Two novel mutations in the MEN1 gene in subjects with multiple endocrine neoplasia-1

Multiple endocrine neoplasia type 1 (MEN1) is characterized by parathyroid, enteropancreatic endocrine and pituitary adenomas as well as germline mutation of the MEN1 gene. We describe 2 families with MEN1 with novel mutations in the MEN1 gene. One family was of Turkish origin, and the index patient had primary hyperparathyroidism (PHPT) plus a prolactinoma; three relatives had PHPT only. The index patient in the second family was a 46-yr-old woman of Chinese origin living in Taiwan. This patient presented with a complaint of epigastric pain and watery diarrhea over the past 3 months, and had undergone subtotal parathyroidectomy and enucleation of pancreatic islet cell tumor about 10 yr before. There was also a prolactinoma. Sequence analysis of the MEN1 gene from leukocyte genomic DNA revealed heterozygous mutations in both probands. The Turkish patient and her affected relatives all had a heterozygous A to G transition at codon 557 (AAG-->GAG) of exon 10 of MEN1 that results in a replacement of lysine by glutamic acid. The Chinese index patient and one of her siblings had a heterozygous mutation at codon 418 of exon 9 (GAC-->TAT) that results in a substitution of aspartic acid by tyrosine. In conclusion, we have identified 2 novel missense mutations in the MEN1 gene.

A novel mutation in the calcium-sensing receptor gene in a Chinese subject with persistent hypercalcemia and hypocalciuria

Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominant disorder characterized by high penetrance of relatively benign, lifelong persistent hypercalcemia and hypocalciuria. By contrast, neonatal severe hyperparathyroidism represents a life-threatening form of hypercalcemia that can cause the early newborn mortality if immediate intervention is not undertaken. Both disorders are due to inactivation mutation of the human calcium-sensing receptor (CaSR) gene on chromosome 3q21-24. Up to now, more than 30 mutations in the CaSR gene associated with FHH have been described. In this study, we analyzed one 79-yr-old male with hypocalciuric hypercalcemia without siblings or children to compare with an additional group of 50 normal Chinese subjects in Taiwan. DNA sequence analysis of the CaSR gene was performed. The result showed that the proband had a heterozygous nonsense mutation in exon 7 of the CaSR gene at codon 648 (CGA-->TGA/Arg-->Ter). This mutation, located in the COOH-terminal of the first intracellular loop of the CaSR, predicts a markedly truncated protein. We have identified a novel R648X mutation in the CaSR gene in one patient with FHH in Taiwan

Polyethylene glycol method is superior to ammonium sulfate and protein-A sepharose-4B method in fractionating thyroid stimulating immunoglobulin in Graves' disease

BACKGROUND

The purpose of this study is to compare the performance of three methods, i.e., ammonium sulfate, polyethylene glycol (PEG) and protein A sepharose 4B in fractionation of thyroid stimulating immunoglobulin.

METHODS

Twelve patients with Graves' disease and twelve age-, sex-matched normal controls were recruited. 0.9 ml of saturated ammonium sulfate was added slowly to 1.1 ml of sera of all subjects and was stirred until reaching 45% saturation. The precipitation was allowed to form at 4 degrees C overnight. The solution was centrifuged at 10,000 x g for 5 minutes. The precipitate was washed twice with 45% ammonium sulfate, dissolved in 0.55 ml of distilled water equal to half of the initial volume of the serum and dialyzed against 200 volumes of phosphate-buffered saline (PBS) for 48 hours. Another 0.5 ml of serum sample from the same patients was mixed with 1.5 ml of 20% polyethylene, followed by centrifugation at 2,800 g for 20 minutes. The pellet was dissolved in 0.6 ml of Hanks' medium without NaCl containing 1.5% bovine serum albumin, 20mM HEPES: 1 ml of sera was applied to 0.75 g of protein A sepharose-4B in PBS buffer and eluted with glycine, pH 2.3. By adding immunoglobulin (Ig) from the different methods to the FRTL-5 tissue culture, we determined the cAMP generation.

RESULTS

Patients with Graves' disease were found to have higher serum thyroxine and triiodothyronine concentrations (p < 0.001) and significantly higher free thyroxine concentration than normal subjects. Ig elicited stronger response in cyclic AMP generation when prepared with PEG method, as compared with the other two methods (p < 0.001). With sepharose-4B Ig preparation, 10 out 12 patients (83.33%) showed positive thyroid stimulating immunoglobulin (TSI) while with ammonium sulfate precipitation, nine out 12 patients (75%) showed positive TSI. On the other hand, all patients showed positive TSI with PEG precipitation. When the degree of thyrotoxicosis was classified in terms of thyroid hormone concentrations, there was no correlation between TSI titers and thyroid hormone concentration.

CONCLUSIONS

Polyethylene glycol is superior to both ammonium sulfate and protein A sepharose-4B in fractionating TSI in terms of sensitivity and convenience in operation.

The characterization of adenyl cyclase activity in FRTL-5 cell line

The purpose of this study is to characterize the adenyl cyclase (AC) activity in Fisher rat thyroid cell line when stimulated with several agonists, such as: forskolin, sodium fluoride, Gpp(NH)p (guanosine-5'-(beta, gamma -imino) triphosphate or thyrotropin. The following studies such as: dose-response, pH, temperature, time-response, millieu concentration, 3H-thymidine uptake, Km and Vm study were also performed. Adenyl cyclase activity was measured as adenosine 3', 5'-cyclic monophosphate generated by cell cultures in 120- minutes incubation at 37 degrees C. The basal AC activity was 15.0 +/- 7.0 (mean +/- SEM, n = 6) pmol/100,000 cells/120 minutes. Forskolin at 0.1 mM increased the AC activity to 10 folds of basal AC activity. Thyroid stimulating hormone at 1 mU/ml and 10 mU/ml increased the AC activity 2 and 15 folds, respectively. Sodium fluoride stimulation study demonstrated dual actions of fluoride on adenylate cyclase; when the cells were assayed with increasing concentration of NaF, the AC activity increased as the concentration of NaF increased from 0.01 to 1 mM, but decreased strikingly as that concentration increased from 1 mM to 100 mM. When the concentration of nonhydrolyzable guanine nucleotide analogs increased in the presence of TSH, there was first an increase in adenylate cyclase activity, followed by a decrease at higher concentration. The amount of cAMP generation was much higher (P < 0.05) in hypotonic than in isotonic millieu. When the incubation temperature raised to 56 degrees C, all the AC activity was diminished. The optimal pH for AC activity was in the range of 7.4 and 8.0.(ABSTRACT TRUNCATED AT 250 WORDS)