Transcriptomic analysis of early B-cell development in the chicken embryo

Authors: NUTHALAPATI, NIKHIL - Mississippi State University; Evans, Jeffrey - Jeff; TAYLOR, ROBERT - West Virginia University; Branton, Scott; NANDURI, BINDU - Mississippi State University; PHARR, GREGORY - Mississippi State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2019
Publication Date: 6/25/2019
Citation: Nuthalapati, N., Evans, J.D., Taylor, R.L., Branton, S.L., Nanduri, B., Pharr, G.T. 2019. Transcriptomic analysis of early B-cell development in the chicken embryo. Poultry Science. 0:1-13. https://doi.org/10.3382/ps/pez354.
DOI: https://doi.org/10.3382/ps/pez354

Interpretive Summary: Humoral (antibody) immunity is mediated by B-cells that mature in the chicken bursa of Fabricius which is itself a primary lymphoid tissue important for B-cell development. In the embryonic period between embryonic days (ED) 8-14, pre-bursal stem cells enter the epithelium of the bursal anlage and proliferate, forming the nascent lymphoid follicles. It is hypothesized that early bursal B-cell differentiation is guided by signals through cytokine receptors. This project used transcriptomic analysis to evaluate gene expression across early B-cell development. RNA-seq was performed with total RNA isolated from bursal B-cells at ED 16 and ED 19. Approximately 90 million high quality clean reads were obtained from the cDNA libraries. The analysis revealed differentially expressed genes involved in the Jak-STAT pathway, Wnt signaling pathway, MAPK signaling pathway, metabolic pathways including tyrosine metabolism, Toll-like receptor signaling pathway, and cell-adhesion molecules. The genes predicted to encode surface receptors, signal transduction proteins and transcription factors identified in this study represent gene candidates for controlling B-cell development in response to differentiation factors in the bursal microenvironment. With increased understanding of the genes involved in B-cell differentiation, it will be possible to predict soluble or surface expressed factors in the embryonic bursa that regulate the expression of these genes, therefore identifying roles for the non-lymphoid cells present in the embryonic bursal follicles.

Technical Abstract: The chicken bursa of Fabricius is a primary lymphoid tissue important for B-cell development. Our long-term goal is to understand the role of bursal microenvironment in an early B-cell differentiation event initiating repertoire development through immunoglobulin gene-conversion in the chick embryo. We hypothesize that early bursal B-cell differentiation is guided by signals through cytokine receptors. Our theory is based on previous evidence for expression of the receptor tyrosine kinase superfamily members and interleukin receptors in unseparated populations of bursal B-cells and bursal tissue. Knowledge of the expressed genes that are responsible for B-cell differentiation is a prerequisite for understanding the bursal microenvironment’s function. This project uses transcriptomic analysis to evaluate gene expression across early B-cell development. RNA-seq was performed with total RNA isolated from bursal B-cells at embryonic day (ED) 16 and ED 19 (n=3). Approximately 90 million high quality clean reads were obtained from the cDNA libraries. The analysis revealed differentially expressed genes involved in the Jak-STAT pathway, Wnt signaling pathway, MAPK signaling pathway, metabolic pathways including tyrosine metabolism, Toll-like receptor signaling pathway, and cell-adhesion molecules. The genes predicted to encode surface receptors, signal transduction proteins and transcription factors identified in this study represent gene candidates for controlling B-cell development in response to differentiation factors in the bursal microenvironment.