Presenter of 1 Presentation
UNCOVERING THE ROLE OF CHOLESTEROL TRANSPORTER, GRAMD1B, IN THE DEVELOPMENT AND SPREAD OF TAU PATHOLOGY.
Abstract
Aims
We seek to uncover early disease mechanisms of Frontotemporal lobar degeneration with Tau pathology (FTLD-Tau) and Alzheimer’s Disease (AD) by using human neural organoids (hNOs) with the microtubule associated protein tau (MAPT) R406W gene mutation. We identified a cholesterol transporter, GRAM Domain Containing 1B (GRAMD1B), is significantly increased in excitatory neurons (EX) of mutants compared to isogenic controls. The pathophysiological role of GRAMD1B in the brain is unknown. Our objective is to elucidate the relationship between cholesterol transporter, GRAMD1B, tau pathology, and lipid metabolism in neurodegeneration.
Methods
We applied a comprehensive set of techniques to hNOs including single-cell RNA sequencing, shotgun lipidomics, micro-electrode arrays, RNAScope single molecule fluorescent in situ hybridization (smFISH), western blot assay, and immunostaining. We further characterized GRAMD1B in human post-mortem brain tissue in relationship to pathological tau, free cholesterol, and lipid droplets by immunostaining.
Results
We analyzed the transcriptomic profile of FTLD-Tau patient-specific and isogenic control hNOs using scRNA-seq. The cholesterol transporter, GRAMD1B, is highly expressed in EX of MAPT R406W hNOs compared to isogenic controls. Changes in GRAMD1B gene expression was confirmed with RNAScope smFISH, and protein expression by immunostaining. MAPT R406W hNOs exhibit increased tau phosphorylation, altered functional activity, and altered lipid profiles of conditioned media. Furthermore, increased GRAMD1B correlated well with pathological tau and increased lipid droplets in human brains with FTLD-Tau and AD. The effects of GRAMD1B on tau phosphorylation and spreading via CDK5R1 and LRP1, respectively, is under investigation.
Conclusions
As far as we know, this is the first study to investigate GRAMD1B in FTLD-Tau and AD pathogenesis. Based on our preliminary findings in hNOs and human postmortem brain, we propose GRAMD1B may be a novel player in FTLD-Tau, AD and other Tauopathies.