PubMed Health⌕ Search

Biomedical subjects

A de Klein

Publications and source records attributed to A de Klein.

At least 37 records · Page 2Linked to original sources
PubMed1993

Linkage to markers for the chromosome region 17q12-q21 in 13 Dutch breast cancer kindreds.

We have performed linkage analysis with five markers for the chromosome region 17q12-q21 in 13 Dutch breast cancer kindreds in order to find support for the claim by Hall et al. that a gene in this region, termed "BRCA1," is associated with predisposition to early-onset familial breast cancer. This work is part of a collaborative study, the results of which are published elsewhere in this issue. Best evidence for linkage was observed with the marker CMM86 (D17S74) in pedigrees with an average age at onset of < or = 47 years (LOD score = 1.77 at 1% recombination). In one breast-ovarian cancer family with a high probability of being linked to 17q, we observed one putative recombinant between D17S250 and D17S579, which suggests that BRCA1 is proximal to D17S579.

Adult↗
PubMed1993

Absence of both subunits of cytochrome b558 in the UM384 cell line relative to the inability to generate superoxide anions.

Phagocytic cells are characterized by their ability to generate superoxide anions upon activation by appropriate stimuli. UM384, a myelomonocytic cell line, was shown to be defective in this oxidase activity as measured by nitroblue tetrazolium or cytochrome c reduction. Cytochrome b558, a unique pigment present in phagocytes and implicated in electron transfer from NADPH to O2, was absent in the differentiated UM384 cells. Both subunits of the cytochrome b558 appeared to be absent or present in strongly reduced amounts compared to the mother cell line U937, as indicated by immunocytochemistry or Western blot analysis using monoclonal antibodies (MABs). On the other hand, cytosolic factors also involved in NADPH oxidase activity were shown to be present, either immunologically or by using the capacity of the cytosol to activate the oxidase in a membrane fraction from bovine neutrophils. At the molecular level, the mRNA that encodes the gp91-phox was shown to be absent in the differentiated UM384 cells, whereas the mRNA that encodes the p22-phox was normally expressed. These results suggest that the defect in superoxide production by the UM384 cells is related to the absence of cytochrome b558, a situation mimicking that observed in phagocytes from patients with X-linked chronic granulomatous disease (X-CGD).

Antibodies, Monoclonal↗
PubMed1992

[Molecular genetic studies in alpha-thalassemia].

A group of 5,000 patients, suspected of haemolytic anaemia, were investigated with molecular genetic methods for deletion types of alpha-thalassemia. In 776 (15.6%) patients a deletion of one or more alpha-globin genes was found. The same group of patients was also investigated for abnormal haemoglobins and beta-thalassaemia. In about 30% of the patients either an alpha-thalassaemia, an abnormal haemoglobin, a beta-thalassaemia, or a combination was diagnosed. In a group of patients with a haemoglobinopathy, the frequency of alpha-thalassaemia was much higher (i.e. 33%) than in individuals without haemoglobinopathy. Preselection of the patients based on the presence of microcytic erythrocytes and/or a decreased ADW0.5 of the erythrocytes gave a high incidence of false-negative and false-positive results. Therefore, haemoglobin examination should not be restricted to protein chemistry, but should include molecular genetic investigations for deletion types of alpha-thalassaemia.

Chromosome Deletion↗
PubMed1992

Cytochrome b558-negative, autosomal recessive chronic granulomatous disease: two new mutations in the cytochrome b558 light chain of the NADPH oxidase (p22-phox).

Chronic granulomatous disease (CGD) is characterized by the failure of activated phagocytes to generate superoxide. Defects in at least four different genes lead to CGD. Patients with the X-linked form of CGD have mutations in the gene for the beta-subunit of cytochrome b558 (gp91-phox). Patients with a rare autosomal recessive form of CGD have mutations in the gene for the alpha-subunit of this cytochrome (p22-phox). Usually, this leads to the absence of cytochrome b558 in the phagocytes (A22(0) CGD). We studied the molecular defect in five European patients from three unrelated families with this type of CGD. P22-phox mRNA was reverse-transcribed, and the coding region was amplified by PCR in one fragment and sequenced. Three patients from one family, with parents that were first cousins, were homozygous for a single base substitution (G-297-->A) resulting in a nonconservative amino acid change (Arg-90-->Gln). This mutation was previously found in a compound heterozygote A22(0) CGD patient. Another patient, also from first-cousin parents, was homozygous for an A-309-->G mutation in the open reading frame that predicts a nonconservative amino acid replacement (His-94-->Arg). The fifth patient was also born from a first-cousin marriage and was shown to be homozygous for the absence of exon 4 from the cDNA. In this patient, a G-->A substitution was found at position 1 of intron 4 in the genomic DNA. Therefore, the absence of exon 4 in the cDNA of this patient is due to a splicing error.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Point mutations in the beta-subunit of cytochrome b558 leading to X-linked chronic granulomatous disease.

The NADPH:O2 oxidoreductase of phagocytic leukocytes is an important enzyme for the bactericidal activity of these cells. Cytochrome b558 is a membrane component of this enzyme. In X-linked chronic granulomatous disease (Xb- CGD) the phagocytes are defective in the beta-subunit (gp91-phox) of this cytochrome. We have studied the genetic defect in a group of six X-linked CGD patients characterized by complete or partial loss of cytochrome b558 with the use of the polymerase chain reaction. All patients had a different single point mutation in the gp91-phox gene, indicating that the genetic defect in Xb- CGD is very heterogeneous. In one patient the mutation leads to a premature termination codon. In the other five cases these mutations predict incorporation of a different amino acid. The mutations were with one exception found in the N-terminal half of the protein, suggesting that this part of cytochrome b558 is important for the binding of the heme or for formation of a stable complex with p22-phox. Two histidyl residues were found that might be ligands of the heme iron.

Alleles↗
PubMed1990

Genetic changes in somatostatin receptor positive breast tumors.

Forty-nine primary breast tumors were analyzed for the expression of the somatostatin receptor (SSR) and genetic changes in the RB tumor suppressor gene. Twenty-four tumor samples were shown to contain receptors for somatostatin and in eight of these SSR-positive tumors we observed a mutation in the RB gene. However, since also in the group of SSR-negative tumors in eight of the 25 cases an alteration of the RB gene was observed, loss of this tumor suppressor gene is not specific for the SSR-positive subgroup of breast tumors. A similar, equal distribution between SSR-positive and SSR-negative breast tumors was observed for the six tumor samples which showed amplification of the neu proto-oncogene.

Breast Neoplasms↗
PubMed1989

Cytogenetic and molecular analysis in Philadelphia negative CML.

We studied the clinical, hematologic, cytogenetic and molecular biologic features in four patients with Philadelphia (Ph) negative chronic myeloid leukemia (CML). In all four cases the clinical and hematologic characteristics were indistinguishable from Ph positive CML. Cytogenetic analysis showed a normal karyotype in two patients and chromosomal translocations apparently not affecting chromosome 22 in the other two cases. Southern blot analysis using probes of the bcr region, demonstrated a bcr break-point in all four patients. In situ hybridization with bcr, c-abl, and c-sis probes showed unusual hybridization sites for 5'-bcr and c-abl indicating complex chromosomal rearrangements affecting three different chromosomes in the four patients investigated. Using polymerase chain reaction (PCR) followed by hybridization to oligonucleotide probes specific for the bcr-abl fusion region, the expression of a chimeric bcr-abl mRNA was detected. In these patients we demonstrated that (a) CML with a breakpoint in the bcr region without cytogenetically detectable Ph chromosome is characterized by the same genomic recombination of 5'-bcr and c-abl as CML with standard Ph translocation and (b) unusual localization of 5'-bcr and c-abl sequences caused by complex Ph translocation does not interfere with transcription of the bcr-abl fusion gene.

Adult↗
PubMed1988

High expression of ets-1 gene in human thymocytes and immature T leukemic cells.

The cellular ets-1 gene homologous to the 5' region of the v-ets sequence of the E26 retrovirus codes for a 6.8-kb mRNA that is translated into a 51-kDa protein in human cells. A survey of mRNA from human tissues showed the thymus as the tissue with the highest level of ets-1 transcription, within other hematopoietic organs and tissues, including spleen, fetal liver, lymph nodes, bone marrow, and peripheral lymphocytes exhibiting low or undetectable levels of hybridization. A high level of ets-1 expression was found in murine thymocyte mRNA as well. Investigation of the ets-1 expression levels in human leukemic samples showed that primary malignant T cells (T-ALLs), corresponding to intrathymic stages of maturation, have a much higher level of ets-1 mRNA than malignant T lymphoid cells with a mature phenotype, such as adult T cell leukemias (ATLs). T-ALLs were also higher in ets-1 expression than the other lymphoid (pre-T-ALL, c-ALL, pre-B-ALL) malignant cells analyzed. Insignificant amounts of the specific ets-1 mRNA were detected in several acute myeloid leukemias representing various degrees of maturation. The elevated ets-1 mRNA in thymocytes suggests a biological role for the ets-1 product in these cells that could be explored to investigate ets-1 function. Finally, the exhibited expression of ets-1 in lymphoid cells and absence from malignant myeloid cells makes it a candidate marker for phenotyping human hematopoietic tumors.

Cell Line↗
PubMed1987

Molecular characterization of the testis specific c-abl mRNA in mouse.

The c-abl gene encodes a protein tyrosine kinase and is transcribed from at least two promoters giving rise to transcripts of two size classes of approximately 5 and 6 kb in length. These mRNAs only differ in their most 5' exon and encode proteins of similar size but with different N-termini. In the mouse testis an additional abundant c-abl mRNA of 4 kb is detected. This mRNA was shown to be expressed in the haploid male germ cells of the adult mouse. Here we describe the cloning and molecular characterization of a cDNA representing the testis specific c-abl transcript. We show that the 4 kb c-abl mRNA arises from alternative polyadenylation of an RNA transcribed from the same promoter as the 5 kb mRNA. The site of polyadenylation is unusual in this shorter transcript as it is not preceded by the highly conserved hexanucleotide AAUAAA. The use of this polyadenylation site removes 1.2 kb of 3' sequences present in the somatic c-abl mRNAs, but does not affect the main open reading frame of the transcript. Using in situ hybridization on whole testis sections it is shown that the 4 kb c-abl mRNA is most abundant in the elongating spermatids.

Animals↗
PubMed1987

T cell receptor-CD3 complex during early T cell differentiation. Analysis of immature T cell acute lymphoblastic leukemias (T-ALL) at DNA, RNA, and cell membrane level.

T cell acute lymphoblastic leukemias (T-ALL) can be regarded as the malignant counterparts of cells in various T cell differentiation stages. To study the expression of the human T cell receptor (TcR)-CD3 complex during the early stages of T cell differentiation, we have analyzed 22 T-ALL at the cell membrane level and the DNA level and 12 of them at the RNA level. According to their immunologic phenotype, the T-ALL could be divided into three main groups: 10 immature T-ALL (CD1-/CD3-), seven common thymocytic T-ALL (CD1+/CD3-or+), and five mature T-ALL (CD1-/CD3+). Among the 10 immature T-ALL three appeared to express the immunologic phenotype of the putative prothymocyte (TdT+/HLA-DR+/CD7+/CD2+/CD5-/CD1-/CD3-), whereas the other seven T-ALL appeared to be immature thymocytic (TdT+/HLA-DR-/CD7+/CD2+/CD5+/CD1-/CD3-). Transcripts of the CD3-delta and CD3-epsilon genes were present in all CD3- and CD3+ T-ALL tested, including prothymocytic T-ALL. However, prothymocytic T-ALL had germline TcR-beta genes and were not rearranged to the characterized TcR-gamma joining regions. The presence of CD3 transcripts and absence of TcR gene rearrangements in prothymocytic T-ALL supports their immature T cell character. Two immature thymocytic T-ALL also had germline TcR-gamma genes and one of them had germline TcR-beta genes. In all other T-ALL the TcR-gamma and TcR-beta genes were rearranged. The presumptive functional 1.3-kilobase TcR-beta transcripts were detected in the majority of T-ALL with rearranged TcR-beta genes. Distinct levels of TcR-gamma transcripts appeared to be present only in some thymocytic T-ALL, i.e., some immature thymocytic T-ALL and common thymocytic T-ALL. TcR-alpha mRNA could only be detected in CD3+ mature T-ALL, but was absent in all CD3+ common thymocytic T-ALL tested. Our data indicate that CD3 gene transcription is one of the earliest events during T cell differentiation and already occurs in prothymocytes. The TcR-gamma and TcR-beta genes rearrange early during thymocytic differentiation and can subsequently be transcribed. High levels of TcR-gamma gene transcription may only occur in a part of the T cells during thymic differentiation, while TcR-beta gene transcription continues during further differentiation. TcR-alpha gene transcription may be the final step in the production of the complete set of TcR and CD3 proteins, resulting in the expression of the TcR alpha beta-CD3 complex at the cell surface of mature T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1986

Persistence of chronic myelocytic leukemia despite deletion of rearranged bcr/c-abl sequences in blast crisis.

We report on a Ph+ chronic myelocytic leukemia (CML) case, cytogenetically characterized by the occurrence of a second Philadelphia (Ph) chromosome in lymphoid blast crisis of T cell lineage. In situ hybridization analyses showed a deletion of translocated c-abl sequences, present on the Ph during chronic state, from both Ph in acute state. Moreover, Southern blot analyses of blastic cells exhibited a rearrangement within bcr, but a deletion of 5' bcr sequences, and Northern blots failed to detect the hybrid 8.5 kb bcr/c-abl transcript usually observed in Ph+ CML.

Base Sequence↗
PubMed1986

Molecular analysis of both translocation products of a Philadelphia-positive CML patient.

The breakpoint regions of both translocation products of the (9;22) Philadelphia translocation of CML patient 83-H84 and their normal chromosome 9 and 22 counterparts have been cloned and analysed. Southern blotting with bcr probes and DNA sequencing revealed that the breaks on chromosome 22 occurred 3' of bcr exon b3 and that the 88 nucleotides between the breakpoints in the chromosome 22 bcr region were deleted. Besides this small deletion of chromosome 22 sequences a large deletion of chromosome 9 sequences (greater than 70 kb) was observed. The chromosome 9 sequences remaining on the 9q+ chromosome (9q+ breakpoint) are located at least 100 kb upstream of the v-abl homologous c-abl exons whereas the translocated chromosome 9 sequences (22q-breakpoint) could be mapped 30 kb upstream of these c-abl sequences. The breakpoints were situated in Alu-repetitive sequences either on chromosome 22 or on chromosome 9, strengthening the hypothesis that Alu-repetitive sequences can be hot spots for recombination.

Adolescent↗