Spatially and temporally distinct patterns of expression for VPS10P domain receptors in human cerebral organoids.
Vacuolar protein sorting 10 protein (VPS10P) domain receptors are a unique class of intracellular sorting receptors that emerge as major risk factors associated with psychiatric and neurodegenerative diseases, including bipolar disorders, autism, schizophrenia, as well as Alzheimer' disease and frontotemporal dementia. Yet, the lack of suitable experimental models to study receptor functions in the human brain have hampered elucidation of receptor actions in brain disease. Here, we have adapted protocols to the study of VPS10P domain receptors in human cerebral organoids and applied these to the detailed characterization of receptor expression during development and in mature tissue, including single-cell RNA sequencing. These studies uncovered spatial and temporal patterns of expression unique to individual receptor species in the human brain. While SORL1 expression is abundant in stem cells and SORCS1 peaks at onset of neurogenesis, SORT1 and SORCS2 show increasing expression coinciding with maturation of neuronal and non-neuronal cell types, arguing for distinct functions in development versus the adult brain. In neurons, subcellular localization also distinguishes between two types of receptors, either mainly localized to the cell soma (SORL1 and SORT1) or also to neuronal projections (SORCS1 and SORCS2), suggesting divergent functions in protein sorting between Golgi and the endo-lysosomal system or along axonal and dendritic tracks. Taken together, our findings provide an important resource concerning temporal, spatial, and subcellular patterns of VPS10P domain receptor expression in cerebral organoids for further elucidation of receptor (dys)functions causative of behavioral and cognitive defects of the human brain. Overall design: Cerebral organoids derived from hiPSCs (human induced pluripotent stem cells) were obtained  using adapted published protocols (Lancaster et al., 2013; Giandomenico et al., 2021). At day 100, 5-6 organoids were collected and made into single cell. Libraries were generated using the Chromium Next GEM Single Cell 3' Reagent Kits v3.1 Dual Index (10X Genomics Inc., USA). Barcoded cells were sequenced on a NovaSeq 6000 instrument (Illumina, USA). Barcode processing and single-cell 3' gene quantification was done using the Cell Ranger Single-Cell Software Suite (v 3.1.0) using the GRCh38 reference genome.