Wiskott-Aldrich Syndrome/X-Linked Thrombocytopenia: WASP Gene Mutations, Protein Expression, and Phenotype

Abstract

Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT), caused by mutations of the WAS protein (WASP) gene, represent different phenotypes of the same disease. To demonstrate a phenotype/genotype correlation, we determined WASP gene mutations in 48 unrelated WAS families. Mutations included missense (20 families) and nonsense (eight) mutations located mostly in exons 1 to 4, and splice-site mutations (seven) and deletions and insertions (13) located preferentially in exons 7 to 11. Both genomic DNA and cDNA were sequenced and WASP expression was measured in cell lysates using peptide-specific rabbit anti-WASP antibodies. WASP was expressed in hematopoietic cell lines including bone marrow–derived CD34+ cells. Missense mutations located in exons 1 to 3 caused mild disease in all but one family and permitted WASP expression, although frequently at decreased concentration. Missense mutations affecting exon 4 were associated with classic WAS and, with one exception, barely detectable WASP. Nonsense mutations caused classic WAS and lack of protein. Insertions, deletions, and splice-site mutations resulted in classic WAS and absent, unstable, truncated, or multiply spliced protein. Using affinity precipitation, WASP was found to bind to Src SH3-containing proteins Fyn, Lck, PLC-γ, and Grb2, and mutated WASP, if expressed, was able to bind to Fyn-glutathione S-transferase (GST) fusion protein. We conclude that missense mutations affecting the PH domain (exons 1 to 3) of WASP inhibit less important functions of the protein and result in a mild phenotype, and that missense mutations affecting exon 4 and complex mutations affecting the 3′ portion of WASP interfere with crucial functions of the protein and cause classic WAS.

Cdc42: An Essential Rho-Type GTPase Controlling Eukaryotic Cell Polarity

“…Patients with Wiskott-Aldrich syndrome have multiple immunological defects, including thrombocytopenia with small platelets, eczema, T-and B-lymphocyte defects, and an increased risk of malignancies and autoimmune diseases (for reviews, see references 144, 261, and 427). The severity of these defects has been directly correlated with mutations within the X-linked recessive gene WASP and with defects in cellular actin cytoarchitecture (122,257,270,285,399,428,475,577,636,637). The ϳ62-kDa WASP (19,271,545) contains several functional domains including an N-terminal WH1 domain (residues 8 to 105), a CRIB domain (residues 238 to 257), a proline-rich domain (residues 312 to 404), two potential actin binding sites with similarity to verprolin and cofilin sequences (residues 430 to 446 and 469 to 489), and an acidic C-terminal region.…”

Macrophages of patients with X‐linked thrombocytopenia display an attenuated Wiskott‐Aldrich syndrome phenotype

“…One of the respective signal transduction cascades was shown to induce the formation of new actin filaments through WASp and to be dependent, among other factors, on phosphatidylinositol 4,5‐bisphosphate (PIP2) 25 X‐linked thrombocytopenia patients with mild disease generally show mutations in exons 1–3, 4 , 22 corresponding to the WH1 domain of WASp 4 …”

“…Both of the XLT mutations correspond to amino acid changes in the WH1 domain of WASp (Figure 1). Missense mutations in this domain are typically observed in XLT 22 …”

Características clínicas e genéticas de pacientes brasileiros com a Síndrome de Wiskott-Aldrich

“…Imai et al (2004) OCHS et al, 2006;ALBERT et al, 2011), embora haja relatos de pacientes com hipergamaglobulinemia (SURI et al, 2012;AMARINTHNUKROWH et al, 2012). (DERRY et al, 1995;OCHS et al, 2006), ao passo que a deficiência de IgA é uma alteração menos frequente, tendo sido descrita em outras publicações (SULLIVAN et al, 1994;BUCHBINDER et al, 2014 (DERRY et al, 1995;ZHU et al, 1997;IMAI et al, 2004;MOULDING et al, 2013 SULLIVAN et al, 1994;ALBERT et al, 2011).…”

“…O gene WAS foi identificado em 1994 através de clonagem posicional e localiza-se no braço curto do cromossomo X na posição Xp11.22-p11.23 (DERRY et al, 1994). Formado por 12 exons, contém 1823 pares de bases e codifica 5 domínios da proteína WASp: domínio WASP-homólogo 1 (WH1), domínio ligante de GTPase (GBD), região rica em prolina (PRR), domínio WH2 e região ácida (AR) (ZHU et al, 1997;IMAI et al, 2003).…”