneous clinical manifestations and different degrees of morbidity and mortality. Some genodermatoses may have oral mucosa and nail involvement, since the oral cavity and cutaneous organ system, including nails, share a close embryologic origin. Nail disorders can manifest with nail hypoplasia or nail hypertrophy. Clinical pictures of affected oral mucosa can be extremely heterogeneous, ranging from asymptomatic papules to painful blisters, leukokeratosis, oral papillomas and fibromas to oral potentially malignant disorders and cancerous lesions. Oral mucosa and nails pathological features may occur synchronously or not and are usually associated with other systemic and skin manifestations. In some cases, oral mucosa and nails diseases may be distinct and constitute the principal sign of the genetic disorder, in other cases they represent only a part of the puzzle for the confirmation of the diagnosis. Continued awareness of the correlation between oral mucosa and nails findings can help physicians to diagnose genodermatosis in a timely manner, allowing more effective clinical management and prevention and/or early detection of complications. This article provides an overview of all specific genodermatoses affecting both oral mucosa and nails. Moreover, the correlation between teeth and nails is summarized in tabular form.

Characterization of the Onychomatricodermis Containing Onychofibroblasts of the Nail Unit : Histology, Immunohistochemistry, and Electron Microscopic Study

BACKGROUND

We recently discovered the presence of specialized nail mesenchyme below the nail matrix and designated it as onychomatricodermis.

OBJECTIVE

We did further research to characterize the histologic, histochemical, immunohistochemical and ultrastructural features of the onychomatricodermis containing onychofibroblasts in the nail unit.

METHODS

Ten polydactyly nail unit specimens and 8 nail matrix biopsies were included. H&E-stained slides were reviewed. We did Alcian blue staining and Masson Trichrome staining, as well as immunohistochemical staining for type I collagen, CD10, CD13 and CD34. In addition, polydactyly nail units were examined by transmission electron microscopy.

RESULTS

In H&E staining, the specialized mesenchyme called onychomatricodermis was observed to be slightly distant from the undersurface of the nail matrix and be less eosinophilic area. Onychomatricodermal onychofibroblasts showed light purple abundant cytoplasm. Masson Trichrome staining revealed fewer collagen fibers within the onychomatricodermis. In Alcian blue staining the onychomatricodermis showed mucin deposition within the onychofibroblasts and around them. Immunohistochemically, type I collagen was expressed much less in the onychomatricodermis while it was strongly expressed elsewhere in the nail unit. In nail matrix biopsy specimens onychomatricodermal onychofibroblasts expressed CD10 and CD13 strongly, and expressed CD34 as well. Ultrastructurally, collagen fibrils were found sparsely within the onychomatricodermis, whereas collagen fibrils were densely distributed in the dermis of other parts of the nail unit.

CONCLUSION

We demonstrated that there was less collagen expression in the onychomatricodermis containing onychofibroblasts. In addition, we found morphological and immunohistochemical features of onychomatricodermal onychofibroblasts (onychofibroblasts of Dongyoun). These findings support the presence of onychomatricodermis containing onychofibroblasts in the nail unit.

Boehmite enhances hair follicle growth via stimulation of dermal papilla cells by upregulating β-catenin signalling

Hair growth, a complex process, has long been the subject of intense research. Recent developments in material technology have revealed boehmite as a new therapeutic modality for use in wound healing and scar reduction, indicating its beneficial effects. Nonetheless, the biological bases of the beneficial effects of boehmite remain unknown. We investigated the hair growth properties of boehmite in vitro and in vivo and observed dose-dependent proliferation of human dermal papilla cells (hDPCs) in vitro and hair regrowth in a mouse model. To investigate the effects of boehmite on the promotion of cell transition to the anagen phase, we evaluated hDPC viability, alkaline phosphatase (ALP) activity, protein expression and vascular endothelial growth factor (VEGF) secretion in vitro and assessed the anagen-promoting effects of boehmite via gross observation and histological analysis in a mouse model. Boehmite increased hDPC viability, ALP activity, AKT/GSK3ß/ß-catenin pathway activity, anagen-related gene expression and VEGF secretion; moreover, it accelerated hair regrowth in a catagen-anagen transition model via upregulation of β-catenin signalling and follicular cell proliferation. Collectively, our results indicate that boehmite accelerates hair growth, partly via its effects on critical events in the active phase of the hair follicle cycle, including the promotion of the proliferation of hDPCs and their immediate progeny to the follicle base.

Physics of animal health: on the mechano-biology of hoof growth and form

Global inequalities in economic access and agriculture productivity imply that a large number of developing countries rely on working equids for transport/agriculture/mining. Therefore, the understanding of hoof conditions/shape variations affecting equids' ability to work is still a persistent concern. To bridge this gap, using a multi-scale interdisciplinary approach, we provide a bio-physical model predicting the shape of equids' hooves as a function of physical and biological parameters. In particular, we show (i) where the hoof growth stress originates from, (ii) why the hoof growth rate is one order of magnitude higher than the proliferation rate of epithelial cells and (iii) how the soft-to-hard transformation of the epithelium is possible allowing the hoof to fulfil its function as a weight-bearing element. Finally (iv), we demonstrate that the reason for hoof misshaping is linked to the asymmetrical design of equids' feet (shorter quarters/long toe) together with the inability of the biological growth stress to compensate for such an asymmetry. Consequently, the hoof can adopt a dorsal curvature and become 'dished' overtime, which is a function of the animal's mass and the hoof growth rate. This approach allows us to discuss the potential occurrence of this multifaceted pathology in equids.

Mutation in Phospholipase C, δ1 (PLCD1) Gene Underlies Hereditary Leukonychia in a Pashtun Family and Review of the Literature

Human hereditary leukonychia is a rare nail disorder characterized by nail plates whitening on all finger and toe nails. Inheritance pattern is both autosomal dominant and recessive. To date, the only gene, phospholipase C, δ1 (PLCD1), on chromosome 3p22.2 has been reported to be involved in hereditary leukonychia. In the present study, a family of Pakhtun ethnicity, carrying leukonychia phenotype was investigated. The family inherited the phenotype in an autosomal dominant fashion. Affected individuals exhibited characteristic features of hereditary leukonychia with involvement of nails on both the hands and feet. Sequence analysis of DNA detected a p.Cys209Arg mutation, reported for the first time in a Pakistani Pashtun family.

Genetics of syndromic and non-syndromic hereditary nail disorders

The nail is a unique epithelial skin appendage made up of a fully keratinized nail plate. The nail can be affected in several systemic illnesses, dermatological diseases, and inherited nail disorders. Nail dystrophies can present as isolated disorders or as a part of syndromes. Substantial progress has been achieved in the management and diagnosis of nail diseases; however, not much is known about the underlying molecular controls of nail growth. The homeostasis and development of the nail appendage depend on the intricate interactions between the epidermis and underlying mesenchyme, and comprise different signaling pathways such as the WNT signaling pathway. Digit-tip regeneration in mice and humans has been a known fact for the past six decades; however, only recently the underlying biological mechanisms by which the nail organ achieves digit regeneration have been elucidated. Moreover, significant progress has been made in identifying nail stem cells and localizing stem cell niches in the nail unit. More fascinating, however, is the role they play in orchestrating the processes that lead to the regeneration of the digit. Further elucidating the role of nail stem cells and the signaling pathways driving epithelial-mesenchymal interactions in the nail unit might contribute to the development of novel therapeutic tools for amputees.

Genetics of human isolated hereditary nail disorders

Human hereditary nail disorders constitute a rare and heterogeneous group of ectodermal dysplasias. They occur as isolated and/or syndromic ectodermal conditions where other ectodermal appendages are also involved, and can occur associated with skeletal dysplasia. 'Nail disorder, nonsyndromic congenital' (OMIM; Online Mendelian Inheritance in Man) is subclassified into 10 different types. The underlying genes identified thus far are expressed in the nail bed and play important roles in nail development and morphogenesis. Here, we review the current literature on nail disorders and present a coherent review on the genetics of nail disorders. This review will pave the way to identifying putative genes and pathways involved in nail development and morphogenesis.

[Genetic hair diseases. An update]

Patients suffering from hair loss or undesirable excessive hair growth are a challenge for dermatologists because the pathogenesis of most hair diseases is not well understood and therapeutic options are limited. This particularly holds true for genetic hair disorders, in which all current treatment attempts are unsuccessful. Furthermore, these diseases also pose a diagnostic challenge due to a broad range of clinical and genetic heterogeneity. However, the enormous progress in molecular biology over the past 20 years, in particular the availability of different new techniques such as whole exome and genome sequencing, has enabled us to elucidate the genetic basis of most monogenic hair disorders, given the availability of suitable index patients and families as well as adequate technical equipment and sufficient financial resources. In this review we provide an update on clinical and genetic aspects of selected monogenic and polygenic hair diseases manifesting with hypertrichosis and hypotrichosis.

Nail stem cells

Our knowledge on stem cells of the hair follicle has increased exponentially after the bulge was characterized as the stem cell niche two decades ago. In contrast, little is known about stem cells in the nail unit. Whereas hair follicles are plentiful and easy to access, the human body has only twenty nails and they are rarely biopsied. Therefore, examining fetal material offers unique advantages. In the following mini-review, our current knowledge on nail stem cells is summarized and analogies to the hair follicle stem cells are drawn.

Genome array of hair follicle genes in lambskin with different patterns

Hu sheep lambskin comes from a specific breed of sheep of China. Hu sheep are considered a protected breed by the Chinese government. The hair follicles of these sheep have three types of waves, large, medium, and small. There are only few histological reports of Hu sheep lambskin, and there are no modern molecular or biological studies, so the molecular mechanisms underlying the formation of hair follicles with different patterns are not currently known. The aim of this article was to study the molecular mechanism of the formation of these types of hair follicles in Hu sheep. Histological and microscopic analysis indicated that the number of follicles with small waves was not significantly higher than the number of follicles with large waves (P>0.05). The diameters of primary and secondary small-wave follicles were significantly smaller than those of large-wave follicles (P<0.05; P<0.01). The ratio between the number primary follicles and the number of secondary follicles was significantly higher among small-wave follicles than among large-wave follicles (P<0.05). Differentially expressed genes in the skin tissue were screened using an Agilent gene chip and RT-PCR. Differential expression analysis revealed 3 groups of large waves and small waves; 1067, 2071, and 3879 differentially expressed genes; and 137 genes common to all 3 groups. Differentially expressed genes were classified using gene ontology. They were found to be mainly involved in cell differentiation, proliferation, apoptosis, growth, immune response, and ion transport. RT-PCR results of 4 differentially expressed genes were consistent with gene chip results. Combined with related literature, our results suggest that BMP7, MMP2, SNAI1, SFXN1, CDKNIC, MT3, and POU1F1 may have important effects on the formation of large-wave and small-wave hair follicles. This study may enrich knowledge of hair follicle development, and may identify the genes responsible for the formation of hair follicles with different patterns.

A case of ectopic cilia in nail-patella syndrome

Both ectopic cilia and nail-patella syndrome (NPS) are rare entities. To our knowledge we report the first case of the two anomalies coexisting in one patient. We present the case of a 2-year-old girl, with no other ophthalmic complication of NPS, who had an excellent cosmetic outcome and no lesion recurrence following surgical excision of ectopic cilia.

Unveiling the roots of monogenic genodermatoses: genotrichoses as a paradigm

The past two decades have seen significant and unprecedented progress in human genetics owing to the advent of novel molecular biological technologies and major developments in computational methods. Dermatology has benefited from and, in some cases, led these advances. In this article, we review major discoveries in the field of inherited hair diseases, which illustrate the changes that genodermatology has undergone in recent years from a mostly descriptive discipline through the elucidation of the molecular basis of numerous disorders, up to the first attempts at translating these new findings into novel preventive and therapeutic tools to the benefit of our patients.

A novel mutation in LPAR6 causes autosomal recessive hypotrichosis of the scalp

BACKGROUND

Autosomal recessive hypotrichosis simplex (ARHS) presents with progressive hair loss mainly affecting the scalp area. In a small number of families, the condition has been associated with mutations in three distinct genes: DSG4, LIPH and LPAR6.

AIM

To identify the molecular basis of ARHS in a consanguineous family of Turkish extraction.

METHODS

We used a combination of microsatellite marker screening and direct sequencing.

RESULTS

We identified a novel missense mutation (c.C587T) in the human LPAR6 gene, resulting in the amino acid substitution p.P196L. The mutation affects a highly conserved amino acid residue, and is predicted to disrupt signalling through the P2Y5 receptor.

CONCLUSIONS

This study provides further evidence supporting a role for the lysophosphatidyl signalling pathway in hair growth and differentiation. In addition, this paper reports, for the first time to our knowledge, the use of homozygosity mapping as a premutation screening tool in the diagnosis of a group of inherited hair disorders.

Proteomic analysis of human nail plate

Shotgun proteomic analysis of the human nail plate identified 144 proteins in samples from Causcasian volunteers. The 30 identified proteins solubilized by detergent and reducing agent, 90% of the total nail plate mass, were primarily keratins and keratin associated proteins. Keratins comprised a majority of the detergent-insoluble fraction as well, but numerous cytoplasmic, membrane, and junctional proteins and histones were also identified, indicating broad use by transglutaminases of available proteins as substrates for cross-linking. Two novel membrane proteins were identified, also found in the hair shaft, for which mRNAs were detected only at very low levels by real-time polymerase chain reaction in other tissues. Parallel analyses of nail samples from volunteers from Inner Mongolia, China gave essentially the same protein profiles. Comparison of the profiles of nail plate and hair shaft from the latter volunteers revealed extensive overlap of protein constituents. Analyses of samples from an arsenic-exposed population revealed few proteins whose levels were altered substantially but raised the possibility of detecting sensitive individuals in this way.

ANE syndrome caused by mutated RBM28 gene: a novel etiology of combined pituitary hormone deficiency

OBJECTIVE AND DESIGN

A homozygous loss-of-function mutation in the gene RBM28 was recently reported to underlie alopecia, neurological defects, and endocrinopathy (ANE) syndrome. The aim of the present study was to characterize the endocrine phenotype of ANE syndrome and to delineate its pathogenesis.

METHODS

Detailed neuroendocrine assessment was performed in five affected male siblings harboring the homozygous p.L351P mutation in RBM28.

RESULTS

All five affected patients, aged 20-39 years, displayed absent puberty, hypogonadism, and variable degrees of short stature. Low IGF1 concentration and a lack of GH response to provocative tests in all siblings were consistent with GH deficiency. Low testosterone and gonadotropin levels with absence or low response to GnRH stimulation indicated hypogonadotropic hypogonadism. ACTH deficiency evolved over time, and glucocorticoid replacement therapy was initiated in four patients. Thyroid analysis showed variable abnormal TSH response to TRH stimulation, suggesting hypothalamic compensated hypothyroidism in four subjects and laboratory hypothyroidism (low free thyroxine) in one patient. Low prolactin levels were shown in one case.

CONCLUSIONS

The endocrine defects characteristic of ANE syndrome are compatible with variable combined anterior pituitary hormone deficiency (CPHD), which evolves gradually over the years, indicating long-term hormonal monitoring. We propose that defects in the cellular Wnt/beta-catenin signaling pathway underlie this endocrinopathy. RBM28 gene defects should be added to the growing list of gene defects associated with syndromic CPHD.

A large duplication in LIPH underlies autosomal recessive hypotrichosis simplex in four Middle Eastern families

Autosomal recessive hypotrichosis simplex (ARHS) manifests with paucity of hair appearing during early childhood. We assessed four affected families. We initially genotyped three of these families for a panel of microsatellite markers spanning all ARHS-associated loci and obtained data suggesting linkage to 3q27, encompassing LIPH, which had previously been shown to be associated with ARHS. Accordingly, a homozygous duplication mutation in exon 2 of this gene (c.280_369dup; p.Gly94_Lys123dup) was found to segregate with the disease in all the families. Through the identification of the first duplication mutation in the human LIPH gene, we provide further evidence supporting a role for the phospholipase signalling pathway in hair growth and differentiation.

Alopecia, neurological defects, and endocrinopathy syndrome caused by decreased expression of RBM28, a nucleolar protein associated with ribosome biogenesis

Single-gene disorders offer unique opportunities to shed light upon fundamental physiological processes in humans. We investigated an autosomal-recessive phenotype characterized by alopecia, progressive neurological defects, and endocrinopathy (ANE syndrome). By using homozygosity mapping and candidate-gene analysis, we identified a loss-of-function mutation in RBM28, encoding a nucleolar protein. RBM28 yeast ortholog, Nop4p, was previously found to regulate ribosome biogenesis. Accordingly, electron microscopy revealed marked ribosome depletion and structural abnormalities of the rough endoplasmic reticulum in patient cells, ascribing ANE syndrome to the restricted group of inherited disorders associated with ribosomal dysfunction.

Autosomal recessive ichthyosis with hypotrichosis caused by a mutation in ST14, encoding type II transmembrane serine protease matriptase

In this article, we describe a novel autosomal recessive ichthyosis with hypotrichosis syndrome, characterized by congenital ichthyosis associated with abnormal hair. Using homozygosity mapping, we mapped the disease locus to 11q24.3-q25. We screened the ST14 gene, which encodes matriptase, since transplantation of skin from matriptase(-/-)-knockout mice onto adult athymic nude mice has been shown elsewhere to result in an ichthyosislike phenotype associated with almost complete absence of erupted pelage hairs. Mutation analysis revealed a missense mutation, G827R, in the highly conserved peptidase S1-S6 domain. Marked skin hyperkeratosis due to impaired degradation of the stratum corneum corneodesmosomes was observed in the affected individuals, which suggests that matriptase plays a significant role in epidermal desquamation.