Taken together, hiSPECS and the cell type‐resolved mouse brain secretome resource are important new tools for many areas in neuroscience, from mechanisms of protein secretion and signal transduction between brain cells in vitro, ex vivo (brain slices), and in vivo (CSF) to functional analysis of nervous system proteins (identification of protease substrates) and cell type‐specific biomarker determination in CSF (e.g., CD44) with high relevance to psychiatric, neurological, and neurodegenerative diseases. This evidence concerns the gene CD44 and neurodegenerative disease.