Abstract
During development, precursor cells are continuously and intimately interacting with their extracellular environment, which guides their ability to generate functional tissues and organs. Much is known about the development of the neocortex in mammals. This information has largely been derived from histological analyses, heterochronic cell transplants, and genetic manipulations in mice, and to a lesser extent from transcriptomic and histological analyses in humans. However, these approaches have not led to a characterization of the extracellular composition of the developing neocortex in any species. Here, using a combination of single-cell transcriptomic analyses from published datasets, and our proteomics and immunohistofluorescence analyses, we provide a more comprehensive and unbiased picture of the early developing fetal neocortex in humans and non-human primates. Our findings provide a starting point for further hypothesis-driven studies on structural and signaling components in the developing cortex that had previously not been identified.