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N Froelich

Publications and source records attributed to N Froelich.

10 recordsLinked to original sources
PubMed2006

HLA-A*02010102L: a laborious assignment.

In the present report we describe the laborious identification of the A*02010102L allele found in three healthy individuals of a French family who have shown a reduced A2 antigen expression using serological tests since the 1980s. PCR-SSP typing showed a classical A*0201 allele. Sequencing of exons 2, 3 and 4 confirmed this assignment. Sequencing of the whole gene (promoter, introns and exons 1-8) revealed one single point mutation (T to C) at position -101 in the enhancer B element region compared to the A*02010101 allele. This single mutation appears to be related to the reduced expression of the A2 antigen. This allele segregates with the haplotype Cw*12, B44, DR7, DQ2, which is different to the one described earlier.

Alleles↗
PubMed2003

Mono-allelic amplification of exons 2-4 using allele group-specific primers for sequence-based typing (SBT) of the HLA-A, -B and -C genes: preparation and validation of ready-to-use pre-SBT mini-kits.

Class I allelic typing based on sequencing is reliable, immutable and easy to analyse when only one allele is amplified using a specific mono-allelic technique. A strategy has been developed to selectively amplify exons 2, 3 and 4 of each allele of the three class I loci, previously identified by generic typing, in order to sequence these alleles from their intronic parts in only one direction. This procedure is based mainly on the polymorphism of exon 1 and intron 1 of the HLA-A, -B and -C genes with allele group-specific forward primers and locus-specific reverse primers so as to perform mono-allelic amplification in a 'One Step' pre-sequence-based typing (pre-SBT) PCR. The 5' polymorphism found at each locus is nevertheless not sufficient to discriminate all allelic combinations. Hence exon 2 and exon 3 polymorphism had to be used in a 'Two Step' pre-SBT PCR method to selectively amplify the two alleles in the 1.8%, 7.6% and 0.9% of unresolved combinations found in our laboratory for, respectively, the HLA-A, -B and -C loci. Preparation and validation of 'ready-to-use' aliquots of primer-mixes, pre-SBT buffer and sets of Dye terminator reaction mixtures containing locus-specific intronic primers makes the procedure easy and efficient. The SBT method is the only allelic typing technique used in our laboratory (to date, 742 HLA-A*, 802 HLA-B* and 615 HLA-Cw* alleles have been sequenced) and our successful participation in the national and international quality controls of 4 years ago testifies to the accuracy of the results.

DNA Primers↗
PubMed2002

Second HLA-A*68 null allele, A*6818 N, identified.

A second HLA-A*68 null allele, HLA-A*6818 N, was identified in our laboratory after discrepant results were obtained between class I serological and molecular typing in a male patient suffering from narcolepsy. HLA-A*6818 N displays a sequence identical to that of the HLA-A*6802 allele, except in exon 2 where 20 nucleotides inserted at codon position 48 are a repeat of the 20 preceding nucleotides. This duplication creates a shift of the reading frame, which leads to a premature non-sense codon at position 59 of the null allele.

Alleles↗
PubMed1999

A null HLA-A*68 allele in a bone marrow donor.

The authors describe an A*68 allele present at the molecular level but not expressed at the cell surface. This non expression results from the deletion of one nucleotide in exon 1, which causes a shift of the reading frame leading to an early non-sense codon in the same exon.

Alleles↗
PubMed1997

An intronic mutation responsible for a low level of expression of an HLA-A*24 allele.

HLA class I typing performed in parallel by molecular biology and serology has revealed cases where an HLA class I allele was identified but the corresponding antigen on the cell surface was not detected. In the present report, we describe three members of a family in whom an HLA-A24 allele identified at the molecular level was typed as A "blank" by lymphocytotoxicity. This serologically blank antigen was nevertheless faintly detectable by isoelectric focusing (IEF) and FACS analyses. Sequencing of the HLA-A*24 allele from the promoter region to the eighth exonic region revealed a point mutation in the acceptor site of the second intron as compared to the normal HLA-A*24 allele. This mutation could lead to incorrect processing of mRNA through a cryptic acceptor site located at the beginning of the third exon and hence to alternative splicing with a frame shift introducing an early stop codon into the fourth exon.

Alleles↗
PubMed1997

A nucleotide insertion in exon 4 is responsible for the absence of expression of an HLA-A*01 allele.

HLA class I typing performed in parallel by molecular biology and serology has revealed cases where an HLA class I allele was identified whereas the corresponding antigen was not detected on the cell surface. In the present report, we describe four members of a family in whom an HLA-A1 allele identified at the molecular level was typed as A "blank" by lymphocytotoxicity. This serologically blank antigen was undetectable by isoelectric focusing (IEF). Sequencing of the HLA-A*01 allele from the promoter region to the eighth exonic region revealed insertion of a "C" nucleotide at the beginning of the fourth exon as compared to the common HLA-A*0101 allele. This mutation causes a frame shift, giving rise to an early stop codon in the fourth exon.

Alleles↗
PubMed1995

[Splenic peliosis. Apropos of 2 cases].

Two cases of splenic peliosis are reported. Clinical and radiographic signs and laboratory results do not contribute greatly to diagnosis which is based on histology findings. Splenic rupture is the major complication and requires immediate splenectomy.

Adult↗