Wiskott-Aldrich syndrome/X-linked thrombocytopenia: WASP gene mutations, protein expression, and phenotype.
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-gamma, 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.
Zhu
Q
Q
Department of Pediatrics, University of Washington School of Medicine, Seattle 98195-6320, USA.
Watanabe
C
C
Liu
T
T
Hollenbaugh
D
D
Blaese
R M
RM
Kanner
S B
SB
Aruffo
A
A
Ochs
H D
HD
D000595:Amino Acid Sequence; D000818:Animals; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D005838:Genotype; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics*; D011817:Rabbits; D017384:Sequence Deletion; D012720:Severity of Illness Index; D013921:Thrombocytopenia / Q000235:genetics*; D014923:Wiskott-Aldrich Syndrome / Q000235:genetics*; D051316:Wiskott-Aldrich Syndrome Protein; D014960:X Chromosome / Q000235:genetics*
D011506:Proteins; C495767:WAS protein, human; D051316:Wiskott-Aldrich Syndrome Protein