Are KAL-1 Gene Mutations Found in Female Patients with Kallmann’s Syndrome or Idiopathic Hypogonadotropic Hypogonadism?

Abstract

Objective: Isolated GnRH deficiency including Kallmann’s syndrome (KS) and idiopathic hypogonadotropic hypogonadism (IHH) has been considered as a genetic defect characterized by a functional deficit in GnRH secretion. Identification of KAL-1 gene (Xp 22.3) as a neural adhesion molecule involved in the migration of GnRH-producing neurons provides a potential basis of this disease. Despite recent advances in the understanding of the pathogenesis of X-linked form of KS as the identification of KAL-1 gene, the genetic basis of the majority of cases of GnRH deficiency in females remains unclear. Although the search for mutations in KAL-1 gene have been reported in males, genomic imprinting with differential expression of parental genes and spontaneous mutations in sporadic cases may raise the possibility of female phenotype in the heterozygous state of X-linked defect. The aim of this study is to determine the frequency of de novo mutations in the KAL-1 gene in female patients with KS and IHH and to elucidate its clinical significance. Design: KAL-1 gene (Xp22.3) deletions and mutations were determined in the samples derived from 10 unrelated females with KS (n=5) or IHH (n=5). Samples from 5 unrelated healthy female volunteers were used for identification of polymorphisms. Materials and Methods: Clinical findings, radiological study and hormonal evaluation were used to define KS and IHH. All of the 10 patients had clinical hypogonadism. Five patients with KS had anosmia and 4 of whom showed hypoplasia of the olfactory bulbs and tracts in the sella MRI. Five patients with IHH underwent pituitary function test and revealed flat response to GnRH test. No one has familial history of delayed puberty or hypogonadism. Among the 14 exons of KAL-1 gene, 10 exons (exon 5–14, known locations of mutations and polymorphisms in the past studies) encoding fibronectin type III repeats were examined in this study. For detection of deletions and mutations, we used the polymerase chain reaction and subsequent single-strand conformational polymorphisms. Results: Gene deletion was not found in 10 patients with PCR amplification. In SSCP analysis of amplified fragments (fragment size of 10 exons: 147 to 302 bp), there were no SSCP variants of homozygous gene mutations (two single-stranded band which has different mobility to controls) and heterozygous sequence variations (four single-stranded bands) in the samples of 10 patients with GnRH deficiency. Conclusions: We used PCR-SSCP for screening of KAL-1 gene sequence variations in 10 unrelated female patients with KS or IHH. Considering the sensitivity of SSCP analysis the genetic defect within the coding region of the KAL-1 gene in female patients with sporadic GnRH deficiency seems to be extremely infrequent, indicating the existence of unidentified genes whose defects would result in the expression of phenotypes in females. DNA sequencing for confirmation of SSCP results is in progress.