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Biomedical subjects

U Francke

Publications and source records attributed to U Francke.

At least 145 records · Page 8Linked to original sources
PubMed1993

A serine/proline-rich protein is fused to HRX in t(4;11) acute leukemias.

Translocations involving chromosome band 11q23 in acute leukemias have recently been shown to involve the HRX gene that codes for a protein with significant similarity to Drosophila trithorax. HRX gene alterations are consistently observed in t(4;11) (q21;q23)-carrying leukemias and cell lines by Southern blot analyses and are accompanied by HRX transcripts of anomalous size on Northern blots. HRX-homologous cDNAs were isolated from a library prepared from t(4;11)-carrying acute leukemia cells. cDNAs representative of transcription products from the derivative 11 chromosome were shown to contain HRX sequences fused to sequences derived from chromosome band 4q21. Fragments of the latter were used to clone and analyze cDNAs for wild-type 4q21 transcripts that predicted a 140-Kd basic protein (named FEL) that is rich in prolines, serines, and charged amino acids. FEL contains guanosine triphosphate-binding and nuclear localization consensus sequences and uses one of two possible 5' exons encoding the first 12 or 5 amino acids. After t(4;11) translocations, 913 C-terminal amino acids of FEL are fused in frame to the N-terminal portion of HRX containing its minor groove DNA binding motifs. These features are similar to predicted t(11;19) fusion proteins, suggesting that HRX consistently contributes a novel DNA-binding motif to at least two different chimeric proteins in acute leukemias.

Amino Acid Sequence↗
PubMed1993

Molecular cloning, cDNA sequence, and chromosomal assignment of the human radixin gene and two dispersed pseudogenes.

Radixin is a cytoskeletal protein that may be important in linking actin to the plasma membrane. Recent cloning of the murine and porcine radixin cDNAs revealed a protein highly homologous to ezrin and moesin. We have cloned and sequenced the human radixin cDNA and found the predicted amino acid sequence for the human protein to be nearly identical to those predicted for radixin in the two other species. By Southern analyses of Chinese hamster x human somatic cell hybrid DNA and of PCR products derived from hybrids, the coding gene (RDX) was mapped to 11q. Fluorescence chromosomal in situ hybridization with a cDNA plasmid further localized this gene to band 11q23. However, PCR amplification with "radixin-specific" primers on the hybrid DNA panel yielded an additional, very similar DNA sequence that was further characterized by direct sequencing of PCR products. This sequence represents a truncated version and the respective locus (RDXP2) was assigned to Xp21.3. Furthermore, by employing a different set of primers, a third sequence was found that was 90% identical to the radixin sequence but contained termination codons and seemed to lack introns. This pseudogene (RDXP1) was mapped to 11p by Southern and PCR analyses.

Amino Acid Sequence↗
PubMed1993

Genes for the dimerization cofactor of hepatocyte nuclear factor-1 alpha (DCOH) are on human and murine chromosomes 10.

Hepatocyte nuclear factor-1 alpha (HNF-1 alpha; gene symbol, TCF1) forms dimers with itself as well as with HNF-1 beta and regulates the expression of several liver-specific genes. Recently, a dimerization cofactor of hepatocyte nuclear factor-1 alpha, called DCOH, has been identified. Here, we report the chromosomal localization of the genes for this cofactor to chromosomes 10 in both humans and mice by Southern blot analyses of somatic cell hybrids.

Animals↗
PubMed1993

Generation of a human chromosome 18-specific YAC clone collection and mapping of 55 unique YACs by FISH and fingerprinting.

A yeast artificial chromosome (YAC) library was constructed from a somatic cell hybrid line in which the human chromosome content had been reduced by repeated subcloning to one or two copies of chromosome 18. Screening of 4700 primary yeast transformants generated 74 clones containing a YAC with a human DNA insert averaging 190 kb in size. The human YACs were localized to subregions of chromosome 18 by in situ hybridization of biotin-labeled Alu-PCR products obtained using total yeast DNA as a template. Comparisons of interspersed repetitive sequence-PCR and restriction fragment fingerprint patterns identified five sets of identical and three sets of overlapping YACs. Dual-label fluorescence in situ hybridization interphase mapping was used to determine the order of some nonoverlapping YACs. STS (sequence-tagged site) content mapping was carried out with PCR primers for 56 chromosome 18-specific markers. The identification of YACs containing four known genes--encoding the pituitary adenylate cyclase activating polypeptide (PA-CAP), the myelin basic protein (MBP), ferrochelatase (FECH), and SSAV1, an endogenous retroviral element related to the SSAV virus--provides a precise cytological map position for the respective loci. Our final collection of 55 randomly isolated, unique, and regionally localized YACs (D18S107-D18S161) is distributed over the entire chromosome and collectively covers approximately 12 Mb, i.e., 16% of the estimated 77 Mb of DNA in euchromatin of chromosome 18. These YACs provide reagents for the isolation of genes in these regions and represent nucleation points for the generation of STS to increase coverage of the chromosome by YAC contigs.

Adenylyl Cyclases↗
PubMed1993

cDNA cloning of the two subunits of human CAAX farnesyltransferase and chromosomal mapping of FNTA and FNTB loci and related sequences.

The CAAX farnesyltransferase is a heterodimeric enzyme that attaches a farnesyl group to a single cysteine in several cellular proteins. Substrates include the p21ras proteins, nuclear lamins, and several retinal proteins, all of which end with a "CAAXbox," where C is cysteine, A is an aliphatic amino acid, and X is methionine or serine. Full-length cDNAs for the alpha and beta subunits of the rat farnesyltransferase have been cloned, and both have been shown to be essential for catalytic activity. Here we have used the rat cDNAs to clone cDNAs for the human alpha and beta subunits. Comparison of the human and rat amino acid sequences revealed a remarkable degree of conservation (93% identity for the alpha subunit and 96% identity for the beta subunit). The functional genes for the alpha and beta subunits of human farnesyltransferase (gene symbols, FNTA and FNTB) were localized to human chromosome bands 8p22-q11 and 14q23-q24, respectively, by Southern blot hybridization and PCR analyses of panels of human x Chinese hamster somatic cell hybrid lines and by fluorescence chromosomal in situ hybridization. We also found several related farnesyltransferase genes. FNTAL1 was assigned to 11q13.4-q14.1, FNTAL2 to chromosome 13, and FNTBL1 to chromosome 9.

Alkyl and Aryl Transferases↗
PubMed1993

Genomic distribution and transcription of solitary HERV-K LTRs.

The human genome contains a family of endogenous retroviruses, HERV-K, with sequence homology to the B-type mouse mammary tumor virus. We have now identified a single HERV-K LTR within the C-type-related human retroviral element S71. The HERV-K LTR is located in the antisense direction between the S71 gag and the pol gene, replacing the 5' half of S71 pol. A number of HERV-K LTR-related cDNA clones were detected by screening various human cDNA libraries with an S71 HERV-K LTR probe, indicating abundant transcription of HERV-K-related LTRs in human tissues. Sequence analysis of four cDNA clones revealed LTR sequences with a nucleotide identity of 70 to 90% with HERV-K10 LTR. Some HERV-K-related LTR sequences contain potential short open reading frames. The analyzed cDNA clones do not harbor any retroviral sequences other than those related to HERV-K LTRs. However, most of the solitary LTRs were found to be coexpressed with cellular sequences. Transcription of these LTRs is probably directed by external cellular promoters. We show that HERV-KLTR-like sequences entered the primate genome about 33-40 million years ago. We estimate the human genome to contain about 25,000 copies of HERV-K-related LTRs, which are distributed over most human chromosomes in an irregular manner.

Animals↗
PubMed1993

Sensitivity of Roberts syndrome cells to gamma radiation, mitomycin C, and protein synthesis inhibitors.

Roberts syndrome (RS) is a rare autosomal recessive disorder characterized by pre- and postnatal growth retardation, limb reduction abnormalities, and craniofacial anomalies. Mitotic chromosomes from RS individuals display repulsion of heterochromatin regions or centromere splitting, leading to a railroad-track appearance of mitotic chromosomes. Abnormalities in metaphase duration, anaphase progression, nuclear morphology, and increased frequency of micronucleation have been reported in RS cells. Cells from RS heterozygotes are normal in these respects, and in vitro complementation of the defects in somatic cell hybrids has been reported. Therefore, in preparation for the isolation of cDNAs that complement the RS defect, we investigated various drug treatments to identify an agent that specifically involves the growth of RS cells. Based on the cytogenetic and cell biologic findings, we chose agents that increase micronucleation or inhibit protein synthesis. We found that RS cells are hypersensitive to gamma radiation, mitomycin C, G418 and hygromycin B, but not to colcemid or streptonigrin when compared to normal cells. DNA content and cell viability analysis confirmed that the sensitivity to gamma irradiation was primarily due to increased cell death.

Abnormalities, Multiple↗
PubMed1993

Fibrillin genes map to regions of conserved mouse/human synteny on mouse chromosomes 2 and 18.

Fibrillin proteins are major structural components of the 10-nm microfibrils found in elastic and nonelastic connective tissues. Previous studies have mapped the human genes for two fibrillins to chromosome bands 15q21 (FBN1) and 5q23-q31 (FBN2) and have demonstrated that FBN1 mutations are associated with Marfan syndrome, while FBN2 is linked to the gene for congenital contractural arachnodactyly. Here, we report the isolation of genomic clones of the corresponding mouse fibrillin genes (Fbn-1 and Fbn-2). By analyzing a mapping panel of mouse x rodent somatic hybrid cell lines, we have assigned the Fbn-1 gene to mouse chromosome 2 and the Fbn-2 gene to mouse chromosome 18. We then sublocalized the fibrillin genes to bands 2F (Fbn-1) and 18D-E1 (Fbn-2) by fluorescence in situ hybridization. These regions are known to exhibit conserved synteny with the regions on human chromosomes 15 and 5 that carry the homologous human fibrillin genes. In addition, the Fbn-1 gene maps in the vicinity of the gene for a connective tissue disorder on mouse chromosome 2 called Tight-skin (Tsk).

Amino Acid Sequence↗
PubMed1993

Human dystroglycan: skeletal muscle cDNA, genomic structure, origin of tissue specific isoforms and chromosomal localization.

Dystroglycan is a novel laminin binding component of the dystrophin-glycoprotein complex which provides a linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. Here we report the cDNA and genomic structure of human dystroglycan. The human dystroglycan is encoded by a single gene (DAG1) mapped to chromosome 3 band p21. The coding sequence is organized into two exons, separated by a large intron. The predicted amino acid sequence of human and rabbit dystroglycan are 93% identical with predicted glycosylation sites being conserved. Human dystroglycan is expressed in a variety of fetal and adult tissues. Our data suggest that muscle and non-muscle isoforms of dystroglycan differ by carbohydrate moieties but not protein sequence. Therefore, we hypothesize that variable glycosylation of the conserved protein core might modulate laminin binding. The relationship of dystroglycan to human diseases is discussed.

Amino Acid Sequence↗
PubMed1993

Mutation screening of complete fibrillin-1 coding sequence: report of five new mutations, including two in 8-cysteine domains.

Marfan syndrome (MFS) is an autosomal dominantly inherited connective tissue disorder characterized by cardiovascular, ocular and skeletal manifestations. Previously, mutations in the fibrillin-1 gene on chromosome 15 (FBN1) have been reported to cause MFS. We have now screened 44 probands with MFS or related phenotypes for alterations in the entire fibrillin coding sequence (9.3 kb) by single strand conformation analysis. We report four unique mutations in the fibrillin gene of unrelated MFS patients. One is a 17 bp deletion and three are missense mutations, two of which involve 8-cysteine motifs. Another missense mutation was found in two unrelated individuals with annuloaortic ectasia but was also present in unaffected relatives and controls from various ethnic backgrounds. By using allele-specific oligonucleotide hybridization, we screened 65 unrelated MFS patients, 29 patients with related phenotypes and 84 control individuals for these mutations as well as for a previously reported mutation and two polymorphisms. Our results suggest that most MFS families carry unique mutations and that the fibrillin genotype is not the sole determinant of the connective tissue phenotype.

Adolescent↗
PubMed1993

The human homolog of the glomerulosclerosis gene Mpv17: structure and genomic organization.

Mice carrying a retroviral insert in both alleles of the Mpv17 gene develop glomerulosclerosis and nephrotic syndrome at young age. Thus, the Mpv17 gene is a recessive disease gene in mice and this mouse strain is a potential animal model for glomerular diseases in man. We here describe the isolation and analysis of a human homolog of this gene. By interspecies hybridisation cDNA clones representing a single RNA species were isolated from human liver. Sequence analysis revealed over 90% identify in a region coding for a protein of 176 amino acids and unknown function in both species. Cloning of the genomic locus revealed a single copy gene which we mapped to the short arm of chromosome 2 at band 2p23-p21. Determination of the intron-exon structure and the junction sequences enabled us to establish a PCR based procedure to isolate the coding region from human genomic DNA. Thus, it is now possible to analyse patients suffering from candidate diseases on the basis of a blood sample if biopsy material is not available.

Animals↗
PubMed1993

Missense mutations impair intracellular processing of fibrillin and microfibril assembly in Marfan syndrome.

Dermal fibroblasts from nine Marfan syndrome patients with missense mutations in the fibrillin-1 gene (FBN1) produced nearly normal amounts of fibrillin as determined by quantitative pulse-chase experiments. However, six of the seven mutations involving substitutions of highly conserved cysteine residues exhibited lower rates of intracellular transport and secretion. This effect is likely due to improper folding, since intracellular fibrillin processing was also affected by the reducing agent dithiothreitol. Normal secretion patterns were seen in three mutations that either change the conformation of EGF-like domains or change consensus amino acids required for Ca(++)-binding. In all nine fibroblasts strains, however, the deposition of fibrillin in the extracellular matrix was reduced to 50% of normal in two and to less than 30% in seven of the nine samples studied. The protein alterations caused by these missense mutations are associated with moderate to severe features of Marfan syndrome and a dominant negative mechanism is suggested to play a major role in their pathogenesis.

Amino Acid Sequence↗
PubMed1993

Gene for the alpha-subunit of the human interleukin-3 receptor (IL3RA) localized to the X-Y pseudoautosomal region.

Interleukin-3 (IL3) and granulocyte/macrophage colony-stimulating factor (CSF2) stimulate proliferation and differentiation of various hemopoietic cell types. As is characteristic of the cytokine receptor family, the receptors for these proteins comprise alpha- and beta-subunits. While IL3 and CSF2 receptors each have unique alpha- subunits, they share a common beta-subunit. By Southern analysis of somatic cell hybrid panels, pulsed-field gel electrophoresis (PFGE), and fluorescence chromosomal in situ hybridization, we have mapped the cloned sequence for the IL3 receptor alpha (IL3RA) to the X-Y pseudoautosomal region at bands Xp22.3 and Yp11.3, near the gene for the alpha-subunit of the CSF2 receptor (CSF2RA). The CSF2RA and IL3RA genes are so close that their order could not be determined by two-color interphase in situ hybridization. They share PFGE fragments generated by different restriction enzymes down to the 50-100-kb size range. Pseudoautosomal inheritance was demonstrated by an EcoRI RFLP detected with the IL3RA cDNA probe.

Animals↗
PubMed1993

Diverse growth hormone receptor gene mutations in Laron syndrome.

To better understand the molecular genetic basis and genetic epidemiology of Laron syndrome (growth-hormone insensitivity syndrome), we analyzed the growth-hormone receptor (GHR) genes of seven unrelated affected individuals from the United States, South America, Europe, and Africa. We amplified all nine GHR gene exons and splice junctions from these individuals by PCR and screened the products for mutations by using denaturing gradient gel electrophoresis (DGGE). We identified a single GHR gene fragment with abnormal DGGE results for each affected individual, sequenced this fragment, and, in each case, identified a mutation likely to cause Laron syndrome, including two nonsense mutations (R43X and R217X), two splice-junction mutations, (189-1 G to T and 71 + 1 G to A), and two frameshift mutations (46 del TT and 230 del TA or AT). Only one of these mutations, R43X, has been previously reported. Using haplotype analysis, we determined that this mutation, which involves a CpG dinucleotide hot spot, likely arose as a separate event in this case, relative to the two prior reports of R43X. Aside from R43X, the mutations we identified are unique to patients from particular geographic regions. Ten GHR gene mutations have now been described in this disorder. We conclude that Laron syndrome is caused by diverse GHR gene mutations, including deletions, RNA processing defects, translational stop codons, and missense codons. All the identified mutations involve the extracellular domain of the receptor, and most are unique to particular families or geographic areas.

Adolescent↗