Wiskott-Aldrich Syndrome Protein Expression Research Articles

WASP and the phenotypic range associated with deficiency

This review reports on the range of clinical phenotypes that are caused by mutations in the Wiskott-Aldrich Syndrome Protein (WASP) gene. The basis of genotype-phenotype correlation in Wiskott-Aldrich syndrome (WAS) is discussed, with regard to expression of the WAS protein (WASp) and of the effects of WASP mutations on WASp function. Advances in preclinical models of gene therapy for WAS are presented. Two recent studies have supported genotype-phenotype correlation in WAS and in related X-linked thrombocytopenia. Expression of the WASp was found to be the best predictor of clinical phenotype. Investigation of autoimmune manifestations associated with WAS has shown that autoimmune hemolytic anemia and elevated serum IgM associate with a more severe clinical course. Finally, while results of hematopoietic stem cell transplantation for WAS continue to improve, several studies have shown the potential benefit of novel therapeutic approaches based on gene transfer. In particular, use of lentiviral vector-driven expression of the WASP gene under autologous promoter sequences has been found to result in increased targeting of hematopoietic stem cells, higher levels of WASp expression, and improved reconstitution of immune function. Availability of tools that allow analysis of WASp expression has provided evidence for a genotype-phenotype correlation in patients with WASP gene defects. Protein expression is an important prognostic indicator. The molecular and cellular abnormalities of WAS-associated defects are being identified, and significant advances in vector-mediated gene transfer have opened possibilities for the treatment of WAS based on gene therapy.

Functional Correction of Lymphocytes and Dendritic Cells of Patients with WAS or XLT, Using Lentiviral Vectors Targeting the Expression of WAS Protein to Hematopoietic Cells.

The WAS gene is mutated in Wiskott-Aldrich syndrome (WAS) and in X-linked thrombopenia (XLT). These diseases associate platelet defects with variable immune dysfunction, as a result of abnormal signalling and impaired cytoskeletal regulation in hematopoeitic cells. Conceivably, severe forms of WAS could be treated by gene therapy because retroviral or lentiviral-mediated WAS gene transfer restores protein expression and function in several WAS protein-deficient models. The purpose of the present study was to improve the safety and efficacy of such lentiviral vectors. Endogenous WAS promoter elements were used to restrict transgene expression to the target cell population and to provide the possibility of regulated expression in these cells. Sequences 0.5 or 1.6 kb upstream of transcription start, were operational in the transfer vector and restricted transgene expression to hematopoietic cells. Vectors utilizing either one of the WAS promoter sequences or the ubiquitously-active PGK-1, SFFV or EF1-a promoters, were compared. Equivalent levels of WAS protein were induced in lymphocytes and dendritic cells (DC), although slightly inferior mRNA levels were obtained in B cells using WAS promoters. At the functional level, all vectors restored a similar degree of proliferation and IL-2 production in T cells and equivalent numbers of podosome cytoskeletal structures in DC. The 0.5 kb or 1.6 kb-long WAS promoter sequences functioned similarly in WAS B lymphocytes or in a model of WASP-deficient T cells generated by RNA interference. No toxicity was induced by over-expression of these vectors in CD34+ cells. Altogether, the data show that lentiviral vectors with WAS promoters function efficiently in several lineages of patient cells and support further development of a hematopoietic-restricted approach for the gene therapy of WAS.

330. Lentiviral Vector Mediated Hematopoietic Stem Cell Gene Therapy Combined with Non-Lethal Conditioning Restores T Cell Function in the Murine Model of Wiskott-Aldrich Syndrome

Top of pageAbstract Wiskott-Aldrich syndrome (WAS) is a severe X-linked immunodeficiency characterized by recurrent infections, thrombocytopenia, eczema and increased risk of autoimmune disorders and lymphomas. The present therapeutic strategy is based on transplantation of bone marrow from HLA-identical sibling donors. Because of the limited availability of such donors, the development of alternative approaches, such as hematopoietic stem cells (HSC) gene therapy is highly desirable. We previously demonstrated that lentiviral vectors encoding the Wiskott-Aldrich syndrome protein (WASP) can efficiently correct the functional defects of patients' T cells [Dupr|[eacute]| L, et al. Mol Ther. 2004, 10:903|[ndash]|15]. In the present study we investigated the efficacy of HSC gene therapy in a WAS knockout murine model (WKO) [Zhang J, et al. J Exp Med. 1999, 190:1329|[ndash]|42]. We tested three lentiviral vectors encoding for human WASP under the control of the following promoters: human PGK promoter (pW), full-length (1.6Kb) human WASP autologous promoter (1.6wW) or minimal (0.5 Kb) human WASP autologous promoter (0.5wW). Lineage depleted WKO female bone marrow cells were transduced with the different vectors and transplanted into non-lethally irradiated WKO male mice. Four months after gene therapy, chimerism in T cells, B cells and bone marrow was more than 80% donor. Human WASP expression was detected in T cells, B cells and platelets. Correction of IL-2 production and proliferation by splenic T cells was observed in the majority of the treated mice. T cell correction was achieved when a threshold number of viral integrations in the T cells was reached. Notably, the 1.6wW vector allowed functional T cell correction with the lowest lentiviral vector copy number (1 proviral integration per donor T cell). HSC gene therapy was well tolerated, and no malignancy occurred in more than 80 transplanted WKO mice, as indicated by blood analysis and autopsy. In conclusion, we demonstrate that HSC gene therapy combined with non-lethal conditioning allows robust engraftment and differentiation of transduced cells without toxicity. Correction of T cell proliferation and IL-2 production was highly reproducible. Future studies will determine whether a non myeloablative conditioning regimen based on busulfan leads to successful HSC gene therapy and whether, in this setting, genetically corrected T cells have a selective advantage over non corrected T cells.

Wiskott-Aldrich Syndrome Protein Is Needed for Vaccinia Virus Pathogenesis

Smallpox, caused by variola virus, was a devastating disease in humans, but how the virus evolved a strategy to spread to tissue remains unknown. Through the use of microarrays, we identified the gene encoding the Wiskott-Aldrich syndrome protein (WASP), one of the five known WASP family members, which has been induced in the course of infection of human cells with different strains of vaccinia virus (VV) (S. Guerra, L. A. Lopez-Fernandez, A. Pascual-Montano, M. Munoz, K. Harshman, and M. Esteban, J. Virol. 77:6493-6506, 2003; S. Guerra, L. A. Lopez-Fernandez, R. Conde, A. Pascual-Montano, K. Harshman, and M. Esteban, J. Virol. 78:5820-5834, 2004). In a mouse model, we evaluated the role of WASP in infection with VV, a close relative of variola virus. WASP(-/-) (KO) mice infected intranasally and intraperitoneally with VV showed reduced weight loss and mortality compared to wild-type (WT) mice. WASP expression correlated with VV replication in the ovaries but not in the liver or spleen. WT mouse macrophages express WASP but not N-WASP; after VV infection, WASP levels increase threefold. KO macrophages lack N-WASP expression and, when VV infected, are incapable of inducing actin tails and producing extracellular virus. These functions were rescued in KO macrophages after ectopic WASP expression. Overall, our findings demonstrate that WASP has a role in orthopoxvirus infections. Use of WASP proteins for virus spread via the actin tail provides a selective advantage for VV, and probably variola virus, dissemination to distant tissues.

A lentiviral vector encoding the human Wiskott–Aldrich syndrome protein corrects immune and cytoskeletal defects in WASP knockout mice

Wiskott-Aldrich syndrome (WAS) is an immune deficiency with thrombopenia resulting from mutations in the WASP gene. This gene normally encodes the Wiskott-Aldrich syndrome protein (WASP), a major cytoskeletal regulator expressed in hematopoietic cells. Gene therapy is a promising option for the treatment of WAS, requiring that clinically applicable WASP gene transfer vectors demonstrate efficacy in preclinical studies. Here, we describe a self-inactivating HIV-1-derived lentiviral vector encoding human WASP and show that it effectively transduced bone marrow progenitor cells of WASP knockout (WKO) mice. Transplantation of these transduced cells into lethally irradiated WKO recipients led to stable expression of WASP and correction of immune, inflammatory and cytoskeletal defects. Splenic T-cell proliferation was restored, podosomes were reinstated on bone-marrow-derived dendritic cells and colon inflammation was reduced. This shows for the first time (a) that cytoskeletal defects can be corrected in WKO mice, (b) that human WASP is biologically active in mice and (c) that a lentiviral vector is effective to express human WASP in vivo over several months. These data support further development of such lentiviral vectors for the gene therapy of WAS.

904. Lentiviral Transduction of Wiskott-Aldrich Syndrome (WAS) Deficient, T-Cells Leads to Long-Term and Progressive WAS Protein Expression and Functional Reconstitution

Top of pageAbstract Previous work has shown that both group I ribozymes and SMaRT™ pre-trans-splicing molecules (PTMs) can be designed to trans-splice into mutant RNA targets and subsequently correct these transcripts. The technology's therapeutic potential hinges on specific and efficient trans-splicing with the intended transcript. We are using quantitative PCR to assess these two parameters with a β-globin target in mammalian cells. Both ribozyme and PTM RNA repair approaches are being used and the results will provide the first direct comparison between these two potential therapeutics. Preliminary efficiency experiments using co-transfection of β-globin target and ribozyme expression vectors into 293T cells followed by QC-RT-PCR resulted in 5–50% trans-splicing levels depending on the promoter used. We are now testing 3' and 5' PTM constructs against the same β-globin target and assessing trans-splicing levels in 293T cells.

A novel termination codon mutation of the WAS gene in a Thai family with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by microthrombocytopenia, eczema, immunodeficiency, and susceptibility to lymphoid malignancy. Loss-of-function mutations in WAS gene have been identified to cause disorders with platelet defects including WAS and X-lined thrombocytopenia. Mutations anticipated to yield truncated or no protein have been associated with the more severe presentations of WAS. Activating mutations in WAS gene result in an entirely different phenotype, an X-linked severe congenital neutropenia. Case report We describe a Thai family with classic WAS. The proband, a one-year-old boy presented with recurrent mucous bloody diarrhea, recurrent otitis media, chronic eczema, thrombocytopenia, and small platelet sizes, the patient's older brother who was also had persistent thrombocytopenia died at the age of seven months from severe pneumonia. Immunoblot analysis demonstrated that the proband's cells lacked WAS protein expression. Mutation analysis of the proband and his mother for the entire coding region of WAS identified a novel type of mutation, a termination codon mutation, X503R. The change is expected to result in an elongated mRNA that would code for a WASP of 581 amino acid residues instead of the normal 502 residues. Because of the absence of WASP expression, we speculated that the termination codon mutation causes reduced mRNA stability. Conclusion Our finding supported that WAS mutations resulted in no protein are associated with a severe phenotype of WAS.

Clinical course of patients with WASP gene mutations

AbstractMutations of the Wiskott-Aldrich syndrome protein (WASP) gene result either in the classic Wiskott-Aldrich syndrome (WAS) or in a less severe form, X-linked thrombocytopenia (XLT). A phenotype-genotype correlation has been reported by some but not by other investigators. In this study, we characterized WASP gene mutations in 50 Japanese patients and analyzed the clinical phenotype and course of each. All patients with missense mutations were WASP-positive. In contrast, patients with nonsense mutations, large deletions, small deletions, and small insertions were WASP-negative. Patients with splice anomalies were either WASP-positive or WASP-negative. The clinical phenotype of each patient was correlated with the presence or absence of WASP. Lack of WASP expression was associated with susceptibility to bacterial, viral, fungal, and Pneumocystis carinii infections and with severe eczema, intestinal hemorrhage, death from intracranial bleeding, and malignancies. Rates for overall survival and survival without intracranial hemorrhage or other serious complications were significantly lower in WASP-negative patients. This analysis provides evidence for a strong phenotype-genotype correlation and demonstrates that WAS protein expression is a useful tool for predicting long-term prognosis for patients with WAS/XLT. Based on data presented here, hematopoietic stem cell transplantation should be considered, especially for WASP-negative patients, while the patients are young to improve prognosis.

A novel termination codon mutation of the WAS gene in a Thai family with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by microthrombocytopenia, eczema, immunodeficiency, and susceptibility to lymphoid malignancy. Loss-of-function mutations in WAS gene have been identified to cause disorders with platelet defects including WAS and X-linked thrombocytopenia. Mutations anticipated to yield truncated or no protein have been associated with the more severe presentations of WAS. Activating mutations in WAS gene result in an entirely different phenotype, an X-linked severe congenital neutropenia. We describe a Thai family with classic WAS. The proband, a one-year-old boy presented with recurrent mucous bloody diarrhea, recurrent otitis media, chronic eczema, thrombocytopenia, and small platelet sizes. The patient's older brother who also had persistent thrombocytopenia died at the age of seven months from severe pneumonia. Immunoblot analysis demonstrated that the proband's cells lacked WAS protein expression. Mutation analysis of the proband and his mother for the entire coding region of WAS identified a novel type of mutation, a termination codon mutation, X503R. The change is expected to result in an elongated mRNA that would code for a WASP of 581 amino acid residues instead of the normal 502 residues. Because of the absence of WASP expression, we speculate that the termination codon mutation causes reduced mRNA stability. Our findings supported that WAS mutations resulted in no protein are associated with a severe phenotype of WAS.

Functional correction of T cells derived from patients with the Wiskott-Aldrich syndrome (WAS) by transduction with an oncoretroviral vector encoding the WAS protein.

T-cell dysfunction is thought to be central to the immunodeficiency state seen in patients with the Wiskott-Aldrich syndrome (WAS). Aspects of the WAS phenotype have been corrected in other cell types on introduction of the normal WAS protein (WASP), but the potential for correction of the T-cell defects has not been evaluated. Here we demonstrate that an oncoretroviral vector encoding WASP and green fluorescent protein (GFP), and pseudotyped with the RD114 envelope protein, efficiently transduces primary human T cells derived from WAS patients. Transcription initiated at the oncoretroviral long terminal repeat (LTR) results in levels of WASP that, while lower than those seen in normal control T cells, resulted in correction of the deficient proliferative response to T-cell receptor (TCR) stimulation characteristic of WAS. IL2 secretion after TCR stimulation was partially corrected. Control primary T cells transduced with the same vector responded normally to TCR stimulation, and showed no increase in WASP expression. The demonstration that correction of T cell defects can be achieved by gene transfer supports continued efforts to develop gene therapy for WAS.

Expression of WASP and Scar1/WAVE1 actin-associated proteins is differentially modulated during differentiation of HL-60 cells.

The Wiskott-Aldrich Syndrome (WAS) is a disease associated with mutations in the WAS gene and characterised by developmental defects in haematopoietic cells such as myeloid cells. The Wiskott-Aldrich Syndrome protein (WASP)-family includes Scar1 and WASP, which are key regulators of actin reorganization in motile cells. To understand the roles of Scar1 and WASP in myeloid cells and their cytoskeletal control in haematopoietic tissues, we have explored their expression during differentiation of the promyeloid cell line HL-60. Undifferentiated HL-60 cells expressed Scar1 and WASP, and differentiation to neutrophils, induced by retinoic acid or non-retinoid agent treatments, led to a decrease in the level of expression of Scar1, whereas WASP expression was unaffected. Differentiation to monocytes/macrophages, induced by phorbol ester treatment, resulted in a decreased expression of both proteins in the adherent mature cells. Vitamin D(3) treatment or cytochalasin D in combination with PMA treatment did not affect WASP expression suggesting that adhesion and cytoskeletal integrity were both essential to regulate WASP expression. Scar1 expression was regulated by differentiation, adhesion, and cytoskeletal integrity. Recently, WASP was found to colocalize with actin in the podosomes. In contrast, we show here that Scar1 did not localize with the podosomes in mature monocytes/macrophages. These observations show for the first time that modulation of Scar1 and WASP expression is a component of the differentiation program of myeloid precursors and indicate that WASP and Scar1 have different roles in mature myeloid cells.

Mixed chimera status of 12 patients with Wiskott-Aldrich syndrome (WAS) after hematopoietic stem cell transplantation: evaluation by flow cytometric analysis of intracellular WAS protein expression

Wiskott-Aldrich syndrome (WAS) is caused by defects in the WAS protein (WASP) gene on the X chromosome. We previously reported that flow cytometric analysis of intracellular WASP expression (FCM-WASP) was useful in the diagnosis of WAS in patients and carriers. In this study, we applied FCM-WASP to evaluate the mixed chimera (MC) status of 12 WAS patients who underwent hematopoietic stem cell transplantation (HST). After HST, donor- and recipient-derived peripheral blood mononuclear cells (PBMCs) could be distinguished easily with this method, since the donor cells were WASP(bright), whereas the defective recipient cells were WASP(dim). Furthermore, with use of 2-color FCM-WASP, the MC status could be characterized by cell lineage. Six of the 12 patients with WAS were found to have MC status after HST, whereas others had complete chimera status. MC status was observed in every cell lineage examined. However, among PBMCs, recipient cells were most commonly observed in the monocyte population. Finally, to investigate the naive/memory status of donor and recipient T cells in these patients, 3-color FCM-WASP using anti-CD45RA or CD45RO was performed. We found that, in contrast to WASP(bright) T cells, most WASP(dim) T cells remained naive (CD45RA(+)/RO(-)) more than a year after HST. No imbalance in the ratio of naive to memory T cells was observed in WAS patients before HST. We conclude that FCM-WASP is a potentially useful method for clinical follow-up of WAS patients who have undergone HST. Our findings may also have important implications for the role of WASP during hematopoietic development.

Retrovirus-mediated WASP gene transfer corrects Wiskott-Aldrich syndrome T-cell dysfunction.

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by thrombocytopenia, eczema, and immunodeficiency. At present, the only definitive therapy for the disease is allogeneic bone marrow transplantation (BMT). Because of the frequent lack of suitable donors and the potential severe complications associated with BMT, the development of gene-based therapeutic strategies for WAS is highly desirable. To study whether corrective gene transfer into WAS T cells can lead to restoration of the immunologic defects of WAS, a retroviral vector expressing the WAS protein (WASP) gene was used to transduce human T-lymphotropic virus type 1-transformed T-cell lines and primary T lymphocytes from patients with WAS. After transduction, WAS T cells showed levels of WASP expression similar to those found in cells from normal individuals. In addition, the reconstituted WASP interacted in vitro with proteins containing SH3 domain such as Grb2, PLC-gamma1, and Fyn, each of which are connected to signaling pathways linked to the actin cytoskeleton. Furthermore, after CD3 cross-linking, transduced WAS T lines showed improvement of actin polymerization and T-cell receptor/CD3 down-regulation. More importantly, primary WAS T lymphocytes transduced with WASP acquired the ability to proliferate in response to anti-CD3 stimulation. These findings suggest that biologic defects of WAS T cells can be corrected in vitro by retrovirus-mediated gene transfer and pose the basis for future investigation of gene therapy as treatment for WAS.

WASp verprolin homology, cofilin homology, and acidic region domain-mediated actin polymerization is required for T cell development.

All members of the Wiskott-Aldrich syndrome protein (WASp) family contain a carboxyl-terminal verprolin homology, cofilin homology, and acidic region (VCA) domain that binds and activates the Arp2/3 complex, thereby linking these proteins to the induction of actin polymerization. Although the VCA domain imbues WASp and other WASp family members with the capacity to modulate cytoskeletal organization, little is known about the impact of this domain activity on lymphoid cell function. Here we demonstrate that T cell-restricted expression of VCA domain-deleted WASp (WASpdeltaVCA) in WAS(-/-) mice engenders a severe early block in T lymphopoiesis associated with impaired T cell antigen receptor alphabeta expression and a consequent failure to generate single-positive CD4(+) and CD8(+) T cells. These latter defects, which are not observed in WAS(-/-) mice, are associated with impaired induction of cellular actin polymerization and a failure in the terminal differentiation of double-negative thymocytes. These findings indicate that WASp family proteins play an essential role in modulating the signaling events required for early thymocyte development and reveal their capacity to subserve this role to depend on VCA domain-mediated actin polymerization.

Restoration of podosomes and chemotaxis in Wiskott–Aldrich syndrome macrophages following induced expression of WASp

We used a direct-viewing (Dunn) chemotaxis chamber to analyse the chemotactic responses of human normal and Wiskott–Aldrich syndrome (WAS) macrophages to the cytokine colony stimulating factor-1 (CSF-1). In five patients with classic WAS, where specialised adhesion complexes called podosomes are absent, chemotaxis of macrophages was abolished. The deficient chemotactic responses of WAS macrophages following cytokine stimulation could be correlated with abnormalities in cell polarisation and actin organisation. In a series of cell microinjection studies we found that normal chemotactic responses were restored in WASp macrophages transfected with a full-length human WAS construct. Expression of exogenous WAS protein (WASp) in these cells also restored normal polarised cell morphology and the ability to form podosomes.

Flow cytometric determination of intracytoplasmic Wiskott–Aldrich syndrome protein in peripheral blood lymphocyte subpopulations

We have produced a novel monoclonal antibody (mAb) directed against Wiskott–Aldrich syndrome protein (WASP) by immunizing mice with the recombinant protein. The mAb designated 5A5 is highly specific to WASP and suitable for Western blot analysis and immunoprecipitation. A flow cytometric assay using the 5A5 mAb identifies expression of intracytoplasmic WASP in lymphocytes from normal individuals. Double staining analysis with cell surface CD3, CD19, and CD56, and intracytoplasmic molecules revealed WASP expression in each subpopulation. With regard to WASP expression in patients with Wiskott–Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT), peripheral blood mononuclear cells (PBMCs) from nine patients and Epstein–Barr virus-transformed B-lymphoblastoid cell lines from seven patients examined did not show WASP expression by flow cytometric analysis. These results were confirmed by Western blot analysis. We conclude that WASP expression in lymphocyte subpopulations from patients with WAS and XLT can be more precisely evaluated by flow cytometry as compared with Western blot analysis. This flow cytometry method is important as a supplement to Western blots, but even more important as an alternative and powerful assay that can contribute to research on WASP as well as diagnosis in a clinical setting.

Determination of carrier status for the Wiskott-Aldrich syndrome by flow cytometric analysis of Wiskott-Aldrich syndrome protein expression in peripheral blood mononuclear cells.

The Wiskott-Aldrich syndrome (WAS) is caused by defects in the WAS protein (WASP) gene on the X chromosome. Previous study disclosed that flow cytometric analysis of intracellular WASP expression (FCM-WASP analysis) in lymphocytes was useful for the diagnosis of WAS patients. Lymphocytes from all WAS patients showed WASPdim instead of WASPbright. Here we report that FCM-WASP analysis in monocytes could be a useful tool for the WAS carrier diagnosis. Monocytes from all nine WAS carriers showed varied population of WASPdim together with WASPbright. None of control individuals possessed the WASPdim population. In contrast, lymphocytes from all the carriers except two lacked the WASPdim population. The difference of the WASPdim population in monocytes and lymphocytes observed in WAS carriers suggests that WASP plays a more critical role in the development of lymphocytes than in that of monocytes. The present studies suggest that a skewed X-chromosomal inactivation pattern observed in WAS carrier peripheral blood cells is not fixed at the hemopoietic stem cell level but progresses after the lineage commitment.

Expression of human Wiskott-Aldrich syndrome protein in patients' cells leads to partial correction of a phenotypic abnormality of cell surface glycoproteins.

The Wiskott-Aldrich syndrome (WAS) is an uncommon X-linked recessive disease characterized by thrombocytopenia, eczema and immunodeficiency. The biochemical defect of this disorder primarily affects cells derived from bone marrow. To understand better the molecular mechanisms underlying this disease and to evaluate the possibility of correcting the genetic defects in hematopoietic cells, a Moloney murine leukemia virus (MoMLV)- based retroviral vector carrying a functional Wiskott-Aldrich syndrome protein (WASp) cDNA driven by an SV40 promoter (LNS-WASp) was constructed. A packaging cell line containing this vector produced a stable level of WAS protein and maintained a high titer of viral output. Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines (B-LCL) from WAS patients, which lack expression of the WAS protein, were transduced by the LNS-WASp retroviral vector and showed expression of WASp by Western blot. Analysis of the O-glycan pattern on cell surface glycoproteins from WAS patients' B-LCL showed an altered glycosylation pattern, due to increased activity of beta-1, 6-N-acetylglucosaminyltransferase (C2GnT). Transduction by the retroviral vector carrying the functional WASp cDNA partially restored the abnormal glycosylation pattern, and was accompanied by a decreasing C2GnT activity. These findings imply a functional linkage between the WAS protein and the expression of the glycosyltransferase involved in the O-glycosylation, and also suggest a potential gene therapy via transferring a functional WASp cDNA into hematopoietic cells for Wiskott-Aldrich syndrome. Gene Therapy (2000) 7, 314-320.

WASP Levels in Platelets and Lymphocytes of Wiskott-Aldrich Syndrome Patients Correlate with Cell Dysfunction

Wiskott-Aldrich syndrome, an inherited blood cell disorder due to mutations of the X-chromosome gene WASP (Wiskott-Aldrich syndrome protein), was characterized originally by thrombocytopenia, immunodeficiency, and eczema. Whereas platelet dysfunction is severe and consistent, immune defects are clinically variable, ranging from negligible to life threatening. To understand this heterogeneity, we quantified WASP in PBMC and platelets, and also in neutrophils, of patients with diverse mutations. A surprisingly complex pattern of WASP expression found for lymphoid cells formed the basis for dividing the patient mutations into four groups. Group A have low WASP levels in PBMC and higher levels in EBV cell lines, as well as near normal WASP RNA levels (7 patients, most with mild disease), suggesting that group A WASP molecules are hypersusceptible to proteolysis. Group B have low WASP levels in PBMC and EBV cells and similar low RNA levels (2 patients, moderate disease). Group C have discordant expression: WASP-positive peripheral T cells and WASP-negative peripheral B cells and EBV cell lines (9 patients, variable disease severity). Noteworthy among group C kindred are several instances of B cell lymphomas. In group D, PBMC and EBV cell lines are WASP negative (7 patients, severe disease). In contrast to the complex lymphoid cell expression patterns, all patient platelets examined were WASP negative (18 diverse patients). WASP absence in platelets provides an apparent molecular explanation for the universally severe platelet dysfunction in this disease, and the cumulative lymphoid cell findings suggest that WASP levels play a substantial role in determining immune outcome.

Absence of Expression of the Wiskott–Aldrich Syndrome Protein in Peripheral Blood Cells of Wiskott–Aldrich Syndrome Patients

Wiskott–Aldrich syndrome (WAS) is an X-linked primary immunodeficiency that is usually associated with thrombocytopenia and eczema. The very variable phenotype of WAS results from defects in the WAS protein (WASP), the function of which is not well understood. In many cases causative mutations have now been identified in theWASgene. Attempts have been made to correlate the nature of the mutations with the severity of the disease. In this study we investigated mutations in 13 patients with WAS and analyzed the expression of WASP in patient blood samples by immunoblot analysis. We found that despite extensive variation in the nature of the mutations in patients with severe WAS symptoms, none express the protein. However, in 1 patient with a mild clinical phenotype WASP expression was detected. Such an analysis could be used as an initial screening procedure for the diagnosis of WAS prior to genotypic analysis.