Electrophoretic polymorphism of a hamster pentraxin, female protein (amyloid P component)

Serum amyloid P protein (SAP) is a ubiquitous vertebrate protein distinguished by its conservative evolution and paucity of polymorphic forms. The SAP homologue in the Syrian hamster (Mesocricetus auratus), called Female Protein [FP(SAP)] is unique because its synthesis is controlled by sex hormones. These observations were limited to the commercially available standard Syrian hamsters that are descendants of three littermates captured in Syria in 1930. The authors examined FP(SAP) expression in nine inbred lines of Syrian hamsters that were derived from 12 wild hamsters captured in 1971. In general, regulation of FP(SAP) was similar in the new wild hamster strains, although a novel electrophoretically slower FP(SAP) was found in three of the strains. The slow FP(SAP) was not distinguished by size, antigenicity, binding capacity, or regulation. The electrophoretic difference was still apparent after deglycosylation. Hybrid offspring coexpressed both fast and slow FP monomers and formed a unique hybrid pentamer that had a new mobility between the fast and slow parent FP(SAP). The origin of this unusual polymorphism could be related to the amyloidogenesis associated with expression of FP(SAP) in the standard Syrian hamster.