Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Workshop: Aquaculture
The IgH locus of the channel catfish is, in most respects, a simpler version of the translocon organization seen in the mammalian IgH locus, with clusters of VH genes, D elements, JH segments, and 2 constant region genes, mu and delta. One major distinguishing characteristic of the catfish IgH locus is the enhancer (Emu3’) which is found between the mu and delta genes, and differs from all of the 6 mammalian IgH enhancers in size, location, and composition of transcription factor-binding motifs. Recent studies have shown that the catfish enhancer is driven by basic helix-loop-helix and octamer transcription factors, in contrast to mammalian IgH enhancers which are driven by a much more diverse group of transcription factors, permitting tight developmental regulation of their function. The position of the Emu3’ enhancer in the catfish IgH locus is such that class switching by chromosomal recombination is impossible without inactivation of the gene . Thus, the enhancer may have played a role in limiting catfish C region genes to only two, i.e. mu and delta, the only isotypes that are expressible by alternative RNA processing rather than chromosomal recombination. The catfish IgH locus contains remnant transposable elements of the Tc1/mariner type. The mobilization of these elements may have played a major role in the duplication of the catfish IgH locus, and also in the evolution of the complex IgH locus present in the tetrapod lineage. Supported by awards MCB9807531 from the NSF and R01-GM62317 and R37-AI19530 from the NIH.