Cellular retinoic acid-binding protein 1 (CRABP1) binds retinoic acid (RA) specifically in the cytoplasm with unclear functions. CRABP1 is highly and specifically expressed in spinal motor neurons (MNs). Clinical and pre-clinical data reveal a potential link between CRABP1 and MN diseases, including the amyotrophic lateral sclerosis (ALS). We established a sequenced MN-muscle co-differentiation system to engineer an in vitro functional 3D NMJ model for molecular studies and demonstrated that CRABP1 in MNs contributes to NMJ formation and maintenance. Consistently, Crabp1 knockout (CKO) mice exhibited an adult-onset ALS-like phenotype with progressively deteriorated NMJs, characterized with behavioral, EchoMRI, electrophysiological, histological, and immunohistochemical studies at 2–20-months old. Mechanistically, CRABP1 suppresses CaMKII activation to regulate neural Agrn expression and downstream muscle LRP4-MuSK signaling, thereby maintaining NMJ. A proof-of-concept was provided by specific re-expression of CRABP1 to rescue Agrn expression and the phenotype. This study identifies CRABP1-CaMKII-Agrn signaling as a physiological pre-synaptic regulator in the NMJ. This study also highlights a potential protective role of CRABP1 in the progression of NMJ deficits in MN diseases.
Bibliographical noteFunding Information:
We like to acknowledge University of Minnesota Viral Vector Core (VVC), Physiology Core, University Imaging Center (UIC) and staff support from Dr. Guillermo Marques and Dr. Mary Brown, and the Minnesota Nano Center (MNC) supported by the National Science Foundation through the National Nanotechnology Coordinated Infrastructure (NNCI) under Award Number ECCS-2025124. We would also like to thank Dr. Stanley Thayer for imaging equipment and analysis software. Figures depicting experimental procedures were Created with BioRender.com. This study was supported by DK54733 and DK60521, and University of Minnesota Medical School Dean’s Commitment to LNW, and F31DK123999 to JN. DJL and S-HO acknowledge support by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR) and the Sanford P. Bordeau Chair in Electrical Engineering.
© 2022, The Author(s), under exclusive licence to ADMC Associazione Differenziamento e Morte Cellulare.
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural
- Research Support, Non-U.S. Gov't