title: Molecularly Defined Subplate Neurons Project Both to Thalamocortical Recipient Layers and Thalamus.
abstract: In mammals, subplate neurons (SPNs) are among the first generated cortical neurons. While most SPNs exist only transiently during development, a number of SPNs persist among adult Layer 6b (L6b). During development, SPNs receive thalamic and intra-cortical input, and primarily project to Layer 4 (L4). SPNs are critical for the anatomical and functional development of thalamocortical connections and also pioneer corticothalamic projections. Since SPNs are heterogeneous, SPN subpopulations might serve different roles. Here, we investigate the connectivity of one subpopulation, complexin-3 (Cplx3)-positive SPNs (Cplx3-SPNs), in mouse whisker somatosensory (barrel) cortex (S1). We find that many Cplx3-SPNs survive into adulthood and become a subpopulation of L6b. Cplx3-SPNs axons project to thalamorecipient layers, that is, L4, 5a, and 1. The L4 projections are biased towards the septal regions between barrels in the second postnatal week. Thus, S1 Cplx3-SPN targets co-localize with the eventual projections of the medial posterior thalamic nucleus (POm). In addition to their cortical targets, Cplx3-SPNs also extend long-range axons to several thalamic nuclei, including POm. Thus, Cplx3-SPN/L6b neurons are associated with paralemniscal pathways and can potentially directly link thalamocortical and corticothalamic circuits. This suggests an additional key role for SPNs in the establishment and maintenance of thalamocortical processing.
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742, USA.|Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
authors.forename: Sarada
authors.initials: S
authors.lastname: Viswanathan
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742, USA.
authors.forename: Aminah
authors.initials: A
authors.lastname: Sheikh
authors.affiliation: Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
authors.forename: Loren L
authors.initials: LL
authors.lastname: Looger
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742, USA.
authors.forename: Patrick O
authors.initials: PO
authors.lastname: Kanold
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D002540:Cerebral Cortex / Q000254:growth & development; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009434:Neural Pathways / Q000254:growth & development*; D009474:Neurons / Q000378:metabolism*; D013788:Thalamus / Q000378:metabolism*; D014738:Vibrissae / Q000378:metabolism
keywords: Cplx3; complexin-3; cortical development; subplate; thalamocortical projections