Autosomal-dominant hypotrichosis with woolly hair: Novel gene locus on chromosome 4q35.1-q35.2
Annika E. SchlaweckRachid Tazi‐AhniniF. Buket BasmanavJaved MohungooSandra M. Pasternack-ZiachManuel MattheisenAna‐Maria OprişoreanuAytaj HumbatovaSabrina WolfAndrew G. MessengerRegina C. Betz
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Abstract:
Hypotrichosis simplex (HS) with and without woolly hair (WH) comprises a group of rare, monogenic disorders of hair loss. Patients present with a diffuse loss of scalp and/or body hair, which usually begins in early childhood and progresses into adulthood. Some of the patients also show hair that is tightly curled. Approximately 10 genes for autosomal recessive and autosomal dominant forms of HS have been identified in the last decade, among them five genes for the dominant form. We collected blood and buccal samples from 17 individuals of a large British family with HS and WH. After having sequenced all known dominant genes for HS in this family without the identification of any disease causing mutation, we performed a genome-wide scan, using the HumanLinkage-24 BeadChip, followed by a classical linkage analysis; and whole exome-sequencing (WES). Evidence for linkage was found for a region on chromosome 4q35.1-q35.2 with a maximum LOD score of 3.61. WES led to the identification of a mutation in the gene SORBS2, encoding sorbin and SH3 domain containing 2. Unfortunately, we could not find an additional mutation in any other patient/family with HS; and in cell culture, we could not observe any difference between cloned wildtype and mutant SORBS2 using western blotting and immunofluorescence analyses. Therefore, at present, SORBS2 cannot be considered a definite disease gene for this phenotype. However, the locus on chromosome 4q is a robust and novel finding for hypotrichosis with woolly hair. Further fine mapping and sequencing efforts are therefore warranted in order to confirm SORBS2 as a plausible HS disease gene.Keywords:
Hypotrichosis
Genetic linkage
Body hair
Positional cloning
Disease gene identification
Candidate gene
A syndrome of hereditary hypotrichosis with an unusual natural history and clinical features was encountered in a Caucasian family of four generations with a total of twenty-four members of whom eleven were affected. The mode of inheritance was autosomal dominant with variable penetrance. The loss of hair involved the scalp, eyebrows, eyelashes and body hair, manifesting itself in the school years and progressing to almost complete baldness. There were no associated abnormalities and no sex limitation. Clinical, genetic, biochemical, mechanical, histological and immunological aspects were studied. Essential differences between this type of hereditary hypotrichosis and others previously recorded are stressed.
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Body hair
Folliculitis
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Identification of the genes for a human disease provides significant insights into the molecular mechanism underlying the pathogenesis of the disease. A human disease gene can be identified by its chromosomal location (positional cloning). Linkage analysis is a key step in positional cloning. For monogenic disorders with a known inheritance pattern, model-based linkage analysis is effective in mapping the disease location. Therefore, model-based linkage analysis can provide a powerful tool to positional cloning of some specific molecular determinants that co-segregate with disease phenotypes in the isolated samples (e.g., large and multiplex impaired pedigrees). This chapter describes model-based human genetic linkage analysis as implemented in the LINKAGE computer package. First, we introduce the basic concepts and principles for genetic analysis of monogenic disorders. Then, we demonstrate the usages of the programs by analyzing several examples of hypothetical pedigrees with the inheritance modes of autosomal-dominant, autosomal-recessive, and genetic heterogeneity.
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Identification of the genes for a human disease provides significant insights into the molecular mechanism underlying the pathogenesis of the disease. A human disease gene can be identified by its chromosomal location (positional cloning). Linkage analysis is a key step in positional cloning. For monogenic disorders with a known inheritance pattern, model-based linkage analysis is effective in mapping the disease location. Therefore, model-based linkage analysis can provide a powerful tool to positional cloning of some specific molecular determinants that co-segregate with disease phenotypes in the isolated samples (e.g., large and multiplex impaired pedigrees). This chapter describes model-based human genetic linkage analysis as implemented in the LINKAGE computer package. First, we introduce the basic concepts and principles for genetic analysis of monogenic disorders. Then, we demonstrate the usages of the programs by analyzing several examples of hypothetical pedigrees with the inheritance modes of autosomal-dominant, autosomal-recessive, and genetic heterogeneity.
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Abstract Background Hypotrichosis with juvenile macular dystrophy (HJMD) is an autosomal recessive disorder characterized by abnormal growth of scalp hair and juvenile macular degeneration leading to blindness. We have explored the genetic basis of HJMD in a large consanguineous family with 12 affected patients, 1–76 years of age, with characteristic phenotypes. Methods We first applied genome‐wide homozygosity mapping to 10 affected individuals for linkage analysis to identify the genomic region of the defective gene. All affected individuals shared a 7.2 Mb region of homozygosity on chromosome 16q21‐22.3, which harbored 298 genes, including CDH3 , previously associated with HJMD. However, whole‐exome sequencing (WES) failed to identify the causative mutation in CDH3 . Results Further investigation revealed a missense variant in a gene closely linked to CDH3 (1.4 Mb distance: FHOD1 : c.1306A>G, p.Arg436Gly). This variant was homozygous in all affected individuals and heterozygous in 18 out of 19 obligate carriers. While this variant was found by bioinformatics predictions to be likely pathogenic, a knock‐in mouse for this variant, made by the CRISPR/Cas, showed no disease phenotype. However, using whole‐genome sequencing (WGS), we were able to identify a novel Alu recombination‐mediated deletion in CDH3 :c.del161‐811_246 + 1,044. Conclusion WGS was able to identify a deep intronic deletion mutation, not detected by WES.
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Hypotrichosis
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The patient, a woman aged 54, was born with normal hair. With age, particularly during adolescence, the hair became sparse on the scalp and formed a peculiar pattern reminiscent of androgenetic alopecia of the Ludwig type, but somewhat asymmetrical (Fig. 1). The remaining hair was rather coarse. Eyebrows and eyelashes were almost absent and the body hair was sparse. Her nails and teeth were normal and other ectodermal structures were likewise [...]
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Body hair
Hair disease
Cabello
Scarring alopecia
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We report on a female aged 13 years, whose scalp hair began to disappear at the age of 9 years, leaving only sparse wispy hairs in the parietal-occipital region. Eyelashes, eyebrows and body hair were unaffected. There were no signs of ectodermal dysplasia on the skin, nails, teeth and eyes nor other congenital abnormalities. The family pedigree showed 15 relatives similarly affected according to an autosomal dominant mode of transmission. Clinical, genetic, histological and ultrastructural aspects led to a diagnosis of hereditary hypotrichosis simplex of the scalp (Toribio-Quiñones type).
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Hair disease
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Hypotrichosis
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