Evidence for pseudodominant inheritance of atrichia with papular lesions

Hairless is a histone H3K9 demethylase

The hairless (HR) protein contains a Jumonji C (JmjC) domain that is conserved among a family of proteins with histone demethylase (HDM) activity. To test whether HR possesses HDM activity, we performed a series of in vitro demethylation assays, which demonstrated that HR can demethylate monomethylated or dimethylated histone H3 lysine 9 (H3K9me1 or me2). Moreover, ectopic expression of wild-type HR, but not JmjC-mutant HR, led to pronounced demethylation of H3K9 in cultured human HeLa cells. We also show that two missense mutations in HR, which we and others described in patients with atrichia with papular lesions, abolished the demethylase activity of HR, demonstrating the role of HR demethylase activity in human disease. By ChIP-Seq analysis, we identified multiple new HR target genes, many of which play important roles in epidermal development, neural function, and transcriptional regulation, consistent with the predicted biological functions of HR. Our findings demonstrate for the first time that HR is a H3K9 demethylase that regulates epidermal homeostasis via direct control of its target genes.

Detection of a novel missense mutations in atrichia with papular lesions

BACKGROUND

Atrichia with papular lesions (APL) is a rare inherited disease characterized by early onset of total hair loss, followed by papular lesions over the extensor areas of the body. Recently, mutations in the human hairless (HR) gene have been implicated in its pathogenesis. The identification of mutations in the HR gene is important for differentiating between APL and alopecia universalis (AU).

OBJECTIVE

We compared the HR genes of patients with presumed AU who showed minimal or no response to treatment with the HR genes of healthy controls.

METHODS

The subjects were 11 patients with presumed AU who had not responded to treatments. Fifty healthy people were included as controls for molecular analysis. To screen for mutations, polymerase chain reaction was performed.

RESULTS

DNA analysis identified a novel heterozygous G-to-A transition at nucleotide position 191 in exon 5. The mutation was not found in the controls, other AU patients, or any unaffected family members except for the patients' mother and maternal grandfather, who were heterozygous HR gene carriers.

CONCLUSION

Our study identifies a novel missense mutation in exon 5 of the HR gene in a Korean APL patient previously diagnosed as AU.

Atrichia with papular lesions resulting from novel compound heterozygous mutations in the human hairless gene

Atrichia with papular lesions is a rare form of complete, irreversible alopecia that is inherited in an autosomal recessive manner. Several studies have implicated mutations in the human hairless gene as the underlying cause of this disorder. We describe two novel heterozygous mutations in exons 3 and 8 of the hairless gene in a 2-year-old Caucasian boy with complete alopecia of his scalp. These novel mutations add to the growing literature of mutations in the hairless gene found in nonconsanguineous families and expands the allelic series of mutations in this gene.

Interactions of the Vitamin D Receptor with the Corepressor Hairless

Atrichia with papular lesions (APL) and hereditary vitamin D-resistant rickets have a similar congenital hair loss disorder caused by mutations in hairless (HR) and vitamin D receptor (VDR) genes, respectively. HR is a VDR corepressor, and it has been hypothesized that VDR.HR suppress gene expression during specific phases of the hair cycle. In this study, we examined the corepressor activity of HR mutants (E583V, C622G, N970S, V1056M, D1012N, V1136D, and Q1176X) previously described as the molecular cause of APL as well as HR variants (P69S, C397Y, A576V, E591G, R620Q, T1022A) due to non-synonymous polymorphisms in the HR gene. We found that the corepressor activities of all but one of the pathogenic HR mutants were completely abolished. HR mutant E583V exhibited normal corepressor activity, suggesting that it may not be pathogenic. In co-immunoprecipitation assays, all of the pathogenic HR mutants bound VDR but exhibited reduced binding to histone deacetylase 1 (HDAC1), suggesting that the impaired corepressor activity is due in part to defective interactions with HDACs. The HR variants exhibited two classes of corepressor activity, those with normal activity (C397Y, E591G, R620Q) and those with partially reduced activity (P69S, A576V, T1022A). All of the variants interacted with VDR and HDAC1 with the exception of P69S, which was degraded. When coexpressed with VDR, all of the HR pathogenic mutants and variants increased the level of VDR protein, demonstrating that this function of HR was not impaired by these mutations. This study of HR mutations provides evidence for the molecular basis of APL.

Atrichia with papular lesions in two Pakistani consanguineous families resulting from mutations in the human hairless gene

Atrichia with papular lesions (APL) is a rare autosomal recessive form of total alopecia, characterized by hair loss soon after birth and the development of papular lesions of keratin-filled cysts over extensive areas of the body. Mutations in the hairless (hr) gene, a putative single zinc finger transcription factor, have been implicated in the pathogenesis of this disorder. In the present study, we describe two novel deletion mutations in exons 2 and 8 of the human hairless gene leading to frameshift and downstream premature termination codons in two consanguineous Pakistani families affected with atrichia.

Novel compound heterozygous nonsense mutations in the hairless gene causing atrichia with papular lesions

BACKGROUND

Atrichia with papular lesions (APL) is a rare autosomal recessive condition resulting from mutations in the hairless (HR) gene.

OBJECTIVE

In the present study, we investigated the molecular basis of APL in a non-consanguineous Korean family.

METHODS

Direct automated DNA sequencing of the HR gene and restriction digestion analysis were used to identify and confirm the mutation in our proband.

RESULTS

Sequencing of the HR gene revealed two novel nonsense mutations in exons 2 and 4 which were subsequently confirmed via enzymatic restriction. No mutations have previously been detected in this population.

CONCLUSION

The growing number of heterozygous mutations in non-consanguineous pedigrees supports the hypothesis that APL is more common than previously expected.

Interaction of hairless and thyroid hormone receptor is not involved in the pathogenesis of atrichia with papular lesions

Atrichia with papular lesions (APL) (MIM 209 500) is a rare autosomal recessive disease characterized by early onset of atrichia, followed by a papular eruption within the first years of life. Recent studies demonstrating linkage to chromosome 8p21 and further mutation detection in the hairless gene (HR) have established the molecular basis of APL. This study describes the case of a 16-year-old female with APL due to a missense mutation, D1012N, in the hr-thyroid hormone receptor interacting domain 2 (TRID2) of the HR. Using functional and biochemical analysis, it was determined that this mutation does not significantly affect hr-thyroid hormone receptor interaction. This result suggests that the TRID2 domain either is dispensable in the hr-TR interaction or is not involved in the pathogenesis of APL.

Atrichia with papular lesions resulting from a novel homozygous missense mutation in the hairless gene

Atrichia with papular lesions (APL) is a rare autosomal recessive disorder resulting in complete and irreversible hair loss shortly after birth. Affected individuals also develop papular lesions of keratin-filled follicular cysts over extensive areas of the body. Mutations in the hairless gene, a putative single zinc-finger transcription factor protein, have been implicated in the pathogenesis of APL. In this report, we describe a novel missense mutation, E583V, in the hairless gene in an Italian family affected with APL. The mutation resides between the LXXLL motif found in TRIPs (thyroid hormone receptor interacting proteins) in exon 5 and the six-cysteine zinc-finger motif in exon 6. The amino acid sequence neighbouring the LXXLL motif and zinc-finger domain is highly conserved in human, monkey, rat, and mouse hairless proteins. Our finding extends the body of evidence that supports the importance of the zinc-finger and LXXLL domains in the function of the hairless protein. Moreover, we continue to find small APL families without consanguinity from around the world.

Compound heterozygosity for mutations in the hairless gene causes atrichia with papular lesions

BACKGROUND

Congenital atrichias represent a complex and heterogeneous group of genodermatoses, which have been shown in several consanguineous families to result from homozygous mutations in the hairless gene (HR).

OBJECTIVES

To identify the molecular basis of congenital atrichia in a non-consanguineous family.

METHODS

Genetic analysis was carried out in a two-generation family with two children with congenital atrichia and one healthy child.

RESULTS

We established a diagnosis of atrichia with papular lesions based on clinical and histopathological data. We identified a heterozygous 11-bp deletion (189-199del) in the two affected children and their mother. In addition, the two affected children and their father were shown to carry a non sense mutation (Q478X), which has previously been described in a Pakistani family. Haplotype analysis revealed that mutation Q478X occurred independently in the two families.

CONCLUSIONS

We have identified the first case of compound heterozygosity for mutations in HR as well as the first instance of a recurrent mutation in this gene. These data further expand our understanding of the molecular pathomechanisms underlying congenital atrichias.

A novel missense mutation affecting the human hairless thyroid receptor interacting domain 2 causes congenital atrichia

Congenital atrichias represent a large and heterogeneous group of inherited hair disorders. In this report, we describe a patient affected with alopecia universalis congenita (MIM 203655). Sequence analysis revealed a G to A transition at cDNA position 3034 of the hairless hr gene present in a homozygous state in the patient and in a heterozygous state in the patient's mother, and absent in the patient's sister. The mutation is predicted to result in the substitution of an asparagine residue for an aspartate amino acid (D1012N) at a position previously shown in the rat to affect hairless binding to thyroid hormone receptor. This study presents the first evidence in humans for the functional importance of the hairless thyroid receptor interacting domain 2.