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J T Epplen

Publications and source records attributed to J T Epplen.

At least 235 records · Page 13Linked to original sources
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↗
PubMed1993

Novel members and germline polymorphisms in the human T-cell receptor Vb6 family.

The human T-cell receptor (Tcr) Vb6 family has been scrutinized for polymorphisms, both in coding as well as in intronic sequences by polymerase chain reaction (PCR), subsequent multiple electroblot hybridizations, and sequence analysis. Multiplex PCR is an efficient means of screening for Tcr variability. Four novel loci could be distinguished and several new alleles are described including two pseudogenes. The Vb6 family is characterized by an intronic stretch of simple repetitive (gt)n sequences. These elements are hypervariable, especially in the Vb6.7 subfamily, where they are particularly long. The unexpected persistence of simple repetitive sequences in Tcr and major histocompatibility complex (MHC) class II genes over extended periods of the vertebrate evolutionary history can be interpreted in parallel terms in both gene families.

Amino Acid Sequence↗
PubMed1993

Genetic and population study of a Y-linked tetranucleotide repeat DNA polymorphism with a simple non-isotopic technique.

A polymorphic microsatellite (Y-27H39) based on a (GATA)n repeat was recently discovered on the short arm of the human Y chromosome. We have used a simple technique based on polymerase chain reaction amplification and native polyacrylamide gel electrophoresis followed by highly sensitive silver staining to study the inheritance, the genetic stability and the allele frequency distribution of this polymorphism in the Brazilian population. We have analyzed 100 randomly chosen Caucasian Brazilian father-son pairs with established paternity. Five alleles, four base-pairs apart, were easily distinguishable. Their frequencies were: A (186 bp), 0.19; B (190 bp), 0.49; C (194 bp), 0.24; D (198 bp), 0.07; E (202 bp), 0.01. In all father-son pairs, there was complete allelic concordance. From these data, the probability of discrimination for forensic cases and the average probability of exclusion for paternity cases were both calculated to be 0.66.

DNA Fingerprinting↗
PubMed1993

Changes of telomere lengths in human intracranial tumours.

The termini of human chromosomes comprise stretches of G-rich repeats that are about 5-20 kilobase (kb) in length. The size of the telomeres can be determined by hybridization with probes specific for these (ttaggg)n sequences after digestion of chromosomal DNA with appropriate restriction enzymes and electrophoretic separation of the fragments. Here, probing with the 32P-labelled synthetic (TTAGGG)3 oligonucleotide revealed length changes of the telomeres occurring in intracranial tumours. Among 60 samples, analysed, 41.7% showed telomere elongation, and 21.7% telomere reduction, whereas 36.7% of the tumours exhibited equal lengths compared with the patients' peripheral blood leukocytes. Most of the elongated glioma telomeres exceeded in length those of untransformed astrocytes derived from human fetal tissue.

Adolescent↗
PubMed1993

Vb6 T-cell receptor elements in artiodactyls: conservation and germline polymorphisms.

By use of primers specific for human T-cell receptor (Tcr) Vb6 gene elements, a typing system for Tcr Vb variability in several artiodactyl species has been established. The amplified polymorphic locus is homologous to the human Vb6 gene element. Like the human counterpart, the artiodactyl Vb6 element contains a polymorphic intronic simple (gt)n repeat stretch. Extensive length polymorphism of this simple repeat sequence in some artiodactyls should allow efficient association studies in a multiplex approach, especially including MHC class II genes. On the protein level the Vb regions display little variability in the inter-species comparison among artiodactyls. The amino acid substitutions are not concentrated in the putative complementarity determining regions, suggesting evolutionary conservation. In addition, the simple repetitive element has been preserved in the same genomic location for more than 7 x 10(7) years. Similar evolutionary persistence has already been demonstrated for a (gt)n(ga)m repeat stretch in the second intron of the MHC-DRB locus. The reasons for these parallel developments in evolution are so far not clear, but they may point to a biological meaning if not function of the intronic simple repeat element.

Amino Acid Sequence↗
PubMed1993

Chromosomal assignment of the human smg GDP dissociation stimulator gene to human chromosome 4q21-q25.

The 3'-end of the cDNA encoding the smg GDP dissociation stimulator (smg GDS) protein shares 100% homology with the previously published expressed sequence tag 00038 site. This site extends the 3'-end of the smg GDS gene by 212 bp. It has been localized to human chromosome 4. Here, we have refined the localization of smg GDP to human chromosome 4q21-q25 using a mapping panel of rodent/human somatic cell hybrids containing different parts of chromosome 4. This chromosomal localization of smg GDP to 4q21-25 overlaps with a region of allele loss in primary hepatocellular carcinoma (4q13-q26).

Animals↗
PubMed1993

Trinucleotide repeat elongation in the Huntingtin gene in Huntington disease patients from 71 Danish families.

IT15 is a novel gene, localized to chromosome 4, and encoding a protein named Huntingtin. A polymorphic CAG repeat in the proposed open reading frame of IT15 has been characterized, and an elongation of this repeat has been correlated to Huntington's Disease. We have investigated the CAG repeat in the Huntingtin gene in 71 unrelated Danish patients with Huntington's Disease, and found repeat lengths of 39 to 70 repeat units in contrast to 9 to 30 CAG's on normal chromosomes. Comparison of repeat length and age at onset of disease symptoms in 52 individuals indicates an inverse correlation between the age at onset and the number of CAG repeat units.

Adolescent↗
PubMed1993

Typing of artiodactyl MHC-DRB genes with the help of intronic simple repeated DNA sequences.

An efficient oligonucleotide typing method for the highly polymorphic MHC-DRB genes is described for artiodactyls like cattle, sheep and goat. By means of the polymerase chain reaction, the second exon of MHC-DRB is amplified as well as part of the adjacent intron containing a mixed simple repeat sequence. Using this primer combination we were able to amplify the MHC-DRB exons 2 and adjacent introns from all of the investigated 10 species of the family of Bovidae and giraffes. Therefore, the DRB genes of novel artiodactyl species can also be readily studied. Oligonucleotide probes specific for the polymorphisms of ungulate DRB genes are used with which sequences differing in at least one single base can be distinguished. Exonic polymorphism was found to be correlated with the allele lengths and the patterns of the repeat structures. Hence oligonucleotide probes specific for different simple repeats and polymorphic positions serve also for typing across species barriers. The strict correlation of sequence length and exonic polymorphism permits a preselection of specific oligonucleotides for hybridization. Thus more than 20 alleles can already be differentiated from each of the three species.

Alleles↗
PubMed1993

Leukaemic T cells from patients with chronic lymphocytic leukaemia of T-cell origin respond to Staphylococcus aureus enterotoxin superantigens.

We investigated the in vitro responsiveness of peripheral blood lymphocytes from two patients with T-cell chronic lymphocytic leukaemia (T-CLL) to Staphylococcus aureus enterotoxin (SE) superantigens. T-cell receptor (TcR) alpha beta (V beta 7.1)-expressing CD4+ leukaemic T cells from patient HE (white blood cell count 480,000/microliters) proliferated in response to SEA and, only at 1000-fold higher concentrations, to SEB, SED, and SEE. CD4+CD8+ TcR alpha beta (V beta 12.1)-expressing leukaemic T cells from patient KO (white blood cell count 120,000/microliters) were activated by SEB but not by the other tested SEs. In both instances, the activation of leukaemic T cells by SE was dependent on the presence of HLA-DR+ cells. Southern blot analysis of TcR beta gene rearrangement confirmed that the proliferating cells were derived from the leukaemic T-cell clone and not from contaminating normal T cells. These data indicate that leukaemic T cells from patients with T-CLL exert a clonally variable responsiveness to SE superantigens. We conclude that recognition of specific antigen and subsequent signal transduction can be initiated via the TcR of leukaemic T-CLL cells.

Antigens, Bacterial↗
PubMed1993

Rapid detection of engraftment using T cell receptor gene polymorphism after allogeneic bone marrow transplantation in an alloimmunized child with severe aplastic anemia.

A severely alloimmunized boy with aplastic anemia received an HLA-identical BMT from his brother. Despite intensive immunosuppression and large marrow dose, peripheral signs of engraftment occurred only late under G-CSF treatment. With leukocyte counts of < 0.5 x 10(9)/l, chimerism could be proven not only by oligonucleotide fingerprinting but also within 48 h by analysis of polymorphism in the TCR gene family. This rapid and sensitive method to detect engraftment before it became quantitatively evident was important for the clinical management of the patient, obviating the need to search for an alternative marrow donor.

Anemia, Aplastic↗
PubMed1992

Diagnostic applications of repetitive DNA sequences.

The potential, the advantages and the different areas of diagnostic applications are discussed for the various categories of repetitive DNA sequences. Since all eukaryotes are characterized by genomic redundancy, these sensitive, rapid and comparatively simple techniques are revolutionizing many a field of clinical and experimental diagnostics.

Animals↗
PubMed1992

Diversity of T cell receptor alpha and beta chain genes expressed by human T cells specific for similar myelin basic protein peptide/major histocompatibility complexes.

T cell receptor (TcR) alpha and beta nucleotide sequences involved in the human autoreactivity to myelin basic protein (MBP) were studied by screening cDNA libraries derived from 11 independent T lymphocyte clones (TCC) established from multiple sclerosis patients and healthy donors. The TCC with defined MBP peptide specificity and HLA-DR restriction expressed multiple TcR. Even TCC recognizing the same human MBP peptide [amino acids (aa) 139-153] in identical or very similar HLA-DR context expressed diverse TcR. Two TCC which recognized peptide aa 139-153 equally well in the context of both HLA-DR2a and -DR1 molecules used distinct TcR alpha but identical beta chains. The knowledge of TcR beta and TcR alpha chain sequences of human MBP-specific T cells will allow studies correlating structure and function of TcR and their targets in MBP autoreactivity. This may have an impact on the development of immunotherapies in multiple sclerosis.

Amino Acid Sequence↗
PubMed1992

On the potential of simple repetitive DNA for fingerprinting in clinical, forensic, and evolutionary dynamic studies.

The purpose of this review is to discuss critically the practical meaning of a specific genome component, simple repetitive desoxyribonucleic acid (DNA) sequences as clinical and forensic and diagnostic and research tools. Previously, multilocus DNA fingerprinting was the major technology employed to visualize such simple repeat sequences. This technique enables many polymorphic loci to be simultaneously detected thus yielding vast amounts of information. With the advent of enzymatic DNA amplification via the polymerase chain reaction (PCR), individual simple repeat loci can be demonstrated, theoretically even from single DNA molecules and so a wealth of additional approaches have also become feasible. In general investigating, small, known, single copy parts of genomes have not posed truly insurmountable problems if enough material was available. There have even been a few (anecdotal) reports on the amplification of simple repeats from ancient DNA (see, e.g. [30]. Here we would like to after a solid basis for an earnest discussion of the applications of these simple repetitive sequences using various methodological approaches relevant for clinical diagnosis, setting aside the obvious unsolved mysteries of their biology.

Animals↗
PubMed1992

Exonic polymorphism vs intronic simple repeat hypervariability in MHC-DRB genes.

Gene products encoded by the major histocompatibility complex often exhibit a high degree of polymorphism. In humans the HLA-DR polymorphism is due to more than 50 alleles with varying exon 2 sequences. Each group of DRB alleles contains a certain form of the basic simple repeat motif (gt)n(ga)m in intron 2. Identical alleles can be differentiated on the basis of the hypervariable repeat. In this study focused on cattle (Bos taurus) we identified different Bota-DRB alleles in a limited survey by amplification via polymerase chain reaction and sequencing. In addition DRB exon 2 sequences were also obtained from eight additional hoofed animal species (seven horned artiodactyls and one pig) revealing artiodactyl-specific polymorphic and nonpolymorphic substitutions. In the genus Bos the intronic simple repeat variability was compared with exonic DRB polymorphism. As in humans all Bota-DRB exons were always associated with specifically organized basic simple repeat structures. Yet the extent of simple repeat variability was lower in cattle compared to humans. Selective breeding in the process of domestication might be responsible for the diminished intronic hypervariability. Nevertheless, the hypermutable simple repeat sequences have been preserved in the same position and with the same principal structure for at least 70 x 10(6) years of evolution. Unexpectedly, the rate of intronic simple repeat and exonic changes appear quite similar.

Alleles↗