title: Selective presence of a giant saccular organelle in the axon initial segment of a subpopulation of layer V pyramidal neurons.
abstract: Recently it has been shown that a giant saccular organelle (GSO) of unknown function is present in the axon initial segment (AIS) of an uncharacterized population of pyramidal cells of the rodent neocortex. Using tract-tracing methods and immunocytochemistry, in the present study we show that in rodents this GSO is present in the AIS of subpopulations of layer V pyramidal neurons projecting to various subcortical, non-thalamic targets, including the spinal cord. GSO-containing neurons express SMI32 and some of them are under the control of the Thy-1 gene promoter. In addition, our results demonstrate that the GSO expresses the inositol 1,4,5-triphosphate receptor 1 (IP3R1) and the sarco (endo) plasmic reticulum Ca(2+) ATPase 2, both in rodent and human neocortex. These results indicate the involvement of the GSO in the regulation of Ca(2+) levels in the AIS in a particular subpopulation of layer V neurons that give rise to subcortical non-thalamic descending projections.
authors.affiliation: Instituto Cajal, CSIC, 28002, Madrid, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Antón-Fernández
authors.forename: Pablo
authors.initials: P
authors.lastname: Rubio-Garrido
authors.forename: Javier
authors.initials: J
authors.lastname: DeFelipe
authors.forename: Alberto
authors.initials: A
authors.lastname: Muñoz
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D008297:Male; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000378:metabolism; D019579:Neocortex / Q000648:ultrastructure*; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure*; D017966:Pyramidal Cells / Q000378:metabolism / Q000648:ultrastructure*; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism
chemical_list: C506944:Atp2a1 protein, mouse; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008840:Microfilament Proteins; C503968:Synpo protein, mouse; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases