Determination of prion protein gene (Prnp) polymorphism and its relationship with apoptosis in turtle, Trachemys scripta.

Prion protein is a glycoprotein which is widely expressed in most tissues, including brain, muscle and lymphoid system. It can display two conformations: normal cellular form (PrPC) and its pathological isoform (PrPSc). During the prion diseases, cellular proteins undergo conformational change to abnormal form. Although the physiological roles of prion protein still remain unknown, the ubiquitous expression of PrPC in mammals suggests its roles in important biological events such as signal transduction, synaptic transmission and programmed cell death. On the other hand, it is known that, in mammals, single nucleotide polymorphisms in prion protein coding genes are greatly affect susceptibility to prion diseases. In the present work, prion protein coding gene (Prnp) was amplified with polymerase chain reaction, sequenced and polymorphisms were determined. Also, apoptotic cell number of polymorphic samples was measured with TUNEL assay. In our work, L203V, N205I, V225A and M237V polymorphisms were determined. In 15 samples, these four polymorphisms (L203V, N205I, V225A and M237V) were seen together. In one sample, three polymorphisms (L203V, N205I and M237V) and in remaining 14 samples L203V, N205I polymorphisms were seen. TUNEL analyses of polymorphic samples were seen that the apoptotic cell number was increased in brain tissues of samples that contain four polymorphisms. These results indicate that Prnp polymorphisms can increase the programmed cell death and this raising may be related with the susceptibility to prion diseases.