Clinical and molecular analysis of human reproductive disorders in Brazilian patients

Cosegregation of a novel mutation in the sixth transmembrane segment of the luteinizing/choriogonadotropin hormone receptor with two Brazilian siblings with severe testotoxicosis

PURPOSE

Testotoxicosis is an autosomal dominant form of gonadotropin-independent precocious puberty caused by heterozygous constitutively activating mutations of the luteinizing hormone/choriogonadotropin receptor (LHCGR) gene. The aim of this study was to describe two Brazilian siblings with testotoxicosis, to confirm the molecular diagnosis, and to perform an in silico analysis of a novel mutation in the hot spot of the LHCGR gene.

MATERIALS AND METHODS

Molecular analysis of the mutation on the LHCGR gene was performed by direct Sanger sequencing, followed by an in silico analysis using HOPE bioinformatics tool to predict a functional defect of the mutant.

RESULTS

Both patients presented with gonadotropin-independent precocious puberty before the age of four years. Genetic analysis revealed a novel non-maternally inherited p.Asp578Val mutation of the LHCGR gene. An in silico analysis showed that the p.Asp578Val mutation disturbed amino acid physicochemical features regarding its size, charge, and hydrophobicity value.

CONCLUSIONS

Clinical and hormonal profile of the siblings here evaluated was not different while compared to those patients previously described. An in silico mutation analysis reinforced the causative role of recurrent activating mutations in the intracellular loop and transmembrane helices of the LHCGR. The segregation of this mutation with the offsprings' phenotype indicated that it is causative.

Molecular analysis of the neuropeptide Y1 receptor gene in human idiopathic gonadotropin-dependent precocious puberty and isolated hypogonadotropic hypogonadism

OBJECTIVE

To investigate the role of mutations or polymorphisms in the NPY-Y1R gene in human idiopathic central pubertal disorders.

DESIGN

Molecular studies.

SETTING

University hospital.

PATIENT(S)

Thirty-three patients with gonadotropin-dependent precocious puberty, 22 with hypogonadotropic hypogonadism, and 50 controls.

INTERVENTION(S)

Genomic DNA extraction, NPY-Y1R gene sequence analysis, cell-surface expression, and functional activity of an identified receptor variant.

MAIN OUTCOME MEASURE(S)

Results of sequencing, cell-surface receptor expression, and receptor function.

RESULT(S)

A heterozygous substitution of lysine (K) by threonine (T) at position 374 in the carboxyl terminal region of NPY-Y1R was identified in a girl with familial GDPP. Her mother, who had pubertal developmental at appropriate age, carried the same genetic variant. Introduction of the K374T variant into an expression vector containing the human NPY-Y1R complementary DNA led to a partial reduction in cell-surface expression of NPY-Y1R in transiently transfected HEK293 cells. This mutation did not lead to a significant reduction in NPY-stimulated activity of the receptor in this heterologous expression system. No other allelic variants of the NPY-Y1R gene were identified in patients or controls.

CONCLUSION(S)

We have identified an inherited heterozygous variant of the NPY-Y1R gene in a girl with precocious puberty; however, this most likely did not contribute to her phenotype. Mutations of the highly conserved NPY-Y1R gene do not appear to represent a frequent mechanism underlying human idiopathic central pubertal disorders.