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F Baas

Publications and source records attributed to F Baas.

At least 73 records · Page 4Linked to original sources
PubMed1996

Caprine homologue of rodent 5'-AMP-activated protein kinase subunit and yeast SNF4/CAT3 is down-regulated by thyroid hormone.

We isolated a cDNA, B12, that was down-regulated by thyroid hormone (TH) in the goat cerebellum, using a polymerase chain reaction (PCR)-based subtractive hybridization and differential screening procedure. Northern blot analysis of RNA from cerebellum of T4-treated and untreated hypothyroid goats confirmed that clone B12 was TH-regulated with an average reduction in expression of 21% after 4 days of T4 supplementation. Other tissues from a T4-treated and an untreated hypothyroid goat also revealed down-regulation of B12, with the highest reduction in expression found in the thyroid gland (38%). Steady-state levels of the approximately 1.8 kb B12 mRNA were higher in brain than in peripheral tissues. In situ hybridization showed that B12 mRNA in the brain is mainly present in various layers of the cerebellum and the cerebral cortex, the hippocampus, and the olfactory tubercle and is predominantly expressed in neurons. Sequence analysis of the caprine B12 cDNA clone, and the murine homologue, revealed 61% similarity to SNF4/CAT3, a regulator involved in the transcriptional control of glucose-repressible genes in yeast, and 99% identity to a rat 5'-AMP-activated protein kinase subunit, which is involved in the regulation of fatty acid, glycogen and isoprenoid metabolism. In view of these homologies, B12 might encode a regulator involved in distinct metabolic pathways and therefore, TH might also affect gene expression indirectly by down-regulation of regulators like B12.

Adenosine Monophosphate↗
PubMed1996

Microsatellite instability in childhood rhabdomyosarcoma is locus specific and correlates with fractional allelic loss.

Replication errors (RERs) were initially identified in hereditary nonpolyposis colon cancer and other tumors of Lynch syndrome II. Mutations in genes involved in mismatch repair give rise to a mutator phenotype, resulting in RERs. The mutator phenotype is thought to predispose to malignant transformation. Here we show that in the embryonal form of childhood rhabdomyosarcoma, RERs also occur, but in contrast to hereditary nonpolyposis colon cancer, only a subset of the microsatellite loci analyzed show RERs. The occurrence of RERs is strongly correlated with increased fractional allelic loss (P < 0.001), suggesting that the occurrence of RERs is a secondary phenomenon in rhabdomyosarcoma. Coincidental loss of genes involved in mismatch repair, possibly due to their proximity to tumor suppressor genes involved in tumor progression of embryonal form of childhood rhabdomyosarcoma, could explain the observed phenomenon.

Alleles↗
PubMed1996

Clinically distinct codon 69 mutations in major myelin protein zero in demyelinating neuropathies.

Mutations in the major peripheral myelin protein zero (P0) gene on chromosome 1q21-q23 have been found with the hereditary demyelinating polyneuropathy Charcot-Marie-Tooth type 1B. Here, we describe 2 patients with distinct neurological characteristics, carrying different substitutions at the same codon--Arg69His and Arg69Cys. The patients were heterozygous for the mutation, which in both appeared to be de novo. Histological examination of sural nerve biopsy specimens revealed defective myelin as well as marked differences, confirming the importance of P0 in the compaction of myelin.

Adult↗
PubMed1996

Raf-1 kinase, epidermal growth factor receptors, and mutant Ras proteins in colonic carcinomas.

Epidermal growth factor receptors (EGFR) and ras mutations are known to play a significant role in controlling cell growth and tumor promotion. Both of them transmit mitogenic signals to the nucleus by activation of Raf-1 kinase. In this study, the expression of EGFR and mutant Ras proteins, and, for the first time, the expression, phosphorylation and kinase activity of Raf-1 kinase have been determined in paired samples of colorectal cancer and mucosa. The tumor and mucosa samples did not differ significantly with regard to Raf-1 kinase content and activity. A major difference between tumors and mucosa was found, however, in the phosphorylation of Raf-1. Most of the mucosa samples (13/20), but only 1/20 of the cancer samples, contained hyperphosphorylated Raf-1. EGFR were significantly (p = 0.0025) decreased in the tumors. The decreased phosphorylation of Raf-1 in colonic carcinomas could be the result of activation of Raf-1 phosphatases or inactivation of kinases phosphorylating Raf-1. New forms of treatment based on EGFR overexpression do not seem to be suitable for the majority of colonic cancers.

Adenocarcinoma↗
PubMed1996

Effect of thyroid hormone deficiency on RC3/neurogranin mRNA expression in the prenatal and adult caprine brain.

Thyroid hormone deficiency has profound effects on the brain during development and less marked effects on the adult brain. These effects are considered to be the result of the direct regulation of specific target genes by thyroid hormone. Previous studies have shown that the expression of the neuronal gene RC3, encoding a 78-amino-acid calmodulin-binding protein kinase C substrate, is under the influence of thyroid hormone in vivo. In congenitally hypothyroid foetal goat at term (approximately 150 days of gestation), RC3 mRNA expression was reversibly decreased in the striatum but not in other brain regions. In the present study we investigated the role of thyroid hormone in RC3 mRNA expression at earlier stages of fetal development and in mature goats using in situ hybridization. There was a consistent decrease (35-80%) in the signal for RC3 mRNA per neuron in the striatum of hypothyroid adult and fetal goats of 90, 120 and 150 days of gestation compared to normal goats of the same age. In contrast, no consistent difference was observed in the cerebral cortex at any age studied. These data indicate that in both fetal and adult goats thyroid hormone, at least partly, affects the expression of RC3 mRNA in the striatum and not the cerebral cortex.

Animals↗
PubMed1996

Type VI collagen mutations in Bethlem myopathy, an autosomal dominant myopathy with contractures.

Among the diverse family of collagens, the widely expressed microfibrillar type VI collagen is believed to play a role in bridging cells with the extracellular matrix. Several observations imply substrate properties for cell attachment as well as association with major collagen fibers. Previously, we have established genetic linkage between the genes encoding the three constituent alpha-chains of type VI collagen and Bethlem myopathy. A distinctive feature of this autosomal dominant disorder consists of contractures of multiple joints in addition to generalized muscular weakness and wasting. Nine kindreds show genetic linkage to the COL6A1-COL6A2 cluster on chromosome 21q22.3 (refs 3,4; manuscript submitted) whereas one family shows linkage to markers on chromosome 2q37 close to COL6A3 (ref. 5). Sequence analysis in four families reveals a mutation in COL6A1 in one and a COL6A2 mutation in two other kindreds. Both mutations disrupt the Gly-X-Y motif of the triple helical domain by substitution of Gly for either Val or Ser. Analogous to the putative perturbation of the anchoring function of the dystrophin-associated complex in congenital muscular dystrophy with mutations in the alpha 2-subunit of laminin, our observations suggest a similar mechanism in Bethlem myopathy.

Base Sequence↗
PubMed1996

Genetic localization of Bethlem myopathy.

Bethlem myopathy is a rare autosomal dominant myopathy characterized by slowly progressive limb-girdle muscular atrophy and weakness, and contractures of multiple joints. To identify the genetic localization we used highly polymorphic microsatellite markers in a genome-wide search in six Dutch families. After excluding genetic linkage with 52 markers distributed evenly over the autosomes, significant linkage was present with the 21q22.3 locus PFKL (two-point lod score of Zmax = 6.86 at theta = 0.03). There was no indication of genetic heterogeneity. The pattern of recombinations observed with adjacent markers indicated a localization distal to PFKL. Recombination of a marker within the collagen 6a1 gene (COL6A1) excluded this apparent candidate gene in one of the Bethlem myopathy families. The disease gene is most likely located in the region between COL6A1 and the telomere of chromosome 21q.

Child↗
PubMed1995

Role of glutathione in the export of compounds from cells by the multidrug-resistance-associated protein.

Multidrug-resistance-associated protein (MRP) is a plasma membrane glycoprotein that can confer multidrug resistance (MDR) by lowering intracellular drug concentration. Here we demonstrate that depletion of intracellular glutathione by DL-buthionine (S,R)-sulfoximine results in a complete reversal of resistance to doxorubicin, daunorubicin, vincristine, and VP-16 in lung carcinoma cells transfected with a MRP cDNA expression vector. Glutathione depletion had less effect on MDR in cells transfected with MDR1 cDNA encoding P-glycoprotein and did not increase the passive uptake of daunorubicin by cells, indicating that the decrease of MRP-mediated MDR was not due to nonspecific membrane damage. Glutathione depletion resulted in a decreased efflux of daunorubicin from MRP-transfected cells, but not from MDR1-transfected cells, suggesting that glutathione is specifically required for the export of drugs from cells by MRP. We also show that MRP increases the export of glutathione from the cell and this increased export is further elevated in the presence of arsenite. Our results support the hypothesis that MRP functions as a glutathione S-conjugate carrier.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Mechanisms of MRP over-expression in four human lung-cancer cell lines and analysis of the MRP amplicon.

Some multidrug resistant cell lines over-express the gene encoding the multidrug-resistance-associated protein (MRP). In all cell lines reported thus far, over-expression is associated with gene amplification. We have studied the predominant mechanisms of MRP over-expression in 4 human lung-cancer cell lines that cover a range of drug-resistance levels, and we have analyzed the MRP amplicon. In the SW-1573-derived, weakly resistant cell line 30.3M, MRP mRNA is elevated 3-fold in the absence of gene amplification. Run-on analysis shows that the increased MRP gene expression in this cell line is due to transcriptional activation. In the highly resistant GLC4/ADR and COR-L23/R cells, MRP gene amplification predominates, whereas in the moderately resistant MOR/R cells, gene amplification is combined with a mechanism resulting in an additional increase in the level of MRP mRNA. Fluorescence in situ hybridization shows that, in the GLC4/ADR cells, amplified MRP sequences are present both in double minute chromosomes (DM) and in homogeneously staining regions (HSR). By pulsed-field gel electrophoresis we show that the MRP-containing DM are 1 Mb in length. Chromosome-16-specific repetitive sequences adjacent to the MRP gene are also present in the DM and HSR, compatible with the involvement of these sequences in recombination events underlying MRP gene amplification. Our results show that low levels of drug resistance may arise by transcriptional activation of the MRP gene, whereas at high levels of drug resistance amplification of the MRP gene predominates, possibly facilitated by the presence of recombination-prone sequences.

ATP-Binding Cassette Transporters↗
PubMed1995

Déjérine-Sottas neuropathy is associated with a de novo PMP22 mutation.

We identified a de novo mutation in the peripheral myelin protein (PMP22) gene of a patient with Déjérine-Sottas neuropathy. Single-stranded conformation analysis of PCR-amplified DNA fragments showed an additional fragment for exon 1 in the patient, which was absent in the unaffected parents. Sequence analysis showed a de novo point mutation C85-->A that results in an amino acid substitution His12Gln in the first transmembrane domain of PMP22. This provides further evidence that sporadic cases of Déjérine-Sottas neuropathy can be due to dominant single base substitutions.

Amino Acid Sequence↗
PubMed1995

Identification of five novel inactivating mutations in the human thyroid peroxidase gene by denaturing gradient gel electrophoresis.

Thyroid peroxidase (TPO) is the key enzyme in the synthesis of thyroid hormones. Defects in the TPO gene are reported to be the cause of congenital hypothyroidism due to a Total Iodide Organification Defect (TIOD). This type of defect, where iodide taken up by the thyroid gland cannot be oxidized and bound to protein, is the most common hereditary inborn error causing congenital hypothyroidism in the Netherlands. Denaturing Gradient Gel Electrophoresis (DGGE) of PCR amplified genomic DNA was used to screen for mutations in the TPO gene of TIOD patients from nine apparently unrelated families, and seven different mutations were detected. Three frameshift mutations were found: a 20 bp duplication in exon 2, a 4 bp duplication in exon 8, and an insertion of a single nucleotide (C) at pos. 2505 in exon 14. In addition, four single nucleotide substitutions were identified: one single-base mutation resulted in a premature termination codon (C-->T at pos. 1708 in exon 10), two single-base substitutions changed an amino acid in highly conserved regions of the gene (Tyr-->Asp in exon 9 and Glu-->Lys in exon 14). The fourth single-base mutation located at the exon 10/intron 10 border altered a conserved Gly into Ser and could also affect splicing. Nine TIOD patients from five families were compound heterozygotes and six patients from four families were homozygous for one of the mentioned mutations in the TPO gene.

Base Sequence↗
PubMed1995

RC3/neurogranin structure and expression in the caprine brain in relation to congenital hypothyroidism.

In view of the profound effects of thyroid hormone deficiency on the central nervous system (CNS), neuronal genes regulated by thyroid hormone could potentially be involved in the development of the CNS. Expression of the neuronal gene RC3/neurogranin was shown to be induced by thyroid hormone in the rat. No data are available on RC3 expression in mammals with prenatal brain development, like humans. To study RC3 mRNA expression in a genetic in vivo model of congenital hypothyroidism, which also resembles the human situation in the timing of brain development relative to birth, we used an inbred strain of congenitally hypothyroid goats. We isolated a cDNA for the caprine RC3 homolog. The deduced amino acid sequence had 99% similarity with the rat and bovine protein sequence. An analysis of the developmental expression of RC3 mRNA levels showed a 3-fold increase between E90 and P0. In situ hybridization analysis showed that in euthyroid goats, the RC3 expression pattern was region-specific and resembled that in rats. However, in contrast to rats, hypothyroid goats showed only a reduced RC3 mRNA expression in the striatum. Hypothyroidism had no effect on RC3 mRNA expression in all other brain regions. T4-treatment of the hypothyroid fetus increased RC3 mRNA expression in the striatum to euthyroid control levels. These data suggest that thyroid hormone is a regulator of RC3 gene expression in the caprine brain, and that the striatum is highly sensitive to thyroid hormone deficiency.

Amino Acid Sequence↗
PubMed1995

Altered MRP is associated with multidrug resistance and reduced drug accumulation in human SW-1573 cells.

We have analysed the contribution of several parameters, e.g. drug accumulation, MDR1 P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP) and topoisomerase (topo) II, to drug resistance in a large set of drug-resistant variants of the human non-small-cell lung cancer cell line SW-1573 derived by selection with low concentrations of doxorubicin or vincristine. Selection with either drug nearly always resulted in MDR clones. The resistance of these clones could be explained by reduced drug accumulation and was associated with a decrease rather than an increase in the low MDR1 mRNA level. To test whether a decrease in MDR1 mRNA indirectly affected resistance in these cells, we introduced a MDR1-specific hammerhead ribozyme into wild-type SW-1573 cells. Although this led to a substantial reduction in MDR1 mRNA, it did not result in resistance. In all resistant clones we found an altered form of the multidrug resistance-associated protein (MRP), migrating slightly slower during SDS-polyacrylamide gel electrophoresis than MRP in parental cells. This altered MRP was also present in non-P-gp MDR somatic cell hybrids of the SW-1573 cells, demonstrating a clear linkage with the MDR phenotype. Treatment of crude cellular membrane fractions with N-glycanase, endoglycosidase H or neuraminidase showed that the altered migration of MRP on SDS-PAGE is due to a post-translational modification. There was no detectable difference in sialic acid content. In most but not all doxorubicin-selected clones, this MDR phenotype was accompanied by a reduction in topo II alpha mRNA level. No reduction was found in the clones selected with vincristine. We conclude from these results that selection of the SW-1573 cell line for low levels of doxorubicin or vincristine resistance, predominantly results in MDR with reduced drug accumulation associated with the presence of an altered MRP protein. This mechanism can be accompanied by other resistance mechanisms, such as reduced topo II alpha mRNA in case of doxorubicin selection.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Reduced topoisomerase II activity in multidrug-resistant human non-small cell lung cancer cell lines.

Multidrug-resistant (MDR) cell lines often have a compound phenotype, combining reduced drug accumulation with a decrease in topoisomerase II. We have analysed alterations in topoisomerase II in MDR derivatives of the human lung cancer cell line SW-1573. Selection with doxorubicin frequently resulted in reduced topo II alpha mRNA and protein levels, whereas clones selected with vincristine showed normal levels of topo II alpha. No alterations of topo II beta levels were detected. To determine the contribution of topo II alterations to drug resistance, topo II activity was analysed by the determination of DNA breaks induced by the topo II-inhibiting drug 4'-(9-acridinylamino)methane-sulphon-m-anisidide (m-AMSA) in living cells, as m-AMSA is not affected by the drug efflux mechanism in the SW-1573 cells. The number of m-AMSA-induced DNA breaks correlated well (r = 0.96) with in vitro m-AMSA sensitivity. Drug sensitivity, however, did not always correlate with reduced topo II mRNA or protein levels. In one of the five doxorubicin-selected clones m-AMSA resistance and a reduction in m-AMSA-induced DNA breaks were found in the absence of reduced topo II protein levels. Therefore, we assume that post-translational modifications of topo II also contribute to drug resistance in SW-1573 cells. These results suggest that methods that detect quantitative as well as qualitative alterations of topo II should be used to predict the responsiveness of tumours to cytotoxic agents. The assay we used, which measures DNA breaks as an end point of topo II activity, could be a good candidate.

Amsacrine↗
PubMed1995

High-resolution DNA Fiber-FISH for genomic DNA mapping and colour bar-coding of large genes.

We have applied two-colour fluorescence in situ hybridization (FISH) to DNA fibers and combined it with digital imaging microscopy for the mapping of large cosmid contigs. The technique was validated using a set of unique plasmids and a cosmid contig both originating from the thyroglobulin (Tg) gene and previously mapped by restriction analysis. The resolution proved to be close to the theoretical lower limit of approximately 1 kb, ranging > or = 400 kb. Subsequently a 400 kb cosmid contig derived from a DMD-YAC was directly mapped by Fiber-FISH. The resulting map is in full agreement with the restriction map. Two-colour Fiber-FISH mapping thus showed to be capable for accurately sizing gaps and overlaps, and to identify chimeric or repeat sequence containing cosmids across a 400 kb region at once. The generated 400 kb 'colour bar-code' was subsequently used to map two DMD deletion breakpoints in patient DNA with an accuracy of 1-2 kb. The results underscore the value of this method for the delineation of chromosomal rearrangements for positional cloning and single patient clinical studies.

Chimera↗
PubMed1994

The human multidrug resistance-associated protein MRP is a plasma membrane drug-efflux pump.

The multidrug-resistance associated protein MRP is a 180- to 195-kDa membrane protein associated with resistance of human tumor cells to cytotoxic drugs. We have investigated how MRP confers drug resistance in SW-1573 human lung carcinoma cells by generating a subline stably transfected with an expression vector containing MRP cDNA. MRP-overexpressing SW-1573 cells are resistant to doxorubicin, daunorubicin, vincristine, VP-16, colchicine, and rhodamine 123, but not to 4'-(9-acridinylamino)methanesulfon-m-anisidide or taxol. The intracellular accumulation of drug (daunorubicin, vincristine, and VP-16) is decreased and the efflux of drug (daunorubicin) is increased in the transfectant. The decreased accumulation of daunorubicin is abolished by permeabilization of the plasma membrane with digitonin, showing that MRP can lower the intracellular daunorubicin level against a concentration gradient. Anti-MRP antisera predominantly stain the plasma membrane of MRP-overexpressing cells. We conclude that MRP is a plasma membrane drug-efflux pump.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Prevalence of the 1.5-Mb 17p deletion in families with hereditary neuropathy with liability to pressure palsies.

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder of the peripheral nerves leading to increased susceptibility to mechanical traction or compression. Some patients have been shown to be carriers of a 1.5-Mb deletion in chromosome 17p11.2, which corresponds to the duplicated region present in most patients with Charcot-Marie-Tooth disease type 1A. Recently, evidence has been presented that the deletion is not the only cause of HNPP. To determine the prevalence of the 1.5-Mb deletion, we have examined 22 unrelated families with HNPP in the following two ways: by polymerase chain reaction analysis of marker loci D17S122 and D17S261, and by gene dosage measurements with DNA probes for D17S122 (VAW409R3a) and D17S125 (VAW412R3a) and for the PMP-22 gene. The efficiency and sensitivity of these methods is discussed. Our results show that the prevalence of the 17p deletion in our families with HNPP is 68%. One patient, presenting as a sporadic case, was found to be affected by a de novo deletion in the paternal chromosome. Single-strand conformation analysis of the protein-coding region of the PMP-22 gene did not reveal any mutation in patients from the 7 families lacking the 17p deletion. As a group, these families could not be distinguished by clinical, electrophysiological, or morphological features from the families with the deletion.

Chromosomes, Human, Pair 17↗