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Liu X , Li YS , Shinton SA , Rhodes J , Tang L , Feng H , Jette CA , Look AT , Hayakawa K , Hardy RR
Zebrafish B Cell Development without a Pre-B Cell Stage, Revealed by CD79 Fluorescence Reporter Transgenes
J Immunol. 2017 Sep 01;199(5) :1706-1715
PMID: 28739882    PMCID: PMC5563169    URL: https://www.ncbi.nlm.nih.gov/pubmed/28739882
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CD79a and CD79b proteins associate with Ig receptors as integral signaling components of the B cell Ag receptor complex. To study B cell development in zebrafish, we isolated orthologs of these genes and performed in situ hybridization, finding that their expression colocalized with IgH-mu in the kidney, which is the site of B cell development. CD79 transgenic lines were made by linking the promoter and upstream regulatory segments of CD79a and CD79b to enhanced GFP to identify B cells, as demonstrated by PCR analysis of IgH-mu expression in sorted cells. We crossed these CD79-GFP lines to a recombination activating gene (Rag)2:mCherry transgenic line to identify B cell development stages in kidney marrow. Initiation of CD79:GFP expression in Rag2:mCherry+ cells and the timing of Ig H and L chain expression revealed simultaneous expression of both IgH-mu- and IgL-kappa-chains, without progressing through the stage of IgH-mu-chain alone. Rag2:mCherry+ cells without CD79:GFP showed the highest Rag1 and Rag2 mRNAs compared with CD79a and CD79b:GFP+ B cells, which showed strongly reduced Rag mRNAs. Thus, B cell development in zebrafish does not go through a Raghi CD79+IgH-mu+ pre-B cell stage, different from mammals. After the generation of CD79:GFP+ B cells, decreased CD79 expression occurred upon differentiation to Ig secretion, as detected by alteration from membrane to secreted IgH-mu exon usage, similar to in mammals. This confirmed a conserved role for CD79 in B cell development and differentiation, without the requirement of a pre-B cell stage in zebrafish.
Liu, Xingjun Li, Yue-Sheng Shinton, Susan A Rhodes, Jennifer Tang, Lingjuan Feng, Hui Jette, Cicely A Look, A Thomas Hayakawa, Kyoko Hardy, Richard R eng P30 CA006927/CA/NCI NIH HHS/ 2017/07/26 06:00 J Immunol. 2017 Sep 1;199(5):1706-1715. doi: 10.4049/jimmunol.1700552. Epub 2017 Jul 24.