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Persistence of Functional Sensory Maps in the Absence of Cortical Layers in the Somsatosensory Cortex of Reeler Mice.

Guy J, Wagener RJ, Möck M, Staiger JF - Cereb. Cortex (2014)

Bottom Line: We found that the loss of cortical layers in reeler mice had surprisingly little incidence on these properties.Because intrinsic imaging measures hemodynamic signals, we furthermore investigated the cortical blood vessel pattern of both genotypes, where we also did not detect major differences.In summary, the loss of the reelin protein results in a widespread disturbance of cortical development which compromises neither the establishment nor the function of an ordered, somatotopic map of the facial whiskers.

View Article: PubMed Central - PubMed

Affiliation: Institut für Neuroanatomie, Universitätsmedizin Göttingen, Georg-August-Universität, Göttingen D-37075, Germany julien.guy@med.uni-goettingen.de.

No MeSH data available.


Cytoarchitecture of the barrel field in LIVtdTomato WT and reeler mice. (A and B) Coronal sections through the barrel field of LIVtdTomato WT and reeler, respectively. (C and D) Tangential sections through the barrel field of LIVtdTomato WT and reeler, respectively. A subset of barrels and barrel equivalents clusters of dTomato positive cells are marked for comparison (white asterisks). Both sections were obtained from comparable depths of ∼400 μm below the pia. ALBSF, anterior lateral barrel subfield; Au1, primary auditory cortex; HC, Hippocampus; PMBSF, posterior medial barrel subfield; RV, right ventricle; V1, primary visual cortex; VB, ventrobasal nucleus. Scale bar: 1000 μm.
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BHU052F1: Cytoarchitecture of the barrel field in LIVtdTomato WT and reeler mice. (A and B) Coronal sections through the barrel field of LIVtdTomato WT and reeler, respectively. (C and D) Tangential sections through the barrel field of LIVtdTomato WT and reeler, respectively. A subset of barrels and barrel equivalents clusters of dTomato positive cells are marked for comparison (white asterisks). Both sections were obtained from comparable depths of ∼400 μm below the pia. ALBSF, anterior lateral barrel subfield; Au1, primary auditory cortex; HC, Hippocampus; PMBSF, posterior medial barrel subfield; RV, right ventricle; V1, primary visual cortex; VB, ventrobasal nucleus. Scale bar: 1000 μm.

Mentions: In order to visualize the cytoarchitecture of the barrel field in both genotypes, we took advantage of our LIVtdTomato reeler and WT mice lines, in which Cre recombinase is expressed under the Scnn1a promoter (nonvoltage gated sodium channel, subunit alpha) while dTomato is expressed in a Cre-dependent manner (Madisen et al. 2010). The resulting distribution of dTomato positive cells is illustrated in Figure 1, where Figure 1A,C are photographs of coronal and tangential sections through the somatosensory cortices of a WT mouse, respectively. In the coronal section, dTomato positive cells are found in LIV of the neocortex and to a lesser degree in thalamic structures, with the strongest expression located in the posterior medial barrel subfield (PMBSF). More specifically, dTomato positive cells form clusters, or barrels, in LIV of the PMBSF (examples are marked with white asterisks in Fig. 1). Such structures are also obvious in a tangential section through the PMBSF (Fig. 1C), where the characteristic barrel field, organized in arcs and rows, is visible and individual barrels can indeed be recognized (Woolsey and Van der Loos 1970; Welker 1976). Thus, dTomato expression appears to be enriched in LIV of the LIVtdTomato mouse cortex and can hence provide a mean to reliably identify single barrels in WT animals and their equivalents in reeler. Clusters of dTomato expressing cells are also present in the cortex of reeler animals (Fig. 1B) although they are not restricted to a single layer but rather span almost the entire cortical thickness, in agreement with the loss of lamination characteristic of this mutant (Dekimoto et al. 2010; Wagener et al. 2010; Boyle et al. 2011). These clusters are also visible in tangential sections (Fig. 1D) where they form a recognizable barrel field. A previous study from our laboratory established that barrel equivalents in reeler have a significantly less symmetrical shape than their WT counterpart, are smaller, but occupy a proportionally equivalent size when taking the overall hypotrophy of the reeler brain into account (Wagener et al. 2010). The cellular composition of the reeler cortex has been the subject of scrutiny as well, revealing for instance that the total number of cells within a radial column does not differ from WT (Goffinet 1984; Polleux et al. 1998). Although the composition of the cortical neuronal population has been shown to differ between genotypes, with a relative increase in the proportion of late generated neurons and a corresponding decrease in the share of early generated neurons in reeler (Polleux et al. 1998), the number of LIV equivalent cells, which form barrel-like clusters, does not differ from WT (Wagener et al. 2010). Overall, the main cytoarchitectonic feature of the reeler barrel field is a disturbance of its radial organization while its tangential organization is essentially preserved (Caviness et al. 1976; Caviness and Rakic 1978; Wagener et al. 2010; Boyle et al. 2011).Figure 5.


Persistence of Functional Sensory Maps in the Absence of Cortical Layers in the Somsatosensory Cortex of Reeler Mice.

Guy J, Wagener RJ, Möck M, Staiger JF - Cereb. Cortex (2014)

Cytoarchitecture of the barrel field in LIVtdTomato WT and reeler mice. (A and B) Coronal sections through the barrel field of LIVtdTomato WT and reeler, respectively. (C and D) Tangential sections through the barrel field of LIVtdTomato WT and reeler, respectively. A subset of barrels and barrel equivalents clusters of dTomato positive cells are marked for comparison (white asterisks). Both sections were obtained from comparable depths of ∼400 μm below the pia. ALBSF, anterior lateral barrel subfield; Au1, primary auditory cortex; HC, Hippocampus; PMBSF, posterior medial barrel subfield; RV, right ventricle; V1, primary visual cortex; VB, ventrobasal nucleus. Scale bar: 1000 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4537421&req=5

BHU052F1: Cytoarchitecture of the barrel field in LIVtdTomato WT and reeler mice. (A and B) Coronal sections through the barrel field of LIVtdTomato WT and reeler, respectively. (C and D) Tangential sections through the barrel field of LIVtdTomato WT and reeler, respectively. A subset of barrels and barrel equivalents clusters of dTomato positive cells are marked for comparison (white asterisks). Both sections were obtained from comparable depths of ∼400 μm below the pia. ALBSF, anterior lateral barrel subfield; Au1, primary auditory cortex; HC, Hippocampus; PMBSF, posterior medial barrel subfield; RV, right ventricle; V1, primary visual cortex; VB, ventrobasal nucleus. Scale bar: 1000 μm.
Mentions: In order to visualize the cytoarchitecture of the barrel field in both genotypes, we took advantage of our LIVtdTomato reeler and WT mice lines, in which Cre recombinase is expressed under the Scnn1a promoter (nonvoltage gated sodium channel, subunit alpha) while dTomato is expressed in a Cre-dependent manner (Madisen et al. 2010). The resulting distribution of dTomato positive cells is illustrated in Figure 1, where Figure 1A,C are photographs of coronal and tangential sections through the somatosensory cortices of a WT mouse, respectively. In the coronal section, dTomato positive cells are found in LIV of the neocortex and to a lesser degree in thalamic structures, with the strongest expression located in the posterior medial barrel subfield (PMBSF). More specifically, dTomato positive cells form clusters, or barrels, in LIV of the PMBSF (examples are marked with white asterisks in Fig. 1). Such structures are also obvious in a tangential section through the PMBSF (Fig. 1C), where the characteristic barrel field, organized in arcs and rows, is visible and individual barrels can indeed be recognized (Woolsey and Van der Loos 1970; Welker 1976). Thus, dTomato expression appears to be enriched in LIV of the LIVtdTomato mouse cortex and can hence provide a mean to reliably identify single barrels in WT animals and their equivalents in reeler. Clusters of dTomato expressing cells are also present in the cortex of reeler animals (Fig. 1B) although they are not restricted to a single layer but rather span almost the entire cortical thickness, in agreement with the loss of lamination characteristic of this mutant (Dekimoto et al. 2010; Wagener et al. 2010; Boyle et al. 2011). These clusters are also visible in tangential sections (Fig. 1D) where they form a recognizable barrel field. A previous study from our laboratory established that barrel equivalents in reeler have a significantly less symmetrical shape than their WT counterpart, are smaller, but occupy a proportionally equivalent size when taking the overall hypotrophy of the reeler brain into account (Wagener et al. 2010). The cellular composition of the reeler cortex has been the subject of scrutiny as well, revealing for instance that the total number of cells within a radial column does not differ from WT (Goffinet 1984; Polleux et al. 1998). Although the composition of the cortical neuronal population has been shown to differ between genotypes, with a relative increase in the proportion of late generated neurons and a corresponding decrease in the share of early generated neurons in reeler (Polleux et al. 1998), the number of LIV equivalent cells, which form barrel-like clusters, does not differ from WT (Wagener et al. 2010). Overall, the main cytoarchitectonic feature of the reeler barrel field is a disturbance of its radial organization while its tangential organization is essentially preserved (Caviness et al. 1976; Caviness and Rakic 1978; Wagener et al. 2010; Boyle et al. 2011).Figure 5.

Bottom Line: We found that the loss of cortical layers in reeler mice had surprisingly little incidence on these properties.Because intrinsic imaging measures hemodynamic signals, we furthermore investigated the cortical blood vessel pattern of both genotypes, where we also did not detect major differences.In summary, the loss of the reelin protein results in a widespread disturbance of cortical development which compromises neither the establishment nor the function of an ordered, somatotopic map of the facial whiskers.

View Article: PubMed Central - PubMed

Affiliation: Institut für Neuroanatomie, Universitätsmedizin Göttingen, Georg-August-Universität, Göttingen D-37075, Germany julien.guy@med.uni-goettingen.de.

No MeSH data available.