Investigation of the male pattern baldness major genetic susceptibility loci AR/EDA2R and 20p11 in female pattern hair loss

BACKGROUND

The aetiology of female pattern hair loss (FPHL) is largely unknown. However, it is hypothesized that FPHL and male pattern baldness (AGA) share common susceptibility alleles. The two major susceptibility loci for AGA are the androgen receptor (AR)/ectodysplasin A2 receptor (EDA2R) locus on the X-chromosome, and a locus on chromosome 20p11, for which no candidate gene has yet been identified.

OBJECTIVES

To examine the role of the AR/EDA2R and 20p11 loci in the development of FPHL using 145 U.K. and 85 German patients with FPHL, 179 U.K. supercontrols and 150 German blood donors.

METHODS

Patients and controls were genotyped for 25 single nucleotide polymorphisms (SNPs) at the AR/EDA2R locus and five SNPs at the 20p11 locus.

RESULTS

Analysis of the AR/EDA2R locus revealed no significant association in the German sample. However, a nominally significant association for a single SNP (rs1397631) was found in the U.K. sample. Subgroup analysis of the U.K. patients revealed significant association for seven markers in patients with an early onset (P = 0·047 after adjustment for the testing of multiple SNPs by Monte Carlo simulation). No significant association was obtained for the five 20p11 variants, either in the overall samples or in the analysis of subgroups.

CONCLUSIONS

The observed association suggests that the AR/EDA2R locus confers susceptibility to early-onset FHPL. Our results do not implicate the 20p11 locus in the aetiology of FPHL.

Susceptibility variants on chromosome 7p21.1 suggest HDAC9 as a new candidate gene for male-pattern baldness

BACKGROUND

Male-pattern baldness (androgenetic alopecia, AGA) is the most common form of hair loss among humans. Research has shown that it is caused by genetic factors. Numerous studies have unequivocally identified two major genetic risk loci for AGA: the X-chromosomal AR/EDA2R locus, and the PAX1/FOXA2 locus on chromosome 20.

OBJECTIVES

To identify further candidate genes for AGA, and thus gain further insights into this phenotype.

METHODS

A German sample of 581 severely affected cases and 617 controls was used to perform a genome-wide association study. The identified associated locus was further analysed by fine-mapping, and then independently replicated in an Australian sample. Expression and pathway analyses were performed to characterize the susceptibility gene identified.

RESULTS

The most significant association signal was obtained for rs756853 (P = 1·64 × 10(-7) ), which is located intronically in the histone deacetylase 9 (HDAC9) gene. Fine-mapping and a family-based analysis revealed that rs756853 and the 6-kb distal rs2249817 were the most highly associated single nucleotide polymorphisms. The association finding was replicated in an independent Australian sample, when the analysis was restricted to severely affected cases and unaffected controls (P = 0·026). Analysis of rs2249817 in a combined sample of severely affected German and Australian cases and unaffected controls revealed a strong association signal (P = 9·09 × 10(-8) ). Tissue expression studies demonstrated HDAC9 expression in various tissues, including tissues of relevance to AGA. No strong genotypic effects were observed in genotype-specific expression or splice studies. Pathway analyses supported the hypothesis that HDAC9 plays a functional role in AGA via interaction with the AR gene.

CONCLUSIONS

The present study suggests that HDAC9 is the third AGA susceptibility gene.

Systematic investigation of genetic variability in 111 human genes-implications for studying variable drug response

In order to identify single-nucleotide polymorphisms (SNPs) and analyze their characteristics in a set of 111 genes, we resequenced exons and flanking regions in an average of 170 chromosomes from individuals of European origin. Genetic variability was decreased in noncoding regions highly conserved between human and rodents, indicating functional relevance of these regions. Furthermore, diversity of coding nonsynonymous SNPs was found lower in regions encoding a known protein sequence motif. SNPs predicted to be of functional significance were more common amongst rare variants. Despite the significant recent growth of SNP numbers in public SNP databases, only a small fraction of these rare variants is represented. This may be relevant in the investigation of the genetic causes of severe side effects, for which rare variants are plausible candidates. Estimation of htSNPs reduces the genotyping effort required in capturing common haplotypes, for certain genes, however, this accounts for only a small fraction of haplotype diversity.

Variation in evoked potential measures over the menstrual cycle: a pilot study

The P3 component of a visual event related potential (ERP) was studied for five consecutive weeks in six women with normal menstrual cycles. Serum concentrations of luteinizing hormone (LH), estradiol (E2) and progesterone were studied during the same period. Increases in P3 amplitude, although nonsignificant, were noted in the week preceding onset of menses. No significant changes in reaction times to target/nontarget stimuli were noted over the same time period.