The genetics of hair shaft disorders

A human identification system for hair shaft using RNA polymorphism

Hair is one of the common pieces of evidence at crime scenes, with abundant mitochondrial DNA but limited nuclear DNA in its shaft. It also helps to narrow the investigation scope to maternal lineage but fails to provide unique individual information. We assumed that RNA in hair shafts would be an alternative resource used to perform human identification based on the facts that (1) RNA retains the polymorphic information; (2) the multi-copy of RNA in a cell resists degradation as compared to the one-copy of nuclear DNA. In this study, we explored the potential of RNA polymorphism in hair shafts for forensic individual identification. A SNaPshot typing system was constructed using 18 SNPs located on 11 genes (ABCA13, AHNAK, EXPH5, KMT2D, KRT35, PPP1R15A, RBM33, S100A5, TBC1D4, TMC5, TRPV2). The RNA typing system was evaluated for sensitivity, species specificity, and feasibility for aged hair samples. Hair samples from a Shanxi population in China were used for the population study of the system. The detection limit of the assay was 2 ng RNA. The CDP of these 11 genes was 0.999969 in the Shanxi population. We also identified the concordance of the RNA and DNA typing results. In summary, we developed an RNA typing method to perform human identification from hair shafts, which performed as accurately as nuclear DNA typing. Our method provides a potential basis for solving the human identification problem from hair shafts, as well as other biological materials that lack nuclear DNA.

Genetics of hair graying with age

Hair graying is an early and obvious phenotypic and physiological trait with age in humans. Several recent advances in molecular biology and genetics have increased our understanding of the mechanisms of hair graying, which elucidate genes related to the synthesis, transport, and distribution of melanin in hair follicles, as well as genes regulating these processes above. Therefore, we review these advances and examine the trends in the genetic aspects of hair graying from enrichment theory, Genome-Wide association studies, whole exome sequencing, gene expression studies, and animal models for hair graying with age, aiming to overview the changes in hair graying at the genetic level and establish the foundation for future research. Meanwhile, by summarizing the genetics, it's of great value to explore the possible mechanism, treatment, or even prevention of hair graying with age.

DNA and protein analyses of hair in forensic genetics

Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.

Apoptotic extracellular vesicles are metabolized regulators nurturing the skin and hair

Over 300 billion of cells die every day in the human body, producing a large number of endogenous apoptotic extracellular vesicles (apoEVs). Also, allogenic stem cell transplantation, a commonly used therapeutic approach in current clinical practice, generates exogenous apoEVs. It is well known that phagocytic cells engulf and digest apoEVs to maintain the body's homeostasis. In this study, we show that a fraction of exogenous apoEVs is metabolized in the integumentary skin and hair follicles. Mechanistically, apoEVs activate the Wnt/β-catenin pathway to facilitate their metabolism in a wave-like pattern. The migration of apoEVs is enhanced by treadmill exercise and inhibited by tail suspension, which is associated with the mechanical force-regulated expression of DKK1 in circulation. Furthermore, we show that exogenous apoEVs promote wound healing and hair growth via activation of Wnt/β-catenin pathway in skin and hair follicle mesenchymal stem cells. This study reveals a previously unrecognized metabolic pathway of apoEVs and opens a new avenue for exploring apoEV-based therapy for skin and hair disorders.

•

Exogenous infused apoEVs are partly metabolized from the integumentary skin and hair follicles.

•

ApoEVs activate Wnt/β-catenin pathway to facilitate their elimination in a wave-like pattern.

•

Exercise can enhance apoEV metabolism through Wnt/β-catenin pathway.

•

MSC-derived apoEVs promote wound healing and hair growth.

Usefulness of Trichoscopy over Hair Light Microscopy in Menkes Disease

Menkes disease (MD) is a rare X-linked recessive neurodegenerative disorder caused by mutations in the ATP7A gene, with a high mortality rate within the first 3 years of life. It typically affects males and is characterized by impaired copper distribution and malfunction of several copper-dependent enzymes. Patients develop progressive muscle hypotonia associated with neurological damage and hair shaft dysplasia - particularly pili torti. Pili torti is usually very subtle in the first 3 months of life and gradually increases during the first year. Light microscopy examination in search for pili torti requires the observation of more than 50 hair shafts. In contrast, trichoscopy with a hand-held dermatoscope allows to easily identify the hair shaft defect. We report a case of a Hispanic male infant with MD in whom we show that trichoscopy is superior to hair light microscopy in revealing pili torti.

Independent DSG4 frameshift variants in cats with hair shaft dystrophy

Investigations of hereditary phenotypes in spontaneous mutants may help to better understand the physiological functions of the altered genes. We investigated two unrelated domestic shorthair cats with bulbous swellings of the hair shafts. The clinical, histopathological, and ultrastructural features were similar to those in mice with lanceolate hair phenotype caused by loss-of-function variants in Dsg4 encoding desmoglein 4. We sequenced the genomes from both affected cats and compared the data of each affected cat to 61 control genomes. A search for private homozygous variants in the DSG4 candidate gene revealed independent frameshift variants in each case, c.76del or p.Ile26fsLeu*4 in case no. 1 and c.1777del or p.His593Thrfs*23 in case no. 2. DSG4 is a transmembrane glycoprotein located primarily in the extracellular part of desmosomes, a complex of adhesion molecules responsible for connecting the keratin intermediate filaments of neighbouring epithelial cells. Desmosomes are essential for normal hair shaft formation. Both identified DSG4 variants in the affected cats lead to premature stop codons and truncate major parts of the open-reading frame. We assume that this leads to a complete loss of DSG4 function, resulting in an incorrect formation of the desmosomes and causing the development of defective hair shafts. Together with the knowledge on the effects of DSG4 variants in other species, our data suggest that the identified DSG4 variants cause the hair shaft dystrophy. To the best of our knowledge, this study represents the first report of pathogenic DSG4 variants in domestic animals.

Athena: Speciality Certificate Examination case for Paediatrics and Genetics - A case of brittle hair

The parents of a 1-year-old boy are concerned regarding his hair being very brittle. He is being investigated for seizures. He has significant delay in psychomotor development. He had complete lack of scalp and eyebrow hair at birth. On examination, his hair was sparse, coarse in texture and twisted. Hair microscopy demonstrated pili torti. He had a low serum ceruloplasmin and serum copper. A diagnosis of Menkes Syndrome (MS) was made.

Novel extraction chemistry and alternative amplification strategies for use with rootless hair shafts

Rootless hair shafts are often considered unsuitable for STR genotyping due to the known high failure rate. The same samples can be reliably processed with mitochondrial sequencing. However, the minimal discriminatory power of widely implemented control region mitochondrial sequencing techniques limits its utility in some forensic casework. In this research, multiple variables were tested to provide information on rootless hair shaft sample genotyping success. Results showed external decontamination procedures decreased drop-in alleles but also greatly reduced profile recovery. The novel InnoXtract^™ chemistry was comparable to automated EZ1 DNA Investigator extraction. With thoroughly decontaminated hairs, InnoTyper^® 21 amplification generated random match probabilities higher than STR chemistry in 71.875% of samples and 18.75% of samples benefitted from the use of InnoTyper^® 21 amplification compared with estimated mtDNA profile rarity. Compared with the capillary electrophoresis-based amplification chemistries tested, the ForenSeq™ DNA Signature Prep chemistry paired with massively parallel sequencing was the most discriminatory amplification strategy tested.

Wanted, dead and alive: Why a multidisciplinary approach is needed to unlock hair treatment potential

Human recorded history is littered with attempts to improve the perceived appearance of scalp hair. Throughout history, treatments have included both biological and chemical interventions. Hair "quality" or "perceived appearance" is regulated by multiple biological intervention opportunities: adding more hairs by flipping follicles from telogen to anagen, or delaying anagen follicles transiting into catagen; altering hair "apparent amount" by modulating shaft diameter or shape; or, in principle, altering shaft physical properties changing its synthesis. By far the most common biological intervention strategy today is to increase the number of hairs, but to date this has proven difficult and has yielded minimal benefits. Chemical intervention primarily consists of active material surface deposition to improve shaft shine, fibre-fibre interactions and strength. Real, perceptible benefits will best be achieved by combining opportunity areas across the three primary sciences: biology, chemistry and physics. Shaft biogenesis begins with biology: proliferation in the germinative matrix, then crossing "Auber's Critical Line" and ceasing proliferation to synthesize shaft components. Biogenesis then shifts to oxidative chemistry, where previously synthesized components are organized and cross-linked into a shaft. We herein term the crossing point from biology to chemistry as "The Orwin Threshold." Historically, hair biology and chemistry have been conducted in different fields, with biological manipulation residing in biomedical communities and hair shaft chemistry and physics within the consumer care industry, with minimal cross-fertilization. Detailed understanding of hair shaft biogenesis should enable identification of factors necessary for optimum hair shaft production and new intervention opportunities.

Telogen effluvium: a comprehensive review

Excessive hair shedding is a common and alarming phenomenon, usually complained about by women. The disorder, named telogen effluvium (TE), bears several problems which are discussed in this essay. They are as follows: 1) how profuse a hair loss must be for TE to be diagnosed; 2) its heterogeneity that needs to be properly classified; 3) its distinction from androgenetic alopecia (AGA) with which it is often associated; 4) its main symptom, trichodynia, which is unclear how frequent and how diagnostic could be; 5) why histopathology has been reported to be nonspecific; and 6) its management, from diagnosis to treatment. A common mistake of the dermatologist is to minimize the complaint. Instead, the disorder may have a profound impact on the patients' mind and would require attention, time, and empathy.

Pili Annulati with Severe Trichorrhexis Nodosa: A Case Report and Review of the Literature

Pili annulati is generally classified as a hair shaft disorder without fragility. However, increased susceptibility to weathering is common. Severe breakage due to trichorrhexis nodosa is uncommon. We report a case and review the literature on this topic.

A Practical Approach to the Diagnosis and Management of Hair Loss in Children and Adolescents

Hair loss or alopecia is a common and distressing clinical complaint in the primary care setting and can arise from heterogeneous etiologies. In the pediatric population, hair loss often presents with patterns that are different from that of their adult counterparts. Given the psychosocial complications that may arise from pediatric alopecia, prompt diagnosis and management is particularly important. Common causes of alopecia in children and adolescents include alopecia areata, tinea capitis, androgenetic alopecia, traction alopecia, trichotillomania, hair cycle disturbances, and congenital alopecia conditions. Diagnostic tools for hair loss in children include a detailed history, physical examination with a focused evaluation of the child’s hair and scalp, fungal screens, hair pull and tug test, and if possible, light microscopy and/or trichoscopy. Management of alopecia requires a holistic approach including psychosocial support because treatments are only available for some hair loss conditions, and even the available treatments are not always effective. This review outlines the clinical presentations, presents a diagnostic algorithm, and discusses management of these various hair loss disorders.

Hair diseases: a big problem on a small surface

Civilizational progress initially contributes to the problem of hair loss and then to alopecia as regards both frequency and therapeutic dilemmas. The work presents trichological problems which occur more rarely, i.e. drug-induced, anagen and telogen alopecia, congenital and acquired structural hair disorders, psychic disturbances concerning the hair as well as the hair during menopause. Then, the article briefly describes contagious (infectious) diseases as well as diseases with inflammatory etiology which are accompanied by exfoliation and (frequently) pruritus. Finally, alopecia cicatricans is discussed. Alopecia areata and androgenetic alopecia are omitted herein because they occur more often and will be described in another work. Any disproportions and upset balance concerning correct functioning of mechanisms within the scalp hair system are the evidence of pathologies.

Loose Anagen Syndrome: A Retrospective Chart Review of 37 Cases

BACKGROUND/OBJECTIVES

Loose anagen syndrome (LAS) is a disorder of abnormal anchorage of the hair to the scalp. Its symptoms include an inability to grow hair long and hair that is easily pulled out.

METHODS

We conducted a retrospective chart review of patients with LAS over the last 10 years at the Children's Hospital of Philadelphia and found 37 cases.

RESULTS

LAS was more common in females and was found in all hair colors and skin types.

CONCLUSION

Diagnosis of LAS should be made based on history, microscopic findings, and hair bulb and shaft features.

Light microscopic hair shaft analysis in ectodermal dysplasia syndromes

The objective of the study was to catalog hair shaft abnormalities in individuals with ectodermal dysplasia (ED) syndromes using light microscopy and to compare findings with those in unaffected controls. Light microscopy was performed in a nonblinded manner on hair shafts from 65 participants with seven types of ED (hypohidrotic ED, ED-ectrodactyly-cleft lip or palate, ankyloblepharon-ectodermal defects-cleft lip and palate, Clouston syndrome, Goltz syndrome, Schopf-Schulz Passarge syndrome, and oculodentodigital dysplasia) and 41 unaffected controls. Hair donations were collected at the 28th Annual National Family Conference held by the National Foundation for Ectodermal Dysplasia. Control participants were recruited from a private dermatology practice and an academic children's hospital outpatient dermatology clinic. Sixty-five affected participants and 41 unaffected controls were included in the analysis. We assessed the hair shafts of ED and control participants for abnormalities visible using LM. Light microscopy identified various pathologic hair shaft abnormalities in each type of ED, although none of the findings were statistically significantly different from those of the control group. Light microscopy is a poor adjuvant tool in the diagnosis of ED syndromes. Most findings are nonspecific and not sufficiently sensitive.

Unusual and recently described cutaneous atrophic disorders

Cutaneous atrophic conditions are typically caused by changes in the dermis or subcutaneous tissue, sometimes consisting of the loss of a single fiber type. Since a significant decrease of subepidermal tissue is necessary for these lesions to be macroscopically atrophic, many conditions may not be appreciated as atrophy in the clinical setting. Clinicians should be familiar with the common or classic disorders causing cutaneous atrophy; however, there are a few new or rarely described atrophic conditions which are more difficult to identify and may not be atrophic clinically. This paper serves to describe the salient clinical and histological features of these new or rare disorders.

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.

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

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

Short anagen syndrome

Short anagen syndrome (SAS) is a recently described disease, but is rarely reported in the literature probably because of its under-recognized status. It is characterized by the inability to grow long hair because of an idiopathic short anagen phase. The condition is not associated with hair shaft fragility or hair unruliness. The patients complain of abnormally short scalp hair and report that they never had a haircut. The condition is benign and most of the reported cases had no associated systemic diseases or skin disorders. Hair length tends to improve spontaneously after puberty. The main differential diagnoses include loose anagen hair syndrome (LAS).

Light microscopy of the hair: a simple tool to "untangle" hair disorders

Light microscopy of the hair forms an important bedside clinical tool for the diagnosis of various disorders affecting the hair. Hair abnormalities can be seen in the primary diseases affecting the hair or as a secondary involvement of hair in diseases affecting the scalp. Hair abnormalities also form a part of various genodermatoses and syndromes. In this review, we have briefly highlighted the light microscopic appearance of various infectious and non-infectious conditions affecting the hair.

Female adolescent hair disorders

Hair abnormalities can have tremendous psychosocial impacts on adolescents and young adults, and may cause a great amount of anxiety regarding physical appearance, associated illnesses, and potential clinical course. The pathophysiology of such disorders may vary,with potential congenital, infectious, autoimmune, nutritional, or environmental causes. Hair abnormalities may present as changes in hair appearance or quality, becoming weathered or fractured.An abnormal increase in hair is present in hypertrichosis and hirsutism, whereas a thinning or shedding of hair is evident in patients with telogen effluviumand alopecia areata. Diagnosis is focused on a detailed clinical history and physical exam, in addition to laboratory testing, a variety of clinical diagnostic tests, and scalp biopsy, which may be necessary to confirm some diagnoses. Many hair disorders have no cure, but clinicians can have a positive impact on their patients by identifying the abnormality and educating the patient regarding disease course. However, some conditions such as infectious hair disorders or scarring alopecia should be identified promptly to initiate treatment and ensure clinical improvement or optimal outcome.