Secondary expansion of the transient subplate zone in the developing cerebrum of human and nonhuman primates

Abstract

The subplate (SP) was the last cellular compartment added to the Boulder Committee's list of transient embryonic zones [Bystron I, Blakemore C, Rakic P (2008) Nature Rev Neurosci 9(2):110-122]. It is highly developed in human and nonhuman primates, but its origin, mode, and dynamics of development, resolution, and eventual extinction are not well understood because human postmortem tissue offers only static descriptive data, and mice cannot serve as an adequate experimental model for the distinct regional differences in primates. Here, we take advantage of the large and slowly developing SP in macaque monkey to examine the origin, settling pattern, and subsequent dispersion of the SP neurons in primates. Monkey embryos exposed to the radioactive DNA replication marker tritiated thymidine ([ 3 H]dT, or TdR) at early embryonic ages were killed at different intervals postinjection to follow postmitotic cells' positional changes. As expected in primates, most SP neurons generated in the ventricular zone initially migrate radially, together with prospective layer 6 neurons. Surprisingly, mostly during midgestation, SP cells become secondarily displaced and widespread into the expanding SP zone, which becomes particularly wide subjacent to the association cortical areas and underneath the summit of its folia. We found that invasion of monoamine, basal forebrain, thalamocortical, and corticocortical axons is mainly responsible for this region-dependent passive dispersion of the SP cells. Histologic and immunohistochemical comparison with the human SP at corresponding fetal ages indicates that the same developmental events occur in both primate species.cerebral cortex | brain evolution | transient lamination | neuronal migration | neural stem cells B ecause of its exceptionally large size, it may not be coincidence that the subplate (SP) zone was originally discovered (1) and its function proposed on the basis of analysis of the developing cortex in human and nonhuman primates (NHPs) (2-4). For example, examination of the embryonic cerebral wall in the macaque monkey showed that thalamic axons form transient synapses with SP neurons before entering the superjacent cerebral cortex, inspiring the term waiting compartment (5). In addition, subsequent research in humans and NHPs indicated that the SP is particularly large subjacent to the association areas, such as the prefrontal cortex, and that a substantial number of SP cells survive and remain scattered within the white matter of the adult telencephalon as interstitial neurons (3, 4). Despite intensive research in various mammalian species in the last 40 y (reviewed in refs. 5-11), the origin as well as evolutionary and developmental mechanisms that underlie the extraordinary expansion and regional diversification of the SP in human are not well understood (10,12).A generally accepted hypothesis, based on studies of the human fetal brain, is that the SP evolves from the deeper stratum of the primordial preplate (PP) after its separation (split) from the marginal zone (M...

Interactive histogenesis of axonal strata and proliferative zones in the human fetal cerebral wall

“…3d, arrow). Expansion of the SP from the deep loose portion of the CP (Kostović and Rakić 1990; Duque et al 2016) appeared to ‘‘create’’ more space for the ingrowth of SS fibers, as discernable on in vivo MRI scans showing SP formation (Fig. 3g).…”

Sculpting Cerebral Cortex with Serotonin in Rodent and Primate

“…Specific to human, the SP zone is the largest transient compartment of the fetal neocortical anlage, about four times thicker than the cortical plate around midgestation [66,100]. In humans and non-human primate, most SP neurons generated in the ventricular zone initially migrate radially, together with prospective layer VI neurons and secondarily get widespread into the expanding SP zone around midgestation [101]. Interestingly, at this stage, dispersion of SP cells in the extended SP zone is concomitant with the invasion of monoaminergic [102], thalamocortical and corticocortical axons in the cortical anlage [103].…”

The distribution, number, and certain neurochemical identities of infracortical white matter neurons in a lar gibbon (Hylobates lar) brain

“…Despite neurochemical and morphological differences between species, it is assumed that they are a phylogenetically conserved trait of the mammalian brain (Mortazavi et al, 2016). The density of WMICs decreases during ontogeny from the prenatal to the adult brain (Duque, Krsnik, Kostovic, & Rakic, 2016;Kanold & Luhmann, 2010), but this change varies depending on the cortical region examined, brain size and the extent of cortical gyrencephaly (García-Marin et al, 2010;Kostovic & Rakic, 1980Suárez-Solá et al, 2009). Hodological studies of WMICs indicate that they are integrated into the circuitry of the overlying region of cortical gray matter (Clancy et al, 2001;Frazer et al, 2017;Shering & Lowenstein, 1994;Tomioka et al, 2005;Tomioka & Rockland, 2007;von Engelhardt et al, 2011), while functionally, subpopulations have been linked to vasodilation (Suárez-Solá et al, 2009), homeostatic sleep regulation (Kilduff, Cauli, & Gerashchenko, 2011), the regulation of information transfer (Colombo, 2018), and the regulation of arousal and transthalamic cortico-cortical communication (Hoerder-Suabedissen et al, 2018;Molnár, 2018).…”