BCR repertoire analysis of wild-type and Cic-null B-1a cells

Purpose: B-1a cells have a distinct BCR repertoire compared with that of B-2 cells. To examine whether CIC loss affects the BCR repertoire in B-1a cells, we analyzed mRNA sequences of immunoglobulin heavy (Igh) and light (Igk and Igl) chain genes in B-1a cells from 12-week-old control and Cicf/f;Cd19-Cre mice. Methods: Peritoneal cavity B-1a cells (IgM+, CD19+, CD5+, CD43+) were sorted by a MoFlo-XDP (Beckman Coulter). Total RNA was extracted using TRIzol Reagent (GeneAll), according to the manufacturer's instructions. Long Read iR-Profile Reagent System (iRepertoire) was used to generate NGS libraries covering BCR chains including Igh, Igk, and Igl. Briefly, nested inside and outside primers selectively amplified all V- and C- regions and incorporated communal adaptors. Following clean up, only target amplicons, which contain 5' and 3' communal adaptors, were exponentially amplified. Amplified libraries were multiplexed for sequencing on the Illumina Miseq platform. Sequence reads were de-multiplexed according to the barcode sequences. Results: Trimmed reads were mapped to germline V, D and J reference sequences downloaded from the IMGT database. IgH diversity and the usage of variable (V) segments in heavy (Ighv) chain and light (Igkv and Iglv) chain genes were comparable between control and Cic-null B-1a cells. Analysis of non-templated (N)-nucleotide addition at V(D)J junctions revealed that Cic-null B-1a cells have a higher proportion of zero to two N-nucleotides-containing-BCRs than control cells. Conclusions: Our study presents the first comparative BCR repertoire analysis of wild-type and Cic-null B-1a cells. We concluded that CIC deficiency does not dramatically alter the BCR repertoire in B-1a cells. Overall design: We analyzed mRNA sequences of immunoglobulin heavy (Igh) and light (Igk and Igl) chain genes in B-1a cells from 12-week-old control and Cicf/f;Cd19-Cre mice.