SC*994C>T causes the Sc(null) phenotype in Pacific Islanders and successful transfusion of Sc3+ blood to a patient with anti-Sc3.

Antigens in the SC blood group system are expressed by the human erythrocyte membrane-associated protein (ERMAP).Two molecular bases have been reported for the Sc,un phenotype:SC307del2 and SC994C>T. We report our investigation of the molecular background of five Sc,n1 individuals from the Pacific Islands and describe the successful transfusion of Sc3+ blood to a patient with anti-Sc3 in her plasma. SC (ERMAP) exons 2,3, and 12 and their flanking intronic regions were analyzed. TheSC994C>T change introduces a restriction enzyme cleavage site for Tsp45I, and polymerase chain reaction (PCR) products from exon 12 were subjected to this PCR-restriction fragment length polymorphism (RFLP) assay. The five samples had the variant SC994T/T. One sample, from a first cousin of one Marshallese proband, was heterozygous for SC1514C/T (in the 3' untranslated region); the other four samples were SC1514C/C(consensus sequence). Samples from white donors (n = 100) and African American donors (n = 99) were tested using the Tsp45IPCR-RFLP assay; all gave a banding pattern that was consistent with the SC994C/C consensus sequence. In all five samples,our analyses showed homozygosity for the nonsense nucleotide change SC994C>Tin an allele carrying the nucleotide associated with SLd. Further investigation determined that one of the probands reported previously with the SC994C>T change was from the Marshall Islands (which form part of the Micronesian Pacific Islands) and the other was from an unspecified location within the large collection of Pacific Islands. Taken together, the five known probands with the SC994C>T silencing nucleotide change were from the Pacific Islands.