Screening of germline mutations in the CDKN2A and CDKN2B genes in Swedish families with hereditary cutaneous melanoma

BACKGROUND: Approximately 10% of human cutaneous melanomas occur in families in which several members are affected. The familial predisposition to this disease is often associated with dysplastic nevus syndrome, a condition in which afflicted family members have multiple dysplastic nevi (atypical moles). The chromosome region 9p21 and markers on chromosomes 1p and 6p have been linked to melanoma susceptibility. The tumor suppressor genes CDKN2A and CDKN2B have been mapped to the 9p21 region, and genetic analyses have revealed the presence of germline CDKN2A alterations in melanoma families. The reported frequencies of such alterations, however, vary among these families. PURPOSE: The present investigation was carried out to determine the frequencies of CDKN2A and CDKN2B germline gene mutations among members in a population-based cohort of Swedish melanoma families (i.e., melanoma kindreds). METHODS: DNA was prepared from blood samples obtained from 181 individuals belonging to 100 melanoma kindreds. The polymerase chain reaction (PCR) technique, followed by single-strand conformation polymorphism (SSCP) and nucleotide sequence analyses, were used to identify the types and frequencies of mutations in exons 1, 1beta, 2, and 3 of the CDKN2A gene and in exons 1 and 2 of the CDKN2B gene. RESULTS: CDKN2A gene aberrations were independently identified by both SSCP and nucleotide-sequence analyses. Nucleotide-sequence analysis identified a single point mutation leading to a substitution of leucine for proline in codon 48 of exon 1 in a family with a history of melanoma and several other cancers. A second abnormality, leading to an insertion of an extra arginine residue at codon number 113 of exon 2, was seen in four separate families. The CDKN2A exon-3 coding region had the wild-type sequence in all samples. No germline mutations were found in the alternative exon 1beta of the CDKN2A gene or in exons 1 and 2 of the CDKN2B gene. CONCLUSIONS: The present investigation demonstrates that CDKN2A germline gene mutations were observed in 7.8% of the 64 Swedish melanoma kindreds that each included at least two first-degree relatives with melanoma and dysplastic nevus syndrome. No CDKN2A exon 1beta or CDKN2B mutations were identified. The critical genes responsible for the inheritance of a susceptibility to develop melanoma among family members in this population have yet to be identified.     

Screening for tumour suppressor p16(CDKN2A) germline mutations in Israeli melanoma families

Approximately ten percent of patients with malignant melanoma have family histories of the disease, suggesting a genetic predisposition. Germline mutations in tumour suppressor p16 gene have been implicated as disease causing mutations in some of the melanoma families. The frequency of families with p16 germline mutations among melanoma prone families varies from eight to fifty percent. The range of the variability is influenced apparently by the number of melanoma affected individuals within the family, as well as by other, yet unidentified factors. Ethnic background is known to determine both the frequency and the nature of germline alterations. Recently, specific mutations in tumour suppressor genes involved in breast cancer and in colon cancer were found at elevated frequency among Ashkenazi Jews. This report describes results of a screening for p16 germline alterations in a collection of Israeli melanoma families. We have analyzed genomic DNA from thirty one Ashkenazi and non-Ashkenazi Jewish melanoma families, as well as from thirty melanoma patients without an apparent family history of the disease. The entire coding region of the p16 gene was screened by single strand conformation polymorphism analysis and direct DNA sequencing. We have detected a number of carriers with the Ala148 Thr polymorphism at the end of the second exon and several instances of 500(G=>C) substitution at the 3' untranslated portion of the gene.     

Haplotype and phenotype analysis of six recurrent BRCA1 mutations in 61 families: results of an international study

Central to the Mu transpositional recombination are the two chemical steps; donor DNA cleavage and strand transfer. These reactions occur within the Mu transpososome that contains two Mu DNA end segments bound to a tetramer of MuA, the transposase. To investigate which MuA monomer catalyzes which chemical reaction, we made transpososomes containing wild-type and active site mutant MuA. By pre-loading the MuA variants onto Mu end DNA fragments of different length prior to transpososome assembly, we could track the catalysis by MuA bound to each Mu end segment. The donor DNA end that underwent the chemical reaction was identified. Both the donor DNA cleavage and strand transfer were catalyzed in trans by the MuA monomers bound to the partner Mu end. This arrangement explains why the transpososome assembly is a prerequisite for the chemical steps.     

BRCA1 and BRCA2 in breast cancer families from Wales: moderate mutation frequency and two recurrent mutations in BRCA1

Mutations in the BRCA1/BRCA2 genes account for varying proportions of breast cancer families studied, and demonstrate considerable variation in mutational spectra coincident with ethnic and geographical diversity. We have screened for mutations in 17 families from Wales with two or more cases of breast cancer under age 50 and/or ovarian cancer. Eight out of 17 (47%) families had demonstrable mutations. Six out of 17 (35%) carried BRCA1 mutations and 2 out of 17 (12%) carried BRCA2 mutations. Two recurrent mutations in BRCA1 were identified, which appear to represent founder mutations in this population. These data support the existence of additional breast and ovarian cancer susceptibility genes.     

Molecular characterization of germline mutations in neurofibromatosis 2 in two families

Neurofibromatosis 2 (NF2) is an autosomal dominant disorder that predisposes patients to central nervous system tumors. It is caused by mutations in the NF2 tumor suppressor gene, which is located on chromosome 22q12. We studied 2 multigenerational NF2 families (three members of family 1 and the proband of the family) by gene mutation analysis and clinical assessment. One member of family 1 had a 169 C-->T point mutation at codon 57 of exon 2 and had a severe phenotype. His father had a silent 1113 C-->T point mutation at codon 371 of exon 11 and had a normal phenotype. The proband of family 2 had a deletion at nucleotide 720 G (codon 240) of exon 8. This led to a frameshift and termination at codon 250, and a severe NF2 phenotype. Our results indicate that clinical abnormalities can be present in carriers. Nonsense and frameshift mutations in the NF2 tumor suppressor gene are associated with phenotypes. The clinical abnormalities can develop at a young age.     

Germline RET proto-oncogene mutations in two Taiwanese families with multiple endocrine neoplasia type 2A

To elucidate the germline RET proto-oncogene mutations in Taiwanese families with multiple endocrine neoplasia type 2A (MEN 2A), we extracted DNA from peripheral blood leukocytes of 28 members of two families with MEN 2A. Oligonucleotide primers for exons 10 and 11 were used to analyze the nucleotide sequence of codons 609, 611, 618, and 620 of exon 10, and codon 634 of exon 11 of the RET proto-oncogene. Two fragments of genomic DNA were amplified by polymerase chain reaction (PCR). The amplified PCR products were separated and purified from primers and free nucleotides in agarose gels, and the expected 187-bp and 234-bp bands were cut from the gels and sequenced. Thirteen family members in the two MEN 2A kindreds had mutations in codon 634 of exon 11. In kindred 1 (15 members available for this study), a heterozygous codon 634 mutation in nine members and a homozygous codon 634 mutation in one member led to the substitution of Phe (TTC) for Cys (TGC). Three members of kindred 2 (13 members available for this study) had a heterozygous base pair change in codon 634, which led to the substitution of Arg (CGC) for Cys (TGC). In this study, we found two mutation events occurring in two MEN 2A kindreds and also discovered a homozygous point mutation in one woman that led to heterozygous mutations in all of her children.     

Alterations of CDKN2 gene structure in childhood acute lymphoblastic leukemia: mutations of CDKN2 are observed preferentially in T lineage

We analyzed homozygous deletions and mutations of the CDKN2(p16(INK4A)/MTS1) gene, using polymerase chain reaction and Southern blot analysis, in 120 children with acute lymphoblastic leukemia (ALL). Homozygous deletion was found in 17 of 89 (19%) precursor B-ALL patients, in 11 of 24 (46%) T-ALL patients, and in 0 of 7 other phenotype ALL patients. After excluding 28 (23%) patients who showed a homozygous deletion of CDKN2, we found that three patients (3%) had mutation at exon 2 of CDKN2 using PCR-SSCP and sequencing strategy. One had a CGA to TGA nonsense mutation (Arg to stop) at codon 72, one had a 1-bp deletion at codon 117, and the third had a 2-bp deletion at codon 70, resulting in frameshifts in the two latter patients. All three of these patients were T phenotype ALL, and the incidence of mutation in the 24 T-ALL patients examined was 13%. In contrast, no mutation was detected in the remaining patients with precursor-B or other type ALL (0/96). Our results suggest that mutational inactivation of the CDKN2 gene may contribute to the leukemogenic growth, especially in some patients with T-ALL.     

MTAP、CDKN2A和CDKN2B在弥漫大B细胞淋巴瘤中的表达及其临床意义

目的 研究弥漫大B细胞淋巴瘤(DLBCL)MTAP、CDKN2A和CDKN2B基因的表达及其临床意义.方法 以实时定量聚合酶链反应(PCR)方法检测40例DLBCL及19例淋巴结反应性增生组织中MTAP、CDKN2A和CDKN2B基因的表达情况,结合临床特征进行分析,并进行随访.结果 DLBCL组MTAP、CDKN2A和CDKN2B基因表达水平较淋巴结反应性增生组降低,差异有统计学意义(P值分别为0.024、0.044和0.047);三者表达均与Ann Arbor临床分期相关(P值分别为0.004、0.001和0.027);与患者的性别、年龄、淋巴结外病变累及、ECOG体力评分、骨髓累及、血清乳酸脱氢酶水平均无明显相关(均P＞0.05).其中MTAP与CDKN2A基因表达情况还与B症状(P值分别为0.003和0.028)和国际预后指数(IPI)相关(P值分别为0.001和0.011).此外,生存分析结果显示,MTAP、CDKN2A和CDKN2B基因表达水平与患者总生存期相关(P值分别为0.022、0.019和0.042).结论 MTAP、CDKN2A和CDKN2B基因在DLBCL中呈低水平表达,与疾病进展和患者预后有关,可作为反映其生物学行为和评估患者临床疗效的分子标志物.     

Bilateral apocrine carcinoma of the breast. Molecular and immunocytochemical evidence for two independent primary tumours

The amount of exercise necessary to cause bone structural change in humans is unknown. We examined whether a single bout of intense exercise in vivo leads to acute and subacute changes in the physical properties of bone as measured by ultrasound. It was hypothesized that structural changes such as accumulation of fatigue microdamage would result in a decrease in velocity of sound (VOS) and broadband ultrasound attenuation (BUA) across the calcaneus. We performed a prospective cohort study in 111 (97 M, 14 F) entrants of the 1996 Melbourne marathon (42.3 km) and 28 (10 M, 18 F) nonrunning controls. Runners had a mean (SD) age of 45.3 +/- 11.4 years (range 20-75), had completed 15.2 +/- 17.3 prior marathons (0-88), and had been running regularly for 14.2 +/- 9.2 years (0.25-50). An ultrasound densitometer (Cuba Clinical, McCue) was used to measure VOS and BUA across the right calcaneus. Runners were tested on three occasions: 1-3 days prior to, immediately after (<2 hours), and 5-6 days following the marathon. Seventy-three (66%) runners presented for all three measurements. Controls were tested on three occasions with the same time intervals as the runners. BUA values in the runners were significantly elevated by 5.0% immediately after the marathon but returned to baseline levels by the third test session (P = 0. 0001). Changes in BUA values in the controls were not significant and all were less than 0.7% (P = 0.88). Age was a significant independent predictor of the BUA change between test 1 and test 2 in the runners (beta = 0.2094; SE = 0.0917; P = 0.03). VOS measurements were not significantly different across the three testing sessions in both the runners (P = 0.07) and the controls (P = 0.33). Therefore, ultrasound measurements of BUA and VOS did not detect evidence of lasting structural change in the calcaneus following a marathon.     

FH-Sydney 1 and 2: two novel frameshift mutations in exon 10 of the low-density lipoprotein receptor gene detected by heteroduplex formation

We report two novel frameshift mutations in exon 10 of the low-density lipoprotein receptor gene that lead to familial hypercholesterolemia in separate lineages. The lesions, FH-Sydney 1 and FH-Sydney 2, were detected by a modified heteroduplex analysis of exon-specific polymerase chain reaction (PCR) amplified DNA, and characterized at the molecular level by sequencing. Restriction enzyme digestion of PCR amplified DNA confirmed the presence of the mutant alleles in affected family members and their absence in nonaffected family members in both lineages. FH-Sydney 1 is a 4-bp duplication at position 1373, while FH-Sydney 2 is a 2-bp deletion at position 1478. The predicted result of both mutations is the premature truncation of the receptor at stop codons generated downstream of the mutations. Neither mutation was detected in a survey of 54 unrelated familial hypercholesterolemia patients.     

Identification of two different mutations causing protein S deficiency in two unrelated Belgian families using a nonisotopic scanning and sequencing method

Hereditary protein S deficiency is a risk factor for developing recurrent venous thromboembolic disease and is caused by a defect in the protein S 1 (PROS1) gene. Identification of the mutation in the PROS1 gene can overcome diagnostic uncertainty in family members with borderline protein S levels. We describe a novel nonisotopic method for molecular diagnosis of protein S deficiency, using fluorescein-labeled amplification and sequencing primers. As a first step, all exons of the PROS1 gene are selectively amplified, and heteroduplex analysis is performed. As a second step, all exons are analyzed by direct sequencing. Using this method, we have characterized the molecular defect in two Belgian families with hereditary protein S deficiency type I: a frameshift mutation in exon XIV (1881insTC) and a missense mutation caused by a T-to-C transition, resulting in substitution of Leu405 by Pro (L405P).     

Amacrine cells in Necturus retina: evidence for independent gamma-aminobutyric acid- and glycine-releasing neurons

About one-half of on-off ganglion cells have inhibitory postsynaptic potentials (IPSP's) which are blocked by strychnine, while the remainder have IPSP's which are blocked by picrotoxin or bicuculline. These antagonists do not abolish light activity of the presynaptic inhibitory neuron, the amacrine cell. The existence of separate gamma-aminobutyric acid- and glycine-releasing amacrine cells is implied by these results.     

Identification of two missense mutations in the GIP receptor gene: a functional study and association analysis with NIDDM: no evidence of association with Japanese NIDDM subjects

Gastric inhibitory polypeptide (GIP) potently stimulates insulin secretion from pancreatic islets in the presence of glucose as an incretin. Because the insulinotropic effect of GIP is reduced in NIDDM, it should be clarified whether defects in the GIP receptor gene contribute to the impaired insulin secretion in NIDDM. Using genomic DNA samples from Japanese NIDDM and non-NIDDM subjects, we have investigated the entire coding region of the GIP receptor gene by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP). We have identified two missense mutations, Gly198-->Cys (Gly198Cys) in exon 7 and Glu354-->Gln (Glu354Gln) in exon 12. Investigation of the function of GIP receptor with either of these mutations reveals a half-maximal stimulation value of GIP-induced cAMP response in Chinese hamster ovary cells expressing the GIP receptor with Gly198Cys of 6.3 +/- 1.2 x 10(-10) mol/l (n = 3), which was considerably higher than that of the normal GIP receptor, 9.4 +/- 3.8 x 10(-12) mol/l GIP (n = 3), whereas that of the GIP receptor with Glu354Gln was not significantly different from that of the normal GIP receptor. To assess the possible role of the GIP receptor gene in genetic susceptibility to NIDDM, we have examined the allelic frequencies of Gly198Cys and Glu354Gln in NIDDM and control subjects. Association studies show no relationship between NIDDM and either of the two mutations.     

No common major gene for apolipoprotein A-I and HDL3-C levels: evidence from bivariate segregation analysis

Apolipoprotein A-I (apo A-I) is the most abundant protein in high-density lipoprotein (HDL) particles, and it plays an important role in HDL metabolism. Both apo A-I and HDL cholesterol (HDL-C) levels are inversely associated with risk of cardiovascular disease. Segregation analyses suggest apo A-I levels are under the control of one or more major loci. Since HDL particles are heterogeneous in their composition and size, genetic influence on its subfractions (i.e., HDL2 and HDL3) could vary. A previous report showed evidence of a major locus controlling HDL3-C levels in a subset of the current study population. Because quantitative trait loci involved in complex diseases are likely to have pleiotropic effects on several related traits, it is possible to have a common major gene involved in regulating apo A-I and HDL3-C levels. We performed a bivariate segregation analysis of apo A-I and HDL3-C levels in 1,006 individuals from 137 families ascertained through probands undergoing elective, diagnostic coronary angiography at the Johns Hopkins Hospital. The results showed significant genetic correlation between these two traits, but the hypothesis of a common major gene was rejected. Bivariate segregation analysis favored a model with two genes controlling apo A-I and a third gene independently controlling HDL3-C, and the genetic correlation between these two traits is due to residual additive polygenes. Overall, results from this study suggest that there are distinct genetic mechanisms for apo A-I and HDL3-C levels. Future studies, especially linkage analysis, should consider distinct genetic mechanisms and multiple major gene loci.     

A multistable movement display: evidence for two separate motion systems in human vision

Two competing sensations of apparent movement were produced by the rapid alternation of two multielement stimulus frames. Either sensation could be made dominant by, appropriate manipulations of the stimulus display. The results suggest that there are two systems capable of generating movement signals in man. One system depends on preliminary processing of form, and the second system does not.     

Germline mutations of the RET proto-oncogene in pedigree with MEN type 2A: DNA analysis and its implications for pediatric surgery

To assess the feasibility of screening for multiple endocrine neoplasia type 2A (MEN 2A), the authors used DNA sequence analysis to evaluate the RET proto-oncogene in a kindred with MEN 2A. The kindred consisted of 95 members (1 to 79 years of age) and their spouses, and spanned five generations. Genomic DNA was extracted from peripheral blood lymphocytes or lymphoblastoid cell lines established from the family members, and the RET gene was amplified by polymerase chain reaction (PCR) using RET-specific primers (10q 11.2) and was sequenced. Periodic endocrine screening also was performed, by measuring the plasma calcitonin concentration after provocation with pentagastrin (0.5 microgram/kg intravenously) to assess its reliability for detecting the associated neoplasms. Nineteen patients were confirmed to have MEN 2A by medical records or the screening program. The DNA sequence of the PCR products from clinically established MEN 2A patients showed a mutation at codon 634 (TGC-->CGC) that resulted in an amino acid change from cysteine to arginine. Endocrine screening tests showed that six other family members had a mutated RET protooncogene. DNA sequencing can detect high-risk cases at a preclinical stage of the disease. The establishment of mutated MEN 2A gene carriers allows pediatric surgeons to consider total thyroidectomy at a very early stage of neoplasm development (C-cell hyperplasia) or even prophylactically.     

Genetic analysis of protein C deficiency in nineteen Japanese families: five recurrent defects can explain half of the deficiencies

OBJECTIVE: The lack of sensitivity and specificity of conventional imaging techniques based on morphological critera is responsible for considerable limitations in the staging and surveillance of oral cancer. Therefore, this study investigates the contribution of [F18]-2-fluordesoxyglucose (FDG) positron emission tomography (PET) to tumor management with special regard to lymphnode involvement and therapeutic monitoring after radiotherapy. DESIGN: Prospective observational study. PATIENTS: Twenty-one patients with advanced oral cancer, predominantly T3/T4. INTERVENTION: FDG-PET scans before and after preoperative radio(chemo)therapy. Standardized uptake values (SUV) were determined for the tumor site and lymphnode areas. PET scans were correlated to histological findings after ablative tumor surgery. RESULTS: FDG-PET yielded superior sensitivity and specificity for tumor and lymphnode assessment. The effect of radiotherapy was reflected by the metabolic activity of the tumor, which shows a close correlation between the decrease of FDG uptake and histologic tumor regression. PET detected distant metastases and simultaneous tumors. CONCLUSION: FDG-PET is a challenging imaging technique with the potential to improve staging procedures for oral cancer. In the monitoring of metabolic activity of the tumor in the course of radio(chemo)therapy, FDG-PET allows objective measurement of the treatment response.     

Genetic heterogeneity of autosomal dominant cerebellar ataxia type 1: clinical and genetic analysis of 10 French families

We performed linkage analysis between the gene responsible for spinal cerebellar ataxia 1 (SCA1) and the highly polymorphic chromosome 6 locus, D6S89, in 10 French families with autosomal dominant cerebellar ataxia (ADCA) type 1. These families were clinically indistinguishable except for one family with loss of hearing and vision. Very close linkage was observed in four families, with no evidence of recombination between SCA1 and D6S89. Linkage with D6S89 was excluded in the six others, thus demonstrating genetic heterogeneity for ADCA type 1. The D6S89 marker, which is very closely linked to the disease locus, can be used to identify SCA1 families and will lead to predictive testing.     

The bluetail transposon: evidence for independent cis-regulatory domains and domain boundaries in the bithorax complex

An extremely large cis-regulatory region generates the parasegment-specific expression patterns of the homeotic genes in the bithorax complex. We present evidence supporting the idea that this cis-regulatory region is subdivided into independent cis-regulatory domains. We describe a Ubx-lacZ transposon which is inserted into one of these domains, iab-7. The PS12-specific pattern of LacZ expression from this reporter indicates that it is subject to the control of the iab-7 cis-regulatory domain, but is protected from the effects of adjacent regulatory domains. Protection on the proximal side appears to be provided by the Fab-7 boundary element. Deletion of this boundary results in the ectopic activation of iab-7 in PS11 (where the iab-6 cis-regulatory domain normally functions). We show that the Fab-7 boundary, like other boundaries, has an unusual chromatin structure.