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Patterns of Receptor Revision in the Immunoglobulin Heavy Chains of a Teleost Fish^1,2

Miles D. Lange^*, Geoffrey C. Waldbieser and Craig J. Lobb^3,*

^* Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216; and U.S. Department of Agriculture, Catfish Genetics Research Unit, Thad Cochran National Warmwater Aquaculture Center, Stoneville, MS 38776

H chain cDNA libraries were constructed from the RNA derived from seven different organs and tissues from the same individual catfish. Sequence analysis of >300 randomly selected clones identified clonal set members within the same or different tissues, and some of these represented mosaic or hybrid sequences. These hybrids expressed V_H members of the same or different V_H families within different regions of the same clone. Within some clonal sets multiple hybrids were identified, and some of these represented the products of sequential V_H replacement events. Different experimental methods confirmed that hybrid clones identified in the cDNA library from one tissue could be reisolated in the cDNA pool or from the total RNA derived from the same or a different tissue, indicating that these hybrids likely represented the products of in vivo receptor revision events. Murine statistical recombination models were used to evaluate cryptic recombination signal sequences (cRSS), and significant cRSS pairs in the predicted V_H donor and recipient were identified. These models supported the hypothesis that seamless revisions may have occurred via hybrid joint formation. The heptamers of the cRSS pairs were located at different locations within the coding region, and different events resulted in the replacement of one or both CDR as well as events that replaced the upstream untranslated region and the leader region. These studies provide phylogenetic evidence that receptor revision may occur in clonally expanded B cell lineages, which supports the hypothesis that additional levels of somatic H chain diversification may exist.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ This work was supported in part by National Institutes of Health Grant AI23052.

² The sequence(s) presented in this article has been submitted to GenBank under accession number(s) EU492547-EU492867.

³ Address correspondence and reprint requests to Dr. Craig J. Lobb, University of Mississippi Medical Center, Department of Microbiology, 2500 North State Street, Jackson, MS 39216-4505 USA. E-mail address: clobb{at}microbio.umsmed.edu

⁴ Abbreviations used in this paper: RSS, recombination signal sequence; AID, activation-induced cytidine deaminase; AK, anterior kidney; BLAST, basic local alignment search tool; cRSS, cryptic recombination signal sequence; CS, clonal set; FR, framework region; GL, gill lamellae; I, intestine; LDR, leader region; RIC, recombination signal information content; SK, skin; SP, spleen; UT, untranslated region.