Mice deficient in Tau and SNCA have been challenged with prions and in both cases no difference in incubation time was seen [40 and 41]. Mutations in SNCA are associated with familial PD and in contrast, mice expressing mutant SNCA (A53T) show a reduction in incubation time [ 42]. High throughput technologies such as GWAS and expression profiling suggest many candidate genes

but the key challenge is to translate PI3K inhibitor this to phenotypic relevance (Table 1). Therefore, the goal is to develop an in vitro screen for functional validation. This is being done using neuroblastoma derived cell lines that are highly susceptible to prion infection and are able to sustain chronic infection. The scrapie cell assay (SCA) allows rapid bioassay of prions by counting the numbers of individual infected cells in a culture following serial splits after exposure to an unknown prion isolate and then comparing to standard curves and can be combined with RNAi technology to knockdown gene expression either transiently or stably to investigate the effect if any on prion propagation [ 35 and 43]. The assay can be automated and used either in its full format or using chronically infected cells to measure curing of infection when

target genes PI3K Inhibitor Library datasheet are manipulated. The SCA is prion strain selective and cannot fully substitute for the disease process in brain or the peripheral pathogenesis before neuroinvasion in natural infections Flucloronide and so some important genes will not report in this system. However, the assay should capture genes involved in the fundamentals of cellular prion infection, propagation and clearance thus providing triage for prioritising candidate genes for future studies. The gold standard for functional validation is to generate a mouse model such as a transgenic, or knockout and look

for a perturbation of phenotype such as incubation time. Generating mouse models can be time consuming and expensive, however, rapidly expanding public repositories such as the International Mouse Knockout Consortium (www.knockoutmouse.org) are generating null alleles for all mouse genes in embryonic stem (ES) cell lines which should considerably speed up the process. Alternatives include the use of viral vectors for RNAi delivery to targeted regions of the brain for which proof of concept has already been provided with Prnp knockdown [ 44]. There is no doubt that genes other than PRNP contribute to prion disease susceptibility and considerable progress has been made towards their identification, however, in human it is becoming clearer that there may be many common variants but these are of modest effect.