Selection for B cells with productive IgL gene rearrangements occurs in the bursa of Fabricius during chicken embryonic development.
The vast majority of immunoglobulin-expressing mature chicken B lymphocytes contain one functionally rearranged and one unrearranged allele of the immunoglobulin light chain (IgL) gene. Therefore, nearly all IgL V-J rearrangements present in mature chickens are in-frame. In contrast, the Ig genes of mature mammalian B cells contain a high proportion of out-of-frame V-J joints. To investigate the basis for this difference, gene rearrangement at the chicken IgL locus was characterized during embryonic development and in mature B-cell lines. Joining of the single functional variable (VL) segment with the single joining (JL) segment occurs in cells in multiple tissues during a transient period of chicken embryogenesis. Only one-third of the V-J joints cloned from days 10-12 of development are in-frame. An increasing proportion of in-frame V-J joints is observed within the bursa of Fabricius at successively later stages of development. Our data suggest that the bursa of Fabricius serves during embryonic development as a site of selective amplification of cells that have undergone productive V-J joining, such that nearly all V-J joints present in postembryonic B cells are in-frame. The high frequency of rearranged alleles joined in-frame that is found in posthatching bursal cells and mature B-cell lines appears to result from a low frequency with which cells undergo IgL rearrangement at both alleles, rather than from an increase in the precision of V-J joining in avian species.
McCormack
W T
WT
Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor 48109.
Tjoelker
L W
LW
Barth
C F
CF
Carlson
L M
LM
Petryniak
B
B
Humphries
E H
EH
Thompson
C B
CB
D000483:Alleles; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology*; D001483:Base Sequence; D002060:Bursa of Fabricius / Q000166:cytology / Q000196:embryology*; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics / Q000276:immunology*; D005785:Gene Conversion; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D005803:Genes, Immunoglobulin; D007144:Immunoglobulin J-Chains / Q000235:genetics; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D008969:Molecular Sequence Data; D012641:Selection, Genetic
D007144:Immunoglobulin J-Chains; D007147:Immunoglobulin Light Chains; D007135:Immunoglobulin Variable Region