Disentangling the roots of inherited hair disorders

Novel sequence variants in the LIPH and LPAR6 genes underlies autosomal recessive woolly hair/hypotrichosis in consanguineous families

Autosomal-recessive woolly hair/hypotrichosis (ARWH/H) is a rare genetic disorder of hair caused by variants in the LIPH and LPAR6 genes. The disease is characterized by congenital tightly curled hair leading to sparse hair later in life. In the present report genetic characterization of three consanguineous families of Pakistani origin, displaying clinical features of ARWH/H, was performed. Haplotype and DNA sequence analysis of the LIPH gene revealed a novel homozygous nonsense variant (c.688C > T; p.Gln230*) in family A. In two other families, B and C, sequence analysis of the LPAR6 gene revealed a novel homozygous frameshift variant (c.68_69dupGCAT; p.Phe24Hisfs*29) and a previously reported missense variant (c.188A > T; p.Asp63Val), respectively. Taken together, our findings will expand the spectrum of variants reported in the LIPH and LPAR6 genes.

Genetik der monogenen isolierten Alopezien

Die monogen vererbten isolierten Alopezien umfassen eine Gruppe klinisch und genetisch heterogener Formen von Haarlosigkeit/-verlust. Die klinische Unterteilung der isolierten Alopezien erfolgt nach Erkrankungsbeginn, betroffenen Regionen und Struktur des Haarschafts. Frauen und Männer sind gleichermaßen betroffen, die Vererbung ist autosomal-dominant oder autosomal-rezessiv. Seit der Identifizierung des Keratingens KRT86 als Ursache für die so genannte Monilethrix im Jahr 1997 konnten in der letzten Dekade Mutationen in 9 weiteren Genen für verschiedene Formen isolierter Alopezien identifiziert werden, darunter weitere Keratingene (KRT81 und KRT83) für die Monilethrix, das Hairless-Gen für die Atrichia congenita/papuläre Atrichie, das Corneodesmosingen für die autosomal-dominante Form der Hypotrichosis simplex sowie die Gene Desmoglein 4, Lipase H und der G-Protein gekoppelte Rezeptor P2RY5 (LPAR6) für autosomal-rezessive Formen der Hypotrichose. Molekulargenetische und pathophysiologische Untersuchungen dieser seltenen Haarentwicklungsstörungen trugen entscheidend dazu bei, grundlegende Mechanismen des Haarausfalls und somit auch physiologische Mechanismen des Haarwachstums besser zu verstehen.

Mutations in the lipase H gene underlie autosomal recessive woolly hair/hypotrichosis

Woolly hair (WH) is characterized by the presence of fine and tightly curled hair. WH can appear as a symptom of some systemic diseases, or without associated findings (nonsyndromic WH). Nonsyndromic WH is known to be inherited as either an autosomal-dominant (OMIM 194300) or recessive (ARWH; OMIM 278150) trait. In this study, we identified 11 consanguineous families of Pakistani origin with ARWH, as well as associated features including sparse and hypopigmented hair shafts. We first checked for mutations in the P2RY5 gene, which encodes an orphan G-protein-coupled receptor that we recently identified as a cause of ARWH. However, none of the 11 families had mutations in the P2RY5 gene. To identify the disease locus, we performed linkage studies in one of these families using the Affymetrix 10K array, and identified a region of suggestive linkage on chromosome 3q27. This region contains the lipase H (LIPH) gene which has been recently shown to underlie an autosomal-recessive form of hypotrichosis. Mutation analysis resulted in the identification of a total of 5 pathogenic mutations in the LIPH of all 11 families analyzed. These results show that LIPH is a second causative gene for ARWH/hypotrichosis, giving rise to a phenotype clinically indistinguishable from P2RY5 mutations.

Autosomal recessive woolly hair with hypotrichosis caused by a novel homozygous mutation in the P2RY5 gene

During the last decade, several causative genes for hereditary hair diseases have been identified, which have disclosed the molecular mechanisms involved in hair follicle morphogenesis and cycling. We and others recently reported that mutations in the P2RY5 gene, encoding an orphan G protein-coupled receptor, underlie autosomal recessive woolly hair (WH)/hypotrichosis. Although these findings clearly reveal the involvement of P2RY5 mutations in hereditary hair diseases, the clinical manifestations of P2RY5 mutations have not completely been elucidated because of limited information to date. In this study, we ascertained a consanguineous family of Iranian origin with an affected girl showing sparse and hypopigmented scalp hair. She exhibited the WH phenotype with normal hair density at birth, but progressed with age to develop hypotrichosis. Direct sequencing analysis resulted in the identification of a novel homozygous mutation in the P2RY5 gene of the patient, which results in a non-conservative amino acid change, G146R, at the protein level. Our findings extend the mutation spectrum of P2RY5 mutations, and further support a crucial role of P2Y5 in hair growth in humans.

Genome-wide linkage analysis of an autosomal recessive hypotrichosis identifies a novel P2RY5 mutation

While there have been significant advances in understanding the genetic etiology of human hair loss over the previous decade, there remain a number of hereditary disorders for which a causative gene has yet to be identified. We studied a large, consanguineous Brazilian family that presented with woolly hair at birth that progressed to severe hypotrichosis by the age of 5, in which 6 of the 14 offspring were affected. After exclusion of known candidate genes, a genome-wide scan was performed to identify the disease locus. Autozygosity mapping revealed a highly significant region of extended homozygosity (lod score of 10.41) that contained a haplotype with a linkage lod score of 3.28. Results of these two methods defined a 9-Mb region on chromosome 13q14.11-q14.2. The interval contains the P2RY5 gene, in which we recently identified pathogenic mutations in several families of Pakistani origin affected with autosomal recessive woolly and sparse hair. After the exclusion of several other candidate genes, we sequenced the P2RY5 gene and identified a homozygous mutation (C278Y) in all affected individuals in this family. Our findings show that mutations in P2RY5 display variable expressivity, underlying both hypotrichosis and woolly hair, and underscore the essential role of P2RY5 in the tissue integrity and maintenance of the hair follicle.