title: Differential expression of secreted phosphoprotein 1 in the motor cortex among primate species and during postnatal development and functional recovery.
abstract: We previously reported that secreted phosphoprotein 1 (SPP1) mRNA is expressed in neurons whose axons form the corticospinal tract (CST) of the rhesus macaque, but not in the corresponding neurons of the marmoset and rat. This suggests that SPP1 expression is involved in the functional or structural specialization of highly developed corticospinal systems in certain primate species. To further examine this hypothesis, we evaluated the expression of SPP1 mRNA in the motor cortex from three viewpoints: species differences, postnatal development, and functional/structural changes of the CST after a lesion of the lateral CST (l-CST) at the mid-cervical level. The density of SPP1-positive neurons in layer V of the primary motor cortex (M1) was much greater in species with highly developed corticospinal systems (i.e., rhesus macaque, capuchin monkey, and humans) than in those with less developed corticospinal systems (i.e., squirrel monkey, marmoset, and rat). SPP1-positive neurons in the macaque monkey M1 increased logarithmically in layer V during postnatal development, following a time course consistent with the increase in conduction velocity of the CST. After an l-CST lesion, SPP1-positive neurons increased in layer V of the ventral premotor cortex, in which compensatory changes in CST function/structure may occur, which positively correlated with the extent of finger dexterity recovery. These results further support the concept that the expression of SPP1 may reflect functional or structural specialization of highly developed corticospinal systems in certain primate species.
authors.affiliation: Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Takao
authors.initials: T
authors.lastname: Oishi
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Higo
authors.forename: Shigeo
authors.initials: S
authors.lastname: Murayama
authors.forename: Akira
authors.initials: A
authors.lastname: Sato
authors.forename: Ichiro
authors.initials: I
authors.lastname: Takashima
authors.forename: Yoko
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Yumi
authors.initials: Y
authors.lastname: Murata
authors.forename: Kimika
authors.initials: K
authors.lastname: Yoshino-Saito
authors.forename: Tadashi
authors.initials: T
authors.lastname: Isa
authors.forename: Toshio
authors.initials: T
authors.lastname: Kojima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D005786:Gene Expression Regulation; D006801:Humans; D009044:Motor Cortex / Q000293:injuries / Q000378:metabolism*; D053495:Osteopontin / Q000235:genetics* / Q000378:metabolism; D011323:Primates; D011712:Pyramidal Tracts / Q000378:metabolism / Q000503:physiopathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020127:Recovery of Function; D013045:Species Specificity
chemical_list: D012333:RNA, Messenger; D053495:Osteopontin