Refinement of a locus for Marie Unna hereditary hypotrichosis to a 1.1-cM interval at 8p21.3

Identification of mutations in U2HR in two Chinese families with Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is a rare autosomal dominant genodermatosis characterized by coarse, wiry, twisted hair developing during early childhood, with subsequent progressive hair loss. Recently, mutations in U2HR, an inhibitory upstream open reading frame in the 5' untranslated region of the human hairless gene (HR), were identified as the underlying cause of MUHH. We investigated two unrelated Chinese multigenerational families with MUHH. By sequencing U2HR in the two families, we identified two previously reported mutations, c.1A >T (p.Met1?) and c.104A>G (p*35Wext1263*). Both these mutations cosegregated with the disease phenotype in the two families.

Identification of a novel U2HR mutation in a Korean woman with Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is a rare autosomal dominant genodermatosis characterized by progressive non-scarring hair loss. Mutation of the U2HR gene, located in chromosome 8p21, is generally responsible for MUHH development. Until now, 17 mutations of U2HR have been identified from various ethnic backgrounds, but U2HR mutations have been identified mostly in Chinese families and only one Japanese patient with MUHH among Asian populations. Here, we report the first Korean case of MUHH with a novel heterozygous missense mutation (c.80C>T) in U2HR that has not been documented to date. Genetic analysis further revealed that this mutation is responsible for the hair morphology phenotype presented in this case. This finding contributes to expansion of the mutant spectrum of U2HR, supporting the possibility of racial differences in terms of genetic mutations of MUHH.

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.

Marie Unna hereditary hypotrichosis caused by a novel mutation in the human hairless transcript

Recently the causes for various forms of hypotrichosis and atrichia have been identified, increasing our understanding of the pathways involved in hair cycling and morphogenesis. Loss-of-function mutations of an inhibitory upstream ORF in the human hairless transcript were found as the cause for autosomal dominant Marie Unna hereditary hypotrichosis. At present, only two studies identified several pathogenic mutations. We ascertained a Jewish Ashkenazi family with hypotrichosis simplex of the Marie Unna type in a mother and her two children. Sequencing of the upstream ORF U2HR in the 5' UTR of the hairless gene resulted in the identification of a novel heterozygous missense mutation c.74C > T resulting in the amino acid change p.P25L. Functional assays confirmed that this mutation led to increased translation of the main HR ORF. This finding extends the mutations' spectrum of U2HR, and emphasizes its major role in hair growth.

Identification of a U2HR gene mutation in Turkish families with Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is an autosomal dominant form of isolated alopecia. The disorder is characterized by the absence or scarcity of scalp hair, eyebrows and eyelashes at birth. Coarse wiry hair begins to grow during childhood, but this is followed by progressive hair loss, which usually begins around puberty. A recent study identified mutations in U2HR, an inhibitory upstream open reading frame in the 5'-untranslated region of the human hairless gene. We investigated three reportedly unrelated Turkish multigeneration families with MUHH. Using direct sequencing of U2HR we were able to identify the c. 2T>A (p.M1K) mutation in one index patient of each family. The mutation cosegregates perfectly with the disease in all members of the families. To our knowledge, this is the first time that a mutation in U2HR has been identified in families from the Middle East. The observation of a common mutation is suggestive of a possible founder effect.

Overexpression of Hr links excessive induction of Wnt signaling to Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is a rare autosomal dominant hair disorder. Through the study of a mouse model, we identified a mutation in the 5'-untranslated region of the hairless (HR) gene in patients with MUHH in a Caucasian family. The corresponding mutation, named 'hairpoor', was found in mutant mice that were generated through N-ethyl-N-nitrosourea mutagenesis. Hairpoor mouse mutants display partial hair loss at an early age and progress to near alopecia, which resembles the MUHH phenotype. This mutation conferred overexpression of HR through translational derepression and, in turn, decreased the expression of Sfrp2, an inhibitor of the Wnt signaling pathway. This study indicates that the gain in function of HR also results in alopecia, as seen with the loss of function of HR, via abnormal upregulation of the Wnt signaling pathway.

Loss-of-function mutations of an inhibitory upstream ORF in the human hairless transcript cause Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is an autosomal dominant form of genetic hair loss. In a large Chinese family carrying MUHH, we identified a pathogenic initiation codon mutation in U2HR, an inhibitory upstream ORF in the 5' UTR of the gene encoding the human hairless homolog (HR). U2HR is predicted to encode a 34-amino acid peptide that is highly conserved among mammals. In 18 more families from different ancestral groups, we identified a range of defects in U2HR, including loss of initiation, delayed termination codon and nonsense and missense mutations. Functional analysis showed that these classes of mutations all resulted in increased translation of the main HR physiological ORF. Our results establish the link between MUHH and U2HR, show that fine-tuning of HR protein levels is important in control of hair growth, and identify a potential mechanism for preventing hair loss or promoting hair removal.

Identification of a novel locus for Marie Unna hereditary hypotrichosis to a 17.5 cM interval at 1p21.1-1q21.3

Marie Unna hereditary hypotrichosis (MUHH) is a rare autosomal dominant disorder characterized by coarse, wiry, twisted hair developed in early childhood and followed by the development of alopecia. A locus for this disorder was localized to chromosome 8p, but no gene responsible for it has been identified. To map and determine whether MUHH is a genetically heterogeneous disorder and identify the disease gene locus in a four-generation Chinese family with MUHH. We performed a genome-wide scan in this family. Two-point linkage analysis was performed using Linkage programs version 5.10 software and haplotype was constructed with Cyrillic Version 2.02 software. We failed to confirm the previous locus for MUHH at chromosome 8p and obtained the conformed evidence for linkage at chromosome 1. Two-point logarithm of odds ratio scores > or =3 were observed at markers D1S2746 and D1S2881. Haplotype analysis localized this locus to a 42 Mb region. The previous results and this study have shown that MUHH is a genetically heterogeneous disorder. Our family was mapped to a 17.5 cM region between markers D1S248 and D1S2345.