Angiotensin converting enzyme gene polymorphism in Turkish asthmatic patients.

Asthma is a chronic inflammatory disease of the airways. Several candidate genes have been identified with a potential role in the pathogenesis of asthma, including the angiotensin converting enzyme (ACE) gene. We aimed to investigate the frequency of an ACE gene polymorphism in Turkish asthmatic patients and to determine its impact on clinical parameters and disease severity. Ninety-seven asthmatic patients (M/F 25/72, mean age 39 +/- 13 years) and 96 healthy subjects (M/F 26/70, mean age 38 +/- 12 years) were included. At baseline, all participants completed a questionnaire on demographics, symptoms, triggering factors, severity of asthma, and the presence of atopism. Blood samples were obtained from all patients and genomic DNA was isolated. The frequency of the ACE genotypes (I = insertion and D = deletion) among asthmatics and controls were compared: asthmatics showed a 40.2% prevalence of the DD genotype (n = 39), ID was 45.4% (n = 44), and II was 14.4% (n = 14.4). In the control subjects, the frequency of DD was 18.8% (n = 18), ID was 50% (n = 48) and II was 31.3% (n = 30). The DD ACE genotype was significantly more frequent in asthmatics compared with controls (p < 0.001). Asthmatics with the ID ACE genotype showed a higher frequency of drug allergies, although this was not statistically significant (p = 0.08). Asthmatics with the DD genotype appeared to have a higher incidence of asthmatic episode exacerbations due to viral infections, but again this was not statistically significant (p = 0.08). Patients with mild or moderate-severe asthma had similar frequencies of these mutations. We found a higher frequency of the ACE DD gene mutation in Turkish asthmatic patients compared with non-asthmatics, suggesting that this ACE gene polymorphism may be a risk factor for asthma but does not increase the severity of the disease.

Two novel mutations in the sixth transmembrane segment of the thyrotropin receptor gene causing hyperfunctioning thyroid nodules.

Autonomously functioning thyroid nodules (AFTNs) can present as hyperfunctioning adenomas or toxic multinodular goiters. In the last decade, a large number of activating mutations have been identified in the thyrotropin receptor (TSHR) gene in autonomously functioning thyroid nodules. Most have been situated close to, or within the sixth transmembrane segment and third intracellular loop of the TSHR where the receptor interacts with the Gs protein. In this study we describe two novel mutations in the sixth transmembrane segment of the TSHR causing hyperfunctioning thyroid nodules. Genomic DNAs were isolated from four hyperfunctioning thyroid nodules, normal tissues and peripheral leukocytes of two patients with toxic multinodular goiter. After amplifying the related regions, TSHR and G(s)alpha genes were analyzed by single-strand conformation polymorphism (SSCP) analysis. The precise localization of the mutations was identified by automatic DNA sequence analysis. Functional studies were done by site-directed mutagenesis and transfection of a mutant construct into COS-7 cells. We identified two novel TSHR mutations in two hyperfunctioning thyroid nodules: Phe631Val in the first patient and Iso630Met in the second patient. Both mutant receptors display an increase in constitutive stimulation of basal cyclic adenosine monophosphate (cAMP) levels compared to the wild-type receptor. This confirms that these mutant receptors cause hyperfunctioning thyroid nodules.

Does a Leu 512 Arg thyrotropin receptor mutation cause an autonomously functioning papillary carcinoma?

In the last decade, studies were first done to determine the frequency of Gsalpha and later thyrotropin receptor (TSHR) mutations in benign autonomously functioning thyroid nodules (AFTN). Different frequencies ranging from 0% to 38% for GSp mutations and from 20% to 86% for TSHR mutations were found. There were only some limited case reports related to TSHR genetic alterations in malignant AFTN. Their role in autonomously functioning thyroid carcinomas is not well established. We present a patient who had thyroidectomy for toxic multinodular goiter and a papillary carcinoma was demonstrated histopathologically. Genomic DNA was isolated from two solid areas in the hot nodule and peripheral leukocytes of the patient. After amplifying the related regions, TSHR and GSalpha genes were analyzed by single-strand conformation polymorphism (SSCP) analysis. The precise localization of the mutations was identified by automatic DNA sequence analysis. An activating mutation of the TSHR gene (Leu 512 Arg) was found in the autonomously functioning papillary carcinoma. It is believed that this mutation causes constitutive activation of the cyclic adenosine monophosphate (cAMP) signal transduction pathway and thereby causes thyrotoxicosis and a hot thyroid nodule in an autonomously functioning papillary carcinoma.

A case of McCune-Albright syndrome associated with Gs alpha mutation in the bone tissue.

The syndrome of McCune-Albright syndrome (MAS) is clasically defined as a triad presentation with the findings of polyostotic fibrous dysplasia, café-au-lait spots, and sexual precocity. However, not all patients present with complete symptoms. A 52-year-old man was diagnosed as having a variant of McCune-Albright syndrome with the following findings: polyostotic fibrous dysplasia, acromegaly due to pituitary tumor and subclinical hyperthyroidism due to toxic multinodular goiter. Sexual precocity and café-au-lait spots were not noted. Acromegaly was confirmed by laboratory examination (IGF-1, glucose suppression test and TRH stimulation test). Long acting somatostatin analogue was used as treatment. Although the pituitary tumor could not be removed due to technical problems, mass lesions on the cranium were removed subtotally. Histopathological evaluation demonstrated that the lesion complied with fibrous dysplasia. Genomic DNAs were isolated from the craniofacial bones and peripheral leucocytes of the patient. After amplifying the related regions, Gs alpha (Gs alpha) gene was analysed by automatic DNA sequence analysis. An activating mutation of the Gs alpha gene (Arg 201 Cys) was found in the genomic DNA isolated from the bone tissue of the patient, but not in the genomic DNA isolated from the blood. We described a case of MAS associated with Gs alpha mutation in the bone tissue, presenting with polyostotic fibrous dysplasia, subclinical hyperthyroidism and acromegaly.

Mutations in the thyrotropin receptor signal transduction pathway in the hyperfunctioning thyroid nodules from multinodular goiters: a study in the Turkish population.

Many studies have been carried out to determine G(s) alpha and TSHR mutations in autonomously functioning thyroid nodules. Variable prevalences for somatic constitutively activating TSHR mutations in hot nodules have been reported. Moreover, the increased prevalence of toxic multinodular goiters in iodine-deficient regions is well known. In Turkey, a country with high incidence rates of goiter due to iodine deficiency, the frequency of mutations in the thyrotropin receptor signal transduction pathway has not been evaluated up to now. In the present study, a part of the genes of the TSHR, G(s)alpha and the catalytic subunit of the PKA were checked for activating mutations. Thirty-five patients who underwent thyroidectomy for multinodular goiters were examined. Genomic DNAs were extracted from 58 hyperactive nodular specimens and surrounding normal thyroid tissues. Mutation screening was done by single-strand conformational polymorphism (SSCP) analysis. In those cases where a mutation was detected, the localization of the mutation was determined by automatic DNA sequencing. No G(s)alpha or PKA mutations were detected, whereas ten mutations (17%) were identified in the TSHR gene. All mutations were somatic and heterozygotic. In conclusion, the frequency of mutations in the cAMP signal transduction pathway was found to be lower than expected in the Turkish population most likely because of the use of SSCP as a screening method and sequencing only a part of TSHR exon 10.