|Authors||Alić, I., Goh, P.A., Murray, A., Portelius, E., Gkanatsiou, E., Gough, G., Mok, K.Y., Koschut, D., Brunmeir, R., Yeap, Y.J., O'Brien, N.L., Groet, J., Shao, X,, Havlicek, S., Dunn, N.R., Kvartsberg, H., Brinkmalm, G., Hithersay, R,, Startin, C., Hamburg, S., Phillips, M., Pervushin, K., Turmaine, M., Wallon, D., Rovelet-Lecrux, A., Soininen, H., Volpi, E., Martin, J.E., Foo, J.N., Becker, D.L., Rostagno, A., Ghiso, J., Krsnik, Ž., Šimić, G., Kostović, I., Mitrečić, D., LonDownS Consortium, Francis, P.T., Blennow, K., Strydom, A., Hardy, J., Zetterberg, H. and Nižetić, D.|
A population of >6 million people worldwide at high risk of Alzheimer’s disease (AD) are those with Down Syndrome (DS, caused by trisomy 21 (T21)), 70% of whom develop dementia during lifetime, caused by an extra copy of β-amyloid-(Aβ)-precursor-protein gene. We report AD-like pathology in cerebral organoids grown in vitro from non-invasively sampled strands of hair from 71% of DS donors. The pathology consisted of extracellular diffuse and fibrillar Aβ deposits, hyperphosphorylated/pathologically conformed Tau, and premature neuronal loss. Presence/absence of AD-like pathology was donor-specific (reproducible between individual organoids/iPSC lines/experiments). Pathology could be triggered in pathology-negative T21 organoids by CRISPR/Cas9-mediated elimination of the third copy of chromosome-21-gene BACE2, but prevented by combined chemical β and γ-secretase inhibition. We found that T21-organoids secrete increased proportions of Aβ-preventing (Aβ1-19) and Aβ-degradation products (Aβ1-20 and Aβ1-34). We show these profiles mirror in cerebrospinal fluid of people with DS. We demonstrate that this protective mechanism is mediated by BACE2-trisomy and cross-inhibited by clinically trialled BACE1-inhibitors. Combined, our data prove the physiological role of BACE2 as a dose-sensitive AD-suppressor gene, potentially explaining the dementia delay in ~30% of people with DS. We also show that DS cerebral organoids could be explored as pre-morbid AD-risk population detector and a system for hypothesis-free drug screens as well as identification of natural suppressor genes for neurodegenerative diseases.