ABSTRACT
Studies using induced pluripotent stem cells (iPSCs) are gaining momentum in brain disorder modelling, but optimal study designs are poorly defined. Here, we compare commonly used designs and statistical analysis for different research aims. Furthermore, we generated immunocytochemical, electrophysiological, and proteomic data from iPSC-derived neurons of five healthy subjects, analysed data variation and conducted power simulations. These analyses show that published case-control iPSC studies are generally underpowered. Designs using isogenic iPSC lines typically have higher power than case-control designs, but generalization of conclusions is limited. We show that, for the realistic settings used in this study, a multiple isogenic pair design increases absolute power up to 60% or requires up to 5-fold fewer lines. A free web tool is presented to explore the power of different study designs, using any (pilot) data.
Subject(s)
Brain Diseases , Induced Pluripotent Stem Cells , Humans , Proteomics , Case-Control Studies , Healthy VolunteersABSTRACT
Synapse development requires spatiotemporally regulated recruitment of synaptic proteins. In this study, we describe a novel presynaptic mechanism of cis-regulated oligomerization of adhesion molecules that controls synaptogenesis. We identified synaptic adhesion-like molecule 1 (SALM1) as a constituent of the proposed presynaptic Munc18/CASK/Mint1/Lin7b organizer complex. SALM1 preferentially localized to presynaptic compartments of excitatory hippocampal neurons. SALM1 depletion in excitatory hippocampal primary neurons impaired Neurexin1ß- and Neuroligin1-mediated excitatory synaptogenesis and reduced synaptic vesicle clustering, synaptic transmission, and synaptic vesicle release. SALM1 promoted Neurexin1ß clustering in an F-actin- and PIP2-dependent manner. Two basic residues in SALM1's juxtamembrane polybasic domain are essential for this clustering. Together, these data show that SALM1 is a presynaptic organizer of synapse development by promoting F-actin/PIP2-dependent clustering of Neurexin.
Subject(s)
Actins/metabolism , Calcium-Binding Proteins/metabolism , Membrane Glycoproteins/metabolism , Nerve Tissue Proteins/metabolism , Neural Cell Adhesion Molecules/metabolism , Phosphatidylinositol 4,5-Diphosphate/metabolism , Synapses/metabolism , Animals , Cell Adhesion Molecules, Neuronal/metabolism , Cells, Cultured , HEK293 Cells , Hippocampus/cytology , Hippocampus/metabolism , Humans , Membrane Glycoproteins/genetics , Mice , Nerve Tissue Proteins/genetics , NeurogenesisABSTRACT
Synaptic dysfunction is associated with many brain disorders, but robust human cell models to study synaptic transmission and plasticity are lacking. Instead, current in vitro studies on human neurons typically rely on spontaneous synaptic events as a proxy for synapse function. Here, we describe a standardized in vitro approach using human neurons cultured individually on glia microdot arrays that allow single-cell analysis of synapse formation and function. We show that single glutamatergic or GABAergic forebrain neurons differentiated from human induced pluripotent stem cells form mature synapses that exhibit robust evoked synaptic transmission. These neurons show plasticity features such as synaptic facilitation, depression, and recovery. Finally, we show that spontaneous events are a poor predictor of synaptic maturity and do not correlate with the robustness of evoked responses. This methodology can be deployed directly to evaluate disease models for synaptic dysfunction and can be leveraged for drug development and precision medicine.