Proteome-wide effects of Down syndrome explored with human induced pluripotent stem cell-derived cerebral organoids
In order to better understand the cellular and molecular processes associated with Down syndrome (DS) in the human central nervous system (CNS), we generated a model of early neuronal development that capitalizes on the use of human induced pluripotent stem cells (IPSc) as a starting template. We obtained IPSc from an individual where lines had been created that both contained (C2; T21), and had lost the extra copy of chromosome 21 (C2-43; D21). With some modifications to the method first described by Lancaster et al (Nature, 2013), we successfully generated human cerebral organoids from both the C2 and C2-43 cell lines and used them for imaging experiments with whole-mount immunostaining and laser scanning confocal microscopy as well as a deep proteome profile with label-free quantitation of over seven thousand proteins in each sample. Our imaging analysis shows that at the time of our sample preparation, neurons had been generated that populated the outer edges of the tissue, with evidence of populations of radial glia restricted to the inner regions of the tissue; a distribution of cell types indicative of radial migration and differentiation, similar to the development of human cortex. Our proteomics analysis shows many proteins changing in significant abundance due to Trisomy 21, with striking alterations in members of the Wnt and Notch signaling pathways, as well as catecholamine metabolism, axon guidance, and cell adhesion. These early data are the first to demonstrate the utility of IPSc-derived cerebral organoids in the study of complex genetic conditions with a spectrum of neurological phenotypes.