Genome-wide analysis of small heat shock protein function in ageing

Maintaining protein homeostasis is critical for healthy ageing. Indeed, misfolding of proteins and their consequent aggregation causes many common diseases, notably neurodegenerative disorders such as Alzheimer's. Small heat shock proteins (sHSPs) play an important role in proteostasis by binding to misfolded proteins and preventing their aggregation. Studies in yeast, Drosophila and C. elegans have shown that inactivation of sHSPs shortens lifespan, whereas increased sHSP gene expression extends lifespan. Clearly, sHSPs are important and evolutionarily conserved determinants of healthy ageing. However, the functionally relevant client proteins that sHSPs protect and the cellular processes they help to maintain remain unknown. We propose to address this key question by initially performing genome-wide functional screens in yeast, and subsequently testing for conserved relevance in an animal model. Yeast are ideal for this approach as combinations of deletion mutations covering the entire genome can be engineered into individual strains using robotic procedures and the phenotypes of the resulting double/triple mutants can be quantified by automated imaging and computational analysis. Lydall brings considerable expertise in this approach and pioneered the development of Quantitative Fitness Analysis (QFA) to provide rigorous automated quantification of yeast growth rates. Morgan works on yeast ageing and provided the first evidence for a role of sHSPs in yeast lifespan determination. In this project, libraries of mutants with sHSP genes deleted will be generated to enable functional mapping of sHSP genetic interactions on a genome-wide scale. QFA findings will be reconfirmed experimentally and all validated genes subjected to bioinformatic analyses to identify functionally relevant cellular pathways and processes. Significantly enriched functional groups will then be tested for effects on ageing and protein aggregation in yeast by mutating appropriate genes. Any such identified genes with orthologues in higher organisms will then be tested for conserved effects on lifespan and protein homeostasis in nematodes, capitalising on the expertise of Barclay in the use of C. elegans. Altogether, this project will provide training in modern genetic and genomic techniques using two key model organisms and will provide systems-level insights into the conserved functions of sHSPs in healthy ageing.