Figure 4

Schematic of putative cat CMAH protein deduced from mRNA. a. The ATG at -102 bp may be the true activation site in the cat, implying an extension to exon 1 exists in the cat, 5' to CMAH exon 1 that has been declared in mouse Cmah. Blood type A cats have at least one allele that creates the depicted fully functional protein. b. An 18 bp insertion is homozygous in the genomic sequence of type B cats. This insertion disrupts the reading frame created by the -102 bp ATG, causing a TGA stop codon. Approximately 50% of the mRNA of the type B cat had this insertion. c. Approximately 50% of the mRNA from the blood type B cats had the 3' portion of intron 1 spliced directly to exon 2, completely skipping exon 1, including the insertion. Two ATG sequences are present in this intronic leader but are not in frame. The first in-frame ATG occurs at bp 139 in exon 2 for cats with this mis-spliced mRNA species. The insertion and G139A mutation is concordant with the b allele. Cats that are blood type A but carry the b allele had all three species of mRNA. d. The mRNA from cats of the rare blood type AB did not extend to the -102 bp start and did not have the 18 bp insertion. The traditional ATG start at bp 1 would be the first in-frame start site. Approximately 50% of the mRNA from the blood type AB cat also had mRNA species as depicted in figure 5c but not the G139A mutation as found on the b allele.