IGHV gene insertions and deletions in chronic lymphocytic leukemia: "CLL-biased" deletions in a subset of cases with stereotyped receptors.
Nucleotide insertions/duplications or deletions in immunoglobulin heavy chain genes have been found in 24/760 patients (3.15%) with chronic lymphocytic leukemia (CLL). In 21/24 cases, the inserted/duplicated or lost nucleotides occurred in multiples of 3; therefore, the original reading frame was maintained and a potentially intact receptor was coded. The pattern and location of insertions/duplications or deletions in CLL and their restriction to mutated IGHV rearranged genes strongly suggests that they resulted from somatic hypermutation. Their incidence in CLL is consistent with previous reports in normal, auto-reactive and neoplastic human B cells, thus seemingly indicating that these modifications generally arise without any particular disease-specific associations. A striking exception to this rule was identified in CLL IGHV3-21-expressing cases: one amino acid was deleted from the CDR2 region in 16/63 (25.4%) mutated CLL IGHV3-21 sequences (including public database-derived IGHV3-21 CLL cases + the present series) vs. only 2/257 (0.78%) public database-derived mutated non-CLL IGHV3-21 sequences; 15/16 CLL IGHV3-21 sequences carrying this deletion belonged to a subset with unique, shared HCDR3 and light chain CDR3 motifs. This finding further supports the idea of selective antigenic pressures playing a pathogenetic role in some CLL cases.
Belessi
Chrysoula J
CJ
Hematology Department, Nikea General Hospital, Athens, Greece.
Davi
Frédéric B
FB
Stamatopoulos
Kostas E
KE
Degano
Massimo
M
Andreou
Thanassis M
TM
Moreno
Carol
C
Merle-Béral
Hélène
H
Crespo
Marta
M
Laoutaris
Nikolaos P
NP
Montserrat
Emili
E
Caligaris-Cappio
Federico
F
Anagnostopoulos
Achilles Z
AZ
Ghia
Paolo
P
D000595:Amino Acid Sequence; D001483:Base Sequence; D022801:Complementarity Determining Regions / Q000235:genetics; D017353:Gene Deletion; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011947:Receptors, Antigen, B-Cell / Q000235:genetics*; D011948:Receptors, Antigen, T-Cell / Q000235:genetics; D027041:Somatic Hypermutation, Immunoglobulin
D022801:Complementarity Determining Regions; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell