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Josephine C Dorsman

Publications and source records attributed to Josephine C Dorsman.

12 recordsLinked to original sources
PubMed2006

Fanconi anemia is associated with a defect in the BRCA2 partner PALB2.

The Fanconi anemia and BRCA networks are considered interconnected, as BRCA2 gene defects have been discovered in individuals with Fanconi anemia subtype D1. Here we show that a defect in the BRCA2-interacting protein PALB2 is associated with Fanconi anemia in an individual with a new subtype. PALB2-deficient cells showed hypersensitivity to cross-linking agents and lacked chromatin-bound BRCA2; these defects were corrected upon ectopic expression of PALB2 or by spontaneous reversion.

BRCA2 Protein↗
PubMed2006

BRCA1 and p53 protein expression in cultured ovarian surface epithelial cells derived from women with and without a BRCA1 germline mutation.

AIM: Mutations in the BRCA1 and TP53 genes are early genetic events leading to (hereditary) ovarian carcinoma. The human ovarian surface epithelium (OSE) is considered the tissue of origin of at least a subset of these tumours. Therefore, OSE cell cultures derived from women harbouring BRCA1 germline mutations can be a potential model to study hereditary ovarian carcinogenesis. In fact, previous in vitro studies indicate phenotypical differences between OSE from women with and without such germline mutations. Therefore, we have assessed whether differences in the expression of BRCA1 and p53 proteins in cultured OSE cells could contribute to these observations. STUDY DESIGN: Thirty-two OSE cultures derived from women harbouring a BRCA1 mutation (Predisposed OSE [POSE]) and ten cultures from women without a cancer predisposition (Non predisposed OSE [NPOSE]) were grown under standard conditions. Immunocytochemistry was performed to assess the expression of the BRCA1- and p53 proteins. Ki67 immunocytochemical expression was assessed to determine possible differences in cell cycle status between the two groups. In addition, to study whether wild type p53 was expressed, induction of p53 by cis-platinum was assessed by Western blot. RESULTS: On the basis of Ki67 expression, three different groups were analyzed. In the group with all cultures that expressed Ki67 no significant difference was observed in BRCA1 (P = 0.19) and p53 expression (P = 0.09). In the group with moderate to high Ki67 expression no difference in BRCA1 expression (P = 0.50) was observed. However, p53 expression was significantly lower in the case group (P = 0.01). The same observation for p53 was made in the group with only high Ki67 expression (P = 0.02). Furthermore, the expression of both BRCA1 and p53 positively correlates with Ki67 expression. In POSE and NPOSE, p53 was induced by cis-platinum to a similar extent. CONCLUSION: Our study indicates differences in the expression of p53, but not in the expression of BRCA1 between POSE and NPOSE. In addition, our findings do suggest the absence of losses of the wild type BRCA1 and p53 genes in the studied OSE cultures. This indicates that losses in these genes cannot account for observed differences in phenotypical traits between POSE and NPOSE, but that differences in levels of p53 might contribute.

Adult↗
PubMed2006

Serous borderline tumor of the ovary presenting with cervical lymph node involvement: a report of 3 cases.

Supradiaphragmatic lymhadenopathy is extremely rare in patients with a serous borderline ovarian tumor (BOT), and clinically difficult to recognize. We describe 3 cases of serous BOT that primarily presented with arm thrombosis due to supradiaphragmatic lymphadenopathy. In all the 3 cases, fine needle aspiration cytology initially indicated metastatic adenocarcinoma. The primary tumor was not immediately apparent, and multiple diagnostic examinations had to be done before the definitive diagnosis of serous BOT, International Federation of Gynecology and Obstetrics stage IV could be made. In the meanwhile, erroneous therapies had been given in 1 case. After surgical removal of the adnexal masses and full surgical staging, all the 3 patients remained free of disease after a follow-up period of 48 to 84 months. In conclusion, supradiaphragmatic lymph node involvement can be present in patients with serous BOTs, and can even be the presenting symptom. When fine needle aspiration cytology of such a lymph node is compatible with adenocarcinoma of unknown primary, serous BOT should be included in the differential diagnosis and pelvic examination should be performed.

Adenocarcinoma↗
PubMed2005

Small N-terminal mutant huntingtin fragments, but not wild type, are mainly present in monomeric form: Implications for pathogenesis.

N-terminal fragments of huntingtin containing an expanded polyglutamine stretch play an important role in the molecular pathogenesis of Huntington's disease. Their ultimate accumulation in insoluble protein aggregates constitutes an important pathological hallmark of Huntington's disease. We report on systematic biochemical comparison studies of soluble wild type and mutant N-terminal huntingtin fragments. The results show that soluble wild type exon 1 fragments are predominantly present in higher molecular weight complexes with a molecular size of approximately 300 kDa, while their mutant counterparts are mainly present in their monomeric form. In contrast, longer N-terminal fragments corresponding to peptides produced by caspase cleavage do not display these differential properties. These findings suggest that especially an increased amount of monomeric form of small N-terminal mutant huntingtin fragments may facilitate aberrant interactions both with itself via the polyglutamine stretch and with other proteins and thereby contribute to molecular pathogenesis.

Animals↗
PubMed2005

Mutant huntingtin represses CBP, but not p300, by binding and protein degradation.

Huntington's disease can be used as a model to study neurodegenerative disorders caused by aggregation-prone proteins. It has been proposed that the entrapment of transcription factors in aggregates plays an important role in pathogenesis. We now report that the transcriptional activity of CBP is already repressed in the early time points by soluble mutant huntingtin, whereas the histone acetylase activity of CBP/p300 is gradually diminished over time. Mutant huntingtin bound much stronger to CBP than normal huntingtin, possibly contributing to repression. Especially at the later time points, CBP protein level was gradually reduced via the proteasome pathway. In sharp contrast, p300 was unaffected by mutant huntingtin. This selective degradation of CBP was absent in spinocerebellar ataxia 3. Thus, mutant huntingtin specifically affects CBP and not p300 both at the early and later time points, via multiple mechanisms. In addition to the reduction of CBP, also the altered ratio of these closely related histone acetyltransferases may affect chromatin structure and transcription and thus contribute to neurodegeneration.

Animals↗
PubMed2005

Epitope mapping of monoclonal antibody 4C8 recognizing the protein huntingtin.

Huntington's disease is a dominantly inherited, devastating neurodegenerative disorder, caused by a polyglutamine expansion (>37) in the N-terminal region of huntingtin, a protein of unknown function. In patients and normal individuals, N-terminal fragments of huntingtin are found, and the N-terminal fragments of mutant huntingtin are cytotoxic. The functions of wild-type huntingtin and the mechanisms underlying the toxic effects of mutant huntingtin are still ill defined. To get more insight into these topics, monoclonal antibodies (MAbs) are indispensable tools. Antibodies raised against the N-terminus are especially important. Among these, the 4C8 mouse MAb has been extensively used in various approaches. In this study, we have mapped the epitope of 4C8 to a 15-amino acid (aa) region spanning from aa 443 to 457 of the human protein, and found that mutation of three consecutive glutamic acids present in this region disrupts the recognition by 4C8. These results allow a more accurate interpretation of the results obtained by usage of the 4C8 antibody and broaden the utility of this antibody.

Amino Acid Sequence↗
PubMed2005

Mutant huntingtin represses CBP, but not p300, by binding and protein degradation.

Huntington's disease can be used as a model to study neurodegenerative disorders caused by aggregation-prone proteins. It has been proposed that the entrapment of transcription factors in aggregates plays an important role in pathogenesis. We now report that the transcriptional activity of CBP is already repressed in the early time points by soluble mutant huntingtin, whereas the histone acetylase activity of CBP/p300 is gradually diminished over time. Mutant huntingtin bound much stronger to CBP than normal huntingtin, possibly contributing to repression. Especially at the later time points, CBP protein level was gradually reduced via the proteasome pathway. In sharp contrast, p300 was unaffected by mutant huntingtin. This selective degradation of CBP was absent in spinocerebellar ataxia 3. Thus, mutant huntingtin specifically affects CBP and not p300 both at the early and later time points, via multiple mechanisms. In addition to the reduction of CBP, also the altered ratio of these closely related histone acetyl transferases may affect chromatin structure and transcription and thus contribute to neurodegeneration.

Animals↗
PubMed2004

Cultures of ovarian surface epithelium from women with and without a hereditary predisposition to develop female adnexal carcinoma.

AIM: Conflicting evidence exists on whether in vivo morphological characteristics can distinguish Ovarian Surface Epithelium (OSE) of ovaries obtained from women with and without a predisposition to develop female adnexal (ovarian and fallopian tube) carcinoma. This study aims to detect differences in growth potential and morphology that are maintained or specifically expressed in vitro. STUDY DESIGN: Ovarian surfaces were scraped to retrieve OSE cells from 56 women at hereditary high risk for female adnexal carcinoma, of whom 33 are BRCA1 and four are BRCA2 mutation carriers (Predisposed OSE, POSE) and from 26 women without such risk (Non Predisposed OSE, NPOSE). Number of passages and total cell yield until last passage, as well as morphology was compared between both groups. To confirm morphology, the expression of epithelial, mesothelial, and fibroblast markers was assessed. RESULTS: Both POSE and NPOSE cultures displayed similar growth potential and morphology. The expression of epithelial markers cyto-keratins 7 and 8 was similar between both groups. Only in cultures in which cells did not uniformly exhibit these markers, the percentage of cells expressing these markers was significantly lower at last passage when compared to the initial culture. In these latter cultures, cells that were morphologically indistinguishable from fibroblasts were observed. Mesothelial marker calretinin was expressed in 75% of cells of both POSE and NPOSE cultures and correlates with cyto-keratins 7 and 8 expression. CA 125 expression was equally low in POSE and NPOSE cultures (4.3%). Fibroblast markers FSM and vimentin were expressed in 100% and collagen IV was expressed in 16% of cells in all cultures. CONCLUSION: OSE cells derived from women with a hereditary predisposition to develop female adnexal cancer possess similar in vitro characteristics as OSE from women without this predisposition. On basis of our results, it seems advisable to study only 100% cyto-keratins 7 and 8 positive OSE cultures, since contamination of fibroblasts in some primary OSE cultures cannot be ruled out.

Adnexa Uteri↗
PubMed2003

Genome-wide-array-based comparative genomic hybridization reveals genetic homogeneity and frequent copy number increases encompassing CCNE1 in fallopian tube carcinoma.

Fallopian tube carcinoma (FTC) is a rare, poorly studied and aggressive cancer, associated with poor survival. Since tumorigenesis is related to the acquisition of genetic changes, we used genome-wide array comparative genomic hybridization to analyse copy number aberrations occurring in FTC in order to obtain a better understanding of FTC carcinogenesis and to identify prognostic events and targets for therapy. We used arrays of 2464 genomic clones, providing approximately 1.4 Mb resolution across the genome to map genomic DNA copy number aberrations quantitatively from 14 FTC onto the human genome sequence. All tumors showed a high frequency of copy number aberrations with recurrent gains on 3q, 6p, 7q, 8q, 12p, 17q, 19 and 20q, and losses involving chromosomes 4, 5q, 8p, 16q, 17p, 18q and X. Recurrent regions of amplification included 1p34, 8p11-q11, 8q24, 12p, 17p13, 17q12-q21, 19p13, 19q12-q13 and 19q13. Candidate, known oncogenes mapping to these amplicons included CMYC (8q24), CCNE1 (19q12-q21) and AKT2 (19q13), whereas PIK3CA and KRAS, previously suggested to be candidate driver genes for amplification, mapped outside copy number maxima on 3q and 12p, respectively. The FTC were remarkably homogeneous, with some recurrent aberrations occurring in more than 70% of samples, which suggests a stereotyped pattern of tumor evolution.

Carcinoma↗
PubMed2002

Strong aggregation and increased toxicity of polyleucine over polyglutamine stretches in mammalian cells.

Expansion of a Glutamine (Gln) repeat above a specific critical size in certain proteins gives rise to aggregation-prone proteins that cause neurodegenerative disorders, such as Huntington's disease. However, proteins with long hydrophilic polyglutamine repeats are more frequently found in nature than proteins with long homogeneous repeats of other amino acids, such as hydrophobic (Ala)(n) and (Leu)(n). To explore this finding, the effects of expression in mammalian cells of polyglutamine and polyleucine encoded by mixed DNA repeats were compared. It was found that polyleucine is significantly more toxic than polyglutamine. In addition, we show that polyleucine stretches display a high propensity for aggregation utilizing two complementary biochemical assays and that polyleucine stretches can also be detected by the monoclonal antibody 1C2, which specifically recognizes expanded pathogenic and aggregation-prone glutamine repeats. Together, these results suggest that polyglutamine stretches are in fact relatively well tolerated and that nature may select more strongly against DNA stretches that encode long hydrophobic homopolymeric amino acid stretches, such as polyleucine -- possibly owing to their strong propensity for aggregation. In keeping with this notion, an increasing number of diseases are found to be associated with expansion of stretches of hydrophobic amino acids, including oculopharyngeal muscular dystrophy (OPMD), which is associated with expansion of a hydrophobic polyalanine stretch.

Antibodies, Monoclonal↗
PubMed2002

Scaffold/matrix attachment region elements interact with a p300-scaffold attachment factor A complex and are bound by acetylated nucleosomes.

The transcriptional coactivator p300 regulates transcription by binding to proteins involved in transcription and by acetylating histones and other proteins. These transcriptional effects are mainly at promoter and enhancer elements. Regulation of transcription also occurs through scaffold/matrix attachment regions (S/MARs), the chromatin regions that bind the nuclear matrix. Here we show that p300 binds to the S/MAR binding protein scaffold attachment factor A (SAF-A), a major constituent of the nuclear matrix. Using chromatin immunoprecipitations, we established that both p300 and SAF-A bind to S/MAR elements in the transiently silent topoisomerase I gene prior to its activation at G(1) during cell cycle. This binding is accompanied by local acetylation of nucleosomes, suggesting that p300-SAF-A interactions at S/MAR elements of nontranscribed genes might poise these genes for transcription.

Acetylation↗