Mutations in the P2RY5 gene underlie autosomal recessive hypotrichosis in 13 Pakistani families

BACKGROUND

Autosomal recessive hypotrichosis is a rare genetic irreversible hair loss characterized by sparse scalp hair, sparse to absent eyebrows and eyelashes, and sparse axillary and body hair. Affected male individuals have normal beard hair.

OBJECTIVES

To search for pathogenic mutations in the human P2RY5 gene in Pakistani families with autosomal recessive hereditary hypotrichosis.

METHODS

In the present report, 16 unrelated consanguineous Pakistani families having multiple affected individuals with autosomal recessive hypotrichosis were investigated. Linkage in these families was searched by genotyping microsatellite markers linked to autosomal recessive hypotrichosis loci LAH1, LAH2 and LAH3. Thirteen of the families showed linkage to the LAH3 locus on chromosome 13q14.11-q21.32. These families were then subjected to direct sequencing of the P2RY5 gene, which encodes a G protein-coupled receptor.

RESULTS

Sequence analysis of the P2RY5 gene revealed two novel missense mutations (c.742A>T; p.N248Y and c.830C>T; p.L277P) in three families. Five previously described mutations including three missense (c.188A>T; p.D63V, c.436G>A; p.G146R, c.562A>T; p.I188F), one insertion (c.69insCATG; p.24insHfsX52) and one complex deletion (c.172-175delAACT; 177delG; p.N58-L59delinsCfsX88) were detected in the other 10 families.

CONCLUSIONS

Mutations revealed in the present study extend the body of evidence implicating the P2RY5 gene in the pathogenesis of human hereditary hair loss.

Mutation in the HPGD gene encoding NAD+ dependent 15-hydroxyprostaglandin dehydrogenase underlies isolated congenital nail clubbing (ICNC)

BACKGROUND

Isolated congenital nail clubbing (ICNC) is a rare autosomal recessive disorder characterised by enlargement of the terminal segments of fingers and toes with thickened nails due to proliferation of the connective tissues and abnormal function of the nail matrix. In the present study, we investigated a large Pakistani family with 11 affected individuals having hereditary congenital nail clubbing as a single invariable clinical feature without any associated ectodermal, skeletal or systemic imperfection.

OBJECTIVE

To identify a gene underlying the ICNC phenotype.

METHODS

A genome wide homozygosity linkage mapping strategy was used to identify the gene causing ICNC. DNA sequencing was performed to screen 10 candidate genes located in the linkage interval.

RESULTS

We assigned the disease locus for the ICNC to a 13.25 cM region on chromosome 4q32.3-q34.1. This region corresponds to 12.27 Mbp according to the sequence based physical map (Build 36.1) and flanked by markers D4S2952 and D4S415. A maximum two point LOD score of 2.98 ( theta= 0.00) was obtained at marker D4S2368 while a maximum multipoint LOD score of 3.62 was obtained with several markers along the disease interval. Sequence analysis of the candidate genes, in the ICNC linkage interval, revealed a homozygous missense mutation (c.577T>C; p.S193P) in exon 6 of the human HPGD gene encoding NAD(+) dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH).

CONCLUSIONS

The involvement of 15-PGDH in the pathogenesis of ICNC may open up interesting perspectives into the function of this enzyme in nail morphogenesis/development.

A novel locus for ectodermal dysplasia of hairs, nails and teeth type maps to chromosome 18q22.1-22.3

Ectodermal dysplasias (EDs) are developmental disorders affecting tissues of ectodermal origin including hair, nails, teeth and sweat glands. Ectodermal dysplasia of hair, nails and teeth is a rare type of congenital disorder characterized by sparse and thin hair, dystrophic finger-and toenails and missing and abnormal teeth. In an effort to understand the molecular basis of this form of ED a family of Pakistani origin with an autosomal recessive pattern of inheritance was ascertained from a remote region in Pakistan. The clinical features of the affected individuals included thin and fine hair on the scalp, dystrophic and flat nails, absent or sparse eyebrows and eyelashes, missing and abnormal teeth, and thin body hair. A human genome scan carried out using microsatellite markers mapped the disease locus in this family to chromosome 18q22.1-18q22.3. A maximum two-point LOD score of 2.73 (theta= 0.0) was obtained at marker D18S541. Multipoint linkage analysis resulted in a maximum LOD score of 3.42 obtained with several markers, including D18S1125, ATA82B02, D18S848, D18S488, D18S1091, and D18S485, which supported the linkage. The linkage interval is flanked by markers D18S857 and D18S815, which corresponds to a region of 17.32 cM according to Rutgers combined linkage and physical map (build 36). This region covers 8.63 Mb according to the sequence-based physical map. Three candidate genes, CDH7, CDH19 and ZNF407, from the linkage interval were sequenced and found to be negative for functional sequence variants. This study is the first step towards the identification of a gene involved in hair, nails and teeth type ED.

Ectodermal dysplasia of hair and nail type: mapping of a novel locus to chromosome 17p12-q21.2

BACKGROUND

Ectodermal dysplasias (EDs) describe a large and complex group of disorders characterized by abnormal development of the skin and appendages (hair, nails, teeth and sweat glands). Of the approximately 200 different EDs, about 30 have been studied at the molecular level. In an effort to understand the molecular bases of ED of hair and nail type, we studied a Pakistani consanguineous family with multiple affected individuals.

OBJECTIVES

To localize the gene responsible for the autosomal recessive form of ED of hair and nail type.

METHODS

Genotyping of nine members of the family, including five affected and four normal individuals was performed using microsatellite markers mapping to candidate regions, harbouring genes involved in related phenotypes. Five epithelial keratin genes located in the candidate region were sequenced to identify the pathogenic mutation.

RESULTS

We mapped the disease locus to a 24.2-cM interval flanked by markers D17S839 and D17S1299 on chromosome 17p12-q21.2 (Z(max) = 4.4). DNA sequencing of five epithelial keratin candidate genes, present in the disease locus, did not reveal any pathogenic mutation in the affected individuals.

CONCLUSIONS

The gene for ED of hair and nail type has been mapped to chromosome 17p12-q21.2 in a Pakistani consanguineous family. Failure to detect mutations in epithelial keratin genes suggests that the mutation may lie either in regulatory regions of one of the epithelial keratin genes or in another unknown gene, located in the linkage interval, with a possible role in the development of ectodermal appendages.

Mapping of a gene for alopecia with mental retardation syndrome (APMR3) on chromosome 18q11.2-q12.2

Alopecia with mental retardation syndrome (APMR) is a rare autosomal recessive disorder characterized by total or partial absence of hair from the scalp and other parts of the body and associated with mental retardation. Previously, we have reported the mapping of two alopecia and mental retardation genes (APMR1 and APMR2) on human chromosome 3. In the present study, after excluding both of these loci through linkage analysis, a whole genome scan was performed by genotyping 396 polymorphic microsatellite markers located on 22 autosomes and the X and Y chromosomes. A disease locus was mapped to a 10.9 cM region, flanked by markers D18S866 and D18S811, on chromosome 18q11.2-q12.2. A maximum two-point LOD score of 3.03 at theta= 0.0 was obtained with marker D18S1102. Multipoint linkage analysis resulted in maximum LOD scores of 4.03 with several markers in the candidate region. According to the Rutgers combined linkage-physical map of the human genome (build 36) this region covers 12.17 Mb. DNA sequence analysis of nine candidate genes including DSC3, DSC1, DSG1, DSG4, DSG3, ZNF397, ZNF271, ZNF24 and ZNF396 did not reveal any sequence variants in the affected individuals of the family presented here.

A novel locus for alopecia with mental retardation syndrome (APMR2) maps to chromosome 3q26.2-q26.31

Congenital alopecia may occur either alone or in association with ectodermal and other abnormalities. On the bases of such associations, several different syndromes featuring congenital alopecia can be distinguished. Alopecia with mental retardation syndrome (APMR) is a rare autosomal recessive disorder, clinically characterized by total or partial hair loss and mental retardation. In the present study, a five-generation Pakistani family with multiple affected individuals with APMR was ascertained. Patients in this family exhibited typical features of APMR syndrome. The disease locus was mapped to chromosome 3q26.2-q26.31 by carrying out a genome scan followed by fine mapping. A maximum two-point logarithm of odds (LOD) score of 2.93 at theta=0.0 was obtained at markers D3S3053 and D3S2309. Multipoint linkage analysis resulted in a maximum LOD score of 4.57 with several markers, which supports the linkage. The disease locus was flanked by markers D3S1564 and D3S2427, which corresponds to 9.6-cM region according to the Rutgers combined linkage-physical map of the human genome (build 35) and contains 5.6 Mb. The linkage interval of the APMR locus identified here does not overlap with the one described previously; therefore, this locus has been designated as APMR2.