Biomedical subjects

Rainer Blasczyk

Publications and source records attributed to Rainer Blasczyk.

22 records · Page 2Linked to original sources

PubMed2002

The nature of introns 4-7 largely reflects the lineage specificity of HLA-A alleles.

For most HLA-A alleles the phylogeny of the 3' non-coding regions has not yet been studied systematically. In this study, we have determined the sequences of introns 4-7 in 50 HLA-A variants, and have computed nucleotide substitution rates and phylogenetic relationships. The A2/A28, A9, and A10 groups were characterized by clear lineage specificity. For the A19 group, lineage specificity was weaker. A*3001 clustered together with the alleles of the A1/A3/A11/A36 serological family, but not with the A19 group alleles. Reduced lineage specificity was also observed for the alleles of the A1/A3/A11/A36groups. The 3' intron sequences of A*8001 were clearly distinct from all other alleles studied. In several cases two allelic groups shared identical intron sequences, whereby the patterns varied with the introns. A similar situation has been previously described for the 5' introns. Since recombination is the major mechanism of HLA diversification, the intronic lineage specificity corresponds to the comparatively lower recombination rate of the HLA-A 3' exons. The low level of recombination within the 3' region of HLA-A is supported by the low CpG content with a maximum of 3.0% in this region compared with up to 10.7% in the 5' region. Apart from phylogenetic studies of HLA diversity and diversification, the sequence data obtained in our study may prove valuable for the development of a haplotype-specific sequencing strategy for the HLA-A3' exons and for the explanation of recombination events in newly described HLA class I alleles.

Base Sequence↗

PubMed2002

Loss of single HLA class I allospecificities in melanoma cells due to selective genomic abbreviations.

Expression of human leucocyte antigen (HLA) Class I molecules is essential for the recognition of malignant melanoma (MM) cells by CD8(+) T lymphocytes. A complete or partial loss of HLA Class I molecules is a potent strategy for MM cells to escape from immunosurveillance. In 2 out of 55 melanoma cell cultures we identified a complete phenotypic loss of HLA allospecificities. Both patients have been treated unsuccessfully with HLA-A2 peptides. To identify the reasons underlying the loss of single HLA-A allospecificities, we searched for genomic alterations at the locus for HLA Class I alpha-chain on chromosome 6 in melanoma cell cultures established from 2 selected patients with MM in advanced stage. This deficiency was associated with alterations of HLA-A2 gene sequences as determined by polymerase chain reaction-sequence specific primers (PCR-SSP). Karyotyping revealed a chromosomal loss in Patient 1, whereas melanoma cell cultures established from Patient 2 displayed 2 copies of chromosome 6. Loss of heterozygosity (LOH) using markers located around position 6p21 was detected in both cases. By applying group-specific primer-mixes spanning the 5'-flanking region of the HLA-A2 gene locus the relevant region was amplified by PCR and subsequent sequencing allowed alignment with the known HLA Class I reference sequences. Functional assays using HLA-A2-restricted cytotoxic T-cell clones were performed in HLA-A2 deficient MM cultures and revealed a drastically reduced susceptibility to CTL lysis in HLA-A2 negative cells. We could document the occurrence of selective HLA-A2 deficiencies in cultured advanced-stage melanoma metastases and identify their molecular causes as genomic alterations within the HLA-A gene locus.

Alleles↗

PubMed2002

Non-expression of HLA-A*2901102 N is caused by a nucleotide exchange in the mRNA splicing site at the beginning of intron 4.

We describe the identification of the novel human leukocyte antigen (HLA) blank allele A*2901102 N which was detected in an individual of mixed race. The serological HLA class I typing was A1; B7,44 whereas PCR-SSP indicated the presence of an additional A*29 allele. The pedigree analysis demonstrated that the new blank allele segregated with the haplotype A*29null B*07, inherited from the individual's Vietnamese father. A single G-->Tau transversion was detected at position 1 of intron 4, which is a highly conserved nucleotide position in vertebrate splice donor sites. Accordingly, it is very likely that this nucleotide exchange inhibits the splicing of intron 4, resulting in a premature stop codon further downstream. Despite this alteration, transcription into mRNA was demonstrated.

Alleles↗

PubMed2002

A weak blood group A phenotype caused by a new mutation at the ABO locus.

BACKGROUND: A number of alleles have been described for ABO encoding for common and rare ABO blood group phenotypes. Critical mutations in the coding sequence of ABO that may confer the different specificity and activity of the glycosyltransferases encoded by this gene locus have been identified. STUDY DESIGN AND METHODS: Three unrelated patients from Germany, Turkey, and Bosnia who were diagnosed as having variant A subgroups were subjected to extended ABO typing. Serologic investigations were performed with standard methods. The genetic basis of the ABO phenotypes was determined by haplotype-specific sequence analysis of the last two exons (exons 6 and 7) of ABO and the intervening intron. RESULTS: The RBCs of all three patients showed serologic A characteristics being similar to subgroup A(x). The serum of all three patients contained weakly reactive anti-A. In all three patients, sequence analysis indicated an A allele with a nucleotide sequence identical to ABO(*)A101 except for a single-base substitution in exon 7 at position 502, where C was replaced by G. This point mutation resulted in an amino acid exchange from arginine to glycine at position 168. The nucleotide sequence of intron 6 of the A allele was found to be identical to the ABO(*)A101 sequence in each patient. CONCLUSION: This study suggests that a variant A phenotype can arise from the new R168G polymorphism, reflecting the importance of this region for the ABO transferase efficiency.

ABO Blood-Group System↗