Substrain-related dependence of Cu(I)-ATPase activity among prion protein-null mice.

The prion protein (PrPC) binds copper and affects copper metabolism, albeit among a poorly understood functional landscape. Much of the data on physiological roles of PrPC were obtained in mice of mixed genetic background deficient of the PrPC-coding gene Prnp. This strategy is currently under scrutiny due to the flanking gene problem, in particular related with a polymorphism, typical of both the 129Sv and 129Ola mouse substrains, in the Sirpa gene located in the vicinity of Prnp. Here we report an investigation of biochemical properties of Cu(I)-ATPases as a function of genotype in two strains of PrPC-deficient mice. We found that both the brain and liver of Prnp-null mice of mixed B6;129Sv background had diminished activity, accompanied by increased catalytic phosphorylation of Cu(I)-ATPase, as compared with the respective wild-type animals. However, no such differences were found between Prnp-null and wild-type mice of a B10;129Ola background. Activity of Cu(I)-ATPase was strongly reduced in brain tissue from mice of 129Sv strain, when compared with wild-type either of B6;129Sv, and especially of mice of the B6 strain. No differences between wild-type and Prnp-null brain tissue were noted in the expression of either Atp7a or b genes, and RFLP analysis indicated that the Sirpa129 polymorphism was present in both the B6;129Sv and B10;129Ola Prnp-null mouse colonies used in this study. The results suggest a novel substrain-dependent effect of 129Sv, but not 129Ola, genotype upon the regulation of the Cu(I)-ATPase catalytic cycle in Prnp-null mice, rather than either a Prnp-dependent, or a 129 strain-dependent effect.

Cortical malformations are associated with a rare polymorphism of cellular prion protein.

Studies in animals lacking the cellular prion protein (PrP(c)) gene (Prnp) showed higher neuronal excitability in vitro and increased sensitivity to seizures in vivo. The authors previously reported a rare polymorphism at codon 171 (Asn-->Ser) of human Prnp to be associated with mesial temporal lobe epilepsy related to hippocampal sclerosis. They demonstrated that the same variant allele is also associated with symptomatic epilepsies related to different forms of malformations of cortical development.

Surgical outcome in mesial temporal sclerosis correlates with prion protein gene variant.

BACKGROUND: Mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS) is the most common surgically remediable epileptic syndrome. Ablation of the cellular prion protein (PrP(c)) gene (PRNP) enhances neuronal excitability of the hippocampus in vitro and sensitivity to seizure in vivo, indicating that PrP(c) might be related to epilepsy. OBJECTIVE: To evaluate the genetic contribution of PRNP to MTLE-HS. METHODS: The PRNP coding sequence of DNA from peripheral blood cells of 100 consecutive patients with surgically treated MTLE-HS was compared to that from a group of healthy controls adjusted for sex, age, and ethnicity (n = 180). The presence of PRNP variant alleles was correlated with clinical and presurgical parameters as well as surgical outcome. RESULTS: A variant allele at position 171 (Asn-->Ser), absent in controls, was found in heterozygosis (Asn171Ser) in 23% of patients (p < 0.0001). The PRNP genotypes were not correlated with any clinical or presurgical data investigated. However, patients carrying the Asn171Ser variant had a five times higher chance of continuing to have seizures after temporal lobectomy (95% CI 1.65 to 17.33, p = 0.005) than those carrying the normal allele. At 18 months after surgery, 91.8% of patients with the normal allele at codon 171 were seizure free, in comparison to 68.2% of those carrying Asn171Ser (p = 0.005). CONCLUSIONS: The PRNP variant allele Asn171Ser is highly prevalent in patients with medically untreatable MTLE-HS and influences their surgical outcome. The results suggest that the PRNP variant allele at codon 171 (Asn171Ser) is associated with epileptogenesis in MTLE-HS.