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C Epplen

Publications and source records attributed to C Epplen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Friedreich's ataxia. Revision of the phenotype according to molecular genetics.

Friedreich's ataxia is an autosomal recessively inherited neurodegenerative disorder caused by expansions of an unstable GAA trinucleotide repeat in the STM7/X25 gene on chromosome 9q. We studied the (GAA)n polymorphism in 178 healthy controls and 102 patients with idiopathic ataxia. The repeat size ranged from 7 to 29 (GAA)n motifs on normal chromosomes and from 66 to 1360 trinucleotide repetitions in Friedreich's ataxia patients. Meiotic instability of expanded alleles was observed without significant differences in maternal and paternal transmissions. Thirty-six of 102 patients were typed homozygous for expanded (GAA)n alleles. Twenty-seven of these presented with the typical Friedreich's ataxia symptoms and nine patients with an atypical Friedreich's ataxia phenotype. Before molecular genetic diagnosis had been performed seven of these patients had been classified as early onset cerebellar ataxia and two as idiopathic sporadic cerebellar ataxia of late onset. In contrast, in one family with typical Friedreich's ataxia phenotype we did not find an expanded allele; this suggests that there can be either point mutations in the X25 gene on both chromosomes or locus heterogeneity in Friedreich's ataxia. The phenotypic spectrum of Friedreich's ataxia is much broader than considered before. Early onset, areflexia, extensor plantar responses and reduced vibration sense should no longer be considered essential diagnostic criteria of Friedreich's ataxia. In comparison with the non-Friedreich's ataxia group hypertrophic cardiomyopathy seems to be the only symptom specific for Friedreich's ataxia. However, it is not obligatory. The phenotype is significantly influenced by the number of GAA repeats with close genotype-phenotype relationships when the smaller of the two alleles is considered. Repeat length correlated inversely with age at onset, onset of dysarthria and progression rate. In conclusion, molecular genetic analysis appears mandatory for the diagnosis and genetic counselling of Friedreich's ataxia. The molecular genetic test should be applied not only to patients with typical Friedreich's ataxia phenotype but also in all cases of idiopathic autosomal recessive or sporadic ataxia.

Adolescent↗
PubMed1996

Multilocus fingerprinting and single locus analyses in the great tit for paternity determination.

In order to arrive at detailed information about the occurrence of alternative reproductive tactics in the great tit (Parus major) we examined parental lineages by multilocus fingerprinting in 51 great tit broods containing 429 nestlings. In 45% of the broods at least one nestling was found to stem from copulations with males other than the social mate of the female. Single broods contained up to 62% extra-pair young (EPY). Single locus profiling revealed how many fathers were involved in extra-pair paternity (EPP) within each brood: In most cases a single male is the genetic father of all EPY in a given brood.

Alleles↗
PubMed1995

Indirect gene diagnoses for complex (multifactorial) diseases--a review.

The analysis of multifactorial diseases requires the efficient investigation of large numbers of (gene) loci and patient (family) samples. Since simple repetitive DNA markers are dispersed all over the chromosomes, molecular techniques employing these tools render most conventional screening procedures obsolete. Examples of tumors, autoimmune diseases and infections are presented to validate concepts of indirect gene diagnoses via simple, tandemly arranged, repetitive DNA sequences. The salient advantages of microsatellite technologies vs. those of multilocus DNA fingerprinting are weighed.

Animals↗
PubMed1995

Indirect DNA/gene diagnoses via electrophoresis--an obsolete principle?

In principle, gene defects can be investigated directly or indirectly via informative polymorphisms in their vicinity. But because many defects are not yet defined molecularly, these inherited diseases can only be diagnosed indirectly via analysis of informative family situations. Since (multiple) mutation analyses, e.g. via DNA sequencing, are time-consuming and expensive, indirect analysis may still be performed initially--particularly in diseases caused by heterogenous mutations. We focus on diagnoses of neurological and (auto)immune diseases by polymerase chain reaction and separation of the DNA fragments via gel electrophoreses. Even after gene defects have been identified, indirect analysis might be necessary, for example in Huntington's chorea. Although this genetic defect has been characterized as a trinucleotide disease, indirect DNA diagnosis is still performed in particular cases for psychological reasons. The causes of autoimmune diseases are multifactorial and the inheritance is complex, involving several genes. Genome-wide screening programs may involve indirect approaches via analyses of polymorphic microsatellites. Large parts of the immunological genome can be covered when 20 or more genes are investigated simultaneously. Thus the genetic bases of autoimmune diseases are disclosed. Microsatellites themselves could have a biological meaning. We therefore discuss also DNA/protein interactions for simple tandem repeats, the major targets for indirect gene diagnoses. Only indirect evidence exists that certain simple repeats influence genomic (in)stability. Taken together, indirect gene diagnoses supplement direct approaches in a variety of different purposes and in combination with standard electrophoresis techniques.

Animals↗
PubMed1995

Immunoprinting reveals different genetic bases for (auto)immuno diseases.

The genetic basis of complex (auto)immune diseases has been studied for an ovine nematode infection, human rheumatoid arthritis (RA), early onset pauciarticular arthritis (EOPA) and multiple sclerosis (MS). Immunoprinting combines the powerful simplicity of polymerase chain reaction (PCR)-based amplification of discrete, highly informative microsatellite loci with the principle of genetic associations. This approach has allowed us to define novel genetic risk factors in adult RA patient categories whereas EOPA forms in juveniles display other prominent genetic contributions. Differentially regulated tumor necrosis factor (TNF) expression may lead to a better understanding of the causal pathogenesis of EOPA while T cell receptor (TCR) gene polymorphisms appear crucial for RA manifestations in certain patient groups. Statistically significant marker associations have still to be defined for MS in larger panels of patient and control cohorts. The clinical course of the disease will probably have to be taken into account when associations with lymphokine levels are evaluated. In essence a convoluted myriad of negative and a few positive disease association data have been generated efficiently by immunoprinting. As expected, the interrelationships are truly complicated between the polymorphic genetic instances predisposing to autoimmune disease. Nevertheless, risk factors may be defined on an individualized basis by indirect gene diagnosis revealing predispositions and providing a more solid basis for differential diagnosis and treatment.

Adult↗
PubMed1995

Immunoprinting: various genes are associated with increased risk to develop rheumatoid arthritis in different groups of adult patients.

To identify genes that contribute to the manifestation of rheumatoid arthritis we performed association studies via microsatellite analyses of immunorelevant loci (HLA-DRB, 5 T cell receptor loci, TNFa IL1, IL2, IL5R and CD40L). A total of 183 patients and 275 healthy controls were typed in terms of HLA and grouped according to the known predisposing HLA-DRB1 genes (DRB1*04; relative risk approx. 5; DRB1*01, relative risk approx. 2; a third group carried neither allele). Microsatellite polymorphisms characterizing the TCRBV6S3, CD3D, IL1A, IL2, and IL5R genes did not show significant associations with rheumatoid arthritis, whereas TCRBV6S1, TCRBV6S7, TNFa, and CD40L genes may influence relative protection or risk in certain groups of patients. Analysis of a microsatellite marker adjacent to the transcription element alpha (TEA) in the T cell receptor alpha delta complex indicates that in the cohort carrying neither the DRB1*04 nor the DRB1*01 allele the relative risk to acquire rheumatoid arthritis is increased (> 13) or decreased (< 0.07), depending on the inherited microsatellite allele adjacent to the TEA locus. Sequence analysis of the closely linked TEA region from patients and controls revealed a novel dimorphism. Only the newly identified TEA allele leads to binding of a nuclear protein that may be involved in the regulated expression of the TCRDA genes. Subsequent typing of rheumatoid arthritis patients and controls revealed, however, that the association of the microsatellite marker is largely independent of the TEA allele, confirming incomplete linkage in the 2 kb region of the TCRDA locus. These results are discussed in the context of hot spots of recombination in this genomic region and other linked candidate sequences that predispose to develop rheumatoid arthritis.

Alleles↗
PubMed1995

Efficient reidentification of chromosome slides from human metaphase spreads via microsatellite polymerase chain reaction.

In order to exclude inadvertent mixing of slides carrying metaphase spreads, chromosomal DNA was re-extracted several months after routine slide preparation (hypotonic treatment, spreading, fixation, staining, embedding and microscopic inspection) in different laboratories. The DNA yield was largely dependent on the number of cells originally fixed and the batch of the embedding material. Average fragment sizes ranged below 200 nucleotides. The polymerase chain reaction systems for DNA amplification included several polymorphic microsatellite loci specifically selected for short amplification products. Reidentification with a high probability for identity was possible by comparison with microsatellite alleles obtained from the peripheral blood of the individuals investigated. Possible applications, the differentiation potential and the limitations of the methodology are discussed.

Alleles↗
PubMed1995

Immunoprinting excludes many potential susceptibility genes as predisposing to early onset pauciarticular juvenile chronic arthritis except HLA class II and TNF.

DNA profiles (immunoprints) were generated for 120 patients suffering from early onset pauciarticular chronic arthritis (EOPA-JCA) and > 500 healthy controls utilizing highly polymorphic microsatellites in the vicinity of immunorelevant genes. Six T cell receptor (TCR) markers for the CD3D, TCRDVAJ, TEA, TCRBV6S1, BV6S3, BV6S7 and BV13S2 genes were analysed. Furthermore markers for the cell surface molecule CD40L, for cytokine genes (IL-1A, IL-2, IFN-alpha, FGF-alpha, TNF-alpha), the chromosomal region of the IRF2 and the cytokine receptor gene IL5RA were studied as well as two polymorphisms within the promotor region of the TNF-alpha gene. Coding region polymorphisms were evidenced indirectly by repeat length variation or they were predicted from the microsatellite distribution profiles and then confirmed by direct sequence analysis. Statistical evaluations were performed with respect to known predispositions, predominance of females (> 80%) and HLA-DR and -DQ haplotypes. Cell surface molecules (TCR, CD40L, IL5RA) as well as almost all cytokines (IL-1A, IFN alpha, FGFA, IRF2 region) were excluded as predisposing in our JCA panel. The TNF-alpha microsatellite alleles (GT)10-12 contribute considerably to manifestation of the disease, in HLA-DRB1*11(12) individuals (RR = 12.8). The TNF-alpha allele is not found in linkage disequilibrium with HLA-DRB1*11(12) and may be present on either chromosome 6. Thus, a novel susceptibility factor probably within the TNFA/TNFB gene region has been identified via linkage with the TNF-alpha microsatellite allele. Apparently complex compositions of the genetic background rather than single genes provide the precondition for manifestation of the autoimmune disease EOPA-JCA. Immunoprinting unravels the variability of the immunological genome via the semi-directed microsatellite approach efficiently.

Age of Onset↗
PubMed1994

Selected di- and tetranucleotide microsatellites from chromosomes 7, 12, 14, and Y in various Eurasian populations.

Microsatellite polymorphisms of nine Eurasian populations (> 1200 chromosomes) were analyzed for the following loci: i) intronic (gt)n stretches of three T cell receptor (TCR) B loci on chromosome 7 (TCRBV6S1, TCRBV6S3, TCRBV6S7); ii) an intergenic (gt)n repeat in the region between the TCRDV3 and TCRAJ61 elements on chromosome 14; iii) two tetranucleotide simple repeats (D12S66, D12S67), not linked to known genes on chromosome 12; iv) a Y-chromosomal (gata)n polymorphism (DYS19). In general, allele frequencies and heterozygosity rates were similar, but specific alleles were missing in one or more populations. Distinct DYS19 alleles predominated in particular cohorts. Different allele frequencies were observed for the TCR loci in European and Asian populations. Tetranucleotide polymorphisms were distributed normally, whereas TCR alleles displayed bimodal frequency profiles. For TCRBV6S1 and TCRBV6S7, this profile reflects a diallelic protein polymorphism that correlates exactly with the length of the intronic repeats.

Alleles↗
PubMed1994

Expression of (cac)n/(gtg)n simple repetitive sequences in mRNA of human lymphocytes.

Di- and trinucleotide tandem repeat sequences are ubiquitously interspersed and are often polymorphic in the human genome. We have analyzed the transcription of simple (cac)n/(gtg)n repeats in the cDNA of RNA from human lymphocytes. When using such motifs as probes in RNA hybridization experiments, distinct signals are scarcely demonstrable. In order to investigate mRNA sequences that contain such simple repeats, 1 million phage clones from cDNA libraries were screened with the probe (CAC)5. From 50 hybridizing phages, 38 clones were successfully isolated and characterized. The lengths of the transcripts ranged from 120 bp to 3.5 kb. More than 15 different additional simple repeat motifs were found immediately next to or distant to the (cac)n/(gtg)n repeat. In 12 clones, significant homologies were identified with a wide variety of unrelated genes, such as a processed pseudogene of human ubiquitin, serin protease inhibitor genes, a gene candidate from yeast, and sequence-tagged sites of man and mouse. Of the clones, 18% represented mRNA of MHC class I promotor binding protein; 79% displayed novel single copy sequences or partial similarity to many different organelle and nuclear genomes of animal, fungal, bacterial, and viral sequences. These data indicate that short (cac)n/(gtg)n stretches (n < or = 6) are sometimes contained in open reading frames, but more often in the 3' and 5' untranslated portions of mature mRNAs. Longer stretches of perfect simple (cac)n/(gtg)n repeats can rarely be recovered, even from the hnRNA of human lymphocytes.

Amino Acid Sequence↗
PubMed1994

Exploiting the informativity of 'meaningless' simple repetitive DNA from indirect gene diagnosis to multilocus genome scanning.

Most eukaryotic genomes are characterized by excessively large amounts of non-coding DNA sequences among which redundant (repetitive) elements constitute a sizable portion. The functional role of an abundant subclass of repetitive sequences--simple, tandemly arranged repeats--remained mysterious so far. Even the biological meaning of most of these elements appears quite refractory to present-day techniques in molecular genetics. Notwithstanding simple repetitive sequences have been developed into superb tools for various aspects of eukaryotic genome research: Using oligonucleotide probes carrying simple repeat motifs multilocus DNA fingerprinting can be applied for individual identification and genetic relationship analyses in plants, animals and humans. Microsatellite analyses via polymerase chain reaction of simple repeat blocks allow for efficient investigations of such divers subject matters as criminal stains, detailed genome maps and indirect gene diagnoses.

Communicable Diseases↗
PubMed1993

Simple repetitive (GAA)n loci in the human genome.

In order to investigate the organization (and inheritance) of simple tandem (GAA)n repeats in the human genome, different restriction enzymes were employed for DNA digestion followed by separation of the resulting fragments by agarose gel electrophoresis. Frequently cutting enzymes (4 bp recognition sites) revealed highly complex multilocus banding patterns after conventional horizontal submarine gels. Fragments larger than 25 kb, resulting from digestions with rarely cutting enzymes (6 bp recognition sites), were separated by pulsed-field gel electrophoresis (PFGE). Hybridizations were carried out directly in the gel matrix. Nearly all of the enzymes produce at least one predominant signal band after hybridization with (GAA)6. The frequency of (GAA)n stretches was estimated on human chromosome 4 by probing a respective cosmid library. In comparison with other simple di-, tri- and tetranucleotide repeats, (GAA)n stretches appear underrepresented. Hybridization of a fetal human brain cDNA library indicated very few expressed (GAA)n repeats. These data are discussed with particular reference to genomic organization and other simple repetitive trinucleotide stretches.

Chromosome Mapping↗
PubMed1993

On the essence of "meaningless" simple repetitive DNA in eukaryote genomes.

Various kinds of simple tandemly repetitive DNA sequences are abundantly interspersed in the genomes of practically all eukaryotic species studied. The comparatively elevated mutation rates of simple repeat blocks result in highly polymorphic and therefore extremely informative investigation systems for studies on forensic, ecological and genetic relationship questions. Recently the techniques for analyzing simple repeats have achieved great effectivity and simplicity. Beyond their utility as tools for differentiation and individualization, certain of these repeated elements harbor quite unexpected qualities which may be discussed in the context of their biological meaning. i) A specific subset of simple (cac)n or (gtg)n repeats is expressed in mature mRNA and total cellular RNA. ii) Despite the apparently high mutation rate certain (gt)n or mixed (gt)n/(ga)m stretches of intronic simple repeats are preserved in immunologically relevant genes for at least 70 x 10(6) years and they bind nuclear protein molecules with high affinities. Consequently in addition to their tool character, the biological aspects of simple repeated DNA should be taken into consideration.

Animals↗
PubMed1993

Towards covering immunological genes with highly informative markers: a trans-species approach.

To establish a highly informative screening system for immunologically relevant genes ("immunoprinting") we co-amplified via polymerase chain reaction (PCR) polymorphic exons plus adjacent intronic simple repetitive dinucleotide stretches in the T-cell receptor (Tcr) Vb6 and Major Histocompatibility Complex (MHC)-DRB loci in man and several ungulate species. In both gene families the basic structure of the simple repeat was found to be preserved for more than 70 x 10(6) years in all investigated species. The simple repeats exhibit extensive length variability. Distinct exon sequences are correlated with a defined repeat length and substructure. In addition, PCR and the oligonucleotides for typing were applicable to a broad range of species from different mammalian orders. Multiplex PCR of different members of the Tcr Vb6 family and MHC-DRB resulted in a complex pattern similar to an oligolocus fingerprint. Hence immunoprinting can be employed for searching for associations of immunologically relevant genes with diseases even across species barriers.

Animals↗
PubMed1993

The paradox of MHC-DRB exon/intron evolution: alpha-helix and beta-sheet encoding regions diverge while hypervariable intronic simple repeats coevolve with beta-sheet codons.

Twenty-one different caprine and 13 ovine MHC-DRB exon 2 sequences were determined including part of the adjacent introns containing simple repetitive (gt)n(ga)m elements. The positions for highly polymorphic DRB amino acids vary slightly among ungulates and other mammals. From man and mouse to ungulates the basic (gt)n(ga)m structure is fixed in evolution for 7 x 10(7) years whereas ample variations exist in the tandem (gt)n and (ga)m dinucleotides and especially their "degenerated" derivatives. Phylogenetic trees for the alpha-helices and beta-pleated sheets of the ungulate DRB sequences suggest different evolutionary histories. In hoofed animals as well as in humans DRB beta-sheet encoding sequences and adjacent intronic repeats can be assembled into virtually identical groups suggesting coevolution of noncoding as well as coding DNA. In contrast alpha-helices and C-terminal parts of the first DRB domain evolve distinctly. In the absence of a defined mechanism causing specific, site-directed mutations, double-recombination or gene-conversion-like events would readily explain this fact. The role of the intronic simple (gt)n(ga)m repeat is discussed with respect to these genetic exchange mechanisms during evolution.

Alleles↗