SAP mutation and identification of patients.

(A) The gene mutation present in the index case consisted of a G to T mutation in exon 2 of SAP that leads to an arginine to leucine transposition at Arg55 (bold letters). (B) A pedigree was constructed based on the index case. The symbols used are proband (arrow), males (box), females (circle), deceased (line through), affected male (black fill), female carriers (dotted fill), and unaffected subjects (no fill). The SAP mutation introduces a restriction endonuclease recognition site into exon 2 of the SAP gene. DNA isolated from (1) index case and (5) affected male cousin; (2) mothers of index case; (3) sister of index case; (4) brother of index case; (6) unaffected male cousin and (7) unrelated healthy control were subjected to PCR amplification with primers specific for SAPexon 2, and the amplified product was digested with BfaI and visualized on an agarose gel (C). The numbers on the pedigree match the numbers on the agarose gel. Affected male patients are identified by 2 bands of the digested products, whereas carriers have a mixture of the undigested and digested exon 2. The unaffected relative (6) died of a condition unrelated to XLP.