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At least 559 records · Page 31Linked to original sources
PubMed2001

Comprehensive analysis of SMAD4 mutations and protein expression in juvenile polyposis: evidence for a distinct genetic pathway and polyp morphology in SMAD4 mutation carriers.

Juvenile polyposis syndrome (JPS; OMIM 174900) is a rare disorder which is characterized by the presence of hamartomatous polyps throughout the gastrointestinal tract and an increased risk of gastrointestinal malignancy. Mutations of the SMAD4 gene on chromosome 18q21.1 have been shown to cause a subset of JPS cases, with estimates ranging from 20% to >50%. Characterization of the genes that cause the remainder of JPS cases relies on the certainty that SMAD4 is not the causative gene. We have undertaken a comprehensive analysis of germline SMAD4 mutations in a cohort of JPS patients to define the spectrum of mutations that cause JPS. We have analyzed a series of polyps from these patients for SMAD4 protein expression. We have also performed a blinded assessment of polyp material to look for morphological differences between polyps from patients with and without a germline SMAD4 mutation. The results indicate that almost all germline SMAD4 mutations are readily detectable by screening genomic DNA using polymerase chain reaction-based methods; SMAD4 can be excluded as the causative gene in the majority of our JPS cohort. Loss of SMAD4 expression occurs in most polyps from SMAD4 mutation carriers, even those with missense germline mutations. SMAD4 loss in polyps is, however, not a feature of cases that are not caused by SMAD4 mutations, indicating that these polyps develop along a SMAD4-independent pathway. The morphology of polyps from SMAD4 mutation carriers is subtly different from other JPS polyps, notably including a more prominent epithelial component in the former.

Amino Acid Sequence↗
PubMed1999

The Big Blue(R) transgenic mouse mutation detection assay: the mutation pattern of sectored mutant plaques.

There are mutational artifacts in the Big Blue(R) assay and it is important to characterize the source and nature of these mutations. Differences were reported in the mutation patterns of a small sample of 23 sectored and 91 circular mutant plaques derived from skin using the Big Blue(R) transgenic mouse mutation detection system [G. R. Stuart, N.J. Gorelick, J.L. Andrews, J.G. de Boer, B.W. Glickman, The genetic analysis of lacI mutations in sectored plaques from Big Blue transgenic mice, Environ. Mol. Mutagen 28 (1996) 385-392.]. We have extended these observations by analyzing 46 sectored and 224 circular mutant plaques derived from seven tissues. The frequency of sectored mutant plaques is estimated to be 16% with no significant variation with tissue type. However, the patterns of mutation for sectored mutants and mouse-derived mutations differed significantly (p=0.04). Base substitutions in sectored mutant plaques do not show the asymmetries found in circular mutants consistent with integration of a GC rich transgene into the AT rich mammalian genome. Sectored mutants have mutation patterns consistent with a mixture of mouse, in vitro and Escherichia coli-derived mutations. Data on the relative frequencies of different mutant plaque morphologies suggests that overlapped plaques are substantially contaminated by sectored plaques at recommended plating densities.

Animals↗
PubMed2001

High prevalence of the H1069Q mutation in East German patients with Wilson disease: rapid detection of mutations by limited sequencing and phenotype-genotype analysis.

BACKGROUND/AIMS: Wilson disease is caused by a large number of different mutations in the ATP7B gene. Wilson disease patients from a homogeneous ethnical background (Saxonia) were studied for distribution and phenotypes of ATP7B mutations. METHODS: Eighty-two patients were analyzed. The H1069Q mutation was assayed by a polymerase chain reaction-based restriction fragment length polymorphism test. Exons 8 and 15 were sequenced in all, and the entire gene in 30, non-H1069Q-homozygotes. RESULTS: Four novel and 12 known mutations were found. Thirty-two (39%) Wilson disease patients were homozygous and 39 (48%) heterozygous for the H1069Q mutation (allele frequency 63%). Together with sequence analysis of exons 8 and 15 mutations in both alleles were identified in 65% of patients. Only one patient had both mutations at other locations. In H1069Q homozygotes symptoms started later (21.3+/-7.2 years) than in H1069Q compound heterozygotes (14.6+/-5.8, P<0.001) or H1069Q negatives (10+/-4.4, P<0.001), and they had more frequently neurologic symptoms (93 vs. 47%, P<0.001) and Kayser-Fleischer rings (82 vs. 51%, P<0.001). Mutation status did not correlate with liver biopsy findings, serum ceruloplasmin levels or (64)Cu-assay results. CONCLUSIONS: In spite of many known ATP7B mutations, only few occur in this homogeneous population. Limited genetic testing is useful to confirm Wilson disease in this population.

Adenosine Triphosphatases↗
PubMed2000

Absence of somatic RET gene mutation in sporadic parathyroid tumors and hyperplasia secondary to uremia, and absence of somatic Men1 gene mutation in MEN2A-associated hyperplasia.

Germline mutations of the MEN1 gene are found in more than 85% of multiple endocrine neoplasia type 1 (MEN 1) patients, and germline mutations of the RET gene are found in more than 95% of multiple endocrine neoplasia type 2 (MEN2) patients. Parathyroid hyperplasia is seen in more than 90% of MEN 1 and about 15% of MEN2A patients. To date, somatic MEN1 mutations are reported in about 20% of sporadic parathyroid tumors. To elucidate the genetic basis of parathyroid tumor development, we examined somatic RET gene mutations in sporadic parathyroid tumors and hyperplasia secondary to uremia, and somatic MEN1 gene mutations in parathyroid hyperplasia from MEN2A patients. A total of 145 parathyroid tumors comprising 129 sporadic parathyroid tumors, 14 hyperplastic lesions secondary to uremia, and two hyperplastic lesions from MEN2A patients were examined. DNA was extracted from fresh frozen parathyroid tissue. Exons 2-10 of the MEN1 gene and exons 10 and 11 of the RET gene were sequenced. No somatic RET gene mutations were found in the 129 sporadic parathyroid tumors or 14 parathyroid hyperplastic lesions secondary to uremia. No somatic MEN1 gene mutations were found in the two parathyroid hyperplasia from MEN2A patients. These data suggest that RET gene mutation may not be involved in the development of sporadic parathyroid tumors and hyperplasia secondary to uremia and that MEN1 gene mutation may not be or is rarely associated with development of parathyroid hyperplasia in MEN2A patients.

Aged↗
PubMed1997

Remote conformational effects of the Gly-62 --> Leu mutation of the Tn10-encoded metal-tetracycline/H+ antiporter of Escherichia coli and its second-site suppressor mutation.

Substitution of Gly-62 of the Tn10-encoded metal-tetracycline/H+ antiporter caused a functional defect corresponding to the volume of the substituent [Yamaguchi, A., Someya, Y., and Sawai, T. (1992) J. Biol. Chem. 267, 19155-19162]. A spontaneous revertant exhibiting tetracycline resistance was isolated from Escherichia coli cells carrying the tetA(B) gene encoding the G62L mutation. The revertant showed a second-site mutation at codon 30 of TTA (Leu) to TCA (Ser). Site-directed mutagenesis studies revealed that the L30S mutation could suppress the effects of the G62A, G62C, G62N, and G62V mutations as well as the G62L mutation. Positions 62 and 30 are located in hydrophilic loops estimated to be in the cytoplasm and periplasm, respectively. Their sidedness was confirmed by the fact that, in intact cells, the [14C]N-ethylmaleimide (NEM) binding to the G62C mutant was not affected by preincubation with a membrane-impermeant sulfhydryl reagent, whereas the binding to the L30C mutant was blocked by the reagent. The reactivity of the L30C and L29C mutants with [14C]NEM was drastically decreased when Gly-62 was replaced by Leu, indicating that the residues around position 30 became embedded in the intramembrane region due to the remote conformational effect of the G62L mutation across the membrane. Moreover, the reactivity of the L29C/G62L mutant with [14C]NEM was restored with the L30S mutation. These results clearly indicate that the second-site suppression by the L30S mutation was based on the blocking of the remote conformational change around position 30 across the cell membrane caused by the G62L mutation.

Amino Acid Sequence↗
PubMed1997

Mutation prevalence among 47 unrelated Japanese patients with Gaucher disease: identification of four novel mutations.

Utilizing PCR and PCR-SSCP analysis we investigated the prevalence of glucocerebrosidase gene mutations in 47 unrelated Japanese patients with Gaucher disease. Sixty alleles (63.8%) and 20 alleles (21.3%) were identified by analysis for common mutations and PCR-SSCP analysis, respectively. The L444P and F213I mutations were common, accounting for 41 alleles (43.6%) and 14 alleles (14.9%). R496C, D409H, S366G and 1447-1466 del ins TG mutations were identified in 5, 3, 3 and 3 alleles, respectively. The other mutations were unique. In spite of vigorous screening, 14 alleles (14.9%) could not be identified. Four novel mutations were identified by PCR-SSCP analysis: G189V, S366G, K413Q and R433G. These data indicate that besides the L444P mutation no other frequent mutation is present and there is broad heterogeneity of the glucocerebrosidase gene mutations in Japanese patients with Gaucher disease.

Alleles↗
PubMed1998

Absence of 185delAG mutation of the BRCA1 gene and 6174delT mutation of the BRCA2 gene in Ashkenazi Jewish men with prostate cancer.

Epidemiological studies have demonstrated a clustering of breast and prostate cancers in some families. Moreover, there is an increase in the number of cases of prostate cancer in families with inherited mutations of the breast cancer susceptibility gene BRCA1. We assessed the role of BRCA1 and BRCA2 in prostate cancer. We tested for the BRCA1 185delAG frameshift mutation, found in 0.9% of Ashkenazi Jews, and the BRCA2 6174delT mutation, found in 1% of Ashkenazi Jews, in Ashkenazi Jewish men with prostate cancer. We studied 60 Ashkenazi men with prostate cancer. A family history was obtained by interview or a self-report questionnaire. Histological confirmation of diagnosis was obtained for all subjects. Ethnic background was confirmed for all subjects by self-report or interview. Mutations of BRCA1 and BRCA2 were detected by amplification of lymphocyte DNA from peripheral blood according to standard polymerase chain reaction (PCR) and dot blot procedures. Patients' ages ranged from 55 to 80 years (mean +/- s.d. 70 +/- 5.25). There were six men with a family history of prostate cancer; three of these had a father with prostate cancer. Five of the men had a family history of breast cancer, in a mother, a sister or an aunt. None of the men had a family history of both breast and prostate cancer. None of the 60 men carried the 185delAG BRCA1 or 6174delT BRCA2 mutations. Of 268 Ashkenazi Jewish women with sporadic breast cancer, tested in an unrelated study, 16 carried either the 185delAG mutation of BRCA1 or the 6174delT mutation of BRCA2. There was a significant difference in the incidence of the BRCA1 and BRCA2 mutations in the breast and prostate cancer cases (P = 0.05, two-tailed Fisher's exact test). The contribution of germline BRCA1 and BRCA2 mutations to prostate cancer incidence is probably small and could be limited to specific subgroups.

Aged↗
PubMed2002

Pathogenic mutations and rare variants of the APC gene identified in 75 Belgian patients with familial adenomatous polyposis by fluorescent enzymatic mutation detection (EMD).

Familial adenomatous polyposis (FAP) is a dominant inherited colorectal cancer syndrome which is caused by germline mutations in the adenomatous polyposis coli (APC) gene. Enzymatic mutation detection (EMD) has potential advantages over the standard protein truncation test (PTT) that is currently used in screening the APC gene for mutations. First we wanted to validate the EMD technique in comparison to PTT. Secondly, we wanted to develop an efficient working protocol for EMD screening of APC. Seventy-five unrelated patients were screened for mutations. All mutations that had previously been detected by PTT were also identified by EMD; the sizes of the cleavage fragments were as expected according to the position of the mutations within the amplicons. A new screening strategy based on EMD allows the analysis of the APC gene in 31 overlapping PCR fragments. In total, EMD efficiently detected the 26 truncating mutations in this series. In addition, two rare variants were also detected: the first is the typical Ashkenazi missense mutation I1307K while the second variant, E1317Q, has been identifed in Belgian patients and controls, and should no longer be considered as a pathogenic mutation, but rather classified as a polymorphism.

Adenomatous Polyposis Coli↗
PubMed2003

Influence of missense mutation and silent mutation of LHbeta-subunit gene in Japanese patients with ovulatory disorders.

The frequency of variant LHbeta containing two point mutations (T(986)-C and T(1008)-C) and its relationship to reproductive disorders differ widely between ethnic groups. In a Japanese population, variant luteinizing hormone (LH) correlates with ovulatory disorders. Here we examined the relationship between two missense mutations and five silent mutations (C(894)-T, G(1018)-C, C(1036)-A, C(1098)-T and C(1423)-T) in the LHbeta gene, and ovulatory disorders. We studied 43 patients with ovulatory disorders, 79 patients with normal ovulatory cycles, and 23 healthy men who agreed to join our DNA analysis. PCR-amplified LHbeta-subunit gene sequences were compared with a base sequence of wild-type LH reported after direct sequencing. The highest frequency (0.945) of novel allele was observed at the position of the C(1036)-A transition. No homozygotes for wild-type LHbeta (C(1036)) were identified. The frequency of novel allele in patients with polycystic ovary syndrome, endometriosis, premature ovarian failure and luteal insufficiency was significantly different from that of healthy women. The frequencies of novel alleles (C(894)-T, C(1098)-T and C(1423)-T) in patients with ovulatory disorders were significantly higher than those with normal ovulatory cycles. The mean incidence of point mutation in patients with ovulatory disorders was higher than in those with normal ovulatory cycles. Among patients with variant LH, five silent mutations were identified in 87.5% of patients with ovulatory disorders, whereas only a few silent mutations were identified in patients with normal ovulatory cycles. In a Japanese population, five silent mutations of variant LH could have influenced two missense mutations and/or other unknown missense mutations, causing ovulatory disorders.

Endometriosis↗
PubMed2003

Two Italian kindreds with familial hypocalciuric hypercalcaemia caused by loss-of-function mutations in the calcium-sensing receptor (CaR) gene: functional characterization of a novel CaR missense mutation.

OBJECTIVES: Description of two unrelated Italian kindreds with familial hypocalciuric hypercalcaemia (FHH), an autosomal dominant disease mostly caused by heterozygous inactivating mutations of the Ca2+ sensing receptor (CaR). PATIENTS AND DESIGN: We studied 11 members of the two families. Genomic DNA was isolated from peripheral blood leucocytes in all family members and in 50 unrelated Italian controls. Total serum and ionized calcium, PTH, creatinine, phosphate, magnesium, and urinary calcium clearance to creatinine clearance ratio were measured. Direct sequencing of the entire coding region of the CaR was performed in the probands. Functional studies were performed in COS-7 cells transiently expressing the mutated CaR. RESULTS: In the proband of family A direct sequencing revealed a novel heterozygous Y218C missense mutation in exon 4. The same mutation was identified in the affected but not in the unaffected family members or in any of the 50 unrelated Italian controls. Transient expression of the Y218C CaR in COS-7 cells revealed a blunted Ca2+-evoked accumulation of inositol trisphosphates, indicating that the Y218C is a loss-of-function mutation. Cotransfection experiments showed that the mutant receptor had no impact on the function of the wild-type receptor, suggesting that a reduced expression of the normal CaR, rather than a dominant-negative effect, accounted for the functional impairment. In the proband of family B an already described heterozygous P55L missense mutation in exon 2 of the CaR gene was found. The same mutation was identified in the affected family members. CONCLUSIONS: We described two familial hypocalciuric hypercalcaemia kindreds with loss-of-function mutations of the Ca2+ receptor gene and identified a novel heterozygous mutation (Y218C) characterized by a blunted response to Ca2+ stimulation compared to the wild-type receptor and no interference with the function of the wild-type Ca2+ receptor.

Adult↗
PubMed2001

Third complementarity-determining region of mutated VH immunoglobulin genes contains shorter V, D, J, P, and N components than non-mutated genes.

The third complementarity-determining region (CDR3) of immunoglobulin variable genes for the heavy chain (VH) has been shown to be shorter in length in hypermutated antibodies than in non-hypermutated antibodies. To determine which components of CDR3 contribute to the shorter length, and if there is an effect of age on the length, we analysed 235 cDNA clones from human peripheral blood of VH6 genes rearranged to immunoglobulin M (IgM) constant genes. There was similar use of diversity (D) and joining (JH) gene segments between clones from young and old donors, and there was similar use of D segments among the mutated and non-mutated heavy chains. However, in the mutated heavy chains, there was increased use of shorter JH4 segments and decreased use of longer JH6 segments compared to the non-mutated proteins. The overall length of CDR3 did not change with age within the mutated and non-mutated categories, but was significantly shorter by three amino acids in the mutated clones compared to the non-mutated clones. Analyses of the individual components that comprise CDR3 indicated that they were all shorter in the mutated clones. Thus, there were more nucleotides deleted from the ends of VH, D, and JH gene segments, and fewer P and N nucleotides added. The results suggest that B cells bearing immunoglobulin receptors with shorter CDR3s have been selected for binding to antigen. A smaller CDR3 may allow room in the antibody binding pocket for antigen to interact with CDRs 1 and 2 as well, so that as the VDJ gene undergoes hypermutation, substitutions in all three CDRs can further contribute to the binding energy.

Adult↗
PubMed2001

Mutations in the mouse TSH receptor equivalent to human constitutively activating TSH receptor mutations also cause constitutive activity.

Constitutively activating mutations in the human thyroid-stimulating hormone (TSH) receptor (TSHr) have been identified as the most prevalent molecular cause of non-autoimmune hyperthyroidism. To investigate the feasibility of an animal model for non-autoimmune hyperthyroidism, we introduced two mutations in the mouse TSHr which had previously been identified in the human TSHr. The two human mutations showed strong differences in TSH binding, basal cAMP and IP accumulation. In the human TSHr, the Ile 486 Phe mutation causes a high increase of basal cAMP accumulation and also basal stimulation of the inositol phosphate pathway, whereas the Val 509 Ala mutation results in a low increase of basal cAMP accumulation without affecting IP signaling. RNA was isolated from mouse thyroid tissue and reverse transcribed. A 2.4 kb PCR product from the mouse TSHr was cloned into the pGEM-T vector system. Ile was substituted with Phe at codon 486 and Val with Ala at codon 509. These mutated mouse TSHrs were subcloned in the pSVL expression vector. After transient expression in COS-7 cells, basal and TSH-stimulated cAMP and IP accumulation, cell surface expression and TSH binding were determined and directly compared to the human TSHr. Whereas constitutively activating mutations of the human parathyroid hormone (PTH)/PTH-related peptide receptor showed little or no change in basal cAMP accumulation when introduced into the rat PTH/PTHrP receptor, these two mouse TSHr mutations resulted in constitutive activity similar to the homologous mutations in the human TSHr. Therefore, it should be possible to establish a mouse model for non-autoimmune hyperthyroidism by homologous recombination to study the pathogenetic mechanisms of non-autoimmune hyperthyroidism.

Animals↗
PubMed2006

Mitochondrial DNA mutations are established in human colonic stem cells, and mutated clones expand by crypt fission.

The understanding of the fixation of mutations within human tissues and their subsequent clonal expansion is a considerable problem, of which little is known. We have previously shown that nononcogenic mutations in the mitochondrial genome occur in one of a number of morphologically normal colonic crypt stem cells, the progeny of which later occupy the whole crypt. We propose that these wholly mutated crypts then clonally expand by crypt fission, where each crypt divides into two mutated daughter crypts. Here we show that (i) mutated crypts in the process of fission share the same mutated mitochondrial genotype not present in neighboring cytochrome c oxidase-positive crypts (the odds of this being a random event are >or=2.48 x 10(9):1); (ii) neighboring mutated crypts have the same genotype, which is different from adjacent cytochrome c oxidase-positive crypts; (iii) mutated crypts are clustered together throughout the colon; and (iv) patches of cytochrome c oxidase-deficient crypts increase in size with age. We thus demonstrate definitively that crypt fission is the mechanism by which mutations spread in the normal human colon. This has important implications for the biology of the normal adult human colon and possibly for the growth and spread of colorectal neoplasms.

Adult↗
PubMed1991

Adaptive evolution that requires multiple spontaneous mutations: mutations involving base substitutions.

A previous study has demonstrated that adaptive missense mutations occur in the trp operon of Escherichia coli. In this study it is shown that, under conditions of intense selection, a strain carrying missense mutations in both trpA and trpB reverts to Trp+ 10(8) times more frequently than would be expected if the two mutations were the result of independent events. Comparison of the single mutation rates with the double mutation rate and information obtained by sequencing DNA from double revertants show that neither our classical understanding of spontaneous mutation processes nor extant models for adaptive mutations can account for all of the observations. Despite a current lack of mechanistic understanding, it is clear that adaptive mutations can permit advantageous phenotypes that require multiple mutations to arise and that they appear enormously more frequently than would be expected.

Biological Evolution↗
PubMed2001

Variation in cancer risks, by mutation position, in BRCA2 mutation carriers.

Cancer occurrence in 164 families with breast/ovarian cancer and germline BRCA2 mutations was studied to evaluate the evidence for genotype-phenotype correlations. Mutations in a central portion of the gene (the "ovarian cancer cluster region" [OCCR]) were associated with a significantly higher ratio of cases of ovarian:breast cancer in female carriers than were mutations 5' or 3' of this region (P<.0001), extending previous observations. The optimal definition of the OCCR, as judged on the basis of deviance statistics, was bounded by nucleotides 3059-4075 and 6503-6629. The relative and absolute risks of breast and ovarian cancer associated with OCCR and non-OCCR mutations were estimated by a conditional likelihood approach, conditioning on the set of mutations observed in the families. OCCR mutations were associated both with a highly significantly lower risk of breast cancer (relative risk [RR] 0.63; 95% confidence interval (95% CI) 0.46-0.84; P=.0012) and with a significantly higher risk of ovarian cancer (RR = 1.88; 95% CI = 1.08-3.33; P=.026). No other differences in breast or ovarian cancer risk, by mutation position, were apparent. There was some evidence for a lower risk of prostate cancer in carriers of an OCCR mutation (RR = 0.52; 95% CI = 0.24-1.00; P=.05), but there was no evidence of a difference in breast cancer risk in males. By age 80 years, the cumulative risk of breast cancer in male carriers of a BRCA2 mutation was estimated as 6.92% (95% CI = 1.20%-38.57%). Possible mechanisms for the variation in cancer risk are suggested by the coincidence of the OCCR with the RAD51-binding domain.

Adult↗
PubMed1998

Zidovudine therapy and HIV type 1 mutations in children with symptomatic HIV type 1 infection: effect of switching to didanosine or zidovudine plus didanosine therapy. Italian Multicenter Study Group on HIV Mutations in Children.

Type and prevalence of zidovudine (ZDV) resistance mutations in HIV-1-infected children in clinically stable condition and on ZDV monotherapy were analyzed to evaluate the effect of switching to didanosine (ddI) monotherapy or to ZDV plus ddI on the pattern of mutations and on the clinical outcome. Monthly clinical and laboratory controls for HIV-1 infection status were performed; at enrollment and every 4 to 6 months after treatment randomization mutant proviral sequences were evaluated in all the children, whereas viral burden was performed only in a small subgroup of patients randomly selected in each of the three treatment groups. ZDV resistance-associated proviral DNA mutations were defined as low-level resistance (LLR) mutations or medium/high-level resistance (MHLR) mutations; clinical outcome was considered as stable or deteriorating. Results showed that at entry into the study the duration of ZDV therapy was significantly correlated with the presence of mutations, and that the level of resistance given by mutations was associated with the severity both of symptoms and immunodeficiency. After randomization to treatment, in patients with mutations that confer LLR a better clinical outcome with ddI monotherapy than with ZDV plus ddI and ZDV alone was observed in the subsequent 6 months, whereas in patients with mutations that confer MHLR no significant difference among the three treatment groups was found. Data showed also that levels of viral burden at the time of changing therapy are related to clinical outcome if measured by plasma viral load. These results suggest that genotypic resistance assays, together with viral load, may prove useful for rational treatment decisions both at the start of therapy and with failure.

Anti-HIV Agents↗
PubMedDate not supplied

Branchio-oto-renal syndrome: identification of novel mutations, molecular characterization, mutation distribution, and prospects for genetic testing.

The branchio-oto-renal syndrome (BOR) is an autosomal dominant disorder characterized by branchial clefts, preauricular sinuses, hearing loss, and renal anomalies. The BOR gene, EYA1, on chromosome 8q13 has recently been cloned and mutations have been identified. In this study, we have analyzed the sites of mutations in the EYA1 gene in BOR patients to determine the spectrum of mutations. We have identified two missense mutations and have compared all the mutations reported to date in the EYA1 gene. In total, 20 mutations have been described, the majority of which are clustered in the carboxy-terminal region of the gene. The clinical features of the BOR individuals have also been compared to determine if the nature of the mutation correlates with the type and severity of the clinical symptoms. Most of the mutations arose de novo and, other than the clustering in carboxy-terminal exons 9-16, no mutation hot spots have been identified. These results provide the basis for molecular genetic testing that will help in the clinical evaluation and genetic counseling of members of BOR families.

Base Sequence↗
PubMed1996

RET mutation screening in MEN2 patients and discovery of a novel mutation in a sporadic medullary thyroid carcinoma.

RET germline mutations were found to predispose to the development of three variants of multiple endocrine neoplasia type 2, MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC). We have screened for RET mutations at exons 10, 11, 13, and 16 in leukocyte DNA extracted from 37 individuals, and have identified RET germline mutations in 12 affected individuals from 9 unrelated families. No RET germline mutation was found in 19 individuals with apparent sporadic diseases. We have also screened for RET mutations at exons 10, 11, and 16 in tumor DNA extracted from 13 freshly frozen medullary thyroid carcinomas (MTC). RET mutation was detected in every tumor, either inherited or sporadic, indicating that RET plays an important role in the development of both inherited and sporadic MTC. We initially screened for RET mutations by direct DNA sequencing of the genomic PCR products amplified from patients' leukocyte or tumor DNA. Recently, we utilized the "Cold SSCP" method, nonradioactive single-stranded conformation polymorphism analysis, to screen for RET mutations and have identified a novel mutation, a 6-bp deletion preceding the cysteine-634, in a sporadic MTC.

Adolescent↗