Identification of Jk transcript mutation in the Finnish Jknull variant.
(A) Partial sequence analysis of the Jk transcript isolated from a wt Jk donor and from Finnish Jknull variant, Jk(S291P), within exon 9. The 2 Jk transcripts differ by a single base substitution T871C (star) changing serine (S) to proline (P) at position 291 in the Jk polypeptide. The display of the sequence diagram is from the Alf-Express DNA sequencer. (B) Left, schematic representation of the Jk(S291P) DNA genotyping assay by PCR-RFLP using primers SP-9 and SP-10. Exon 9 carries 2 polymorphisms that create 2 Mnl I sites, the first at position 838 corresponds to theJK*A/JK*B polymorphism, and the second at position 871 corresponds to the JK*B (S291P) null allele. Right, the 81-bp PCR product encompassing the 2 polymorphisms was cleaved byMnl I into 69- and 12-bp fragments in the Jk(S291P) mutant. As expected, the products from Jk(a−b+), Jk(Δ6), and Jk(Δ7) samples were uncut, whereas the product from Jk(a+b−) was cut into 16- and 65-bp fragments. Only the upper part of the gel containing the higher fragments is shown. Single base substitution is located by a star and size of fragments (bp) are given on the right.
