GKLF in thymus epithelium as a developmentally regulated element of thymocyte-stroma cross-talk.

Gut-enriched Krüppel-like factor (GKLF) is a transcriptional regulator expressed in differentiated epithelia. We identified GKLF transcript as a regulated element in thymic epithelium of recombinase-deficient mice during thymus development induced by anti-CD3 antibody injection. This treatment recapitulates the organogenetic process depending on productive rearrangement of T cell receptor (TCR) beta gene with thymocytes expansion and acquisition of the CD4+8+ double positive phenotype. In wildtype mice, GKLF is expressed very early in embryogenesis and becomes intensely up-regulated in thymus epithelium at day 18 of gestation when TCR beta expressing cells have selectively expanded and express both CD4 and CD8. The results presented here suggest that thymocytes may regulate GKLF transcriptionally in the cortical epithelium at the developmental check-point controlled by TCR beta gene rearrangement. Furthermore, GKLF expression in hematopoietic stroma might suggest the thus far uncharacterised participation of this factor in hematopoiesis.