The embryonic preoptic area is a novel source of cortical GABAergic interneurons - PubMed (original) (raw)

The embryonic preoptic area is a novel source of cortical GABAergic interneurons

Diego M Gelman et al. J Neurosci. 2009.

Abstract

GABA-containing (GABAergic) interneurons play an important role in the function of the cerebral cortex. Through mostly inhibitory mechanisms, interneurons control hyperexcitability and synchronize and shape the spatiotemporal dynamics of cortical activity underlying various brain functions. Studies over the past 10 years have demonstrated that, in most mammals, interneurons originate during development from the subcortical telencephalon--the subpallium--and reach the cerebral cortex through tangential migration. Until now, interneurons have been demonstrated to derive exclusively from two subpallial regions, the medial ganglionic eminence and the caudal ganglionic eminence. Here, we show that another subpallial structure, the preoptic area, is a novel source of cortical GABAergic interneurons in the mouse. In utero labeling and genetic lineage-tracing experiments demonstrate that neurons born in this region migrate to the neocortex and hippocampus, where they differentiate into a distinct population of GABAergic interneurons with relatively uniform neurochemical, morphological, and electrophysiological properties.

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Figures

Molecular characterization of progenitor cells in the embryonic POA. A–E, Coronal sections through the caudal telencephalon at E13.5 showing the expression of Nkx2-1 (A), Shh (B), Olig2 (C), Dbx1 (D), and Nkx6-2 (E) mRNA. Sections B–E are from the same brain and are adjacent to each other. The red dashed lines mark the ventricular zone, whereas the white arrowheads mark the limit between the MGE and the POA. GP, Globus pallidus; H, hippocampus; NCx, neocortex; PCx, piriform cortex; Str, striatum; Th, thalamus. Scale bars: A, 50 μm; B–E, 100 μm.

Figure 2.

The embryonic POA gives rise to cells that migrate to the cortex. A, Schema of the experimental design followed in B–E′. B, B′, A representative case of the distribution of GFP (B)- and Nkx2-1 (B′)-expressing cells in a coronal section through the telencephalon of an E15.5 embryo in which the POA was electroporated at E12.5. The white arrowhead indicates the location of basal forebrain cells derived from the POA. C, C′, High-magnification images of the boxed areas shown in B and B′, respectively. The open arrowheads in B and C mark labeled cells with migratory morphology in the subpallium and in the cortex. D, D′, E, E′, Images of representative cells found in the cortex. These cells typically stain for Calbindin (D, D′) and do not express Lhx6 (E, E′). Scale bars: (in B) B, B′, 250 μm; (in C) C, C′, 100 μm; (in D) D, D′, E, E′, 25 μm.

Figure 3.

Restricted expression of Nkx5-1 in the developing preoptic area. A–C, Coronal sections through the caudal telencephalon at E10.5 (A), E12.5 (B), and E13.5 (C) showing the expression of Nkx5-1 RNA. H, Hippocampus; NCx, neocortex; PCx, piriform cortex; Str, striatum; Th, thalamus. Scale bars: (in A) A–C, 50 μm.

Figure 4.

YFP expression in the developing telencephalon of Nkx5-1-Cre;Rosa26R-YFP embryos. A–C, Coronal adjacent sections through the caudal telencephalon of an E13.5 Nkx5-1-Cre;Rosa26R-YFP embryo showing the expression of Shh (A) and Nkx5-1 (B) mRNA and YFP protein (C). In situ images (A, B) were pseudocolored using Photoshop software. YFP expression (C) closely parallels Nkx5-1 mRNA expression in the adjacent section (B). The arrowheads point to cells that seem to follow a dorsal migration from the POA. D–G, Coronal sections through the telencephalon of E15.5 (D, F) and E17.5 (E, G) Nkx5-1-Cre;Rosa26R-YFP embryos showing the distribution of YFP-expressing cells derived from Nkx5-1-expressing cells in the POA. F, G, High-magnification images of the boxed areas shown in D and E, respectively. ac, Anterior commissure; MZ, marginal zone; CP, cortical plate; IZ, intermediate zone; sp, subplate; SVZ, subventricular zone; VZ, ventricular zone; V–VI, cortical layers V and VI. Scale bars: (in A) A–C, 100 μm; D, E, 250 μm; F, 50 μm; G, 100 μm.

Figure 5.

YFP expression in the adult telencephalon of Nkx5-1-Cre;Rosa26R-YFP mice. A, B, Images of a coronal section through the telencephalon of P30 Nkx5-1-Cre;Rosa26R-YFP mice showing the distribution of YFP-expressing cells. B, High-magnification image of the boxed area shown in A, in which the overall laminar distribution of YFP-expressing cells is visualized. Note that whereas YFP-expressing cells are abundant in medial regions of the preoptic area, very few cells are found in the region of the magnocellular preoptic nucleus (MCPO). C, Many YFP-expressing cells in the neocortex of a P30 Nkx5-1-Cre;Rosa26R-YFP mice have the morphological features of cortical interneurons. D–D″, Immunohistochemistry against YFP (D, D″) and NeuN (D′, D″) in the neocortex of P30 Nkx5-1-Cre;Rosa26R-YFP mice. The arrowheads indicate YFP-expressing cells that express NeuN, whereas the open arrowhead points to a YFP-expressing cell that does not contain NeuN. E, Quantification of the distribution of E12.5 (light gray bars)- and E15.5 (dark gray bars)-born YFP-expressing cells in the neocortex of P30 Nkx5-1-Cre;Rosa26R-YFP mice (n = 3). ***p < 0.001 and **p < 0.01, t test. Error bars indicate SEM. Cg, Cingulate cortex; CPu, caudoputamen nucleus; I–VI, cortical layers I to VI; ICx, insular cortex; Ls, lateral septum; MCx, motor cortex; MPOA, medial preoptic area; Ms, medial septum; SCx, somatosensory cortex. Scale bars: A, 500 μm; B, 250 μm; C, D–D″, 50 μm.

Figure 6.

Distribution of POA-derived interneurons in the neocortex and hippocampus of Nkx5-1-Cre;Rosa26R-YFP mice. A–A‴, Immunohistochemistry against YFP (A, A‴), GABA (A′, A‴), and NPY (A″, A‴) in the neocortex of P30 Nkx5-1-Cre;Rosa26R-YFP mice. The arrowhead points to a YFP-expressing neuron that expresses GABA but not NPY, whereas the open arrowhead indicates a YFP-expressing neuron that coexpresses GABA and NPY. B–B‴, Immunohistochemistry against YFP (B, B‴), Lhx6 (B′, B‴), and NPY (B″, B‴) in the neocortex of P30 Nkx5-1-Cre;Rosa26R-YFP mice. The arrowhead points to a YFP-expressing neuron that expresses NPY but not Lhx6, whereas the open arrowhead indicates a YFP-expressing neuron that is negative for both Lhx6 and NPY. C, Schemas depicting the distribution of YFP-expressing interneurons containing GABA (red dots) or GABA and NPY (blue dots) in the neocortex and hippocampus of a P30 Nkx5-1-Cre;Rosa26R-YFP mouse. The schematic of the sagittal view of the mouse brain indicates the approximate location of the coronal sections drawn in C (numbers 1–6). Scale bar: (in B) A–B‴, 25 μm.

Figure 7.

Cortical interneurons derived from Nkx5-1 cells constitute a relatively homogenous population with adapting firing pattern. A–A″, Single confocal sections acquired during initial steps of a patch-clamp recording: green fluorescence of a cortical YFP cell as seen before pipette patch (A); the same cell in cell-attached (A′) and whole-cell (A″) configuration using a pipette containing Alexa 555. B, Confocal reconstruction of a recorded cell acquired immediately after an electrophysiological session. C–C″, Immunohistochemistry against NPY in an Alexa 555-containing neuron recorded in the neocortex. D, Morphological varieties of POA-derived cortical interneurons in Nkx5-1-Cre;Rosa26R-YFP mice. Images are Neurolucida reconstructions from recorded neurons. The dotted red lines indicate the limits of cortical layer I. E, Current-clamp recordings in whole-cell configuration. Responses to hyperpolarizing and near-threshold depolarizing current steps. Neurons start firing at low frequency (red trace). F, Larger current steps give rise to an adapting firing pattern. Increasing stimulation levels generates faster onset and steady-state frequencies. G, No differences were observed applying prolonged stimulating current steps. Scale bars: A–A″, C–C″, 10 μm; B, 25 μm; D, 100 μm.

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The embryonic preoptic area is a novel source of cortical GABAergic interneurons - PubMed (original) (raw)