Goats naturally devoid of PrP (c) are resistant to scrapie
Authors: Salvesen, Oyvind; Espenes, Arild; Reiten, Malin R.; Vuong, Tram T.; Malachin, Giulia; Tran, Linh; Andreoletti, Olivier; Olsaker, Ingrid; Benestad, Sylvie L.; Tranulis, Michael A.; Ersdal, Cecilie
Prion diseases are progressive and fatal, neurodegenerative disorders described in humans and animals. According to the "protein-only" hypothesis, the normal host-encoded prion protein (PrP (c)) is converted into a pathological and infectious form (PrPSc) in these diseases. Transgenic knockout models have shown that PrP (c) is a prerequisite for the development of prion disease. In Norwegian dairy goats, a mutation (Ter) in the prion protein gene (PRNP) effectively blocks PrP (c) synthesis. We inoculated 12 goats (4 PRNP+/+ , 4 PRNP+/Ter, and 4 PRNPTer/Ter) intracerebrally with goat scrapie prions. The mean incubation time until clinical signs of prion disease was 601 days post-inoculation (dpi) in PRNP+/+ goats and 773 dpi in PRNP+/Ter goats. PrPSc and vacuolation were similarly distributed in the central nervous system (CNS) of both groups and observed in all brain regions and segments of the spinal cord. Generally, accumulation of PrPSc was limited in peripheral organs, but all PRNP+/+ goats and 1 of 4 PRNP+/Ter goats were positive in head lymph nodes. The four PRNPTer/Ter goats remained healthy, without clinical signs of prion disease, and were euthanized 1260 dpi. As expected, no accumulation of PrPSc was observed in the CNS or peripheral tissues of this group, as assessed by immunohistochemistry, enzyme immunoassay, and real-time quaking-induced conversion. Our study shows for the first time that animals devoid of PrP (c) due to a natural mutation do not propagate prions and are resistant to scrapie. Clinical onset of disease is delayed in heterozygous goats expressing about 50% of PrP (c) levels.
The Reference Gene Selection to Study PRNP Gene Expression in Sheep
Authors: Piestrzynska-Kajtoch, Agata; Smolucha, Grzegorz; Oczkowicz, Maria; Kycko, Anna; Polak, Miroslaw P.; Kozaczynski, Wojciech; Kozubska-Sobocinska, Anna; Zmudzinski, Jan F.; Rejduch, Barbara
The PRNP gene is connected to scrapie susceptibility in sheep (prion disease). Its polymorphism and expression may influence the occurrence of the disease. In order to study PRNP gene expression level in different ovine tissues, selection of reference genes is needed. Three housekeeping genes (RPL27, RPS29, OAZ1) were chosen for studying PRNP gene expression in ovine brain cortex, midbrain, cerebellum, brain stem, pituitary gland, spleen, liver, skeletal muscle and heart. The primers for gene sequencing were designed based on bovine reference sequences. RPL27 was found to be the most stable reference gene (for brain tissues M=0.322, SDCt=0.486, Stability Value=0.0089; for all tissues M=0.489, SDCt=0.696; Stability Value=0.0093). Regardless of the housekeeping gene, the expression level of PRNP was higher in brain tissues than in other tissues analyzed. A normalization experiment indicated that all candidate reference genes could be used as endogenous controls for studying PRNP mRNA expression in different ovine tissues. However, RPL27 seemed to be the most stable and appropriate for the experiment with many different tissue types and could be used as one of the reference genes for studying gene expression in ovine tissues. Our results confirmed that the PRNP gene is highly expressed in nervous tissue.