Alterations in the

SH2D1A gene and the SH2D1A protein. (A) Alignment of the wild-type SH2D1A complementary DNA (cDNA) sequence with the nucleotide sequences obtained from patients C.L. and C.G. (left) and C.H. sequences (right). Panels depict the gene segment of interest. Nucleotide differences are indicated in gray. A single nucleotide substitution was detected at position 462 of the SH2D1A cDNA coding region of patients C.L. and C.G. (C462T) (left). After subcloning, approximately half the exon 2 PCR products of C.H. (mother of C.L. and daughter of C.G.) contained the C462T nucleotide substitution (right panel). (B) The SH2D1A cDNA nucleotide sequence was aligned with the sequences obtained from patients A.C., A.B., B.B., B.C., and B.D. (left) and A.A. and B.A. sequences (right). Panels depict the gene segment of interest. Nucleotide differences are indicated in gray. An 8-nucleotide deletion was detected between positions 548 and 555 of the SH2D1A cDNA coding region of patients A.C., A.B., B.B., B.C., and B.D. (left). After subcloning, approximately half the exon 3 PCR products of A.A. (mother of A.B. and A.C.) and B.A. (mother of B.B., B.C., and B.D.) contained the 8-nucleotide deletion detected in their sons (right). (C) Comparison of the 2 mutant protein sequences with wild-type SH2D1A. The single nucleotide C462T substitution detected in family 1 resulted in a change of the triplet CGA that coded for R55 to the stop codon triplet TGA. This generated a shorter SH2D1A protein of 54 amino acids (R55X) (indicated in the figure as F1). The 8-nucleotide deletion in the third exon of family 2 resulted in a change of the protein reading frame, generating a premature ending signal at a position corresponding to Y100 in SH2D1A. The shorter SH2D1A protein of 99 amino acids (Y100X) is indicated in the figure as F2. The gray area indicates the identity of residues among wild-type SH2D1A and the 2 mutant proteins. Asterisks mark the premature stop codon signals.