The role of the transcription factors FoxA1 and FoxA2 in T-cell development and function

Supervisors: Professor Tessa Crompton and Dr Anna Furmanski

Thethymus provides a specialized environment that is essential for the development of blood-borne haematopoietic progenitor cells into mature T-cells. We have shown that the Sonic Hedgehog (Shh) produced by thymic epithelial cells (TEC), and the Hedgehog (Hh) signalling pathway, are important at multiple stages of T-cell development[1], including differentiation from DN to DP and from DP to SP[2-4]. In addition, we showed that Hh signalling to mature peripheral CD4 cells influenced their differentiation to T helper (Th)2[5].

We identified the transcription factor FoxA2 as a transcription factor, downstream of Hh pathway activation (a Hh target gene) in immature thymocytes and peripheral T-cells[3,5]. To our knowledge, FoxA2 has not previously been studied in thymocytes or T-cells, but FoxA2 is essential for mouse development and FoxA2- /- embryos die at E10 with severe defects in node, notochord, neural tube and gut. We have therefore obtained floxed FoxA2 mice in order to generate conditional FoxA2-deficient animals in which FoxA2 is excised form T-lineage cells at different stages of T-cell development. The purpose of this project is to test the hypothesis that the transcription factors FoxA2 and FoxA1 are required at the transition from CD4 -CD8- double negative (DN) cell to CD4+CD8+ double positive (DP) cell, for efficient production of CD4 single positive (SP) cells in the thymus, and for T-cell homeostasis and function in the periphery.

We will complete the following objectives:

(1) We will test if conditional deletion of FoxA2and/or FoxA1 from T-lineage cells influences differentiation from DN to DP cell, and from DP to CD4SP and positive selection.
(2) We will identify FoxA2/A1-target genes in T-lineage cells at different stages of their differentiation.
(3) We will test if FoxA2/A1 is required for homeostasis and function of peripheral T-cells.

References:
1) Crompton T, Outram SV, Hager -Theodorides AL. Sonic hedgehog signalling in T-cell development and activation. Nat Rev Immunol. 2007;7:726-735.
2) Outram SV, Varas A, Pepicelli CV, Crompton T. Hedgehog signaling regulates differentiation from double-negative to double-positive thymocyte. Immunity. 2000;13:187-197.
3) Rowbotham NJ, Hager-Theodorides AL, Furmanski AL, et al. Sonic hedgehog negatively regulates pre-TCR-induced differentiation by a Gli2- dependent mechanism. Blood. 2009;113:5144 -5156.
4) Furmanski AL, Saldana JI, Rowbotham NJ, Ross SE, Crompton T. Role of Hedgehog signalling at the transition from double-positive to single-positive thymocyte. Eur J Immunol;42:489 -499.
5) Furmanski AL, Saldana JI, Ono M, et al. Tissue-derived hedgehog proteins modulate th differentiation and disease. J Immunol;190:2641-2649.