A novel mutation of the human luteinizing hormone receptor in 46XY and 46XX sisters.
Date
1998Author
Stavrou, Stavros S.
Zhu, Yuan Shan
Cai, LiQun
Katz, Melissa D.
Herrera, Cecilia
Defilló Ricart, Mariano
Imperato McGinley, J.
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We repor t a novel homozygous mutation of the LH receptor (LHR) gene in three siblings: two 46XY and one 46XX. The 46XY
siblings presented with female external genitalia, primary amenorrhea, and lack of breast development. Hormonal evaluation
revealed a markedly elevated LH level with a low testosterone level, which failed to increase after human CG stimulation.
Enzymatic deficiencies of testosterone biosynthesis were eliminated as possible etiologies. Histologic analysis of the inguinal
gonads in a 46XY sibling revealed no Leydig cells; Sertoli cells, spermatogonia, and primary spermatocytes were seen. The
46XX sibling had female external genitalia, normal breast development, and primary amenorrhea. Hormonal analyses showed markedly elevated LH levels and low plasma 17β-estradiol levels. Genetic analysis of the LHR revealed a homozygous
missense mutation at exon 11 of the LHR gene. Guanine was replaced by adenine (GAA→AAA), resulting in a substitution of
lysine for glutamic acid (glu) at amino acid position 354 of the receptor. This mutation is located in the extracellular domain
adjacent to the first transmembrane helix of the LHR. Glutamic acid at position 354 of the LHR has been highly conserved
throughout evolution. Functional analysis of the LHR mutation, using an in vitro mutagenesis-transfection assay, demonstrated
complete loss of function, indicated by the lack of cAMP production after human CG stimulation in transfected human embryonic
kidney 293 cells. Screening of family members demonstrated heterozygosity for the mutation, indicating autosomal recessive
inheritance. Delineation of the specific genetic defect in this family confirms recent reports that a single mutation in the LHR
gene causes male pseudohermaphroditism in 46XY subjects and primary amenorrhea in 46XX subjects. More importantly, it
also defines a new region of the LHR molecule that is critical for biologic activity.
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