Septin9 is involved in T-cell development and [CD8.sup.+] T-cell homeostasis

SEPTIN9 (SEPT9) is a filament-forming protein involved in numerous cellular processes. We have used a conditional knock out allele of Sept9 to specifically delete Sept9 in T-cells. As shown by fluorescence-activated cell sorting, loss of Sept9 at an early thymocyte stage in the thymus results in increased numbers of double-negative cells indicating that SEPT9 is involved in the transition from the double-negative stage during T-cell development. Accordingly, the relative numbers of mature T-cells in the periphery are decreased in mice with a T-cell-specific deletion of Sept9. Proliferation of Sept9-deleted [CD8.sup.+] T-cells from the spleen is decreased upon stimulation in culture. The altered T-cell homeostasis caused by the loss of Sept9 results in an increase of [CD8.sup.+] central memory T-cells. Keywords Sept9 T-cell development [CD8.sup.+] T-cells T-cell homeostasis * T-cell proliferation * Mice ([Sep9.sup.cond]:Mx-Cre)