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Biomedical subjects

U Francke

Publications and source records attributed to U Francke.

At least 73 records · Page 4Linked to original sources
PubMed1997

The pathogenicity of the Pro1148Ala substitution in the FBN1 gene: causing or predisposing to Marfan syndrome and aortic aneurysm, or clinically innocent?

In individuals with the Marfan syndrome (MFS), mutations have been identified in the fibrillin-1 gene (FBN1) at 15q21.1. A proline-to-alanine change at position 1148 in exon 27 (Pro1148Ala) has been reported in probands with MFS, aortic aneurysm or Marfanoid-craniosynostosis. It was suggested that this mutation could be a risk factor for aortic dilatation, since it was rarely observed in control populations. To investigate further the pathogenicity of this substitution, we screened 416 unrelated control individuals by allele-specific oligonucleotide (ASO) hybridization. We found 16 individuals who carried the alanine allele (3.8%), 3 of whom were homozygous. Five were of Latin American and eight were of Asian extraction. We also screened 133 probands with MFS, aortic aneurysm or related connective tissue disorders and found 4 (3%) that were heterozygous for the 1148Ala allele. All positive results were confirmed by DNA sequencing. In 20 individuals with 1148Ala, we confirmed the association with the rarer A allele at the IVS27-5G-->A polymorphism. Our results suggest that the Pro1148Ala change is a polymorphism of ancient evolutionary origin that is more prevalent in Asian and Latin American than in Caucasian or African populations.

Alanine↗
PubMed1997

Is Rett syndrome caused by a triplet repeat expansion?

Rett syndrome is usually sporadic, but rare pedigrees with nonpenetrance in obligate carriers and possible anticipation suggest that it could be caused by a triplet repeat expansion (TRE). Rett probands and controls were systematically screened for expansions of any of the 10 possible triplet repeats by using a modified Repeat Expansion Detection (RED) assay that had been shown to detect expanded disease alleles in myotonic dystrophy and Huntington disease. No significant expansions were found in 26 sporadic and six familial Rett probands. Our results exclude the possibility that Rett syndrome is caused by a large TRE. We cannot exclude, however, causation by a small TRE that is masked by the background of longer polymorphic repeats in the normal population.

Case-Control Studies↗
PubMed1997

A new Rett syndrome family consistent with X-linked inheritance expands the X chromosome exclusion map.

Although familial recurrences of Rett syndrome (RTT) comprise only approximately 1% of the reported cases, it is these cases that hold the key for the understanding of the genetic basis of the disorder. Families in which RTT occurs in mother and daughter, aunt and niece, and half sisters are consistent with dominant inheritance and variable expressivity of the phenotype. Recurrence of RTT in sisters is likely due to germ-line mosaicism in one of the parents, rather than to recessive inheritance. The exclusive occurrence of classic RTT in females led to the hypothesis that it is X-linked and may be lethal in males. In an X-linked dominant disorder, unaffected obligate-carrier females would be expected to show nonrandom or skewed inactivation of the X chromosome bearing the mutant allele. We investigated the X chromosome inactivation (XCI) patterns in the female members of a newly identified family with recurrence of RTT in a maternal aunt and a niece. Skewing of XCI is present in the obligate carrier in this family, supporting the hypothesis that RTT is an X-linked disorder. However, evaluation of the XCI pattern in the mother of affected half sisters shows random XCI, suggesting germ-line mosaicism as the cause of repeated transmission in this family. To determine which regions of the X chromosome were inherited concordantly/discordantly by the probands, we genotyped the individuals in the aunt-niece family and two previously reported pairs of half sisters. These combined exclusion-mapping data allow us to exclude the RTT locus from the interval between DXS1053 in Xp22.2 and DXS1222 in Xq22.3. This represents an extension of the previous exclusion map.

Adolescent↗
PubMed1997

Trinucleotide repeats in the human genome: size distributions for all possible triplets and detection of expanded disease alleles in a group of Huntington disease individuals by the repeat expansion detection method.

Using a modified Repeat Expansion Detection (RED) assay, that was optimized for individual oligonucleotides, unrelated individuals were systematically screened for maximal repeat sizes of each of the ten possible trinucleotide repeats. Cloned trinucleotide repeats were generated and used as standards for the detectability of single copy trinucleotide repeat fragments. When the size distributions of trinucleotide repeats were compared to previously reported data, significant differences were found for the CTT repeat, which corresponds to the expanded GAA repeat in Friedreich ataxia, as well as for ATT, CCT and GTT repeats. Since 30-35% of normal individuals have CTG/CAG trinucleotide repeat sizes of 180 bp or more, we investigated the question whether small-scale CTG/CAG repeat expansions are detectable on a population basis by using the RED technique. We blindly screened 20 HD probands with CAG expansions of the HD gene, ranging in size between 120 and 174 bp, and found that a shift to larger CAG size ranges is clearly detectable when comparing the distribution of maximal repeat sizes in the disease group to a control group. Our study, therefore, demonstrates that the application of the RED assay to a population of probands and a population of controls allows the detection of small-scale CTG/CAG repeat expansions in the size range of the expanded HD gene and present in a single allele. We also provide standards and control data for the detection of other trinucleotide repeat expansions.

Adult↗
PubMed1997

An imprinted mouse transcript homologous to the human imprinted in Prader-Willi syndrome (IPW) gene.

The Prader-Willi syndrome (PWS) is caused by genomic alterations that inactivate imprinted, paternally expressed genes in human chromosome region 15q11-q13. IPW, a paternally expressed gene cloned from this region, is not expressed in individuals with PWS, and is thus a candidate for involvement in this disorder. The IPW transcript does not appear to encode a polypeptide, suggesting that it functions at the level of an RNA. We have now cloned a mouse gene, named Ipw, that has sequence similarity to a part of IPW and is located in the conserved homologous region of mouse chromosome 7. The Ipw cDNA also contains no long open reading frame, is alternatively spliced and contains multiple copies of a 147 bp repeat, arranged in a head-to-tail orientation, that are interrupted by the insertion of an intracisternal A particle sequence. Ipw is expressed predominantly in brain. In an interspecies (M.musculus x M.m.castaneus) F1 hybrid animal, expression of Ipw is limited to the paternal allele. We propose that Ipw is the murine homolog of IPW.

Alleles↗
PubMed1997

A novel human homologue of the Drosophila frizzled wnt receptor gene binds wingless protein and is in the Williams syndrome deletion at 7q11.23.

Williams syndrome (WS) is a developmental disorder with a characteristic personality and cognitive profile that is associated, in most cases, with a 2 Mb deletion of part of chromosome band 7q11.23. By applying CpG island cloning methods to cosmids from the deletion region, we have identified a new gene, called FZD3. Dosage blotting of DNA from 11 WS probands confirmed that it is located within the commonly deleted region. Sequence comparisons revealed that FZD3, encoding a 591 amino acid protein, is a novel member of a seven transmembrane domain receptor family that are mammalian homologs of the Drosophila tissue polarity gene frizzled. FZD3 is expressed predominantly in brain, testis, eye, skeletal muscle and kidney. Recently, frizzled has been identified as the receptor for the wingless (wg) protein in Drosophila. We show that Drosophila as well as human cells, when transfected with FZD3 expression constructs, bind Wg protein. In mouse, the wg homologous Wnt1 gene is involved in early development of a large domain of the central nervous system encompassing much of the midbrain and rostral metencephalon. The potential function of FZD3 in transmitting a Wnt protein signal in the human brain and other tissues suggests that heterozygous deletion of the FZD3 gene could contribute to the WS phenotype.

Amino Acid Sequence↗
PubMed1997

Ascending aortic aneurysm with or without features of Marfan syndrome and other fibrillinopathies: new insights.

More than 70 unique fibrillin-1 mutations have been identified in individuals with a variety of phenotypic changes. These range from severe neonatal lethal forms of Marfan syndrome to adult onset manifestations, mitral valve prolapse syndromes to isolated features such as ectopia lentis, Marfanoid body habitus and ascending aortic aneurysm and/or dissection. Fibrillin-1 mutations result in structurally and functionally defective fibrillin-1 molecules and microfibrils. Recent molecular genetic and fibrillin-1 biosynthesis studies suggest that individuals with fibrillin-1 abnormalities can be further subdivided into groups that are associated with distinct differences in severity and prognosis. In recognition of the expanding scope of related connective tissue disorders, we propose the terms microfibrillar disorder for disorders affecting fibrillin-containing microfibrils, and the more narrow concept of fibrillinopathy for clinical entities associated with abnormalities of fibrillin-1 or fibrillin-2. This latter category includes the previously defined disorders Marfan syndrome, congenital contractual arachnodactyly, and forms of ascending aortic aneurysm and/or dissection.

Adult↗
PubMed1996

Structural, functional analysis and localization of the human CAP18 gene.

CAP18 is an antimicrobial protein found in specific granules of PMNs. The human CAP18 (HCAP18) gene was cloned from a human genomic phage library. Sequence analysis revealed the HCAP18 gene to have 4 exons spanning 3 kb, including 700 bp of upstream DNA. Using 3' RACE no homologs of human HCAP18 were found in human bone marrow or leukocyte populations. By PCR analysis of a somatic cell mapping panel and fluorescence in situ hybridization of a genomic clone to metaphase chromosomes the gene was mapped to chromosome band 3p21.3. Like several other genes expressed late in PMN development the CAP18 gene did not contain typical TATA box or CCAAT sequences. Expression in Cos 7 cells permitted limited mapping of the promoter function in upstream fragments of the HCAP18 gene. Western blot, Northern blot and RT-PCR analysis show HCAP18 to be produced specifically in granulocytes. This work forms the groundwork for future analysis of the genetic regulation of this antimicrobial protein during PMN differentiation.

Antimicrobial Cationic Peptides↗
PubMed1996

Diagnostic test for the Prader-Willi syndrome by SNRPN expression in blood.

BACKGROUND: Prader-Willi syndrome (PWS) is caused by alterations of the paternally derived chromosome 15 or by maternal uniparental disomy. The gene for the small nuclear ribonucleoprotein polypeptide N (SNRPN) is expressed only from the paternally derived chromosome 15, due to epigenetic imprinting. The SNRPN gene is not expressed in any patients with PWS regardless of the underlying cytogenetic or molecular causes. METHODS: To develop a rapid molecular diagnostic assay for PWS, we tested the expression of the SNRPN gene and a control gene in 9 patients with PWS and 40 control individuals by PCR analysis of reverse transcribed mRNA from blood leucocytes. We then tested 11 blood samples from patients with suspected PWS. FINDINGS: SNRPN expression could readily be detected in blood leucocytes by PCR analysis in all control samples but not in samples from known PWS patients. Four suspected plus were negative for SNRPN expression were found to have chromosome 15 rearrangements, while the diagnosis of PWS was excluded in the remaining seven with normal SNRPN expression based on clinical, molecular, and cytogenetic findings. INTERPRETATION: The SNRPN-expression test is rapid and reliable in the molecular diagnosis of Prader-Willi syndrome.

Autoantigens↗
PubMed1996

High-density radiation hybrid map of human chromosome 18 and contig of 18p.

A high-resolution radiation hybrid map of human chromosome 18 has been developed by testing DNA samples of 92 radiation hybrids (RH) from a previously characterized chromosome 18-specific RH panel. Half of the 159 STS markers were tested on RH DNA amplified by primer extension preamplification. This map includes 20 genes and 95 polymorphic markers, most of which have heterozygosity frequencies greater than 65% and, therefore, allow integration with genetic maps. The framework map consists of 137 markers ordered with odds of 1000:1 or better and spaced on average 580 kb apart. A YAC contig map of 18p was generated independently by STS content mapping of YACs using the same primers as for RH mapping. The RH map and the contig map are concordant.

Amino Acid Sequence↗
PubMed1996

Molecular cloning, chromosomal mapping, and characterization of the mouse UDP-galactose:ceramide galactosyltransferase gene.

UDP-galactose:ceramide galactosyltransferase (CGT) (EC 2.4.1.62) catalyzes the final step in the synthesis of galactocerebroside, a glycosphingolipid characteristically abundant in myelin. In this report, we describe the isolation of genomic clones spanning the mouse CGT gene. The mouse CGT gene consists of six exons that span a minimum of 70 kb of DNA and that encode a 541 amino acid translation product with extensive sequence similarity to the rat CGT enzyme and to UDP-glucuronosyltransferases (UGT). The 5'-untranslated region of the mouse CGT gene is encoded by a separate exon located approximately 25 kb upstream of the first protein-encoding exon. Furthermore, the genomic organization of the five coding region exons of the mouse CGT gene resembles that of the human UGT1 and rat UGT2B1 genes. Finally, analysis of somatic cell hybrids by PCR and fluorescence in situ hybridization to metaphase chromosomes has localized the mouse CGT gene to chromosome 3, bands E3-F1.

Amino Acid Sequence↗
PubMed1996

Wiskott-Aldrich syndrome protein, a novel effector for the GTPase CDC42Hs, is implicated in actin polymerization.

The Rho family of GTPases control diverse biological processes, including cell morphology and mitogenesis. We have identified WASP, the protein that is defective in Wiskott-Aldrich syndrome (WAS), as a novel effector for CDC42Hs, but not for the other Rho family members, Rac and Rho. This interaction is dependent on the presence of the G protein-binding domain. Cellular expression of epitope-tagged WASP produces clusters of WASP that are highly enriched in polymerized actin. This clustering is not observed with a C-terminally deleted WASP and is inhibited by coexpression with dominant negative CDC42Hs-N17, but not with dominant negative forms of Rac or Rho. Thus, WASP provides a novel link between CDC42Hs and the actin cytoskeleton, which suggests a molecular mechanism for many of the cellular abnormalities in WAS. The WASP sequence contains two novel domains that are homologous to other proteins involved in action organization.

Actins↗
PubMed1996

Rapid evolution of human pseudoautosomal genes and their mouse homologs.

Comparative studies of genes in the pseudoautosomal region (PAR) of human and mouse sex chromosomes have thus far been very limited. The only comparisons that can presently be made indicate that the PARs of humans and mice are not identical in terms of gene content. Here we describe additional comparative studies of human pseudoautosomal genes and their mouse homologs. Using a somatic cell hybrid mapping panel, we have assigned the mouse homolog of the human pseudoautosomal interleukin 3 receptor alpha subunit (IL3RA) gene to mouse Chromosome (Chr) 14. Attempts to clone the mouse homolog of the human pseudoautosomal adenine nucleotide translocase-3 (ANT3) gene resulted in the isolation of the murine homologs of the human ANT1 and ANT2 genes. The mouse Ant1 and Ant2 genes are very similar in sequence to their human homologs, and we have mapped them to mouse Chromosomes (Chrs) (8 and X respectively) that exhibit conserved synteny with the chromosomes on which the human genes are located. In contrast, the homolog of ANT3 appears to be either very divergent or absent from the mouse genome. Southern blot analysis of DNA from a variety of mammalian species shows restricted conservation of human pseudoautosomal genes, a trend that also applies to the two cloned mouse homologs of these genes and to neighboring human genes in distal Xp22.3. Our observations combined with those of other workers lead us to propose a model for the evolution of the PAR that includes both rapid sequence evolution and the incremental reduction in size of the region during mammalian evolution.

Animals↗
PubMed1996

Mutant fibrillin-1 monomers lacking EGF-like domains disrupt microfibril assembly and cause severe marfan syndrome.

Marfan syndrome (MFS), a heritable connective tissue disorder, is caused by mutations in the gene coding for fibrillin-1 (FBN1), an extracellular matrix protein. One of the three major categories of FBN1 mutations involves exon-skipping. To rapidly detect such mutations, we developed a long RT-PCR method. Either three segments covering the entire FBN1 coding sequence or a single 8.9 kb FBN1 coding segment were amplified from reverse-transcribed total fibroblast RNA. Restriction fragment patterns of these RT-PCR products were compared and abnormal fragments were directly sequenced. Six exon-skipping mutations were identified in a panel of 60 MFS probands. All skipped exons encode calcium binding epidermal growth factor (EGF)-like domains and maintain the reading frame. In five probands, exon-skipping was due to point mutations in splice site sequences, and one had a 6 bp deletion in a donor splice site. Pulse-chase analysis of labelled fibrillin protein revealed normal levels of synthesis but significantly reduced matrix deposition. This dominant-negative effect of the mutant monomers is considered in the light of current models of fibrillin assembly. Probands with this type of FBN1 mutation include the most severe forms of MFS, such as neonatally lethal presentations.

Epidermal Growth Factor↗
PubMed1996

The three genes of the human FCGR1 gene family encoding Fc gamma RI flank the centromere of chromosome 1 at 1p12 and 1q21.

The high-affinity receptor for immunoglobulin G, Fc gamma RI (FCGR1), is encoded by a family of three genes within humans that share over 98% of DNA sequence homology. Efforts to define the location of the FCGR1 genes within chromosome 1 have been made to determine if they are tightly linked to the five other FCGR genes present at 1q23. Our results, obtained through both fluorescence in situ hybridization analysis of human cells and Southern analysis of cell lines containing 1p and 1q, show instead that the three genes flank the centromere of chromosome 1 at bands 1p12 and 1q21. FCGR1B was found at 1p12, whereas both FCGR1A and FCGR1C were localized to 1q21. This places the FCGR1 gene family within a large pericentric linkage group which is conserved between humans and mice. We hypothesize that the three FCGR1 genes were separated by a pericentric inversion known to have occurred on human chromosome 1, which relocated FCGR1A and FCGR1C to the long arm and left FCGR1B positioned on the short arm. We have also performed FCGR1 gene copy number experiments which indicate the existence of three FCGR1 genes within the human genome.

3T3 Cells↗