Novel mutations in the P2RY5 gene in one Turkish and two Indian patients presenting with hypotrichosis and woolly hair

Isolated autosomal recessive woolly hair/hypotrichosis: genetics, pathogenesis and therapies

Isolated autosomal recessive woolly hair/hypotrichosis (ARWH) is a rare hereditary hair disease characterized by tightly curled sparse hair at birth or in early infancy. Patients with ARWH consist of genetically heterogeneous groups. Woolly hair autosomal recessive 1 (ARWH1) (MIM #278150), woolly hair autosomal recessive 2 (ARWH2) (MIM #604379) and woolly hair autosomal recessive 3 (ARWH3) (MIM #616760) are caused by mutations in LPAR6, LIPH and KRT25, respectively. In addition, nonsense variants in C3ORF52 (*611956) were identified in ARWH patients. The frequencies of the mutations in the causative genes in ARWH patients are thought to differ by ethnicity and country/geographical area. Large numbers of ARWH families with LIPH mutations have been described only in populations from Japan, Pakistan and the Volga-Ural region of Russia. In that region of Russia, most ARWH families have an extremely prevalent founder mutation, the deletion of exon 4, in LIPH. In the Pakistani population, 47.2% of ARWH families had the disease due to LIPH mutations and 52.8% of them carried LPAR6 mutations. The prevalent, recurrent LIPH mutation c.659_660delTA (p.Ile220Argfs*29) was found in more than half of Pakistani ARWH families with LIPH mutations. Most Japanese ARWH families (98.7%) harbour LIPH mutations, including the two highly prevalent, recurrent LIPH mutations c.736T>A (p.Cys246Ser) and c.742C>A (p.His248Asn). In ARWH patients whose disease was due to LIPH, LPAR6 or C3ORF52 mutations, the loss of function of LIPH, LPAR6 or C3ORF52 leads to reduced LIPH-LPA-LPAR6 signalling, resulting in the decreased transactivation of EGFR signalling and the phenotype of underdeveloped hairs. Our recent prospective interventional study suggests that topical minoxidil might be a promising treatment for ARWH due to LIPH mutations, although sufficiently effective treatments have not been established for ARWH yet.

An essential role for LPA signalling in telencephalon development

Lysophosphatidic acid (LPA) has wide-ranging effects on many different cell types, acting through G-protein-coupled receptors such as LPAR6. We show that Xenopus lpar6 is expressed from late blastulae and is enriched in the mesoderm and dorsal ectoderm of early gastrulae. Expression in gastrulae is an early response to FGF signalling. Transcripts for lpar6 are enriched in the neural plate of Xenopus neurulae and loss of function caused forebrain defects, with reduced expression of telencephalic markers (foxg1, emx1 and nkx2-1). Midbrain (en2) and hindbrain (egr2) markers were unaffected. Foxg1 expression requires LPAR6 within ectoderm and not mesoderm. Head defects caused by LPAR6 loss of function were enhanced by co-inhibiting FGF signalling, with defects extending into the hindbrain (en2 and egr2 expression reduced). This is more severe than expected from simple summation of individual defects, suggesting that LPAR6 and FGF have overlapping or partially redundant functions in the anterior neural plate. We observed similar defects in forebrain development in loss-of-function experiments for ENPP2, an enzyme involved in the synthesis of extracellular LPA. Our study demonstrates a role for LPA in early forebrain development.

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.

To the Root of the Curl: A Signature of a Recent Selective Sweep Identifies a Mutation That Defines the Cornish Rex Cat Breed

The cat (Felis silvestris catus) shows significant variation in pelage, morphological, and behavioral phenotypes amongst its over 40 domesticated breeds. The majority of the breed specific phenotypic presentations originated through artificial selection, especially on desired novel phenotypic characteristics that arose only a few hundred years ago. Variations in coat texture and color of hair often delineate breeds amongst domestic animals. Although the genetic basis of several feline coat colors and hair lengths are characterized, less is known about the genes influencing variation in coat growth and texture, especially rexoid – curly coated types. Cornish Rex is a cat breed defined by a fixed recessive curly coat trait. Genome-wide analyses for selection (d_i, Tajima’s D and nucleotide diversity) were performed in the Cornish Rex breed and in 11 phenotypically diverse breeds and two random bred populations. Approximately 63K SNPs were used in the analysis that aimed to localize the locus controlling the rexoid hair texture. A region with a strong signature of recent selective sweep was identified in the Cornish Rex breed on chromosome A1, as well as a consensus block of homozygosity that spans approximately 3 Mb. Inspection of the region for candidate genes led to the identification of the lysophosphatidic acid receptor 6 (LPAR6). A 4 bp deletion in exon 5, c.250_253_delTTTG, which induces a premature stop codon in the receptor, was identified via Sanger sequencing. The mutation is fixed in Cornish Rex, absent in all straight haired cats analyzed, and is also segregating in the German Rex breed. LPAR6 encodes a G protein-coupled receptor essential for maintaining the structural integrity of the hair shaft; and has mutations resulting in a wooly hair phenotype in humans.

A novel mutation in the Lipase H gene underlies autosomal recessive hypotrichosis and woolly hair

Mutations in the lipase member H (LIPH) gene cause autosomal recessive hypotrichosis with woolly hair. We report herein on five consanguineous families from Pakistan segregating hypotrichosis and woolly hair. Genetic investigation using polymorphic microsatellite markers revealed homozygosity for a region spanning the HYPT7 locus on chromosome 3 in affected individuals of all five families. Sequence analysis of the LIPH gene revealed a novel nonsense mutation (p.Arg260X) associated with hypotrichosis without woolly hair in one family. In the remaining four families we identified previously described mutations in a homozygous state in affected members. These findings extend the spectrum of known LIPH mutations in the Pakistani population.

LIPH expression in skin and hair follicles of normal coat and Rex rabbits

Natural mutations in the LIPH gene were shown to be responsible for hair growth defects in humans and for the rex short hair phenotype in rabbits. In this species, we identified a single nucleotide deletion in LIPH (1362delA) introducing a stop codon in the C-terminal region of the protein. We investigated the expression of LIPH between normal coat and rex rabbits during critical fetal stages of hair follicle genesis, in adults and during hair follicle cycles. Transcripts were three times less expressed in both fetal and adult stages of the rex rabbits than in normal rabbits. In addition, the hair growth cycle phases affected the regulation of the transcription level in the normal and mutant phenotypes differently. LIPH mRNA and protein levels were higher in the outer root sheath (ORS) than in the inner root sheath (IRS), with a very weak signal in the IRS of rex rabbits. In vitro transfection shows that the mutant protein has a reduced lipase activity compared to the wild type form. Our results contribute to the characterization of the LIPH mode of action and confirm the crucial role of LIPH in hair production.

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.

Lipases and Related Molecules in Cancer

Lipases are enzymes that catalyze the hydrolysis of lipids. Based on protein structures and sequences, lipases can be classified into different protein families. The majority of conventional mammalian lipases are members of the protein super-families of serine esterases and alpha-beta hydrolases. Differential expression of lipases and related alpha-beta hydrolases in tumor cells has been observed. The physiological or patho-physiological functions of these tumor related enzymes are largely unknown. However, lipases are not only involved in energy metabolism but also in the metabolism of bioactive molecules, e.g. phosphatidic acid or arachidonic acid, suggesting that tumor-specifically expressed lipases might be interesting targets for the development of future treatment strategies. Moreover, independent of the patho-physiological function, tumor associated lipases can serve as targets for immunological treatment strategies. In addition, lipases with exclusive expression in single tumor entities can serve as potential diagnostic targets.