Hypogonadotropic hypogonadism due to loss of function of the KiSS1-derived peptide receptor GPR54

Abstract

Hypogonadotropic hypogonadism is defined as a deficiency of the pituitary secretion of follicle-stimulating hormone and luteinizing hormone, which results in the impairment of pubertal maturation and of reproductive function. In the absence of pituitary or hypothalamic anatomical lesions and of anosmia (Kallmann syndrome), hypogonadotropic hypogonadism is referred to as isolated hypogonadotropic hypogonadism (IHH). A limited number of IHH cases are due to loss-of-function mutations of the gonadotropin-releasing hormone receptor. To identify additional gene defects leading to IHH, a large consanguineous family with five affected siblings and with a normal gonadotropin-releasing hormone receptor coding sequence was studied. Homozygosity whole-genome mapping allowed the localization of a new locus within the short arm of chromosome 19 (19p13). Sequencing of several genes localized within this region showed that all affected siblings of the family carried a homozygous deletion of 155 nucleotides in the GPR54 gene. This deletion encompassed the splicing acceptor site of intron 4-exon 5 junction and part of exon 5. The deletion was absent or present on only one allele in unaffected family members. GPR54 has been initially identified as an orphan G protein-coupled receptor with 40% homology to galanin receptors. Recently, a 54-aa peptide derived from the KiSS1 protein was identified as a ligand of GPR54. The present study shows that loss of function of GPR54 is a cause of IHH, and it identifies GPR54 and possibly KiSS1 protein-derived peptide as playing a major and previously unsuspected role in the physiology of the gonadotropic axis.

Fig. 1.

Haplotypes. The common haplotype shared by both parents is shown in gray boxes. IHH2.1, IHH2.2, and IHH2.3 are new CA repeat markers selected in the region of interest. A horizontal line shows the location of the recombination event in patient III.4.

Fig. 2.

(Upper) Localization and sequencing of the GPR54 gene. Markers used in the genotyping and the recombination point in patient III.4 are indicated. (Lower) DNA sequences from unaffected sib III.1 and affected patient III.2 are shown. The primers used for amplification of exon 5 were localized within intron 4 and in the 3′ untranslated region. The cDNA numbering was used to designate nucleotides in exon 5. In intron 4, nucleotides were numbered starting from the end of the intron. Residues of the 3′ end of intron 4 present in both individuals are underlined.

Fig. 3.

Genotyping of exon 5 in family. Exon 5 was amplified from genomic DNA. The PCR products (size in wild-type gene, 524 bp) were analyzed in 2% agarose gel.