title: Osteopontin is an alpha motor neuron marker in the mouse spinal cord.
abstract: Motor neurons (MNs) are designated as alpha/gamma and fast/slow based on their target sites and the types of muscle fibers innervated; however, few molecular markers that distinguish between these subtypes are available. Here we report that osteopontin (OPN) is a selective marker of alpha MNs in the mouse spinal cord. OPN was detected in approximately 70% of postnatal choline acetyltransferase (ChAT)-positive MNs with relatively large somas, but not in those with smaller somas. OPN+/ChAT+ MNs were also positive for NeuN, an alpha MN marker, but were negative for Err3, a gamma MN marker. The size distribution of OPN+/ChAT+ cells was nearly identical to that of NeuN+/ChAT+ alpha MNs. Group Ia proprioceptive terminals immunoreactive for vesicular glutamate transporter-1 were selectively detected on the OPN+/ChAT+ cells. OPN staining was also detected at motor axon terminals at neuromuscular junctions, where the OPN+ terminals were positive or negative for SV2A, a marker distinguishing fast/slow motor endplates. Finally, retrograde labeling following intramuscular injection of fast blue indicated that OPN is expressed in both fast and slow MNs. Collectively, our findings show that OPN is an alpha MN marker present in both the soma and the endplates of alpha MNs in the postnatal mouse spinal cord.
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Keio University, Tokyo, Japan. misawa-hd@pha.keio.ac.jp
authors.forename: Hidemi
authors.initials: H
authors.lastname: Misawa
authors.forename: Mayumi
authors.initials: M
authors.lastname: Hara
authors.forename: Shogo
authors.initials: S
authors.lastname: Tanabe
authors.forename: Mamiko
authors.initials: M
authors.lastname: Niikura
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Moriwaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Okuda
mesh_terms: D000578:Amidines / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002038:Bungarotoxins / Q000493:pharmacokinetics; D002452:Cell Count; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009046:Motor Neurons / Q000378:metabolism*; D009132:Muscles / Q000294:innervation / Q000378:metabolism; D009469:Neuromuscular Junction / Q000187:drug effects / Q000378:metabolism; D053495:Osteopontin / Q000172:deficiency / Q000378:metabolism*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D020671:Posterior Horn Cells / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D011960:Receptors, Estrogen / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D000578:Amidines; D002038:Bungarotoxins; C490916:Esrrg protein, mouse; D011960:Receptors, Estrogen; C493465:Slc17a7 protein, mouse; C506896:Spp1 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; C031455:diamidino compound 253-50; D053495:Osteopontin; D002795:Choline O-Acetyltransferase; D010751:Phosphopyruvate Hydratase