Wu-Xiang Liao

A new molecular variant of luteinizing hormone associated with female infertility

OBJECTIVE To investigate whether the newly described G1502 to A1502 mutation in exon 3 of the LH beta-subunit gene, causing the amino acid substitution of Ser102 for Gly102, is related to female infertility. DESIGN Screening of fertile and infertile women for the G1502 to A1502 mutation in the LH beta-subunit gene. SETTING Clinics and laboratories of the National University Hospital obstetrics and gynecology department, Singapore. PATIENT(S) Two hundred twelve healthy fertile women; 40 infertile women with menstrual disorders, polycystic ovary syndrome, and endometriosis; and 12 women with idiopathic infertility. INTERVENTION(S) Exon 3 of the LH beta-subunit gene was analyzed using polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), and PCR-mediated direct DNA sequencing. MAIN OUTCOME MEASURE(S) The PCR products of patients were analyzed by RFLP, and the results were compared with those of fertile controls. DNA sequencing radiographs were compared between two mutation-bearing patients and four controls. RESULT(S) The mutation was identified in only two infertile women with endometriosis; other women studied were found to be negative for this mutation. CONCLUSION(S) The missense mutation in the LH beta-subunit gene may be implicated in female infertility, possibly endometriosis-associated infertility in some women.

Mitochondrial gene mutations in gestational diabetes mellitus

Mitochondrial DNA mutations have been implicated in many diseases including diabetes mellitus. Although gestational diabetes mellitus (GDM) has been suggested to have genetic determinant and to be etiologically indistinct with non-insulin-dependent diabetes mellitus (NIDDM), its association with mitochondrial gene mutations is still unknown. In this study, 137 patients with GDM and 292 non-diabetic pregnant controls were examined for mitochondrial DNA mutations from the nucleotide 3130-4260 encompassing tRNA-Leu gene and adjacent NADH dehydrogenase 1 gene by polymerase chain reaction, single-stranded conformation polymorphism, restriction fragment length polymorphism and DNA sequencing. One heteroplasmic mutation at the position of 3398 (T-C), which changed a highly conserved methionine to threonine in NADH dehydrogenase subunit 1, was identified in 2.9% GDM patients but not in the controls, indicating its association with GDM (P = 0.01). Two novel mutations, a heteroplasmic C3254A and a homoplasmic A3399T, were also found in GDM subjects, the functional meaning of which merits further investigation. G3316A and T3394C mutations implicated in NIDDM, were seen at higher frequencies in patients with GDM than the controls. Our results suggest that mitochondrial DNA mutations may contribute to the development of GDM in some patients.

Association of molecular variants of luteinizing hormone with menstrual disorders

Luteinizing hormone (LH) promotes ovulation and luteinization of the ovarian follicle, and stimulates steroidogenesis in the ovaries. It is known to be present in different molecular forms, and secretion of abnormal LH has been implicated in menstrual disorders and infertility. The purpose of this study was to determine any association of two recently described LH variants with menstrual disorders in Singapore Chinese women. One of these variants had Trp8 to Arg8 and Ile15 to Thr15 replacements in the LH β‐subunit, while the second variant possessed Ser102 substitution for Gly102.

Identification of seven novel mutations in LH beta-subunit gene by SSCP.

Seven new point mutations have been identified from LH β-subunit gene by PCR-mediated SSCP, and sequencing. One mutation was found changing amino acid from Gln102 to Ser102. The remaining six mutations, which did not change the codings, were in complete linkage disequilibrium. SSCP can be used in the diagnosis of LH-related disorders.

Association of AccI polymorphism in the follicle-stimulating hormone β gene with polycystic ovary syndrome ☆

OBJECTIVE To search for FSH beta-subunit gene mutations in patients with polycystic ovary syndrome (PCOS) and determine the association between the mutations and the syndrome. DESIGN Clinical and molecular studies. SETTING Clinics and laboratories of the National University Hospital Obstetrics and Gynecology Department in Singapore. PATIENT(S) One hundred thirty-five patients with PCOS and 105 normal control subjects. INTERVENTION(S) Exons two and three were screened for mutations by single-stranded conformational polymorphism and DNA sequencing. MAIN OUTCOME MEASURE(S) Polymerase chain reaction followed by restriction enzyme analysis. RESULT(S) No missense mutation was found in the functional units of the FSHbeta gene in patients with PCOS, but a thymine-cytosine substitution in exon 3 (codon 76, TAT to TAC) was identified. The nucleotide change led to creation of an AccI digestion site. The distribution pattern of AccI polymorphism in the patients was significantly different from that in the control group, and the occurrence of homozygous carriers was significantly higher in patients (12.6%) than in the control group (3.8%). The frequency of polymorphism and prevalence of homozygosity were significantly higher in patients with PCOS with obesity (0.50% and 31.0%, respectively) than in those with menstrual disorders only (0.366% and 8.5%, respectively), which correlated with significantly higher androgen levels in the obese patients. CONCLUSION(S) The AccI polymorphism in FSHbeta gene may be associated with PCOS in some women, especially those with obesity.

Molecular Variants of Luteinizing Hormone in Three Populations of Southeast Asia

Three populations of Southeast Asia comprising 191 Chinese, 121 Malays and 150 Indians, were studied with respect to two recently described mutant luteinizing hormone (LH) variants using molecular techniques. One of these variants had Trp8 to Arg8 and Ile15 to Thr15 replacements in exon 2 of the LH β-subunit, while the other variant possessed Ser102 substitution for Gly102 in exon 3. The exon 2 mutants were in complete linkage disequilibrium. The exon 2 variant had an allele frequency of 0.045 in Chinese, 0.062 in Malays and 0.030 in Indians. The allele frequency of the exon 3 variant was 0.018 in Chinese and null in Malays and Indians. The two LH variants may be markers of interest in studies of disturbed pituitary-gonadal function, menstrual disorders and female infertility.

Functional characterization of a natural variant of luteinizing hormone

Abstract. Luteinizing hormone (LH) plays an important role in the gametogenesis in both sexes by promoting the production of sex steroid hormones in the testes and ovaries. We previously described a genetic variant (V) of LH resulted from a mutation (G1502A) in the LH β-subunit gene, causing the glycine102serine change in the protein hormone. This variant was subsequently found to be associated with both male and female infertility. In this study, we determined the functional aspect of this LH variant in vitro. Site-directed mutagenesis was employed to construct the V-LH β-subunit gene. Bioactivities of V-LH expressed in Chinese hamster ovary (CHO) cells cotransfected with the V-β-subunit and native α-subunit genes were compared to those of wild-type (WT) LH. The amino acid replacement did not result in the change of efficacy of α- and β-subunit dimerization of the hormone. However, V-LH had significantly lower receptor-binding activity (P<0.001) and lower biopotency for progesterone production (P<0.001) than WT-LH at the higher concentrations of LH. Considering the latter and its known association with both male and female infertility, it is suggested that the V-LH may be a contributing factor to the pathogenesis of infertility in the carriers of this variant.

New AccI Polymorphism in the Follicle-Stimulating Hormone Beta-Subunit Gene andIts Prevalence in Three Southeast AsianPopulations

A thymine-cytosine substitution was identified in exon 3 (codon 76, TAT to TAC) of the human follicle-stimulating hormone (FSH) β-subunit gene. The nucleotide change led to creation of an AccI digestion site. The frequencies of the A allele (with AccI site) in Chinese (n = 201), Malays (n = 168) and Indians (n = 132) were 0.358, 0.333 and 0.402, respectively. The new FSH β-subunit marker may be useful in gene tracking and association studies.

A new silent C to T polymorphism in the exon 3 of the oxytocin receptor gene

Description of polymorphism: The coding region in exon 3 of the OTR gene (Inoue et al. 1994) was analyzed using PCR-mediated SSCP and direct sequencing. The PCR product was 389 bp in length (contains 50 bp of intron 3). SSCP showed a polymorphism, while sequencing using AmpliCycle Sequencing Kit (Perkin Elmer, Norwalk, CT) revealed a nucleotide variant at position 690 that converted the codon -AAC(asparagine) at amino acid position. 230 to -AAT(asparagine). This substitution created an ApoZ restriction site (RAA TTY), which cut the PCR product into fragments of 106 bp and 283 bp (Fig. I).