Mutational analysis of the luteinizing hormone receptor gene in two individuals with Leydig cell tumors

Abstract

Inactivating mutations of the luteinizing hormone receptor (LHR) gene in males induce Leydig cell agenesis or hypoplasia, while activating mutations cause testotoxicosis. Recently, it was demonstrated that a somatic heterozygous activating mutation of the LHR gene (Asp578His), limited to the tumor, was the cause of Leydig cell adenomas in three unrelated patients. We describe the molecular study of two unrelated boys with gonadotropin-independent hypersecretion of testosterone due to Leydig cell adenomas. Genomic DNA was extracted from the tumor, the adjacent normal testis tissue, and blood leukocytes. Both individuals exhibited an heterozygous missense mutation, limited only to the tumor, consisting of a guanine (G) to cytosine (C) substitution at codon 578 (GAT to CAT), turning aspartic acid into histidine. The presence of the same mutation in different ethnic groups demonstrates the existence of a mutational hot spot in the LHR gene. Indeed, this mutation occurs at the conserved aspartic acid residue at amino acid 578, where a substitution by glycine is the most common mutation observed in testotoxicosis and where a substitution by tyrosine has been linked to a more severe clinical phenotype where diffuse Leydig cell hyperplasia is found. Our results confirm the fact that somatic activating mutations of gonadotropin receptors are involved in gonadal tumorigenesis.

Gonadal defects and hormonal alterations in transgenic mice expressing a single chain human chorionic gonadotropin–lutropin receptor complex

“…The relative increases in basal cAMP produced by most activating mutations found in FMPP patients (Shenker 2002) are smaller than those resulting from YHR, which has basal cAMP production approximately 25-fold higher than the wild-type receptor (Wu et al 1996). Naturally occurring mutations in LHR that result in higher levels of constitutive activation have only been found in sporadic cases of precocious puberty (Laue et al 1995, Muller et al 1998 and in Leydig cell adenomas (Liu et al 1999, Canto et al 2001, with no reports to date in females. Also, many of these activated LHRs can still respond to the high doses of LH required for ovulation (Themmen & Huhtaniemi 2000).…”

“…LHR with this mutation is constitutively active in cell culture in a ligand-independent manner, resulting in elevated levels of cAMP and inositol phosphate (Liu et al 1999, Angelova et al 2002. This mutation has also been identified as a somatic mutation in boys that have testosterone-secreting Leydig cell adenomas and consequently also present with precocious puberty (Liu et al 1999, Canto et al 2001. Therefore, the two receptors provide complementary systems of receptor activation, YHR being ligand mediated and D556H LHR being ligand independent.…”

Constitutively active luteinizing hormone receptors: Consequences of in vivo expression

“…2, A and B). It was surprising that Leydig cell adenomas were not observed in these testes as all known cases of humans with the analogous D578H mutation exhibit adenomas (Liu et al, 1999;Canto et al, 2001;RichterUnruh et al, 2002). Recent studies indicate that in hCG overexpressing mice, Leydig cell adenomas only occur in prepubertal mice and are restricted to fetal Leydig cells (Ahtiainen et al, 2005).…”

“…Females with the activating mutations do not have an apparent phenotype. A particularly potent activating somatic mutation (D578H) has been identified in boys with testicular adenomas wherein the mutation is limited to the adenoma and not the surrounding normal tissue (Liu et al, 1999;Canto et al, 2001;Richter-Unruh et al, 2002).…”

Leydig-Cell Tumour in Children: Variable Clinical Presentation, Diagnostic Features, Follow-Up and Genetic Analysis of Four Cases

“…The majority of these mutations lie within transmembrane domain 6 and third intracellular loop encoded by exon 11 of LHR gene and result in continuous signal transduction and subsequent testosterone production by the Leydig-cells [4,5,6,7,8]. Further, activating mutations of the stimulatory and inhibitory G protein (gsp and gip2) have also been associated with testicular stromal Leydig-cell tumours [9].…”