Biomedical subjects

T Yoshimasa

Publications and source records attributed to T Yoshimasa.

At least 37 records · Page 2Linked to original sources

PubMed1996

The RET proto-oncogene in sporadic pheochromocytomas.

In order to evaluate the role of RET proto-oncogene in the development and growth of pheochromocytomas, we examined mutations in RET and expression of RET in 7 cases of sporadic pheochromocytomas. Tumors were screened for mutations in exons 10 and 11 and codon 918 which are identified in multiple endocrine neoplasia types 2A and 2B. No mutations were found in these regions in all of the sporadic pheochromocytomas examined. On the other hand, RET mRNA was detected in all pheochromocytomas and the levels of RET expression were higher in 5 of 7 pheochromocytomas than in normal adrenal medulla, indicating that RET is overexpressed in a sizable portion of sporadic pheochromocytomas. These results suggest that high levels of expression of RET may have relevance to the development or growth of sporadic pheochromocytomas.

Adrenal Gland Neoplasms↗

PubMed1996

Insulin suppresses endothelial secretion of C-type natriuretic peptide, a novel endothelium-derived relaxing peptide.

We have previously reported that C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, is produced in vascular endothelial cells (ECs) and acts as an endothelium-derived relaxing peptide. We further demonstrated the detection of the gene transcripts of CNP and atrial natriuretic peptide (ANP) B receptor, a specific receptor for CNP, in human blood vessels. We thus propose the existence of a vascular natriuretic peptide system (NPS). CNP secretion was also demonstrated to be stimulated by various growth factors and cytokines. To clarify the significance of vascular NPS in proliferative vascular complications associated with diabetes, hypertension, or atherosclerosis, in the present study we examined the effect of insulin on CNP secretion from cultured ECs. Insulin at a concentration in the physiological range (10(-10)-10(-7) mol/l) potently suppressed CNP secretion, whereas insulin at the same concentration did not suppress endothelin (ET) secretion from EC. IGF-I had no significant effect on CNP secretion. Insulin, therefore, can be a potent inhibitor of CNP secretion through the activation of insulin receptor. Since CNP has been shown to be a potent inhibitor of vascular smooth muscle cell proliferation, the present study suggests the possibility that attenuated activity of vascular NPS is associated with hyperinsulinemia, which might result in proliferative vascular lesions.

Animals↗

PubMed1996

Direct determination of plasma endothelin-I by chemiluminescence enzyme immunoassay.

A highly sensitive sandwich-type chemiluminescence enzyme immunoassay for plasma endothelin-I (ET-1), involving no extraction steps, has been developed. Two populations of polyclonal antibodies were used in the present study: One is specific to the C-terminus of the endothelin family of peptides; the other, a Fab' fragment against the N-terminal core region of ET-1, is coupled with horseradish peroxidase (HRP). Labeled HRP activity was measured by using an enhanced chemiluminescence reaction of luminol/hydrogen peroxide. The assay was sensitive enough to detect 0.5 ng/L (0.05 pg/well) of plasma ET-1 and had no significant cross-reactivities with other related peptides, including endothelin-3 and the endothelin precursor peptide, big ET-1. Reliability of the assay was confirmed by comparison with an extraction-based procedure and a commercial kit.

Adult↗

PubMed1996

C-type natriuretic peptide in chronic renal failure and its action in humans.

We have previously reported that C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, is produced in vascular endothelial cells and acts as an endothelium-derived relaxing peptide. To clarify the clinical significance of CNP in renal disorders, we examined the plasma level of CNP in patients with various cardiovascular diseases, including chronic renal failure (CRF) patients who were under hemodialysis therapy. We also investigated biological effects of intravenously-administered CNP (0.43 nmol/kg) by bolus injection from the peripheral vein in healthy volunteers and measured systemic hemodynamic variables, plasma levels of CNP, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), cGMP, aldosterone and also urine volume, urinary excretions of sodium, potassium, chloride and cGMP. The plasma CNP levels in healthy humans (N = 13) was 1.4 +/- 0.6 fmol/ml. In CRF patients, the plasma CNP significantly increased up to 3.0 +/- 1.1 fmol/ml. The administration of CNP elicited significant increase of plasma cGMP level (from 4.77 +/- 1.25 to 8.33 +/- 1.59 pmol/ml 15 min after the administration) and of urinary cGMP excretion (from 30.7 +/- 4.3 to 74.9 +/- 13.4 nmol/30 min). Intravenously-administered CNP exerted significant diuretic (% increase: +117 +/- 85.0), natriuretic, kalliuretic and chloriuretic actions with the increase of endogenous creatinine clearance. CNP also elicited significant hypotensive actions (delta BPs/delta BPd: -4.3 +/- 1.3/-4.1 +/- 1.0 mm Hg) with the concomitant increase of heart rate (+7.6 +/- 2.6 bpm). Plasma aldosterone concentration significantly decreased from 45.4 +/- 2.3 to 35.4 +/- 4.9 pg/ml 30 minutes after the administration. Taken together, these results suggest a role for CNP in human renal function.

Adult↗

PubMed1995

Rapid ventricular induction of brain natriuretic peptide gene expression in experimental acute myocardial infarction.

BACKGROUND: We have demonstrated that brain natriuretic peptide (BNP) is a cardiac hormone predominantly synthesized in and secreted from the ventricle. We have also reported that, compared with atrial natriuretic peptide (ANP), the plasma concentration of BNP is increased to a greater degree in patients with congestive heart failure and more rapidly in patients with acute myocardial infarction (AMI). METHODS AND RESULTS: To investigate ventricular gene expression of BNP in AMI, we analyzed plasma and ventricular BNP concentrations along with ventricular BNP mRNA in rats with AMI produced by coronary artery ligation. The BNP concentration in the left ventricle increased about 2-fold as early as 12 hours postinfarction and 5-fold 1 day postinfarction compared with sham-operated rats, whereas left ventricular ANP concentration remained unchanged within 1 day. The tissue concentration of BNP increased in the noninfarcted region as well as in the infarcted region. The surviving myocytes in and around the necrotic tissues in the infarcted region were intensely stained with the anti-BNP antiserum, indicating augmented production in the remaining myocytes in the infarcts. The BNP concentration in the right ventricle also increased about 10-fold 12 hours postinfarction, whereas the ANP concentration remained unchanged within 12 hours. Northern blot analysis revealed that BNP mRNA expression was augmented 3-fold in the left ventricle as early as 4 hours postinfarction. In contrast, ANP mRNA expression was unchanged. Reflecting the rapid induction of ventricular BNP production, the plasma BNP concentration rose to about 100 pg/mL 12 hours postinfarction (sham-operated rats, < 70 pg/mL). CONCLUSIONS: These results demonstrate the rapid induction of ventricular BNP gene expression in rats with AMI compared with ANP and suggest that BNP gene expression in the ventricle is regulated distinctively from ANP gene expression against acute ventricular overload. They also suggest that the BNP gene can be one of the acutely responsive cardiac genes for the ventricular overload and suggest a possible pathophysiological role of BNP distinct from ANP in AMI.

Animals↗

PubMed1995

Two vasopressin type 2 receptor gene mutations R143P and delta V278 in patients with nephrogenic diabetes insipidus impair ligand binding of the receptor.

We recently identified vasopressin type 2 receptor gene mutations in two unrelated Japanese families with X-linked nephrogenic diabetes insipidus, which were a missense mutation from Arg143 to Pro (R143P) and a single amino acid deletion of Val278 or 279 (delta V278). To investigate the mechanism by which the mutations cause arginine vasopressin (AVP) resistance in this disorder, we expressed them in mammalian cells and analyzed their functional properties. Stable expression study with Chinese hamster ovary (CHO) cells demonstrated that the R143P mutation reduced receptor binding capacity to 10% of normal. However, the R143P mutant itself had a normal affinity for AVP and stimulated adenylyl cyclase production at up to 50% of the wild-type level, suggesting that the mutant receptors could function normally despite their reduced surface expression. In contrast, the delta V278 mutation totally abolished receptor-ligand binding and subsequent adenylyl cyclase stimulation, indicating that delta V278 mutant is virtually nonfunctional receptor. Northern blotting revealed that mutant CHO cell lines produced levels of receptor mRNA similar to the wild-type cell line. Our results suggest that the two mutations impair binding activity of the receptor without affecting mRNA accumulation, thereby causing AVP resistance through a posttranscriptional mechanism.

Amino Acid Sequence↗

PubMed1995

Structural organization and chromosomal assignment of the human prostacyclin receptor gene.

Prostacyclin receptor is a member of the prostanoid receptor family in the G protein-coupled receptor superfamily with seven transmembrane domains. We report here the isolation and structural organization of the human prostacyclin receptor gene. Southern blot analysis demonstrated a single copy of the human prostacyclin receptor gene in the human genome. The human prostacyclin receptor gene spanned approximately 7.0 kb and was composed of three exons separated by two introns. The first intron occurred in the 5'-untranslated region, 13 bp upstream to the ATG start codon. The second intron was located at the end of the sixth transmembrane domain, thereby separating it from the downstream coding region and the 3'-untranslated region. By primer extension analysis, the transcription initiation sites were mapped 870-872 bp upstream to the ATG start codon. The 1.2-kb human prostacyclin receptor 5'-flanking region lacked conventional TATA and CCAAT boxes, but it contained several cis-acting regulatory elements including an inverted CCAAT box (Y box) and two copies of SP-1 binding sites. Using human-rodent somatic hybrid cell DNA, the human prostacyclin receptor gene was assigned to human chromosome 19. The present study helps establish the genetic basis for prostacyclin receptor research and provides further insight into the molecular mechanisms underlying the prostanoid receptor family.

Amino Acid Sequence↗

PubMed1995

Characterization of the 5'-flanking region and chromosomal assignment of the human brain natriuretic peptide gene.

Brain natriuretic peptide (BNP) is a cardiac hormone that occurs predominantly in the ventricle, and synthesis and secretion of BNP are greatly augmented in patients with congestive heart failure and in animal models of ventricular hypertrophy. In order to elucidate the molecular mechanisms underlying the human BNP gene expression in the heart, the human BNP gene was isolated from a size-selected genomic minilibrary. The 1.9-kb human BNP 5'-flanking region (-1813 to +110) contained an array of putative cis-acting regulatory elements. Various lengths of the cloned 5'-flanking sequences were linked upstream to the bacterial chloramphenicol acetyltransferase (CAT) gene, and their promoter activities were assayed. The 1.9-kb promoter region showed a high-level CAT activity in cultured neonatal rat ventricular cardiocytes. When the CT-rich sequences (-1288 to -1095) were deleted, the high-level activity was reduced to approximately 30%. The 399-bp BNP 5'-flanking region (-289 to +110) showed approximately 10% activity of the 1.9-kb region. Furthermore, using human-rodent somatic hybrid cell lines, the BNP gene was assigned to human chromosome 1, on which the atrial natriuretic peptide gene is localized. The present study leads to a better understanding of the molecular mechanisms for the human BNP gene expression in the heart.

Animals↗

PubMed1995

Umbilical venous guanosine 3',5'-cyclic phosphate (cGMP) concentration increases in asphyxiated newborns.

Guanosine 3',5'-cyclic phosphate (cGMP) is known to be the second messenger of natriuretic peptides and nitric oxide (NO). To investigate the involvement of natriuretic peptides in the regulation of the feto-placental circulation, specific radioimmunoassays were used to measure the concentrations of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and cGMP in the umbilical venous plasma of normal and asphyxiated newborns. The plasma concentrations of ANP, BNP and cGMP in asphyxiated newborns were 48.3 +/- 12.9 pm, 24.5 +/- 9.4 pm and 4.4 +/- 1.6 nM (mean +/- s.e.m., n = 10), respectively. These values were significantly higher than those in the normal newborns (17.4 +/- 1.9 pm, 4.7 +/- 1.0 pm, and 0.78 +/- 0.14 nM, respectively). Moreover, the expression of both ANP-A and ANP-B receptor, biologically active receptors for natriuretic peptides, was detected in term human placenta by Northern bolt analysis. The expression of natriuretic peptide receptors was further confirmed by binding assay using [125I]-labelled ANP and solubilized crude membrane preparations of placental tissue. These findings suggest that cGMP is produced in the placenta, at least partly, by the action of ANP and BNP secreted from fetal heart, in pathophysiological conditions such as fetal hypoxia.

Asphyxia Neonatorum↗

PubMed1995

Endothelin receptors in the human amnion, chorion laeve, decidua vera and placenta.

The levels of endothelin-1 (ET-1) and the characteristics of endothelin (ET) receptors were investigated in the amnion, chorion laeve, decidua vera and placenta by using a specific radioimmunoassay for ET-1 and a saturation binding assay for ET. ET receptor gene expression in these tissues was also examined by Northern blot analysis. The levels of ET-1-like immunoreactivity (ET-1-LI) in the human amnion, chorion laeve, decidua vera and placenta obtained at elective Caesarean section before labour onset at term (mean +/- s.e.m.) were 1260 +/- 380 (n = 6), 3740 +/- 980 (n = 4), 4550 +/- 780 (n = 4) and 2450 +/- 470 (n = 4) pg g-1 wet weight, respectively. The levels of ET-1-LI in the tissues obtained after spontaneous vaginal deliveries at term did not differ from these. Gel-permeation chromatography and reverse-phase high-performance liquid chromatography revealed that the ET-1-LI in these tissues was mainly composed of ET-1. Scatchard analysis of the saturation binding assay for [125I]-labelled ET-1 and [125I]-labelled ET-3 indicated that high concentrations of both ET-A and ET-B subtypes of receptor were present in membrane fractions from the chorion laeve, decidua vera and placenta. However, in membrane fractions from the amnion, no ET receptors could be detected. These results were confirmed by Northern blot analysis using human ET-A and ET-B receptor cDNA probes. Taken together, these results suggest that the amnion is not the site of action of amniotic ET, and that ET may be involved in the regulation of functions of the chorion laeve or decidua vera.

Amnion↗

PubMed1995

Altered gene expression of natriuretic peptide receptor subtypes in the kidney of stroke-prone spontaneously hypertensive rats.

1. To elucidate the physiological and pathophysiological role of the natriuretic peptide system in the progression of hypertensive renal disease, we examined the gene expression of natriuretic peptide receptor subtypes, guanylate cyclase-A (GC-A), guanylate cyclase-B (GC-B) and clearance receptor (C receptor), in the kidney of stroke-prone spontaneously hypertensive rats (SHRSP) at 8 and 20 weeks of age, and compared them with their gene expression in age-matched Wistar-Kyoto (WKY) rats. 2. Northern blot analyses revealed that messages for three natriuretic peptide receptor subtypes were expressed in the kidney, and their expressions were higher in the glomeruli than in the whole kidney in each strain. 3. In 20 week old rats with established hypertension, the glomerular concentration of GC-A mRNA was significantly higher in SHRSP than in WKY. The concentrations of GC-B and C receptor mRNA in the glomeruli tended to increase and decrease, respectively, but they were not statistically significant in SHRSP. 4. In 8 week old rats, the glomerular concentrations of GC-A, GC-B and C receptor mRNA were not significantly different between SHRSP and WKY. 5. This study demonstrates that in the progression of hypertension, the expression of GC-A, which mediates biological actions of natriuretic peptides, is enhanced in the kidney of SHRSP compared to that of WKY. Together with the augmented secretion of the ligands previously revealed, altered expression of natriuretic peptide receptor subtypes in SHRSP may have a deterrent role in the development of hypertension and its renal complications.

Animals↗

PubMed1995

Gene regulation of brain natriuretic peptide in cardiocyte hypertrophy by alpha1-adrenergic stimulation.

1. We previously demonstrated that brain natriuretic peptide (BNP) is a cardiac hormone mainly produced in the ventricle, while the major production site of atrial natriuretic peptide (ANP) is the atrium. The production and secretion of BNP and ANP in the hypertrophied ventricles were markedly augmented, serving as a compensation mechanism against ventricular overload by their natriuretic, diuretic and vasodilatory actions. 2. In the present study, we prepared an in vitro model of cardiocyte hypertrophy using cultured neonatal rat ventricular cardiocytes and alpha1-adrenergic stimulation, and examined the gene expressions of BNP and ANP during the process of cardiocyte hypertrophy. 3. The treatment of cultured ventricular cardiocytes with phenylephrine evoked cardiocyte hypertrophy around 24 h after the treatment, which was characterized by augmented expression of the myosin light chain-2 gene and increase in cell size. 4. In this model of cardiocyte hypertrophy, the steady-state level of BNP mRNA rapidly increased to the maximal level within 1 h after the treatment. In contrast, ANP mRNA began to increase at 3 h, and accumulated during the course of cardiocyte hypertrophy. The secretion of BNP from ventricular cardiocytes was also stimulated more rapidly than the ANP secretion. 5. These results indicate that the gene expression of BNP is distinctly regulated from that of ANP in cardiocyte hypertrophy, and suggest a discrete pathophysiological role of BNP as an 'emergency' cardiac hormone against ventricular overload.

Adrenergic alpha-1 Receptor Agonists↗

PubMed1995

Preparation of a monoclonal antibody against mouse brain natriuretic peptide (BNP) and tissue distribution of BNP in mice.

1. In order to explore the significance of brain natriuretic peptide (BNP), a cardiac hormone secreted from the ventricle, in mice, we prepared a monoclonal antibody against mouse BNP (mBNP) and established a specific radioimmunoassay (RIA) for mBNP. 2. A monoclonal antibody, KY-mBNP-I, was prepared by the fusion of mouse myeloma cells X63-Ag8.653 with spleen cells of the BALB/c mouse immunized with synthetic mBNP[108-121] conjugated to bovine thyroglobulin. KY-mBNP-I belonged to an IgG2a subclass and showed a high affinity for mBNP (Ka = 1.8 x 10(11) mol/L-1). 3. The RIA established that using KY-mBNP-I was highly sensitive and specific for mBNP, with an IC50 value of 3 fmol/tube and cross-reactivities of less than 0.003% with related natriuretic peptides. mBNP-like immunoreactivity (mBNP-LI) was detected in the mouse atrium (0.35 +/- 0.02 nmol/g), ventricle (20.5 +/- 0.5 pmol/g) and kidney (0.50 +/- 0.05 pmol/g), but not in other tissues including brain. 4. Gel filtration analysis revealed that the major component of tissue mBNP-LI was co-eluted with synthetic mBNP[77-121], a 45-amino acid mature peptide. 5. The monoclonal antibody and RIA for mBNP established here will provide useful tools to investigate the functional significance of BNP in mice, coupled with the genetic engineering approach.

Animals↗

PubMed1995

Augmented expression of the endothelin-A receptor gene in cultured mesangial cells from stroke-prone spontaneously hypertensive rats.

1. To elucidate the role of endothelin (ET) receptor in hypertension, we studied the expression of the ET-A receptor (ET-AR) gene and the ET-B receptor (ET-BR) gene in cultured mesangial cells isolated from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rats. 2. The mesangial cells from both SHRSP and WKY expressed ET-AR predominantly. The level of the ET-AR mRNA in mesangial cells from SHRSP was 5-fold higher than that in the cells from WKY. The ET-BR mRNA in the mesangial cells from both strains was hardly detectable by northern blot analysis. 3. These results demonstrate that the expression of the ET-AR gene was markedly augmented in mesangial cells from SHRSP.

Animals↗

PubMed1995

Endothelin-induced activation of mitogen-activated protein kinases in glomerular mesangial cells from normotensive and stroke-prone spontaneously hypertensive rats.

1. Kinase assay in myelin basic protein (MBP) containing polyacrylamide gels revealed that endothelin-1 (ET-1) and ET-3 increased MBP kinase activities in glomerular mesangial cells (MC) from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rat (SHRSP). ET-1 stimulated MBP kinase activities more potently than ET-3. 2. Immunoprecipitation with anti-41-kDa MAPK antiserum showed that the MBP kinases activated by ET-1 correspond to 43- and 41-kDa MAPK. 3. Since Phorbol 12-myristate 13-acetate, a direct activator of protein kinase C, also activated MAPK, protein kinase C was suggested to mediate ET-induced activation of MAPK. 4. These results suggest that MAPK may mediate the ET actions in glomerular mesangial cells from normotensive rats as well as spontaneously hypertensive rats. Since ET is produced by vascular endothelial cells of the kidney and glomerular mesangial cells, the ET signalling pathway may have some physiological and pathophysiological significance in vivo glomerulus.

Animals↗

PubMed1995

Gene expression of prostacyclin receptor in the hypertrophied heart of spontaneously hypertensive rats.

1. Prostacyclin elicits potent vasodilation and inhibition of platelet aggregation through binding to its membrane receptor. The impairment of prostacyclin receptor activity is implicated in various human cardiovascular diseases. We recently succeeded in molecular cloning of cDNA for the mouse, rat, and human prostacyclin receptors. 2. In the present study, we examined the mRNA expression of the prostacyclin receptor in various rat tissues, and further investigated its gene expression in the hypertrophied cardiac ventricles of stroke-prone spontaneously hypertensive rats (SHRSP). 3. In rat tissues, a single RNA band of approximately 3.7 kb was detected by northern blotting analysis using rat prostacyclin receptor cDNA as a probe. In adult Wistar rats, abundant mRNA expression was observed in the aorta, lung and spleen. Substantial amounts of transcript were expressed in the heart, pancreas, thymus and stomach. In contrast, no mRNA expression was detected in the brain. 4. We further examined the mRNA expression of the prostacyclin receptor in the ventricles of 21 week old SHRSP. The ventricles of SHRSP showed remarkable hypertrophy, compared with those of age-matched Wistar-Kyoto (WKY) rats. The expression of prostacyclin receptor mRNA in the hypertrophied ventricles of SHRSP was almost equivalent to that in the ventricles of WKY. 5. The present study revealed the gene expression of the prostacyclin receptor in various rat tissues, and further demonstrated the receptor mRNA expression in hypertensive cardiac hypertrophy. The present study will give a clue to investigate the clinical implication of prostacyclin and its receptor.

Animals↗

PubMed1995

Rapid transcriptional activation and early mRNA turnover of brain natriuretic peptide in cardiocyte hypertrophy. Evidence for brain natriuretic peptide as an "emergency" cardiac hormone against ventricular overload.

We previously demonstrated that brain natriuretic peptide (BNP) is a cardiac hormone mainly produced in the ventricle, while the major production site of atrial natriuretic peptide (ANP) is the atrium. To assess the pathophysiological role of BNP in ventricular overload, we have examined the gene expression of BNP, In comparison with that of ANP, in a model of cardiac hypertrophy using cultured neonatal rat ventricular cardiocytes. During cardiocyte hypertrophy evoked by endothelin-1, Phenylephrine, or PMA, the steady state level of BNP mRNA increased as rapidly as the "immediate-early" induction of the c-fos gene expression, and reached a maximal level within 1 h. Actinomycin D, a transcriptional inhibitor, completely diminished the response, while the translational blocked with cycloheximide did not inhibit it. In contrast, ANP mRNA began to increase 3 h after the stimulation, and accumulated during cardiocyte hypertrophy. The BNP secretion from ventricular cardiocytes was also stimulated, more rapidly than the ANP secretion. Furthermore, the turnover of BNP mRNA was significantly faster than that of ANP mRNA, being consistent with the existence of AUUUA motif in the 3'-untranslated region of BNP mRNA. These results demonstrate that the gene expression of BNP is distinctly regulated from that of ANP at transcriptional and posttranscriptional levels, and indicate that the characteristics of the BNP gene expression are suitable for its possible role as an " emergency" cardiac hormone against ventricular overload.

Animals↗

PubMed1995

Three novel mutations of thyroid hormone receptor beta gene in unrelated patients with resistance to thyroid hormone: two mutations of the same codon (H435L and H435Q) produce separate subtypes of resistance.

We report three novel mutations of the thyroid hormone receptor beta (TR beta) gene in three unrelated Japanese patients with resistance to thyroid hormone (RTH). Patients A and B exhibited generalized resistance phenotype, while patient C displayed more pituitary-selective unresponsiveness. Direct sequencing of TR beta gene exon 10 disclosed novel point mutations in all three patients. A Phe to Ile (TTC-->ATC) substitution at codon 451, a His to Leu (CAT-->CTT) substitution at codon 435, and a His to Gln (CAT-->CAA) substitution at codon 435 were identified in patients A, B, and C, respectively. Sequencing of TR beta gene exons 5-9 as well as TR alpha gene exons 4-9 failed to detect any additional mutations. All three patients were heterozygous for respective mutations. The unaffected parents of patients A and B, having normal thyroid function, possessed no mutations of TR beta gene exon 10, indicating that the F451I and H435L mutations occurred de novo. The F451I mutation is located near the most frequent mutation site in the ligand 2 subdomain. The identical codon mutations H435L and H435Q, which lie at the extreme carboxyl-terminus of the dimerization subdomain near the 9th heptad, were found in clinically different subtypes of RTH: patient B with generalized resistance and patient C with pituitary-selective resistance, respectively. The mutations broaden the growing catalogue of the TR beta gene mutations that could cause different phenotypes, despite the defects at the same codon.

Adult↗