High levels of SOX5 decrease proliferative capacity of human B cells, but permit plasmablast differentiation.

• Main Authors: Mirzokhid Rakhmanov, Heiko Sic, Anne-Kathrin Kienzler, Beate Fischer, Marta Rizzi, Maximilian Seidl, Kerstina Melkaoui, Susanne Unger, Luisa Moehle, Nadine E Schmit, Sachin D Deshmukh, Cemil Korcan Ayata, Wolfgang Schuh, Zhibing Zhang, François-Loic Cosset, Els Verhoeyen, Hans-Hartmut Peter, Reinhard E Voll, Ulrich Salzer, Hermann Eibel, Klaus Warnatz
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2014-01-01
• Series: PLoS ONE
• Online Access: http://europepmc.org/articles/PMC4063782?pdf=render

Currently very little is known about the differential expression and function of the transcription factor SOX5 during B cell maturation. We identified two new splice variants of SOX5 in human B cells, encoding the known L-SOX5B isoform and a new shorter isoform L-SOX5F. The SOX5 transcripts are highly expressed during late stages of B-cell differentiation, including atypical memory B cells, activated CD21low B cells and germinal center B cells of tonsils. In tonsillar sections SOX5 expression was predominantly polarized to centrocytes within the light zone. After in vitro stimulation, SOX5 expression was down-regulated during proliferation while high expression levels were permissible for plasmablast differentiation. Overexpression of L-SOX5F in human primary B lymphocytes resulted in reduced proliferation, less survival of CD138neg B cells, but comparable numbers of CD138+CD38hi plasmablasts compared to control cells. Thus, our findings describe for the first time a functional role of SOX5 during late B cell development reducing the proliferative capacity and thus potentially affecting the differentiation of B cells during the germinal center response.