Identification of HLA-A*0111N: a synonymous substitution, introducing an alternative splice site in exon 3, silenced the expression of an HLA-A allele.
A new variant of the HLA-A*010101 allele designated as HLA-A*0111N, previously known as HLA-A*010101var, was identified in a patient requiring a stem-cell transplantation. The patient was typed by serologic methods as HLA-A2 homozygous and by sequence-based typing (SBT) as A*010101,020601. Flow-cytometric (FCM) analysis with 11 human monoclonal antibodies (mAbs) for the A1 molecule confirmed lack of any cell membrane expression of the A*0111N allele. One-dimensional isoelectric focusing (1D-IEF) of total cell lysate from the patient's cells revealed no cell surface and cytoplasmic A1 protein expression, whereas the HLA-A2 molecule was identified by both FCM analysis and 1D-IEF. DNA sequence analysis showed the presence of a synonymous substitution from G to T at position 597 in codon 175. RNA SBT revealed a deletion of 24 bp in exon 3, position 596 through 619, encoding codons 175 through 182 of the HLA-A*0111N allele. The synonymous substitution introduced a new splice site, resulting in an efficient splicing, because no classical A1 protein could be detected in the patient. This alternative splicing prevented the translation into a correct and stable class I molecule expression on the cell surface.
Reinders
Judith
J
Department of Pathology, University Medical Centre Utrecht (UMC-U), Utrecht, The Netherlands.
Rozemuller
Erik H
EH
Otten
Henny G
HG
Houben
Anna J S
AJ
Dormoy
Anne
A
Mulder
Arend
A
van den Tweel
Jan G
JG
Petersen
Eefke J
EJ
Tilanus
Marcel G J
MG
D000483:Alleles; D017398:Alternative Splicing; D019943:Amino Acid Substitution; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D005434:Flow Cytometry; D020868:Gene Silencing; D015234:HLA-A Antigens / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017422:Sequence Analysis, DNA; D012703:Serotyping
D015234:HLA-A Antigens