Biomedical subjects

Y Peng

Publications and source records attributed to Y Peng.

At least 19 recordsLinked to original sources

PubMed1997

Identification and characterization of a telomerase activity from Schizosaccharomyces pombe.

A telomerase-like primer extension activity has been detected in chromatographic fractions derived from Schizosaccharomyces pombe extracts. This primer extension activity acts preferentially on dG-rich oligodeoxynucleotides, is sensitive to RNase A pretreatment and requires all four deoxynucleotides for optimal polymerization. The extension products are also truncated by the inclusion of any one of the four dideoxynucleotides, consistent with the presence of all four bases in the S.pombe telomeric repeats. The intensity distribution of the extension products and the dideoxynucleotide termination pattern suggest that nucleotide addition is template directed, and that telomere-like sequences are added to the primers. In particular, the sequence d(CGGTTA), a variant of the S.pombe telomeric repeat, can be added directly by the in vitro activity. Partially purified S.pombe telomerase sediments as a 35S particle, suggesting that it exists in vivo as part of a large multi-protein complex.

DNA, Fungal↗

PubMed1997

Arrest of the cell cycle by the tumour-suppressor BRCA1 requires the CDK-inhibitor p21WAF1/CiP1.

Much of the predisposition to hereditary breast and ovarian cancer has been attributed to inherited defects in the BRCA1 tumour-suppressor gene. The nuclear protein BRCA1 has the properties of a transcription factor, and can interact with the recombination and repair protein RAD51. Young women with germline alterations in BRCA1 develop breast cancer at rates 100-fold higher than the general population, and BRCA1-null mice die before day 8 of development. However, the mechanisms of BRCA1-mediated growth regulation and tumour suppression remain unknown. Here we show that BRCA1 transactivates expression of the cyclin-dependent kinase inhibitor p21WAF1/CIP1 in a p53-independent manner, and that BRCA1 inhibits cell-cycle progression into the S-phase following its transfection into human cancer cells. BRCA1 does not inhibit S-phase progression in p21-/- cells, unlike p21+/+ cells, and tumour-associated, transactivation-deficient mutants of BRCA1 are defective in both transactivation of p21 and cell-cycle inhibition. These data suggest that one mechanism by which BRCA1 contributes to cell-cycle arrest and growth suppression is through the induction of p21.

Animals↗

PubMed1997

Cloning, human chromosomal assignment, and adipose and hepatic expression of the CL-6/INSIG1 gene.

Rat CL-6 is the most highly insulin-induced gene in a liver cell line and is expressed in proliferating liver during regeneration and development. CL-6 is now denoted INSIG1 (insulin-induced gene 1). Human INSIG1 was isolated and found to be 80% identical to the rat gene within the translated region. It was located on human chromosome 7 within band q36. The human INSIG1 promoter conferred a high level of expression in both liver and fibroblast cell lines. INSIG1 expression was upregulated at the transcriptional level in rat regenerating liver and induced in a model of murine adipocyte differentiation, suggesting that INSIG1 may play a role in growth and differentiation of tissues involved in metabolic control.

Adipose Tissue↗

PubMed1997

Posttransplant lymphoproliferative disorders: a fine-needle aspiration biopsy study.

Fine-needle aspiration biopsy (FNAB) has been used with high sensitivity and specificity in the diagnosis of both Hodgkin's and non-Hodgkin's lymphoma. However, studies of FNAB of posttransplant lymphoproliferative disorders (PTLDs) are rare. The clinical course of 593 allograft recipients (cardiac, 288; renal, 250; lung, 50; and heart/lung, 5) was reviewed. Twenty-six patients developed PTLD with an overall incidence of 4.4%. Of these patients, 12 underwent FNAB. Their age ranged from 33-67 yr (mean, 55 yr). The interval between transplantation and FNAB ranged between 2-14 mo (average, 8.4 mo). The lungs were the most common site aspirated (7 cases), followed by lymph nodes (3 cases) and other extranodal sites (2 cases, liver and paraspinal mass). The cytologic features of these aspirates could be classified into two categories: a polymorphous smear composed of a spectrum of mature and immature lymphocytes with scattered plasma cells and histiocytes; and a monotonous population of large lymphoid cells consistent with malignant lymphoma, large-cell type. Surgical biopsies were available in 10 (83.3%) cases and confirmed the FNAB diagnosis. In summary, FNAB appears to be a highly sensitive and specific diagnostic tool in patients with PTLD.

Adult↗

PubMed1997

Localization of BRCA1 and a splice variant identifies the nuclear localization signal.

Inherited mutations in BRCA1 confer susceptibility to breast and ovarian neoplasms. However, the function of BRCA1 and the role of BRCA1 in noninherited cancer remain unknown. Characterization of alternately spliced forms of BRCA1 may identify functional regions; thus, we constructed expression vectors of BRCA1 and a splice variant lacking exon 11, designated BRCA1 delta 672-4095. Immunofluorescence studies indicate nuclear localization of BRCA1 but cytoplasmic localization of BRCA1 delta 672-4095. Two putative nuclear localization signals (designated NLS1 and NLS2) were identified in exon 11; immunofluorescence studies indicate that only NLS1 is required for nuclear localization. RNA analysis indicates the expression of multiple, tissue-specific forms of BRCA1 RNAs; protein analysis with multiple antibodies suggests that at least three BRCA1 isoforms are expressed, including those lacking exon 11. The results suggest that BRCA1 is a nuclear protein and raise the possibility that splicing is one form of regulation of BRCA1 function by alteration of the subcellular localization of expressed proteins.

3T3 Cells↗

PubMed1997

HRS/SRp40-mediated inclusion of the fibronectin EIIIB exon, a possible cause of increased EIIIB expression in proliferating liver.

Serine-arginine (SR)-rich proteins are believed to be important in mediating alternative pre-mRNA splicing. HRS/SRp40 expression is elevated in liver cell proliferation during development, regeneration, and oncogenesis. We tested whether HRS expression correlates with the appearance of alternatively spliced fibronectin transcripts during liver growth. HRS was highly expressed during the proliferative phase of liver development, correlating with expression of the fibronectin EIIIB alternative exon. In regenerating liver, HRS protein was induced in a time course consistent with the observed increase in fibronectin transcripts containing the EIIIB exon, particularly in nonparenchymal liver cells. Furthermore, in an in vivo assay, HRS, and not other SR proteins, directly mediated EIIIB exon inclusion in the fibronectin transcript. This alternative splicing was dependent on a purine-rich region within the EIIIB exon to which HRS specifically bound. We have established that HRS has the potential to contribute to the regulation of fibronectin pre-mRNA splicing during liver growth. Changes in fibronectin forms may be important in modifying liver architecture during the proliferative response, thus providing a potential mechanism by which SR proteins may participate in cellular growth control.

Alternative Splicing↗

PubMed1997

Optical resolution of DL-alanine by using immobilized Aspergillus oryzae cells.

Mycelium pellets with diameters of 1-2 mm and containing abundant aminoacylase were obtained by the liquid fermentation of Aspergillus oryzae 3042. By the cross-linking method with reagents of gelatin and formaldehyde, the immobilized A. oryzae cells (IAC) were prepared with much higher activity and reactive properties. The effects of factors on enzymatic activity of IAC were investigated. When substrate concentration was less than 0.15 mol/L, the Michaelis-Menten mechanism was suitable for this reaction.

Alanine↗

PubMed1996

Ryanodine-sensitive component of calcium transients evoked by nerve firing at presynaptic nerve terminals.

Whether Ca2+ released from stores within the presynaptic nerve terminals also contributes to the Ca2+ elevation evoked by action potentials was tested in intact bullfrog sympathetic ganglia. Intraterminal Ca2+ transients (Delta[Ca2+]i) were evoked by electrical shocks to the presynaptic nerves at 20 Hz and were monitored by fura-2 fluorimetry. Ca2+ released through intraterminal ryanodine-sensitive channels accounted for 46% of the peak Ca2+ elevation. Moreover, in half of the terminals when intraterminal release was blocked by ryanodine, Delta[Ca2+]i reached a plateau at 200 +/- 24 nM. Because 20 Hz is a frequency favorable for the release of a neuropeptide, luteinizing hormone releasing hormone (LHRH) from these presynaptic nerve terminals, and because the threshold level for LHRH release is 186 nM, intraterminal Ca2+ release during nerve firing is likely to play a major role in regulating LHRH release. The intraterminal ryanodine channels were facilitated by caffeine as in other tissue. The releasable ryanodine-sensitive store could elevate the intraterminal [Ca2+] by an amount as high as 1.6 microM at a rate as fast as 250 nM/sec. The store could be refilled within 100 sec after a maximal discharge of its content by 20 Hz firing. Oscillation of [Ca2+]i evoked by 20 Hz nerve firing occurred in normal Ringer solution, in ryanodine, and in caffeine with a periodicity of approximately 10 sec. Besides the facilitatory effects on the ryanodine-sensitive channels, caffeine also had inhibitory effects on Delta[Ca2+]i via its action on a different process.

Animals↗

PubMed1996

Longitudinal relation between smoking and white blood cells.

Higher white blood cell counts in smokers compared with nonsmokers have been well documented, but the longitudinal relation between changes in smoking and changes in white blood cells has not been well described. Since 1984, data have been collected semiannually by the Multicenter AIDS Cohort Study (MACS), a four-center prospective cohort study of acquired immunodeficiency syndrome (AIDS) in homosexual men. The study population includes 2,435 participants who were human immunodeficiency virus (HIV) seronegative as of September 1994 and who contributed 20,918 person-visits for this analysis. For individuals who modified their smoking behavior, changes in white blood cell counts occurred primarily during the first 6 months following changes in the amount of cigarettes smoked. Among former smokers who resumed smoking, the extent of the increase in white blood cell count depended on the number of cigarettes smoked. Specifically, increases of 241, 340, and 740 cells/microliter were observed for smokers who resumed smoking < 1, 1 to < 2, and > or = 2 packs/day, respectively. Conversely, smokers who quit smoking had a decrease of white blood cell count: -32, -629, and -1,122 cells/microliter for men who previously smoked < 1, 1 to < 2, and > or = 2 packs/day, respectively. Long-term ex-smokers, however, still had higher white blood cell counts than did never smokers. There was a high within-individual correlation of white blood cell count in persons who reported a consistent level of smoking (i.e., average correlations between two white blood cell counts 6 years apart were 0.51 for never smokers, 0.48 for ex-smokers, 0.56 for men who smoked < 1 pack/day, and 0.43 for men who smoked > or = 1 pack/day). These analyses indicate an acute effect of changes in smoking on changes in white blood cell count, a residual effect of having been a smoker, and high long-term tracking for white blood cell count.

Adult↗

PubMed1996

Generation of an integrated transcription map of the BRCA2 region on chromosome 13q12-q13.

An integrated approach involving physical mapping, identification of transcribed sequences, and computational analysis of genomic sequence was used to generate a detailed transcription map of the 1. 0-Mb region containing the breast cancer susceptibility locus BRCA2 on chromosome 13q12-q13. This region is included in the genetic interval bounded by D13S1444 and D13S310. Retrieved sequences from exon amplification or hybrid selection procedures were grouped into physical intervals and subsequently grouped into transcription units by clone overlap. Overlap was established by direct hybridization, cDNA library screening, PCR cDNA linking (island hopping), and/or sequence alignment. Extensive genomic sequencing was performed in an effort to understand transcription unit organization. In total, approximately 500 kb of genomic sequence was completed. The transcription units were further characterized by hybridization to RNA from a series of human tissues. Evidence for seven genes, two putative pseudogenes, and nine additional putative transcription units was obtained. One of the transcription units was recently identified as BRCA2 but all others are novel genes of unknown function as only limited alignment to sequences in public databases was observed. One large gene with a transcript size of 10.7 kb showed significant similarity to a gene predicted by the Caenorhabditis elegans genome and the Saccharomyces cerevisiae genome sequencing efforts, while another contained a motif sequence similar to the human 2',3' cyclic nucleotide 3' phosphodiesterase gene. Several retrieved transcribed sequences were not aligned into transcription units because no corresponding cDNAs were obtained when screening libraries or because of a lack of definitive evidence for splicing signals or putative coding sequence based on computational analysis. However, the presence of additional genes in the BRCA2 interval is suggested as groups of putative exons and hybrid selected clones that were transcribed in consistent orientations could be localized to common physical intervals.

BRCA2 Protein↗

PubMed1996

Projecting disease when death is likely.

Projection disease incidence, prevalence, and net morbidity is often needed when individuals are likely to die, either disease free or after the disease has developed. Examples of this include remission of cancer or heart disease in elderly people who can die from these or other causes and occurrence of a particular acquired immune deficiency syndrome illness in human immunodeficiency virus type 1 (HIV-1) disease. Death is not an ancillary event but, rather, indicates either and end to disease morbidity or an end to risk to ever develop the disease. Thus, time to disease survival analyses that censor disease-free individuals at death can produce misleading results. The paper describes several useful quantifications of disease and death for this setting. A paradigm that utilizes Kaplan-Meier functions to estimate these quantities is introduced. The approach anchors on a four-stage disease/death model: stage A, living without disease; stage B, dead without ever developing disease; stage C, developed the disease and living; and stage D, dead after developing the disease. An application is made to projecting cytomegalovirus disease in a cohort of HIV-1-infected users of zidovudine and Pneumocystis prophylaxis from the Multicenter AIDS Cohort Study (MACS) during 1989-1993. At 3 years after a CD4+ count below 100/microliters, a man had an 18.7%, 46.3%, 5.3% or 29.9% chance, respectively, to be in stage A, B, C, or D. This man, on average, had 0.28 years of cytomegalovirus morbidity during these 3 years.

AIDS-Related Opportunistic Infections↗

PubMed1996

Survival from early, intermediate, and late stages of HIV infection.

OBJECTIVE: To estimate expected survival time among homosexual men infected with the human immunodeficiency virus type 1 (HIV-1) by (1) the calendar period before (1985-1988) and after (1989-1993) the widespread availability of acquired immunodeficiency syndrome (AIDS) treatments with antiretroviral and prophylactic interventions, and (2) stage of HIV disease. DESIGN: A prospective cohort study. A group of HIV-1-infected homosexual men were followed from July 1985 through June 1993 and evaluated every 6 months for the presence of clinical symptoms and measurement of the CD4 cell count. To measure the effectiveness of AIDS therapies in this nonrandomized study, we used 2 calendar periods as proxy measures of relative intensity of exposure to antiretroviral therapy. Stage of infection was defined by CD4 cell count and presence of HIV-related clinical symptoms or AIDS. SETTING AND STUDY PARTICIPANTS: Homosexual men infected with HIV-1 from the Multicenter AIDS Cohort Study. MAIN OUTCOME MEASURE: Survival time based on stage of HIV infection. RESULTS: The percentage of HIV-1-infected individuals free of AIDS and clinical symptoms at baseline who survived 2.5 years according to baseline CD4 cell counts of 0 to 0.100, 0.101 to 0.200, and 0.201 to 0.350 x 10(9)/L was 22%, 53%, and 83%, respectively, for the 1985-1988 calendar period, compared with 54%, 71%, and 91%, respectively, for men in the 1989-1993 calendar period. Among men free of AIDS with CD4 cell counts of greater than 0.350 x 10(9)/L, the relative hazard of mortality was 1.6 to 2.3 times higher for those with clinical symptoms compared with those free of clinical symptoms. CONCLUSIONS: Survival of AIDS-free HIV-1-infected individuals with CD4 cell counts of less than 0.350 x 10(9)/L has improved since antiretroviral and HIV prophylactic treatments have become available, but the long-term prognosis remains poor.

Antiviral Agents↗

PubMed1996

Endothelin(B) receptor activates NHE-3 by a Ca2+-dependent pathway in OKP cells.

To examine the mechanisms by which endothelin (ET) regulates the Na/H antiporter isoform, NHE-3, OKP cells were stably transfected with ET(A) and ET(B) receptor cDNA. In cells overexpressing ET(B), but not ET(A) receptors, ET-1 increased Na/H antiporter activity (JNa/H). This effect was inhibited by a nonselective endothelin receptor blocker and by a selective ET(B) receptor blocker but was not inhibited by an ET(A) selective receptor blocker. In ET(B)-overexpressing cells, 10(-8) M ET-1 inhibited adenylyl cyclase, but protein kinase A inhibition and pertussis toxin pretreatment did not affect Na/H antiporter activation by ET-1. ET-1 caused a transient increase in cell [Ca2+], followed by a sustained increase. Increases in cell [Ca2+] were partially inhibited by pertussis toxin. ET-1-induced increases in J(Na/H) were 50% inhibited by clamping cell [Ca2+] low with BAPTA, and by KN62, a Ca-calmodulin kinase inhibitor. Inhibitors of protein kinase C, cyclooxygenase, lipoxygenase, and cytochrome P450 and cyclic GMP were without effect. In ET(A)-overexpressing cells, ET-1 increased cell [Ca2+] but did not increase JNa/H. In summary, binding of ET-1 to ET(B) receptors increases Na/H antiporter activity in OKP cells, an effect mediated in part by increases in cell [Ca2+] and Ca-calmodulin kinase. Increases in cell [Ca2+] are not sufficient for Na/H antiporter activation.

Animals↗

PubMed1996

Occurrence of cytomegalovirus retinitis after human immunodeficiency virus immunosuppression.

OBJECTIVE: To estimate the incidence and prevalence of cytomegalovirus retinitis (CMV-R) in late-stage human immunodeficiency virus type 1 disease. DESIGN: Cohort study. SETTING: The Multicenter AIDS Cohort Study, an ongoing 10-year study of human immunodeficiency virus type 1-infected homosexual men with semiannual visits and CD4+ cell testing. STUDY PARTICIPANTS: Three hundred sixty-seven human immunodeficiency virus type 1-infected men from the Multicenter AIDS Cohort Study who were receiving zidovudine and Pneumocystis carinii prophylaxis and who had CD4+ cell counts fall below 0.10 x 10(9)/L (100/microL). MAIN OUTCOME MEASURES: Kaplan-Meier-type estimates for various longitudinal quantifications of incidence and prevalence of CMV-R were obtained. RESULTS: Among these 367 individuals, cytomegalovirus disease developed in 103, of whom 73 (71%) had ocular complications. At 4 years after the first CD4 cell count ( < 0.10 x 10(9)/L), the probability for these subjects to have (1) remained living without CMV-R was 11%, (2) died without experiencing CMV-R was 66%, (3) experienced CMV-R and be living was 6%, and (4) experienced CMV-R and died was 18%. During these 4 years, there was a 25% chance for the development of CMV-R and, on average, 0.211 person-years of CMV-R morbidity. Among those subjects in whom CMV-R developed, about 19% did have CMV-R before a CD4+ cell count of less than 0.05 x 10(9)/L ( < 50/microL) was observed, and 81% had CMV-R after the CD4+ cell count reached this threshold. CONCLUSION: These estimates may be relevant to current clinical practice and help in allocating resources and planning for treatment and prophylaxis against cytomegalovirus disease.

AIDS-Related Opportunistic Infections↗

PubMed1996

Factors accounting for different responses of pulmonary and cerebral vessels to hypoxia.

The roles of sympathicus, sensory neuropeptides (SNP), cyclooxygenase metabolites (COX-M), lipoxygenase metabolites (LOX-M), endothelium derived relaxing factor (EDRF), reactive oxygen (ROS) and potassium channels (PC) in the hypoxic pulmonary vasoconstriction (HPV) and hypoxic cerebral vasodilation (HCVD) were investigated in intact rats, rabbits and dogs. The results showed that during hypoxia, the excitation of sympathicus caused a constriction of both pulmonary and cerebral vessels, while SNP, EDRF and the opening of voltage sensitive PC caused the dilation of both of them; LOX-M mediated HPV and HCVD, COX-M might serve as their modulators; the blockade of ATP sensitive PC induced by hypoxia mediated HPV, but had no effect on HCVD; the reduction of O2-. in the lung might potentiate HPV, however, O2-. remained unchanged in brain during hypoxia. It is suggested that the alterations of LOX-M, ROS and the ATP sensitive PC are the factors accounting for the difference in the response of pulmonary and cerebral vessels to hypoxia.

Animals↗

PubMed1996

Immunoregulatory role of neurotransmitters.

The nervous and endocrine systems modulate the immune system functions through releasing neurotransmitters, neuropeptides and endocrine hormones as they regulate the other physiological functions. The immune system in turn communicates with the nervous and endocrine systems through secreting immunocompetent substances. In this report we review our concepts and evidence concerning the immunoregulatory role of acetylcholine (ACh) and monoamine neurotransmitters which include noradrenaline (NA), 5-hydroxytryptamine (5-HT) and dopamine (DA). The immunoregulatory role comprises two aspects, the modulation of immune functions by neurotransmitters and the effect of the immune system on nervous system functions. The inhibition of ACh biosynthesis in the central nervous system (CNS) caused the enhancement of the humoral immune response of rats to sheep red blood cells (SRBC); by contrast, the inhibition of acetyl-cholinesterase (AChE) activity in the CNS resulted in the suppression of the immune response. It seems that ACh in the brain plays an immunoinhibitory role. The role can be blocked by atropine, a muscarinic antagonist, but not by hexamethonium, a nicotinic antagonist. During the humoral immune response (days 3-6 after SRBC injection), activity of AChE in the hypothalamus and hippocampus was strikingly lower. It is suggested that a functional connection is present in the ACh of the brain and the immune system. In vitro, ACh at 10(-9) to 10(-4) mol/l dose range significantly strengthened the spleen cell proliferation induced by concanavalin (Con A). The action of ACh only occurred either before or just after T lymphocytes were activated through muscarinic cholinergic receptors. In vivo, the depletion of monoamine neurotransmitters or only NA in the CNS caused the impairment of the anti-SRBC response of rats. During the phases of days 2-7 post-immunization, the metabolic alterations of NA, 5-HT and DA emerged in the CNS and the lymphoid organs of rats, which mainly exhibited that in the peak periods of the antibody response, the metabolism of the monoamine neurotransmitters in the hypothalamus and hippocampus was markedly increased, but NA content in the spleen and thymus was significantly decreased. These results provide evidence for the bidirectional information exchange network between the monoamine neurotransmitters and the immune system. Exposure to NA (at 10(-8)-10(-5) mol/l concentration range) in vitro was shown to inhibit the Con A-induced proliferation of the rat spleen cells. This effect of NA was related to the early events involved in the initiation of T cell proliferation and was mediated by either alpha- or beta-adrenergic receptors. The evidence that altering 5-HT level in the central or peripheral nervous systems through various ways of administering the drugs to regulate 5-HT biosynthesis led to the variations of the antibody response, and that cyproheptadine, an antagonist of serotoninergic receptors, can block the action of 5-HT show that 5-HT may exert an immunoinhibitory effect, which appears to be mediated via the peripheral mechanism to relate to the 5-HT receptors. However, the antibody response can cause changes in 5-HT metabolism in the CNS. The possible reasons for these results are discussed. Collectively, the antibody response arouses the metabolic variations of ACh, NA, 5-HT and DA in the central and peripheral nervous systems and then, these alterations can in turn influence immune function through neurotransmitter relevant receptors present on the immunocytes. The purpose of this interaction is most likely to maintain the homeostasis of the immune and other physiological functions.

Adjuvants, Immunologic↗

PubMed1996

The complete BRCA2 gene and mutations in chromosome 13q-linked kindreds.

Breast carcinoma is the most common malignancy among women in developed countries. Because family history remains the strongest single predictor of breast cancer risk, attention has focused on the role of highly penetrant, dominantly inherited genes in cancer-prone kindreds (1). BRCA1 was localized to chromosome 17 through analysis of a set of high-risk kindreds (2), and then identified four years later by a positional cloning strategy (3). BRCA2 was mapped to chromosomal 13q at about the same time (4). Just fifteen months later, Wooster et al. (5) reported a partial BRCA2 sequence and six mutations predicted to cause truncation of the BRCA2 protein. While these findings provide strong evidence that the identified gene corresponds to BRCA2, only two thirds of the coding sequence and 8 out of 27 exons were isolated and screened; consequently, several questions remained unanswered regarding the nature of BRCA2 and the frequency of mutations in 13q-linked families. We have now determined the complete coding sequence and exonic structure of BRCA2 (GenBank accession #U43746), and examined its pattern of expression. Here, we provide sequences for a set of PCR primers sufficient to screen the entire coding sequence of BRCA2 using genomic DNA. We also report a mutational analysis of BRCA2 in families selected on the basis of linkage analysis and/or the presence of one or more cases of male breast cancer. Together with the specific mutations described previously, our data provide preliminary insight into the BRCA2 mutation profile.

BRCA2 Protein↗

PubMed1996

BRCA2 germline mutations in male breast cancer cases and breast cancer families.

The breast cancer susceptibility gene, BRCA2 on chromosome 13q12-13, was recently isolated. Mutations in BRCA2 are thought to account for as much as 35% of all inherited breast cancer as wall as a proportion of inherited ovarian cancer. Many BRCA2-linked families also contain cases of male breast cancer. We have analysed germline DNA from 50 males with breast cancer (unselected for family history) and 26 individuals from site-specific female breast and breast-ovarian cancer families for mutations in BRCA2. All 17 breast-ovarian cancer families have been screened for BRCA1 coding region mutations and none were detected. Conformation-sensitive gel electrophoresis (CSGE) analysis of PCR-amplified DNA followed by direct sequencing was used to detect sequence variants. Three of eleven individuals carry the same mutation, all are of Ashkenazi Jewish descent, supporting the observation by Neuhausen et al. in this issue that there is a common mutation in this population. Eleven truncating mutations and nine polymorphisms were identified -- all were coding region variants. No loss-of-transcript mutations were identified in the sixteen samples for which this analysis was possible. Seven of the nine disease-associated mutations were detected in the 50 men with breast cancers; for thus in our series, BRCA2 mutations account for 14% of male breast cancer, all but one of which had a family history of male and/or female breast cancer.

BRCA2 Protein↗