New perspective on the origin of adaptive evolution: a study on cytidine deaminase in lampreys

This study evaluates the similarity of adaptive immune mechanisms between jawless and jawed vertebrates using lamprey cytidine deaminase (CDA). We identified the ancestral gene Lr-CDAs of the AID/APOBEC deaminase family and evaluated its biological function in vivo. Lr-CDA1 deletion affected the assembly of three types of variable lymphocyte receptors (VLRs). We identified a switch-like region in lamprey gVLRs bound to Lr-CDAs, which upon repression, downregulated VLRB expression. Overall, we propose that lampreys have an early form of class switch recombination (CSR) that is mediated by Lr-CDAs and acts on gVLRs, affecting the assembly, maturation, and diversity regulation of VLR genes in Lethenteron reissneri. This CSR process in lampreys is linked to tumorigenesis and chromosomal translocation markers via Lr-CDAs. We conducted a gene knockout experiment on Lr-CDA1 and collected embryos identified as successful CDA1 knockouts. Then, we conducted gene expression profiling analysis using the RNA-seq data obtained from the CDA1 knockout experimental group and the control group. By comparing the gene expression profiles between experimental and control groups using RNA-seq data analysis, we aim to identify genes that interact with or are regulated by CDA1.