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D J Venter

Publications and source records attributed to D J Venter.

At least 37 records · Page 2Linked to original sources
PubMed1999

Expression of the human P2Y6 nucleotide receptor in normal placenta and gestational trophoblastic disease.

The P2Y family of purinergic receptors are members of the G-protein-coupled receptor superfamily. The P2Y6 subtype is expressed at particularly high levels in the placenta, suggesting that P2Y6 plays an important role in placental function. However, the cellular localization of P2Y6 within the placenta is unknown. This study examined the expression of P2Y6 in first-trimester and full-term placental tissues, as well as examples of gestational trophoblastic disease, by Northern blot analysis and in situ hybridization. P2Y6 message was present at similar levels in first-trimester and full-term placenta, and in situ hybridization revealed that message was most abundant in the cytotrophoblast of the villi and chorionic plate at both gestational stages. The syncytiotrophoblast harbored lower levels of P2Y6 in first-trimester placenta, and by full-term, the syncytiotrophoblast only focally expressed P2Y6 transcripts. Neither the intermediate trophoblast nor nontrophoblastic elements of the placenta expressed P2Y6. Molar disease expressed P2Y6 in the villous trophoblast but not in the proliferative intermediate trophoblast, recapitulating the pattern of first-trimester placenta. Neither choriocarcinoma nor the choriocarcinoma cell lines JEG-3 and JAr expressed P2Y6 transcript. These findings reveal that P2Y6 mRNA production is highly characteristic of the epithelial-like cytotrophoblast and syncytiotrophoblast, whereas expression is absent in the mesenchymal-like intermediate trophoblast. Thus, P2Y6 may play an important role in trophoblastic development, differentiation, and neoplasia.

Blotting, Northern↗
PubMed1999

Population-based estimate of the average age-specific cumulative risk of breast cancer for a defined set of protein-truncating mutations in BRCA1 and BRCA2. Australian Breast Cancer Family Study.

The average breast cancer risk for carriers of a germ-line mutation in BRCA1 or BRCA2 (penetrance) has been estimated from the multiple-case families collected by the Breast Cancer Linkage Consortium (BCLC) to be approximately 80% to age 70. However, women now being tested for these mutations do not necessarily have the intense family history of the BCLC families. Testing for protein-truncating mutations in exons 2, 11, and 20 of BRCA1 and exons 10 and 11 of BRCA2 was conducted in a population-based sample of 388 Australian women with breast cancer diagnosed before age 40. Onset of breast cancer was analyzed in the known and potential mutation-carrying first- and second-degree female relatives of cases found to carry a mutation. Of the 18 mutation-carrying cases (9 BRCA1 and 9 BRCA2), only 5 (1 BRCA1 and 4 BRCA2) had at least one affected relative, so family history of breast cancer was not a strong predictor of mutation status in this setting. The risk in mutation carriers was, on average, 9 times the population risk [95% confidence interval (CI), 4-23; P < 0.001]. Penetrance to age 70 was 40% (95% CI, 15-65%), about half that estimated from BCLC families. By extrapolation, approximately 6% (95% CI, 2-20%) of breast cancer before age 40 may be caused by protein-truncating mutations in BRCA1 or BRCA2. Breast cancer risk in BRCA1 or BRCA2 mutation carriers may be modified by other genetic or environmental factors. Genetic counselors may need to take into account the family history of the consultand.

Adult↗
PubMed1998

The histologic phenotypes of breast carcinoma occurring before age 40 years in women with and without BRCA1 or BRCA2 germline mutations: a population-based study.

BACKGROUND: Women with breast carcinoma diagnosed before age 40 years have a greater prevalence of germline BRCA1 and BRCA2 mutations than women with breast carcinoma diagnosed at older ages. Several recognizable histologic characteristics have been identified in breast carcinoma from studies of BRCA1/2 mutation carriers who belong to multiple-case families. The authors attempted to determine whether breast carcinoma occurring before age 40 years in BRCA1 or BRCA2 mutation carriers who were not selected for family history could be distinguished histologically from one another and from breast carcinoma in women of a similar age without a germline BRCA1 or BRCA2 mutation. METHODS: The study undertook a histologic assessment of breast carcinomas diagnosed before age 40 years identified from a population-based study. RESULTS: Breast carcinoma in BRCA1 mutation carriers was associated with a distinct histologic appearance; these tumors were high grade, and had exceptionally high mean mitotic counts, a syncytial growth pattern, pushing margins, and confluent necrosis. Atypical medullary carcinoma was overrepresented in BRCA1 mutation carriers. All low grade tumors and tumors with low mitotic rates belonged to the group without BRCA1 or BRCA2 mutations. Pleomorphic lobular carcinomas and extensive intraduct carcinomas were more common in BRCA2 mutation carriers. CONCLUSIONS: Breast carcinoma occurring in women with a germline BRCA1 or BRCA2 mutation have recognizable histologic phenotypes, which may be useful in identifying individuals more likely to carry germline mutations. Histologic examination of breast carcinoma should become an important part of the evaluation of women seeking genetic testing for germline mutations in these breast carcinoma susceptibility genes.

Adult↗
PubMed1998

CFTR deltaF508 carrier status, risk of breast cancer before the age of 40 and histological grading in a population-based case-control study.

There has been recent interest in the risk of various cancers in cystic fibrosis (CF) patients and carriers of cystic fibrosis transmembrane conductance regulator (CFTR) mutations. It has been proposed that a CFTR mutation may protect against breast cancer, based on evidence that elevated extracellular adenosine triphosphate (ATP) is known to inhibit breast cancer cell line growth and that CFTR pumps ATP out of epithelial cells. A CFTR mutation would therefore result in higher concentrations of serum ATP. A CFTR knockout mouse model had high serum concentrations of ATP and showed reduced breast tumour implantibility and decreased breast cancer growth rates. We have evaluated the relationship between the deltaF508 CFTR mutation and the risk of breast cancer before the age of 40. The deltaF508 CFTR mutation carrier rate in 272 cases (2.2%) was no different from the carrier rate observed in 171 controls (1.8%). If there was a protective effect resulting from the postulated elevation in serum ATP levels, tumours arising in deltaF508 CFTR carriers would have been expected to be generally less aggressive. When the histological features of the breast cancers with a deltaF508 CFTR mutation were reviewed and graded using a combined architectural and cytological grading system, all were found to be grade III, poorly differentiated tumours, contrary to the predictions. A combination of our data with other large population-based samples of cases and controls is required to resolve this issue.

Adenosine Triphosphate↗
PubMed1998

Estrogen receptor polymorphism at codon 325 and risk of breast cancer in women before age forty.

BACKGROUND: The estrogen receptor (ER) protein is believed to play a role in the development and progression of breast cancer. In a previously published U.S. clinic-based study, a polymorphism in the ER gene (codon 325, CCC --> CCG) was found to be more common in 34 case subjects with a family history of breast cancer than in 154 case subjects without such a history (mean allele frequencies +/- standard error = 0.28+/-0.05 versus 0.11+/-0.02; P<.001). To determine whether this polymorphism is a risk factor for early-onset breast cancer, we conducted a population-based, case-control-family study in Australia. METHODS: Case subjects under the age of 40 years with a first primary breast cancer and control subjects, frequency-matched to the case subjects on the basis of age, and their relatives were interviewed to assess the family history of breast cancer. Polymorphism status of the ER gene was determined for 388 case subjects and 294 control subjects. All statistical tests were two-tailed. RESULTS: There was no association between ER gene polymorphism status and breast cancer, before or after adjustment for risk factors. There was no difference in allele frequencies between case subjects and control subjects (0.232+/-0.015 versus 0.209+/-0.017; P = .4) or between women with and without a family history of breast cancer (P = .3), irrespective of case-control status. The findings were not altered when different definitions of family history of breast cancer were used and when allele frequencies were adjusted for residence and country of birth. CONCLUSION: We found no evidence that the ER codon 325 polymorphism is associated with breast cancer before the age of 40 years or with a family history of breast cancer, despite ample power to detect effects half the magnitude of those previously reported.

Adult↗
PubMed1998

Multiple leiomyosarcomas of both donor and recipient origin arising in a heart-lung transplant patient.

The occurrence of Epstein-Barr virus-associated smooth-muscle tumors in immunocompromised patients has been reported, particularly in the pediatric population. In posttransplantation tumors, the tissue of origin has been either donor or recipient. Mixed-genotype sarcomas within the same patient have not yet been reported. We describe the occurrence of multiple leiomyosarcomas of both donor (arising in the lung allograft) and recipient (arising in the host liver) origin in a 15-year-old boy 3 years after heart-lung transplantation. Analysis of premortem lung tumors demonstrated the presence of Epstein-Barr virus DNA. Despite decreasing immunosuppression and commencing acyclovir, the patient died of systemic Pseudomonas infection. Immunohistochemical analysis revealed that both lung and liver tumors were negative for the Epstein-Barr virus receptor (CD21), and suggests that Epstein-Barr virus entry into the cells was not via this receptor but via an alternate mechanism such as cell fusion.

Adolescent↗
PubMed1998

Tissue hyperplasia and enhanced T-cell signalling via ZAP-70 in c-Cbl-deficient mice.

The c-Cbl protein is tyrosine phosphorylated and forms complexes with a wide range of signalling partners in response to various growth factors. How c-Cbl interacts with proteins, such as Grb2, phosphatidylinositol 3-kinase, and phosphorylated receptors, is well understood, but its role in these complexes is unclear. Recently, the Caenorhabditis elegans Cbl homolog, Sli-1, was shown to act as a negative regulator of epidermal growth factor receptor signalling. This finding forced a reassessment of the role of Cbl proteins and highlighted the desirability of testing genetically whether c-Cbl acts as a negative regulator of mammalian signalling. Here we investigate the role of c-Cbl in development and homeostasis in mice by targeted disruption of the c-Cbl locus. c-Cbl-deficient mice were viable, fertile, and outwardly normal in appearance. Bone development and remodelling also appeared normal in c-Cbl mutants, despite a previously reported requirement for c-Cbl in osteoclast function. However, consistent with a high level of expression of c-Cbl in the hemopoietic compartment, c-Cbl-deficient mice displayed marked changes in their hemopoietic profiles, including altered T-cell receptor expression, lymphoid hyperplasia, and primary splenic extramedullary hemopoiesis. The mammary fat pads of mutant female mice also showed increased ductal density and branching compared to those of their wild-type littermates, indicating an unanticipated role for c-Cbl in regulating mammary growth. Collectively, the hyperplastic histological changes seen in c-Cbl mutant mice are indicative of a normal role for c-Cbl in negatively regulating signalling events that control cell growth. Consistent with this view, we observed greatly increased intracellular protein tyrosine phosphorylation in thymocytes following CD3epsilon cross-linking. In particular, phosphorylation of ZAP-70 kinase in thymocytes was uncoupled from a requirement for CD4-mediated Lck activation. This study provides the first biochemical characterization of any organism that is deficient in a member of this unique protein family. Our findings demonstrate critical roles for c-Cbl in hemopoiesis and in controlling cellular proliferation and signalling by the Syk/ZAP-70 family of protein kinases.

Animals↗
PubMed1998

Expression of the P2Y6 purinergic receptor in human T cells infiltrating inflammatory bowel disease.

The human P2Y6 receptor is a member of the G-protein-coupled P2Y purinergic receptor family that responds to extracellular uridine diphosphate (UDP). In previous work, we cloned the human P2Y6 receptor from an activated T-cell library, and others have shown that it is expressed as a 1.9-kb transcript in several lymphoid tissues. This suggests a role for P2Y6 in T-cell function. However, the precise cellular expression pattern and regulation of P2Y6 in immune cells have not yet been established. In this study, we have examined the expression of P2Y6 in a range of tissues containing leukocytes by a combination of in situ hybridization (ISH), Northern blot analysis, and RT-PCR. Northern hybridization revealed that activated peripheral T cells show increased levels of P2Y6 mRNA. Furthermore, RT-PCR analysis of CD4+ and CD8+ subsets illustrated strong expression in both activated CD4+ and CD8+ T cells. Stimulation of resting and activated T cells with the P2Y6 ligand UDP caused a rise in the intracellular free calcium concentration in only the activated subset, indicating the presence of functional receptor. By ISH, P2Y6 expression was detected in the T cells of the thymic medulla and spleen, whereas no signal was detected in the bone marrow, fetal liver, or lymph nodes. T cells are thought to play an important role in the pathogenesis of inflammatory bowel disease (IBD), and because a recent finding has suggested a role for extracellular nucleotides in mediating colonic epithelial cell damage in IBD, we speculated that the P2Y6 nucleotide receptor may be expressed in the T cells infiltrating IBD. ISH results reveal that P2Y6 is highly expressed in the T cells infiltrating active IBD, whereas P2Y6 expression was absent from the T cells of unaffected bowel. These results demonstrate expression and regulation of P2Y6 expression in T cells, and suggest a role for P2Y6 in the pathogenesis of IBD-mediated intestinal damage.

Blotting, Northern↗
PubMed1997

Chromosomal localization of the human P2y6 purinoceptor gene and phylogenetic analysis of the P2y purinoceptor family.

The G-protein-coupled P2Y purinoceptors mediate a variety of physiological effects in response to extracellular nucleotides. With the recent discovery of several new members from a variety of species, the P2Y purinoceptor family now encompasses types P2Y1 to P2Y6. By fluorescence in situ hybridization and utilization of the National Center for Biotechnology Information (NCBI) database, the human P2Y6 gene was localized to chromosome 11q13.5, between polymorphic markers D11S1314 and D11S916. NCBI database analysis of the remaining human P2Y purinoceptor genes revealed that P2Y2 and P2Y6 mapped to within less than 4 cM, and thus constitute the first described chromosomal clustering of this gene family. Phylogenetic analysis of the P2Y purinoceptor family demonstrated the presence of five evolutionary branches and suggests the occurrence of an ancient gene duplication event.

Chromosome Mapping↗
PubMed1997

Isolation of a candidate human telomerase catalytic subunit gene, which reveals complex splicing patterns in different cell types.

Telomerase is a multicomponent reverse transcriptase enzyme that adds DNA repeats to the ends of chromosomes using its RNA component as a template for synthesis. Telomerase activity is detected in the germline as well as the majority of tumors and immortal cell lines, and at low levels in several types of normal cells. We have cloned a human gene homologous to a protein from Saccharomyces cerevisiae and Euplotes aediculatus that has reverse transcriptase motifs and is thought to be the catalytic subunit of telomerase in those species. This gene is present in the human genome as a single copy sequence with a dominant transcript of approximately 4 kb in a human colon cancer cell line, LIM1215. The cDNA sequence was determined using clones from a LIM1215 cDNA library and by RT-PCR, cRACE and 3'RACE on mRNA from the same source. We show that the gene is expressed in several normal tissues, telomerase-positive post-crisis (immortal) cell lines and various tumors but is not expressed in the majority of normal tissues analyzed, pre-crisis (non-immortal) cells and telomerase-negative immortal (ALT) cell lines. Multiple products were identified by RT-PCR using primers within the reverse transcriptase domain. Sequencing of these products suggests that they arise by alternative splicing. Strikingly, various tumors, cell lines and even normal tissues (colonic crypt and testis) showed considerable differences in the splicing patterns. Alternative splicing of the telomerase catalytic subunit transcript may be important for the regulation of telomerase activity and may give rise to proteins with different biochemical functions.

Alternative Splicing↗
PubMed1996

Spatiotemporally exact cDNA libraries from quail embryos: a resource for studying neural crest development and neurocristopathies.

The neural crest is of fundamental importance in the developments of the head and peripheral nervous system, in the evolution of the vertebrates, and clinically because it gives rise to developmental abnormalities and neoplasms in humans. We have established a resource for studying the development of the neural crest by systematically constructing cDNA libraries from spatiotemporally exact neural crest and related cell populations. Neural crest populations were obtained from vagal and thoracic axial levels and from branchial arches, at premigratory and early and late migratory stages, at localization stages, and after differentiation into dorsal root ganglion cells, Schwann cells, sympathetic neurons, adrenal medullary cells, and melanocytes. Libraries were constructed using several methods developed to approach the issue of making representative libraries from small amounts of tissue. The fidelity and usefulness of the libraries were tested, and this revealed that they expressed a variety of sequences such as integrins, CAMs, growth factors and their receptors, protein-tyrosine kinases, and phosphatases. Differential display also revealed a unique combination of cDNA species. We then selected libraries spatiotemporally appropriate for epithelium-mesenchyme transformation and probed for TGF-beta-related sequences. As anticipated, we confirmed the presence of TGF-beta 2 and dorsalin-1 but could not detect TGF-beta 1. We also revealed new expression sites, defined by the origin of the libraries, of receptors known to be expressed elsewhere (Tsk 7l; TBRII). We anticipate that this collection of cDNA libraries will be of use in studying normal and abnormal neural crest development, by both homology searches and differential expression approaches, with spatiotemporal expression information being inherent in the initial screen.

Animals↗
PubMed1996

Molecular cloning and sequencing of a novel human P2 nucleotide receptor.

A novel human P2 nucleotide receptor has been cloned from a T-cell cDNA library. The predicted amino acid sequence shows characteristics of a G-protein-coupled receptor, and shares 88% homology with a recently characterised rat P2 nucleotide receptor sequence. Distinctive features include an extremely short cytoplasmic tail with only one putative protein kinase C phosphorylation site. Northern blot analysis revealed a 1.9 kb transcript expressed in the placenta.

Amino Acid Sequence↗
PubMed1996

Down's syndrome-like skeletal abnormalities in Ets2 transgenic mice.

Expression of Ets2, a proto-oncogene and transcription factor, occurs in a variety of cell types. During murine development it is highly expressed in newly forming cartilage, including in the skull precursor cells and vertebral primordia. Ets2 is located on human chromosome 21 (ref. 8) and is overexpressed in Down's syndrome (trisomy 21). Here we generate transgenic mice to investigate the consequences of overexpression of Ets2. We find that mice with less than 2-fold Ets2 overexpression in particular organs develop neurocranial, viscerocranial and cervical skeletal abnormalities. These abnormalities have similarities with the skeletal anomalies found in trisomy-16 mice and humans with Down's syndrome, in which the gene dosage of Ets2 is increased. Our results indicate that Ets2 has a role in skeletal development and implicate the overexpression of Ets2 in the genesis of some skeletal abnormalities that occur in Down's syndrome.

Abnormalities, Multiple↗
PubMed1995

Molecular cloning and sequencing of the gene encoding a sheep arginine vasopressin type 1a receptor.

The gene for the sheep arginine vasopressin type 1a (V1a) receptor subtype was cloned from a genomic library. The deduced amino acid sequence shows characteristics of a G-protein coupled receptor and high sequence identity to human and rat V1a receptor sequences (81% and 73%, respectively). Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed a tissue distribution consistent with a type V1a receptor. The genomic DNA (7.1 kb) contains a 1586 bp intron between the putative 6th and 7th transmembrane domains.

Amino Acid Sequence↗
PubMed1995

Disseminated, multiclonal Epstein-Barr virus-associated lymphoproliferative disease in a patient with hematological and immunological anomalies. Molecular analysis correlates with morphological appearance.

We report a case of a 21-year-old woman with hematopoietic, immunological, and congenital dysmorphic abnormalities, who died following rapidly progressive, disseminated Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD). Polymerase chain reaction (PCR) amplification of formalin-fixed paraffin-embedded tissue showed differences in the clonality of each separate lymphoproliferative lesion examined, as determined by immunoglobulin heavy chain (IgH) gene rearrangement. PCR analysis also demonstrated that all lesions contained EBV genome. Since DNA had been extracted from paraffin blocks, a direct comparison of morphology and clonality could be made in each individual lesion. The evidence from this study indicates that the monoclonal tumors arose de novo in multiple sites and that the polyclonal background observed in some lesions reflected a substantial concomitant inflammatory response.

Blotting, Southern↗
PubMed1995

Primary cutaneous Ewing's sarcoma/peripheral primitive neuroectodermal tumors in childhood. A molecular, cytogenetic, and immunohistochemical study.

Childhood cutaneous and subcutaneous malignancies are rare and include metastatic tumors of diverse histogenesis as well as primary lesions, such as sweat gland carcinomas. Some cutaneous malignancies exhibit a small round cell tumor morphology with few definitive differentiating features; they can thus pose a significant diagnostic problem. We describe two primary malignancies of the skin and superficial subcutis, which were originally diagnosed as sweat gland carcinomas on the basis of their morphological features. A cytogenetic analysis performed on one of these lesions showed the t(11;22)(q24;q12) rearrangement, believed to be unique to the Ewing's sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) group of neoplasms. In view of this unexpected result, reverse transcriptase-polymerase chain reaction analysis was performed on both lesions and showed that they expressed EWS/FLI-1 fusion gene mRNA transcripts, the molecular equivalent of t(11;22)(q24;q12). The two tumors also had an immunohistochemical profile suggesting ES/pPNET, including strong expression of the MIC2 antigen. Both patients were treated with wide local excision, and one was given a course of chemotherapy. Neither patient showed evidence of tumor elsewhere after follow-up periods of 2 years and 16 years. These findings suggest that these tumors are indeed a form of primary ES/pPNET arising in the skin or superficial subcutis, which may be of low-grade malignancy and curable by local surgery.

Base Sequence↗
PubMed1994

Lymphoproliferative disease of donor origin arising in patients after orthotopic liver transplantation.

BACKGROUND: Lymphoproliferative disease is a well recognized complication of organ transplantation and in many cases is associated with Epstein-Barr virus (EBV) infection. It is widely though that posttransplantation lymphoproliferative disease (PTLPD) arises from recipient lymphoid cells. However, solid organ allografts are likely to include donor lymphoid tissue around or within the transplanted organ. Therefore, it is possible that transplanted donor lymphocytes may proliferate to form PTLPD: METHODS: The genetic origin of tumor cells was determined by microsatellite DNA fingerprinting using the polymerase chain reaction (PCR). Their EBV association and clonality were established by PCR amplification of DNA extracted from formalin fixed, paraffin embedded tissue using primers to conserved regions of the EBV genome and the immunoglobulin heavy chain gene, respectively. RESULTS: The authors have demonstrated two cases of lymphoproliferative disease that were derived from donor lymphocytes in orthotopic liver transplant recipients. In both cases, the proliferating cells were EBV DNA positive. Furthermore, the PTLPD was restricted to allograft tissue around the porta hepatis. However, the two cases differed in their clonal properties and response to treatment: one case was oligoclonal and regressed after antiviral therapy and a modest reduction of immunosuppression, whereas the other contained two clonal populations and was controlled only after treatment with antineoplastic chemotherapy. CONCLUSION: This study has demonstrated two cases of PTLPD that were derived from donor lymphoid tissue. Although both cases were associated with EBV and remained localized to allograft tissue, their clonality and response to therapy differed.

Adult↗