title: The GnRH receptor gene is preferentially expressed in functioning gonadotroph adenomas and displays a Mae III polymorphism site.
abstract: OBJECTIVE
  Given the central role of the GnRH receptor (GnRHR) in the regulation of the gonadotrophin secretion, it might be implicated directly or indirectly in the pathogenesis of gonadotroph tumours.
  
  
  METHODS
  We determined if GnRHR mRNA was expressed in gonadotroph tumours using RT-PCR and analysed the GnRHR gene for the presence of mutations in its coding region, using direct sequencing of PCR products. Results were analysed according to the pattern of expression of alpha, beta-FSH and beta-LH subunit (SU) genes.
  
  
  METHODS
  RNA was extracted from 20 gonadotroph tumours identified by immunohistochemistry (> 10% of stained cells): 9 adenomas were functioning (high serum gonadotrophin levels), 3 were associated with high alpha-SU levels and 8 were nonfunctioning. Genomic DNA was extracted from 64 normal subjects.
  
  
  RESULTS
  We found GnRHR mRNA in 12 tumours (60%): 8/9 functioning (88%), 1/3 alpha-secreting (33%) and 3/8 nonfunctioning (37.5%) gonadotroph adenomas. There was a significant association between GnRHR expression and immunostaining for beta-FSH (P = 0.014). The nucleotide sequence of the amplified products was identical to that of human pituitary except for the presence, in 3 functioning adenomas, of a silent C to T transition at nucleotide 453 encoding for the serine residue situated in the second intracellular loop at position 151. Heterozygosity provided evidence that both alleles were transcribed in these tumours. This substitution creates a Mae III restriction site. Genomic DNA from normal subjects were then tested for the presence of this new polymorphism. The frequency of the heterozygosity (18.7%) was not significantly different from that found in gonadotroph tumours (25%) and this new Mae III polymorphism site cannot be used as a tumoural marker.
  
  
  CONCLUSIONS
  The GnRHR gene is preferentially expressed in functioning rather than in nonfunctioning gonadotroph adenomas, but no mutations altering the coding region of the gene were found to further substantiate its role in the pathogenesis of gonadotroph tumours.
authors.affiliation: Endocrinologie Cellulaire et Moléculaire de la Reproduction, URA CNRS 1449, Université P & M Curie, Paris, France. mlkottle@snv.jussieu.fr
authors.forename: M L
authors.initials: ML
authors.lastname: Kottler
authors.forename: D
authors.initials: D
authors.lastname: Seret-Bégué
authors.forename: N
authors.initials: N
authors.lastname: Lahlou
authors.forename: M
authors.initials: M
authors.lastname: Assayag
authors.forename: M C
authors.initials: MC
authors.lastname: Carré
authors.forename: J P
authors.initials: JP
authors.lastname: Lagarde
authors.forename: C
authors.initials: C
authors.lastname: Ajzenberg
authors.forename: S
authors.initials: S
authors.lastname: Christin-Maitre
authors.forename: P
authors.initials: P
authors.lastname: Bouchard
authors.forename: J
authors.initials: J
authors.lastname: Mikol
authors.forename: R
authors.initials: R
authors.lastname: Counis
authors.forename: A
authors.initials: A
authors.lastname: Warnet
mesh_terms: D000236:Adenoma / Q000235:genetics* / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001483:Base Sequence; D005260:Female; D015870:Gene Expression; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010911:Pituitary Neoplasms / Q000235:genetics* / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011966:Receptors, LHRH / Q000235:genetics*
chemical_list: D006065:Gonadotropins, Pituitary; D011966:Receptors, LHRH