Exploiting RNA biogenesis to accelerate neuronal maturation and model age-related tauopathies

About This Grant

SUMMARY Incurable neurodegenerative diseases are a growing public health crisis. The ability to generate substantial quantities of disease-pertinent neuron types, with and without predisposing mutations, holds great promise for probing disease mechanisms and developing therapies. However, current protocols yield neurons that fail to mature in vitro and stall at an embryonic identity. This reflects a fundamental gap in knowledge concerning regulatory programs that drive neuronal maturation and limits the potential of stem-cell-based interrogations of age-related neurodegenerative disease. The nervous system employs alternative splicing (AS) to massively expand transcriptomic diversity and protein function. In particular, conserved AS programs consisting hundreds of exons are coactivated at distinct stages during neurodevelopment, including postnatal neurons. In my postdoctoral work, I have found that differentiated neurons, fail to activate the postnatal AS program, and I hypothesize that this postnatal AS program is a conserved, pan-neuronal mechanism driving neuronal maturation. My preliminary data includes contracted and accelerated physiological maturation of mouse embryonic stem cell-derived motor neurons upon global activation of postnatal splicing, suggesting feasibility of my hypothesis. This proposed study aims to expand and generalize the notion that RNA biogenesis strategies such as AS, drive neuronal maturation in human reprogrammed neurons: Aims 1 and 2 ask if activation of the adult alternative splicing program will advance the maturation of human motor and cortical neurons. This will be achieved through overexpression of master splicing factors in postmitotic neurons, evaluation of transcriptomic changes using bulk and single cell approaches, and assessment of physiological maturation. Thereafter, I utilize my approach to build a novel model to study age-related 4R tauopathies: Aim 3 takes advantage of my unique strategy to yield mature tau isoforms and elevated 4R tau in cortical neurons carrying MAPT variants, and to identify mechanisms to reduce tau pathology. Using this unprecedented stem cell-based model, I will assay tau burden, understand gene expression driving disease onset, and target cis-regulators in the MAPT that will decrease tau pathology. Existing reprogramming strategies are incomplete and do not overcome the barrier of the intrinsic aging clock in differentiated human neurons. Thus, it remains vital to continue investigating additional pathways to understand and modify maturation timescales. My undertaking has critical importance in this context: I will explore a novel function for alternative splicing during neurodevelopment, improve understanding of mechanisms that control maturation of human neurons, and demonstrate that my approach is a major advancement for studying age-related neurodegeneration. The insights and technology generated here will have important applications for the exploration of neurodegeneration and will be broadly useful to the scientific community for modeling neurons in health and disease.