A fountain of youth for the human brain.

Ageing is a major risk factor for numerous human maladies such as cancer, stroke, diabetes as well as neurodegenerative diseases such as Alzheimers disease and Parkinsons disease. Ageing itself is increasingly considered as a complex disease and unravelling the mechanisms involved in ageing of the human brain in physiological and pathological conditions has become a critical challenge. Mammalian models such as rodents differ from humans in several hallmarks of ageing and human 2D models lack complex tissue architecture and cell-cell interactions that may contribute to the ageing phenotype. Nonetheless, studies in mouse models and 2D human neurons have identified approaches to study neuronal ag eing. Overexpression of the protein Progerin, as seen in patients suffering from the rare premature ageing disorder Hutchinson-Gilford progeria syndrome, leads to diverse ageing signatures and has proven effective in modelling aspects of neurodegenerative diseases. In the proposed study, we will combine human 3D brain organoid technology with the established Progerin- based ageing model to study brain ageing in a human tissue. Additionally, we will manipulate aged brain tissue with the aim to counteract human neural ageing. We will address three aims. In Aim 1, we will establish the first human tissue model of the aged brain. We have generated human induced pluripotent stem cells that overexpress Progerin in a controlled manner. Moreover, we established 3D human brain tissue culture, cerebral organoids, and currently grow cerebral organoids from the Progerin-overexpressing line. Initial observations recapitulate various aspects of ageing, including DNA damage and loss of heterochromatin. We aim to provide a comprehensive analysis of this model of human brain ageing at molecular and cellular levels. Aim 2 explores the possibility of reverting brain ageing by using a rejuvenation scheme of expressing Yamanaka factors in a controlled fashion. This approach has been successfully employed in multiple tissues, so it will serve as a proof-of-principle experiment to ask if any ageing hallmarks can be reversed in human neurons. We will then move on by identifying factors that ameliorate human brain ageing in Aim 3. For that, we will screen for factors that upon perturbation lead to decreased ageing burden. We will perform a CRISPR-LICHT loss-of-function screen targeting genes identified in aim 1 as well as known ageing pathways. The identified genes will be characterized for their role in brain ageing and may serve as entry points into pharmacological intervention of brain ageing. Overall, our proposal will lead to the first human tissue model of brain ageing, explore the possibility of rejuvenating the human brain and potentially find entry points into the reversion of human brain ageing.