Hair abnormalities in genetic disorders of junctions

Genetic Differences between Male and Female Pattern Hair Loss in a Korean Population

Studies on androgenetic alopecia (AGA or patterned hair loss (PHL)) have suggested different underlying pathological mechanisms between males and females. While many genetic factors for male hair loss have been identified through genome-wide association studies (GWASs), the genetic determinants of female hair loss remain unclear. In this study, we analyzed approximately 1000 individuals (436 males and 568 females) to identify sex-specific genetic factors. We conducted three independent GWASs for the total, male-only, and female-only groups, identifying three novel loci (rs7814359, rs2163085, and rs4793158 of the TSNARE1, FZD1, and GJC1 genes, respectively). rs7814359 showed a significant genome-wide association with AGA in the combined sex group and a weak association in both the male-only and female-only groups. The single nucleotide polymorphism (SNP) rs2163085 showed a significant genome-wide association with AGA in the combined group and notable significance in females. The rs4793158 SNP showed a suggestive association with AGA in both the combined and female-only groups. TSNARE1, related to rs7814359, is involved in vesicle transport. FZD1 is a key regulator of the Wnt signaling pathway. GJC1 is a gap junction protein. The associations of FZD1 and GJC1 with female-specific AGA suggest that sex hormones, such as estrogen, may influence FPHL through these genes. These findings will contribute to our understanding of the sex-specific pathophysiology of AGA.

Hair curvature: a natural dialectic and review

Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways, and others, can explain many alternatives and specific variations of hair bending phenotypes. Mechanisms for hair papilla budding or its division by bisection or fission can explain MPC formation. Epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) transitions, acting in collaboration with epithelial-mesenchymal communications are also considered as mechanisms affecting hair growth and its bending and twisting. These may be treated as sub-mechanisms of an overall development from neural-crest stem cell (NCSC) lineages to differentiated hair follicle (HF) cell types, thus providing a unified framework for hair growth and development.

Woolly hair nevus: a rare entity

Woolly hair nevus is a rare non-hereditary focal condition characterized by unruly and tightly coiled hair. It can appear in childhood or adolescence and may be associated with epidermal or melanocytic nevus. Patients presenting with woolly hair must be examined completely to rule out cardiofaciocutaneous and Noonan syndrome.