Clinical spectrum of MEN2A in a large family caused by the infrequent RET mutation Cys609Phe.

Mutations in RET proto-oncogene cause multiple endocrine neoplasia 2A (MEN2A). Mutations in codons 609 and 611 are not frequent. We identified two MEN2A families with the Cys609Phe RET mutation, which turned out to be the same family. This mutation has been described a couple of times with no clinical details. We have characterized the clinical phenotype of this large kindred. A 54-year-old woman, with a medullary thyroid carcinoma (MTC), and a 33-year-old woman, who was operated on for an adrenal pheochromocytoma, were the index cases. 35 relatives were studied. Sixteen turned out to be carriers and 12 of them have been operated on. This family showed eight patients with C-cell hyperplasia, six patients affected by MTC and two showing pheochromocytoma. A papillary thyroid carcinoma was also found, together with the MTC, in one of the carriers. The phenotype in this large kindred is clearly of MEN2A. In carriers presenting the Cys609Phe mutation, the timing of the presentation of the syndrome is highly unpredictable. Therefore, a strict follow up of MTC must be carried out because of risk, and pheochromocytoma should not be ignored. These results reinforce the scarce data observed on this particular mutation.

[Hirschsprung's disease and medullary carcinoma of the thyroids: two diseases in a monogenetic disorder]. / La enfermedad de Hirschsprung y el carcinoma medular de tiroides: dos enfermedades en una alteración monogénica.

INTRODUCTION: The most common gene involved in Hirschsprung's disease (HD) is protooncogene RET. More than 100 mutations of this gene have been described associated with HD. The mutations that change a cysteine with another aminoacid (mainly in exons 10 and 11) give a risk of familial medullary thyroid carcinoma (FTMC) and MEN 2A. These mutations are found in 5% of patients with HD and have an autosomal dominant inheritance. The FTMC is aggressive and the prophylactic thyroidectomy is the best treatment. We present our results in screening for RET protooncogene mutations associated with TMC in patients with HD. PATIENTS AND METHODS: We have treated 40 patients with HD in the last 15 years. We have classified the patients into two groups: A) high risk of RET protooncogene mutation associated with FTMC (family history of HD, long-segment and/or associated syndromes) and B) low risk (rectosigmoid involvement). We have identified the exons 7, 8, 9, 10, 11, 13, 14 and 15 of the RET protooncogene in 12 of 15 children from group A and 6 from 25 from group B. RESULTS: We have found the p.Cys620Ser mutation (exon 10) in a girl from group A (long-segment). In the family study, we have found the same mutation in her mother, her oncle and her cousin. CONCLUSION: The comprehensive management of children with HD requires screening for RET protooncogene mutations associated with FTMC. In the first-degree relatives of children with a mutation risk, screening is required.

Polymorphisms, haplotypes and mutations in the protamine 1 and 2 genes.

Protamines are the most abundant nuclear proteins and alterations in their expression have been described in infertile patients. Also, protamine haplo-insufficient mice have been described as infertile. Therefore, the protamine 1 and 2 genes have been considered important candidates in different mutational studies. In this article, we review all published articles related to protamine gene mutations and report new data on mutations from patients and controls drawn from the Spanish and Swedish populations. Sequencing of the protamine 1 and 2 genes in a total of 209 infertile patients and 152 fertility-proven controls from the Spanish and Swedish populations identified two novel and rare non-pathogenic missense mutations (R17C and R38M) in the protamine 1 gene and several additional polymorphisms. Furthermore, we have identified and we report for the first time five novel rare haplotypes encompassing the protamine 1 and 2 genes. A review of all available protamine gene mutational studies indicates that none of the reported missense mutations can be considered of proven pathogenicity. However, it is interesting to note that rare protamine 1 promoter variants have been reported only in infertile patients, but not in fertile control groups. Pathogenic high penetrance protamine gene missense mutations, if any, must be extremely rare. However, the detected presence of rare variants and haplotypes in infertile patients deserves further investigation.

Polymorphism of the tumor necrosis factor-alpha receptor 2 gene is associated with obesity, leptin levels, and insulin resistance in young subjects and diet-treated type 2 diabetic patients.

OBJECTIVE: Mice lacking the tumor necrosis factor-alpha receptor 2 (TNFR2) gene fed a high-fat diet gain less weight and display reduced leptin and insulin levels. In humans, plasma levels of the soluble fraction of TNFR2 (sTNFR2) circulate in proportion to the degree of insulin resistance. The purpose of this study was to evaluate a polymorphism in the 3' untranslated region of the TNFR2 gene on chromosome 1 in relation to BMI, leptin levels, and insulin resistance. RESEARCH DESIGN AND METHODS: Using single-strand conformation polymorphism, the polymorphism was analyzed in 107 nondiabetic subjects (60 women, 47 men) and in 110 consecutive patients with type 2 diabetes (79 women, 31 men). In a subset of 33 healthy subjects, insulin sensitivity (minimal model analysis) was also evaluated. RESULTS: Four alleles of the TNFR2 gene were identified (A1, A2, A3, and A4). BMI and serum leptin levels were significantly increased in young carriers of the A2 allele. Plasma sTNFR2 levels were similar among the different TNFR2 gene variants. However, in subjects who did not carry the A2 allele, in young subjects, and in women, plasma sTNFR2 levels were proportional to BMI and leptin levels. In the study sample, carriers of the A2 allele (n = 18) showed significantly increased BMI, fat mass, waist-to-hip ratio, serum total and VLDL triglyceride levels, and leptin levels and had a lower insulin sensitivity index than noncarriers of the A2 variant (n = 15). The frequency of the different alleles among diabetic subjects was similar to that in the control population. However, diet-treated diabetic subjects (n = 49) who were carriers of the A2 allele exhibited significantly higher BMI and leptin levels than diet-treated noncarriers of the A2 allele. CONCLUSIONS: The presence of the A2 allele in the TNFR2 gene may predispose subjects to obesity and higher leptin levels, which may in turn predispose them to insulin resistance or vice versa. The TNFR2 gene may be involved in weight-control mechanisms.

Renin-angiotensin system genetic polymorphisms and salt sensitivity in essential hypertension.

We evaluated the association between salt-sensitive hypertension and 3 different genetic polymorphisms of the renin-angiotensin system. Fifty patients with essential hypertension were classified as salt sensitive or salt resistant, depending on the presence or absence of a significant increase (P<0.05) in 24-hour ambulatory mean blood pressure (BP) after high salt intake. The insertion/deletion (I/D) angiotensin-converting enzyme (ACE) gene, the M235T angiotensinogen (AGT) gene, and the A1166C angiotensin II type 1 (AT1) receptor gene polymorphisms were determined with the use of standard polymerase chain reaction methods. Twenty-four (48%) patients with significantly increased (P<0.05) 24-hour mean BP with high salt intake (from 107.3+/-9.4 to 114.8+/-10.6 mm Hg) were classified as salt sensitive. In the remaining 26 patients (52%), high salt intake did not significantly modify 24-hour mean BP (from 107.6+/-10 to 107. 8+/-9 mm Hg), and they were classified as having salt-resistant hypertension. We did not find any significant association between either M235T AGT or A1166C AT1 receptor genotypes and the BP response to high salt intake. However, patients with essential hypertension homozygous for the insertion allele of the ACE gene (II) had a significantly higher BP increase with high salt intake (9. 8+/-8.1 mm Hg for systolic BP and 5.2+/-4.2 mm Hg for diastolic BP) than that observed in patients homozygous for the deletion allele (DD) (1.2+/-5.9 mm Hg for systolic BP; P=0.0118 and -0.2+/-4.2 mm Hg for diastolic BP; P=0.0274). Heterozygous patients (ID) exhibited an intermediate response. The prevalence of salt-sensitive hypertension also was significantly higher (P=0.012) in II (67%) and DI patients (62%) compared with DD hypertensives (19%). We conclude that a significant association exists between the I/D polymorphism of the ACE gene and salt-sensitive hypertension. Patients with II and DI genotypes have significantly higher prevalence of salt sensitivity than DD hypertensives.

Screening of selected genomic areas potentially involved in thyroid neoplasms.

Loss of heterozygosity (LOH) studies have been used to identify sites harbouring tumour suppressor genes (TSGs) involved in tumour initiation or progression. To further elucidate the genetic mechanisms for follicular and papillary thyroid tumours development, we studied the frequency of LOH in 36 thyroid tumours (21 follicular thyroid adenomas (FAs) and 15 papillary thyroid carcinomas (PTCs)) on 10 specific genomic areas: 3p22, 3p25, 7q21, 7q31, 10q23, 10q25-26, 11q13, 11q23, 13q13 and 17p13.3-13.2 using 20 polymorphic markers. We have selected these areas for two reasons: (a) Even though LOH in thyroid neoplasms has been described in some of these areas, results are controversial, and (b) we have also studied areas described as involved in other epithelial or endocrine tumour types, but not studied up to now in thyroid neoplasms. Two areas showed a high percentage of LOH: 7q31 and 11q23. A 62% LOH was found at 7q31 in the FAs, suggesting, as other authors have proposed, that at least one TSG must be present in the vicinity of the c-met locus. The second area in frequency was at the 11q23 locus, with a 45% LOH in the FAs. This area was studied because it has been described as being involved in the development of epithelial and endocrine cancers. This locus had not been studied before in thyroid neoplasms. This result is interesting because the LOH11CR2A gene is localised at this locus. We suggest that this gene and/or an other TSG nearby may be involved in the progression to FA. In our study, a low percentage of LOH was found in the PTC samples, indicating that TSGs present in the areas we have studied are not significantly involved in their progression. Our data also suggest that TSGs located in areas where no LOH was detected (PTEN, MEN1, Cyclin D1, BRCA2 and RFC3) are not involved or do not have an important role in tumour progression.

Novel point mutation in exon 10 of the RET proto-oncogene in a family with medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) may occur sporadically or as part of the autosomal dominant multiple endocrine neoplasia type 2 (MEN 2). Three hereditary forms of MEN 2 have been identified: MEN 2A, MEN 2B, and familial MTC (FMTC). Missense germ-line mutations in the RET proto-oncogene have been identified as cause of these endocrine diseases. Mutations are found in exons 10 and 11 in MEN 2A and FMTC families and in a small number of families in exons 13, 14, and 15. Although a strong correlation between codon mutations and phenotypes has been described, not all the expected cystein codon mutations have been found. Therefore, the more mutations are found, the better it is possible to establish phenotype-genotype correlations. We report on a novel RET mutation at codon 611 in a family with MTC without other clinical manifestations and of rather benign course.

Angiotensinogen gene M235T and T174M polymorphisms in essential hypertension: relation with target organ damage.

The molecular variants M235T and T174M of the angiotensinogen gene have been linked to essential hypertension in some populations, but there are discrepancies about this association in other studies. We studied 75 patients with essential hypertension (BP > 160/100 mm Hg) from our outpatient clinic, aged 55+/-1 years, 30 men, systolic BP 182+/-2.5, diastolic BP 109+/-1 mm Hg (mean +/- SEM), and a family history of the disease. Target organ damage was evaluated by measuring urinary albumin excretion rate, left ventricular hypertrophy, and fundoscopy. As a control group, 75 healthy subjects with BP < 130/85 mm Hg and with no family history of cardiovascular disease were selected. M235T and T174M angiotensinogen genotypes were determined by PCR and subsequent digestion of the products with SfaNI and NcoI, respectively. The frequency (q) of genotypes of the variant M235T in the patients with essential hypertension was MM 0.31, MT 0.41, and TT 0.28, not significantly different (P = .93) from that of the controls (MM 0.28, MT 0.44, and TT 0.28). For the variant T174M, the genotype frequencies in hypertensives were TT 0.83, TM 0.15, and MM 0.02, which was not significantly different (P = .89) from that of the controls (TT 0.86, TM 0.12, and MM 0.02). Similarly, there was no evidence for association between angiotensinogen genotypes and hypertension in subjects aged < or = 40 years old (n = 24) or with severe (stage III) hypertension (n = 31). Within the group of patients with essential hypertension, there were no differences in genotype distribution between patients with and without retinopathy (n = 31), left ventricular hypertrophy (n = 37), or microalbuminuria (n = 14). This study shows that M235T and T174M variants are not associated either with essential hypertension or with target organ damage in a Spanish sample.

Lack of association between ACE gene polymorphism and left ventricular hypertrophy in essential hypertension.

The possible association between the insertion/deletion (I/D) polymorphism of the angiotensin I converting enzyme (ACE) gene and left ventricular hypertrophy (LVH) was investigated in a group of essential hypertensive patients. Seventy-one essential hypertensive patients (35 men and 36 women), aged 51 +/- 1 years, were genotyped by PCR for the I/D polymorphism of the ACE gene. Cardiac morphology and function were assessed by means of M-mode echocardiography. The relative frequencies of the three genotypes, DD, DI, and II, were respectively: 24%, 55%, and 21%. Mean values of left ventricular mass index were 145, 144, and 150 g/m2 for DD, DI, and II genotypes, without significant differences among them (P = 0.82). Likewise, the prevalence of LVH (76%, 64%, and 87%) was not significantly different among the three genotypes (P = 0.23). We conclude that the ACE gene I/D polymorphism is not associated with LVH in essential hypertension. Journal of Human Hypertension (2000) 14, 47-49.

False-positive results of basal and pentagastrin-stimulated calcitonin in non-gene carriers of multiple endocrine neoplasia type 2A.

Direct DNA analysis permits accurate identification of gene carriers in kindred members with multiple endocrine neoplasia type 2A (MEN 2A). The aim of this study was to assess the specificity of basal and pentagastrin stimulated calcitonin levels in 3 family members with MEN 2A. For this purpose 53 members of 3 consecutive families with MEN 2A were evaluated in a university medical center. Serum calcitonin, basal and stimulated, was determined by a commercial RIA. RET protooncogene analysis was carried out by automatic DNA sequencing and adequate digestion of PCR amplified products for exons 10 and 11. Two distinct mutations in the RET protooncogene were identified. A T-->A transition at position 1783 (codon 618) in exon 10 was detected in one family, and a G-->A replacement at position 1832 (codon 634) in exon 11 in the others. In non-gene carriers we obtained 6.6% of false-positive results for basal calcitonin and 15.4% for the pentagastrin provocative test. We conclude that the specificity of basal and pentagastrin-stimulated calcitonin is rather limited and RET protooncogene analysis must be the first line screening procedure in order to identify gene carriers.

[Genetic study of a new family with Hippel-Lindau type IIB disease]. / Estudio genético de una nueva familia con la enfermedad de Von Hippel-Lindau tipo IIB.

BACKGROUND: Von Hippel-Lindau disease is characterized by the variable presence of cerebellar and retinal haemangioblastomas, phaeocromocytomas and hypernephromas, beginning at early stages of life. Von Hippel-Lindau gene has been located in the short arm of chromosome 3 (3p25.5) and has been involved in the regulation of DNA transcription acting as a suppressor gene. More than 500 different mutations have been described. SUBJECTS AND METHODS: We describe a new family with the type IIB Von Hippel-Lindau disease in which, apart from clinical studies, we performed a genetic screening trying to identify germinal mutations. RESULTS: So far, we have point out 6 patients with the G-->A transversion at codon 167 (R167Q). Two of them with overt clinical disease (phaeocromocytoma in case II.1 and haemangioblastoma in the II.2) at the beginning of the study and one with a non-suspected clinical presentation (phaeocromocytoma and renal carcinoma in case I.1) out of 8 family members studied in three generations. CONCLUSIONS: The genetic screening in this family permitted us to identify three subjects before their clinical onset. The absence of the mutation in two of the younger patients will simplify the clinical follow-up of this family. Genetic screening must be generalized in the follow-up of Von Hippel-Lindau disease families, because of economic advantages and clinical efficacy.

[Pheochromocytoma associated with multiple endocrine neoplasia 2A and sporadic: differential characteristics]. / Feocromocitoma asociado a neoplasia endocrina múltiple 2A y esporádico: características diferenciales.

BACKGROUND: To study distinctive clinical features of pheochromocytoma in the setting of multiple endocrine neoplasia type 2A (MEN 2A) in comparison with sporadic pheochromocytoma. PATIENTS AND METHOD: All patients diagnosed of sporadic pheochromocytoma (n = 29) and in the setting of MEN 2A (n = 16) between 1976 and 1998 in a tertiary hospital were included in the study. The following variables were compared: age at diagnosis, symptoms, presence and characteristics of hypertension, size of the tumor, localization and malignancy. The accuracy of diagnostic tests was also evaluated. RESULTS: The pheochromocytoma associated to MEN 2A had a higher prevalence in our study (35.5%) and the diagnosis was performed earlier than for sporadic pheochromocytoma (29.1 [7.8] vs. 47,5 [10. 9] years; p < 0.001). Other distinctive features in comparison with sporadic pheochromocytoma were: bilaterality (81.25 vs. 3.44%; p < 0. 001), absence of symptoms (44 vs 11%; p < 0.05) and paroxysmal hypertension. Concerning the diagnostic tests, it must be noted the low sensitivity (60%) of vanillylmandelic acid in MEN 2A. CONCLUSIONS: The pheochromocytoma in the setting of MEN 2A is diagnosed at younger age and frequently asymptomatic and bilateral. In view of the high prevalence of MEN 2A in our country, a genetic analysis should be performed in all patients with pheochromocytoma, especially when it is bilateral.

[Genetic polymorphisms of the renin-angiotensin system and essential hypertension]. / Polimorfismos genéticos del sistema renina-angiotensina e hipertensión arterial esencial.

BACKGROUND: The renin-angiotensin system (RAS) plays an important role in blood pressure (BP) regulation. A number of RAS polymorphisms have been linked to essential hypertension (EH), but there is uncertainty about this association in other studies. We examined whether the insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene, and the M235T and T174M polymorphisms of the angiotensinogen (AGT) gene are associated with EH in a Spanish sample of hypertensive patients. MATERIAL AND METHODS: We studied 75 patients with EH (BP > 160/100 mmHg), aged 55 (8.5) years, 30 males, systolic BP (SBP) 182 +/- (22.1) mmHg, diastolic BP (DBP) 109 +/- (9.9) mmHg (mean [SD]) and a strong family history of the disease. As a control group, 75 healthy subjects with no family history of cardiovascular disease were studied. The polymorphisms were determined by PCR amplification of genomic DNA, followed by enzyme digestion for the AGT gene polymorphisms. RESULTS: The genotype distribution and the frequencies of the alleles of the three RAS polymorphisms were similar in hypertensive and control subjects. In addition, we did not find any compound effect of the I/D ACE gene and M235T AGT gene polymorphisms on BP levels in hypertensive and control subjects. CONCLUSIONS: In this sample, the contribution of the ACE I/D polymorphism and the AGT M235T and T174M polymorphisms in the development of EH seems to be less important than previously estimated.

Familial isolated pituitary adenoma caused by a Aip gene mutation not described before in a family context.

The cause of familial isolated pituitary adenomas (FIPA) remains unknown in a high percentage of cases, but the AIP gene plays an important role in the etiology. The aim of the study is to describe a family with FIPA syndrome and the results of genomic studies. A 16-year-old man had a giant prolactinoma resistant tomedical treatment with delayed growth and pubertal development. His mother had been previously diagnosed with a nonfunctioning pituitary macroadenoma. Transsphenoidal endoscopic resection was performed and a genetic study revealed a heterozygous mutation in exon 6: 974G>A (p.Arg325Gln). Because the AIP gene is a tumor suppressor gene, we searched for loss of heterozygosity within the AIP gene by amplifying exon 6 from tumor tissue of the patient. In the electropherogram, only the A allele was amplified (hemizygous state), indicating loss of the normal allele. We report a Spanish family with FIPA in whom a mutation in the AIP gene previously unreported in a familiar context was identified.

Asymptomatic bilateral adrenal pheochromocytoma in a patient with a germline V804M mutation in the RET proto-oncogene.

UNLABELLED: A diagnosis of bilateral pheochromocytoma warrants exclusion of hereditary pheochromocytoma. OBJECTIVE: To describe the first case of a bilateral pheochromocytoma associated with V804M mutation in the RET proto-oncogene. PATIENTS: The index case was a 54-year-old man with bilateral adrenal masses discovered during a CT scan performed for other reasons. MEASUREMENTS: Genetic analysis included exons 8-11 and 13-17 in the RET proto-oncogene, all four exons and flanking intronic regions in the SDHD gene, all eight exons and flanking intronic regions in the SDHB, and all three exons in the VHL gene. RESULTS: Investigations revealed elevated urinary metanephrines (32.3 micromol/day), and laparoscopic bilateral adrenalectomy confirmed bilateral pheochromocytomas. A heterozygous V804M mutation in exon 14 of the RET was found in the index case and in four relatives. Total thyroidectomy, performed in four of five affected members in this kindred, disclosed a medullary thyroid carcinoma in the index case and in a 50-year-old woman, and nodular C-cell hyperplasia in the other two subjects. CONCLUSIONS: This clinical case suggests that individuals carrying the germline V804M mutation should be screened annually for the presence of pheochromocytoma.

Clinical characteristics, beta-cell function, HLA class II and mutations in MODY genes in non-paediatric subjects with Type 1 diabetes without pancreatic autoantibodies.

OBJECTIVE: To study clinical characteristics, beta-cell function, HLA typing and mutations in the hepatocyte nuclear factor (HNF)-1alpha and HNF-4alpha genes in Type 1 diabetes mellitus (T1D) patients without pancreatic autoantibodies. DESIGN AND METHODS: Twenty patients without pancreatic autoantibodies (Ab neg) and 20 with autoantibodies (Ab pos), age/gender matched, were included (age 17-34 years). Islet cell, glutamic acid decarboxylase, tyrosine phosphatase and insulin autoantibodies, basal and stimulated C-peptide were measured. HLA-DRB1-DQA1-DQB1 typing and screening for mutations in the HNF-1alpha and HNF-4alpha genes were performed. RESULTS: No differences were found in clinical presentation, metabolic control and beta-cell function in the two groups (onset or after 12 months). DRB1*0301-DQA1*0501-DQB1*0201 was the most frequent haplotype in both groups but we found a higher proportion of protective T1D haplotypes and Asp(beta57) in the Ab neg group, but in all the cases in combination with susceptible T1D haplotypes. We found two previously reported polymorphisms (HNF-1alpha, Ala98Val; HNF-4alpha, Thr130Ile) in Ab neg and a new variant (Ser165Gly) in the HNF-4alpha gene in an Ab pos subject. Conclusions In a non-paediatric population with newly diagnosed T1D, the absence of islet antibodies does not imply clinical or metabolic differences when compared with those cases with islet antibodies. Despite a similar HLA-DR/DQ typing, the presence of protective alleles and molecular properties in a higher proportion in the Ab neg group suggests that these factors could modulate the presence or absence of islet antibodies. Variants in HNF-1alpha and HNF-4alpha are unlikely to be major contributors to the pathogenesis of diabetes in antibody-negative T1D.