Ml. Lundqvist et al., IG HEAVY-CHAIN OF THE STURGEON ACIPENSER BAERI - CDNA SEQUENCE AND DIVERSITY, Immunogenetics (New York), 48(6), 1998, pp. 372-382
To investigate the gene organization of the ICH locus, and the VH dive
rsity of the Siberian sturgeon, a cDNA library was constructed and scr
eened with VH-specific probes from two holostean fish. Isolated clones
were analyzed and domain-specific probes used in rescreening of the l
ibrary, Southern blot analysis, and northern blots. It was concluded t
hat the Siberian sturgeon has one IGH locus with a translocon type of
organization. Two allelic variants of the mu gene were found, with ide
ntities ranging from 80 to 100% for the different domains (highest for
CH4 and lowest for CH2). Sturgeon CH sequences are most closely relat
ed to those of holostean fish. There are three distinct VH families, V
HI grouping with mammalian dan III, VHII grouping with the teleost dan
, and VHIII grouping with the archaic dan. The variability of the CDR
3 region is substantial, and we identified a number of conserved motif
s in the D segment. Further, we deduced that there are at least nine d
ifferent JH segments in the locus, contributing to the antibody repert
oire of the sturgeon. The variable segments of the three families can
be associated with any of the D or JH segments in the rearrangement. S
turgeon, in addition to the random rearrangement of VH, D, and JH segm
ents, have exonuclease activity, and an introduction of N and probably
P nucleotides at the site of rearrangement.