Effect of prion protein extract on the morphology of chick embryos with special reference to the cerebellum

ABSTRACT

Prion disease is transmitted under natural conditions and involves a variety of mechanism through multiple routes. Prion protein peptides were generated according to amino acid sequences. To study the effect of prion protein extract on the embryo using egg as a model. Thirty chickens, one-day old from Arbor acre strain were used in this study and divided into three groups. The 1[st] group was fed on basal diets and served as a control. The 2[nd] and 3[rd] groups were fed on hyperproteinized diets which contained 50% and 80% concentrates respectively. After four months of feeding, brain, spleen, heart and lung were obtained for the isolation and purification of prion protein [PrP]. The result of SDS-PAGE gel electrophoretic separation of the PrP showed that, all organs contained a major band around 29 - 30 kdt. But purification of the PrP indicated that, the only fraction contained one band in the lung, two bands in the spleen and heart and four bands in the brain. In addition, the normal sequence of isolated PrP was contained 209 amino acids. Chicken fertilized eggs from Arbor acre strain were used in this study and divided into five groups. Group A was a control group. Groups B, C, D, and E that injected with 50 micro L PrP extracted from brain, spleen, heart and lung, respectively of the adult chicken fed on diets containing 80% protein for four months. The eggs were incubated at 37.8°C for 22 days and the injection was performed in the albumin on the 1[st] day of incubation. The eggs were opened on days 3, 5, 7, 9, 11, 15 and 21. Embryos were collected for the morphological examination. On day 15 of incubation, the eggs were opened and the cerebellum was processed for light microscopic study. Indicated that, PrP caused delay in hatching, decreased body weight and reduced body length. The percentages of malformations in embryos were 31.5, 25, 23 and 37% post injection with PrP extracted from brain, spleen, heart and lung respectively. The congenital malformations were malformed eyes, twisting legs, syndactylia and unformed abdominal wall. Cerebellar sections of chick embryos from injected eggs with any source of tissue PrP extracts showed vacuolar degeneration of cerebellar layers. Purkinje cells lost their normal flask-shaped appearance with eccentric nuclei. It was concluded that, a single injection of PrP which was extracted from hyperproteinized fed chicken caused congenital anomalies as well as histopathological changes independent on the source of tissue PrP