Wiskott–Aldrich syndrome protein (WASP) and N-WASP are critical for T cell development

Abstract

cytoskeleton ͉ thymus ͉ migration ͉ colitis ͉ knockout mice L ymphoid progenitors enter the thymus to initiate a complex differentiation process resulting in maturation of T cells (1, 2). The well characterized maturation steps of ␣␤ T cells in the thymus are also governed by trafficking events and positional cues driven by guidance molecules, including chemokines, adhesion molecules, and extracellular matrix components (3-6). Rearrangement of the actin cytoskeleton is regulated during both T cell receptor signaling and T cell migration (7-9), but much less is known about its requirement during T cell development. The small Rho-family GTPases and their guanine nucleotide exchange factors (GEFs), proteins known to regulate the actin cytoskeleton, are clearly required during thymocyte development (10-12). Although these molecules are also known to regulate cell adhesion and migration, their involvement in thymocyte trafficking has not been thoroughly assessed. The small GTPase effector molecule Wiskott-Aldrich syndrome protein (WASP) has also been demonstrated to be a critical regulator of antigen receptor signaling, actin cytoskeletal rearrangements, and lymphocyte migration (13-22). Although WASP deficiency has been correlated with lower numbers of naïve T cells (23), WASP does not seem to play a critical role in T cell development. Moreover, despite a large body of evidence showing a role for WASP in T cell signaling, its role in thymocyte migration has not been studied. WASP belongs to the WASP family of proteins, including WASP, N-WASP, and WAVE/SCAR molecules 1-3 (24). In particular, N-WASP, which shares 50% homology with WASP, may serve specific and redundant function with WASP in hematopoietic cells. In fact, we have shown that expression of N-WASP in WASP-deficient T cells partly restores CD3-mediated proliferation, implying that WASP and N-WASP might share functions in T cells (25).Here we sought to explore the importance of cytoskeletal regulation for thymocyte development by examining the unique and redundant roles of WASP and N-WASP. Using two complementary approaches, we analyzed T cells devoid of WASP and N-WASP and demonstrated that thymopoiesis cannot proceed in the absence of WASP and N-WASP. Results Deletion of WASP and N-WASP in Lymphocytes Using the RAG-2-Deficient Complementation System Leads to a Block in T Cell Development.We have demonstrated that lymphoid development is normal in WASP knockout (WKO) mice (20). We hypothesized that N-WASP might have some overlapping functions with WASP during lymphopoiesis and sought to investigate the unique and redundant activities for WASP and N-WASP in T cell development and function. To circumvent the embryonic lethality of N-WASP germ-line inactivation in mice (26), we used the RAG2-deficient blastocyst complementation system (27). Blastocysts from RAG-2-deficient mice implanted into foster mothers generate animals that fail to rearrange antigen receptor genes and consequently lack mature B and T cells. Injection of gene-targeted ES cells into RAG-2-...

Coordination of IL-7 receptor and T-cell receptor signaling by cell-division cycle 42 in T-cell homeostasis

“…Although WASP −/− mice also are lymphopenic (49), our data suggest that Cdc42 maintains T-cell homeostasis through a WASPindependent mechanism. It is possible that N-WASP compensates for WASP in Cdc42-maintained T-cell homeostasis, given that WASP and N-WASP play redundant roles in T-cell development (50). In view of the published literature on WASP and Par6, our study suggests that WASP and Par6 may regulate T-cell functions independently of Cdc42.…”

Activating WASP mutations associated with X-linked neutropenia result in enhanced actin polymerization, altered cytoskeletal responses, and genomic instability in lymphocytes

“…A hallmark of WASP deficiency in mice is that WASP-deficient T cells fail to respond to T cell receptor activation (Snapper et al, 1998;Zhang et al, 1999;Cotta-de-Almeida et al, 2007). We now show that WASP-I296T-expressing T cells proliferate normally to surface receptor stimulation.…”

“…In vitro migration of B and T cells and spreading of B and T cells was assessed as previously described (Westerberg et al, 2001(Westerberg et al, , 2008Cotta-de-Almeida et al, 2007). For spreading, T cells were incubated on…”

Suppressive effect of mycolactone-containing fraction from Mycobacterium ulcerans on antibody production against co-administered antigens

“…WiskottAldrich syndrome protein (WASP) and neural WASP (N-WASP) were reported as direct binding targets of mycolactone [7,21]. These proteins are members of a family of scaffold proteins transducing signals involved in the dynamic remodeling of the actin cytoskeleton [22][23][24][25]. Mycolactone exerts its effects by hijacking the WASP family, leading to uncontrolled activation of actin in the cytoplasm [21].…”