Identification of a Novel Gene Mutation in a Chinese Pedigree with X-linked Thrombocytopenia.

BACKGROUND: X-linked thrombocytopenia (XLT) is a milder form of Wiskott-Aldrich syndrome (WAS), characterized predominantly by thrombocytopenia with small-sized platelets. Mutations in the WAS gene are responsible for the disease. We herein detected a new mutation in the WAS gene responsible for XLT in a 3-generation Chinese pedigree. METHODS: Peripheral blood samples were collected from 7 members in the family. WAS gene was amplified from genomic DNA isolated from leucocytes, and then direct sequencing was performed. RESULTS: Three male members of this family (the proband, his younger brother and maternal uncle) had thrombocytopenia and decreased mean platelet volume. A homozygous mutation (T>C) was found at nucleotide position 319 in exon 3, causing the amino acid Tyr (T) to be abnormally changed to His (H) at position 107. Two female members (the proband's mother and grandmother) were carriers of the mutation. CONCLUSIONS: XLT is easy to misdiagnose as immune thrombocytopenic purpura (ITP). The diagnosis of XLT should be considered in any male with congenital microthrombocytopenia or early onset of microthrombocytope-nia (< 7 fL). This article adds to the growing number of known mutations associated with XLT.

T-cell receptor diversity is selectively skewed in T-cell populations of patients with Wiskott-Aldrich syndrome.

BACKGROUND: Wiskott-Aldrich syndrome (WAS) is a severe disorder characterized by thrombocytopenia, eczema, immunodeficiency, and increased risk of autoimmune disease and lymphoid malignancies. The immunodeficiency caused by a lack of WAS protein expression has been mainly attributed to defective T-cell functions. Whether WAS mutations differentially influence the T-cell receptor (TCR) diversity of different T-cell subsets is unknown. OBJECTIVE: We aimed to identify the degree and pattern of skewing in the variable region of the TCR ß-chain (Vß) in different T-cell subsets from patients with WAS. METHODS: The TCR repertoire diversity in total peripheral T cells, sorted CD4(+) and CD8(+) T cells, and CD45RA(+) (CD45RA(+)CD45RO(-) cells) and CD45RO(+) (CD45RA(-)CD45RO(+) cells) CD4(+) and CD8(+) T cells from patients with WAS and age-matched healthy control subjects was analyzed and compared by using spectratyping of complementarity-determining region 3. The complementarity-determining region 3 of TCRß transcripts in CD45RA(+)CD4(+) and CD45RA(+)CD8(+) T cells, CD45RO(+)CD4(+) T cells, CD8(+) terminally differentiated effector memory T (Temra) cells, and naive CD8(+) T cells (CD8(+)CD45RO(-)CCR7(+) cells) from patients and control subjects were analyzed and compared by using high-throughput sequencing. RESULTS: The TCR repertoire diversity in CD45RO(+)CD4(+) T cells and CD8(+) Temra cells of patients with WAS was significantly skewed in comparison with that seen in age-matched control subjects. CONCLUSION: Our results indicate that WAS gene mutations selectively influence TCR repertoire development or expansion in CD45RO(+) (memory) CD4(+) T cells.

Clinical aspects and genetic analysis of taiwanese patients with wiskott-Aldrich syndrome protein mutation: the first identification of x-linked thrombocytopenia in the chinese with novel mutations.

BACKGROUND: Wiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency characterized by microthrombocytopenia, eczema, and recurrent infections. However, the more than 500 patient mutations described are mainly based on Caucasian and Japanese populations. This study investigated Taiwanese patients with WASP mutations since 1985 as part of a long-term comprehensive study in primary immunodeficiency diseases (PIDs) covering 23 million inhabitants. METHODS: Clinical manifestations, immunologic functions, and WASP gene sequencing and expressions were analyzed in WAS patients. And, those patients with idiopathic thrombocytopenic purpura and "small" thrombocytopenia were enrolled. RESULTS: Of 16 patients studied in 1993-2009, 12 presented as classic WAS phenotype and four had X-linked thrombocytopenia (XLT). Almost all correlated to the WASP expression level and severity of infections. Causes of mortality in the 12 classic WAS patients were mass bleeding, Staphylococcus aureus sepsis, and cytomegalovirus (CMV) pneumonitis in three non-transplant cases, and EBV-associated lymphoproliferative disorder and CMV pneumonitis in two non-engrafted transplant patients. Splicing mutations of Int 8 (+5) G>A in cousins and insertion of 1023 C in unrelated families presented as both XLT and classic WAS phenotype in the same mutations. Four XLT patients, including two novel mutations of 1023 Ins C (in 2) and "double" missense mutations of 1378 C>T and 1421 T>C had relatively higher CD4+ memory cells and/or activated lymphocytes (CD3+CD69+) compared with those of classic WAS patients. CONCLUSIONS: The lower ratio of XLT to classic WAS patients underestimates the burden of Taiwanese patients with WASP mutations, especially the XLT phenotype. A clustering pattern on exon 1 and five unique mutations (deletion of 45-48 ACCA, IVS 1 (-1) G>C, large deletion of promoter and exon 1 and 2, insertion 1023 C, and 1378 C>T and 1421 T>C) explain the genetic variations in different ethnic groups, despite the possibility of selection and ascertainment bias.

Identification of WASP mutations in 14 Spanish families with Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency caused by mutations in the WASP gene. The disease is known to be associated with extensive clinical variability, and mutation studies indicate that genotypes are also highly variant among WAS patients. In this study, we performed mutation analysis of the WASP gene in 14 unrelated Spanish families by single strand conformation analysis (SSCA) and sequencing, resulting in the identification of a novel mutation and nine known mutations. No mutation was identified in one family. The ten different mutations include point mutations resulting in amino acid substitutions, stop codons, and small deletions and insertions causing frameshifts. Missense mutations were preferentially located in the amino-terminal part of the protein, exons 2 and 4, whereas stop and frameshift mutations were located in the carboxyl-terminal region, exons 10 and 11. However, in two families, two missense mutations in exon 11 were identified. Our study demonstrates that WASP genotypes have some concordance with the patients' phenotypes, although mutation 1019delC, identified in a family with several affected members, resulted in high intrafamilial clinical variability.

Novel mutations, no detectable mRNA and familial genetic analysis of the Wiskott-Aldrich syndrome protein gene in six Japanese patients with Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome (WAS) is a primary X-linked immunodeficiency disease caused by mutations of the Wiskott-Aldrich syndrome protein (WASP) gene. The present molecular studies of six Japanese WAS patients identified five different mutations of WASP, including two novel mutations (45delG, 395insGGAGAT), the latter appearing to have occurred de novo. Familial carriers were detected by polymerase chain reaction-single strand conformational polymorphism analysis, restriction enzyme digestion and direct sequencing of PCR products. Neither mRNA nor the protein product were detectable in any of the patients, while various amounts of WASP protein were expressed in carriers, normal controls, haematopoietic cell lines of all lineages and in one patient after receiving allogeneic bone marrow transplantation. Conclusion Genetic and protein analysis is useful in the definite diagnosis and follow up of Wiskott-Aldrich syndrome patients and in carrier detection, especially of atypical or sporadic patients.