The chicken D locus and its contribution to the immunoglobulin heavy chain repertoire

Abstract

Sixteen D elements were characterized from the chicken genome, 15 of which are extremely homologous. Early expression of this D repertoire was studied for both DJ and VDJ alleles. No N diversification occurs at either DJ or VD junctions. Only P additions were observed, the length of which does not appear restricted to a dinucleotide. A selection for the almost exclusive usage of the first reading frame of the D elements takes place during B cell expansion in the bursa, in parallel with the selection of productive rearrangements. All three reading frames were observed for the DJ allele at each developmental stage, although some bias for the first reading frame occurs already at the junctional stage. The high incidence of D-D junctions observed (25% among DJ sequences) might represent the major functional contribution of this multigene cluster in a system in which diversity will be generated later on by successive superimposed gene conversions. Other possible functions are discussed. The onset of D diversification through gene conversion between day 15 and day 18 of embryonic development is further documented.

Development of B cells expressing surface immunoglobulin molecules that lack V(D)J-encoded determinants in the avian embryo bursa of Fabricius

“…Clone 6.131 contains a single gene-conversion event, spanning codons 22-53, using ⌿V L 12 as donor sequence (5) ). This is consistent with the rapid elimination of out-of-frame V(D)J junctions that occurs selectively in the embryo bursa (15) and precedes the onset of repertoire generation by gene conversion (3). Bursal cells from RCAS-T-infected chicks that lack chains are not B lineage cells because they lack characteristic B cell markers (Fig.…”

“…This has led to considerable speculation that the specificity encoded by the prediversified sIg receptor plays a critical role in B cell development (2,3,(15)(16)(17)(18)(19).…”

“…At the light chain (L) locus, the unique, functional V L 1 gene rearranges to the unique J L segment in all B cells (1). Similarly, at the heavy chain (H) locus, unique V H 1 and J H genes undergo rearrangement with a family of highly conserved D H elements to form a VDJ H complex of limited diversity (2,3). Junctional diversity is limited further because of the lack of N nucleotide additions in chicken V(D)J junctions (4).…”

An Ultra-specific Avian Antibody to Phosphorylated Tau Protein Reveals a Unique Mechanism for Phosphoepitope Recognition

“…In chickens, only single functional V genes exist for the light and heavy chains, containing unique V L -J L ( isotype only), V H -J H (V H 3 family), and D segments (27)(28)(29). To make such a restricted V gene germ line repertoire highly functional, the chicken has evolved a complex V gene diversification mechanism known as "gene conversion" (29,30).…”

“…Surprisingly, chickens also only utilize 15 functional D segments, all of which are highly homologous (28). In contrast to humans and mice, chicken D segments obligately contain cysteine, with the consensus sequence GS(A/G)YC(G/C)(S/ W)XA(Y/E) (where X is non-conserved) (28).…”