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Shigematsu N, Miyamoto Y, Esumi S, Fukuda T. The Anterolateral Barrel Subfield Differs from the Posteromedial Barrel Subfield in the Morphology and Cell Density of Parvalbumin-Positive GABAergic Interneurons. eNeuro 2024; 11:ENEURO.0518-22.2024. [PMID: 38438262 DOI: 10.1523/eneuro.0518-22.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 12/20/2023] [Accepted: 02/23/2024] [Indexed: 03/06/2024] Open
Abstract
Layer 4 of the rodent somatosensory cortex has unitary structures called barrels that receive tactile information from individual vibrissae. Barrels in the anterolateral barrel subfield (ALBSF) are much smaller and have gained less attention than larger barrels in the posteromedial barrel subfield (PMBSF), though the former outnumber the latter. We compared the morphological features of barrels between the ALBSF and PMBSF in male mice using deformation-free tangential sections and confocal optical slice-based, precise reconstructions of barrels. The average volume of a single barrel in the ALBSF was 34.7% of that in the PMBSF, but the numerical density of parvalbumin (PV)-positive interneurons in the former was 1.49 times higher than that in the latter. Moreover, PV neuron density in septa was 2.08 times higher in the ALBSF than that in the PMBSF. The proportions of PV neuron number to both all neuron number and all GABAergic neuron number in the ALBSF were also higher than those in the PMBSF. Somata of PV neurons in barrels and septa in the ALBSF received 1.64 and 1.50 times more vesicular glutamate transporter Type 2-labeled boutons than those in the PMBSF, suggesting more potent feedforward inhibitory circuits in the ALBSF. The mode of connectivity through dendritic gap junctions among PV neurons also differed between the ALBSF and PMBSF. Clusters of smaller unitary structures containing a higher density of representative GABAergic interneurons with differential morphological features in the ALBSF suggest a division of functional roles in the two vibrissa-barrel systems, as has been demonstrated by behavioral studies.
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Affiliation(s)
- Naoki Shigematsu
- Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Yuta Miyamoto
- Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Shigeyuki Esumi
- Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Takaichi Fukuda
- Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
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Variability of brain anatomy for three common mouse strains. Neuroimage 2016; 142:656-662. [DOI: 10.1016/j.neuroimage.2016.03.069] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 03/24/2016] [Accepted: 03/26/2016] [Indexed: 11/23/2022] Open
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Formation of functional areas in the cerebral cortex is disrupted in a mouse model of autism spectrum disorder. Neural Dev 2015; 10:10. [PMID: 25879444 PMCID: PMC4412039 DOI: 10.1186/s13064-015-0033-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 02/27/2015] [Indexed: 12/02/2022] Open
Abstract
Background Autism spectrum disorders (ASD) are a group of poorly understood behavioural disorders, which have increased in prevalence in the past two decades. Animal models offer the opportunity to understand the biological basis of these disorders. Studies comparing different mouse strains have identified the inbred BTBR T + tf/J (BTBR) strain as a mouse model of ASD based on its anti-social and repetitive behaviours. Adult BTBR mice have complete agenesis of the corpus callosum, reduced cortical thickness and changes in early neurogenesis. However, little is known about the development or ultimate organisation of cortical areas devoted to specific sensory and motor functions in these mice that may also contribute to their behavioural phenotype. Results In this study, we performed diffusion tensor imaging and tractography, together with histological analyses to investigate the emergence of functional areas in the cerebral cortex and their connections in BTBR mice and age-matched C57Bl/6 control mice. We found evidence that neither the anterior commissure nor the hippocampal commissure compensate for the loss of callosal connections, indicating that no interhemispheric neocortical connectivity is present in BTBR mice. We also found that both the primary visual and somatosensory cortical areas are shifted medially in BTBR mice compared to controls and that cortical thickness is differentially altered in BTBR mice between cortical areas and throughout development. Conclusions We demonstrate that interhemispheric connectivity and cortical area formation are altered in an age- and region-specific manner in BTBR mice, which may contribute to the behavioural deficits previously observed in this strain. Some of these developmental patterns of change are also present in human ASD patients, and elucidating the aetiology driving cortical changes in BTBR mice may therefore help to increase our understanding of this disorder. Electronic supplementary material The online version of this article (doi:10.1186/s13064-015-0033-y) contains supplementary material, which is available to authorized users.
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Massé IO, Guillemette S, Laramée ME, Bronchti G, Boire D. Strain differences of the effect of enucleation and anophthalmia on the size and growth of sensory cortices in mice. Brain Res 2014; 1588:113-26. [PMID: 25242615 DOI: 10.1016/j.brainres.2014.09.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/05/2014] [Accepted: 09/10/2014] [Indexed: 11/27/2022]
Abstract
Anophthalmia is a condition in which the eye does not develop from the early embryonic period. Early blindness induces cross-modal plastic modifications in the brain such as auditory and haptic activations of the visual cortex and also leads to a greater solicitation of the somatosensory and auditory cortices. The visual cortex is activated by auditory stimuli in anophthalmic mice and activity is known to alter the growth pattern of the cerebral cortex. The size of the primary visual, auditory and somatosensory cortices and of the corresponding specific sensory thalamic nuclei were measured in intact and enucleated C57Bl/6J mice and in ZRDCT anophthalmic mice (ZRDCT/An) to evaluate the contribution of cross-modal activity on the growth of the cerebral cortex. In addition, the size of these structures were compared in intact, enucleated and anophthalmic fourth generation backcrossed hybrid C57Bl/6J×ZRDCT/An mice to parse out the effects of mouse strains and of the different visual deprivations. The visual cortex was smaller in the anophthalmic ZRDCT/An than in the intact and enucleated C57Bl/6J mice. Also the auditory cortex was larger and the somatosensory cortex smaller in the ZRDCT/An than in the intact and enucleated C57Bl/6J mice. The size differences of sensory cortices between the enucleated and anophthalmic mice were no longer present in the hybrid mice, showing specific genetic differences between C57Bl/6J and ZRDCT mice. The post natal size increase of the visual cortex was less in the enucleated than in the anophthalmic and intact hybrid mice. This suggests differences in the activity of the visual cortex between enucleated and anophthalmic mice and that early in-utero spontaneous neural activity in the visual system contributes to the shaping of functional properties of cortical networks.
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Affiliation(s)
- Ian O Massé
- Département d׳anatomie, Université du Québec à Trois-Rivières, Québec, Canada G9A 5H7.
| | - Sonia Guillemette
- Département d׳anatomie, Université du Québec à Trois-Rivières, Québec, Canada G9A 5H7.
| | - Marie-Eve Laramée
- Département d׳anatomie, Université du Québec à Trois-Rivières, Québec, Canada G9A 5H7.
| | - Gilles Bronchti
- Département d׳anatomie, Université du Québec à Trois-Rivières, Québec, Canada G9A 5H7.
| | - Denis Boire
- Département d׳anatomie, Université du Québec à Trois-Rivières, Québec, Canada G9A 5H7; École d׳optométrie, Université de Montréal, Québec, Canada H3C 3J7.
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Abstract
The basal forebrain cholinergic system modulates neuronal excitability and vascular tone throughout the cerebral cortex and hippocampus. This system is severely affected in Alzheimer's disease (AD), and drug treatment to enhance cholinergic signaling is widely used as symptomatic therapy in AD. Defining the full morphologies of individual basal forebrain cholinergic neurons has, until now, been technically beyond reach due to their large axon arbor sizes. Using genetically-directed sparse labeling, we have characterized the complete morphologies of basal forebrain cholinergic neurons in the mouse. Individual arbors were observed to span multiple cortical columns, and to have >1000 branch points and total axon lengths up to 50 cm. In an AD model, cholinergic axons were slowly lost and there was an accumulation of axon-derived material in discrete puncta. Calculations based on published morphometric data indicate that basal forebrain cholinergic neurons in humans have a mean axon length of ∼100 meters. DOI:http://dx.doi.org/10.7554/eLife.02444.001 The human brain is made up of roughly 80 to 100 billion neurons, organized into extensive networks. Each neuron consists of a number of components: a cell body, which contains the nucleus; numerous short protrusions from the cell body called dendrites; and a long thin structure called an axon that carries the electrical signals generated in the cell body and the dendrites to the next neuron in the network. One of the most studied networks in the human brain is the basal forebrain network, which is made up of large neurons that communicate with one another using a chemical transmitter called acetylcholine. This network has a key role in cognition, and its neurons are among the first to degenerate in Alzheimer's disease. However, relatively little is known about the structure of these ‘cholinergic’ neurons because their large size makes them difficult to study using standard techniques. Now, Wu et al. have visualized, for the first time, the complete 3D structure of cholinergic neurons in the mouse forebrain. The mice in question had been genetically modified so that only ten or so of their many thousands of cholinergic neurons expressed a distinctive ‘marker’ protein. This made it possible to distinguish these neurons from surrounding brain tissue in order to visualize their structures. The resulting pictures clearly illustrate the neurons' complexity, with individual axons in adult mice displaying up to 1000 branches. Measurements showed that each cholinergic axon in the mouse brain is roughly 30 centimeters long, even though the brain itself is less than 2 centimeters from front to back. Based on measurements by other researchers, Wu et al. calculated that the axons of single cholinergic neurons in the human brain are about 100 meters long on average. The extreme length and complex branching structure of cholinergic forebrain neurons helps to explain why each neuron is able to modulate the activity of many others in the network. It could also explain their vulnerability to degeneration, as the need to transport materials over such long distances may limit the ability of these neurons to respond to damage. DOI:http://dx.doi.org/10.7554/eLife.02444.002
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Affiliation(s)
- Hao Wu
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States
| | - John Williams
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Jeremy Nathans
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States Department of Opthalmology, Johns Hopkins University School of Medicine, Baltimore, United States
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Wu H, Luo J, Yu H, Rattner A, Mo A, Wang Y, Smallwood PM, Erlanger B, Wheelan SJ, Nathans J. Cellular resolution maps of X chromosome inactivation: implications for neural development, function, and disease. Neuron 2014; 81:103-19. [PMID: 24411735 DOI: 10.1016/j.neuron.2013.10.051] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2013] [Indexed: 01/07/2023]
Abstract
Female eutherian mammals use X chromosome inactivation (XCI) to epigenetically regulate gene expression from ∼4% of the genome. To quantitatively map the topography of XCI for defined cell types at single cell resolution, we have generated female mice that carry X-linked, Cre-activated, and nuclear-localized fluorescent reporters--GFP on one X chromosome and tdTomato on the other. Using these reporters in combination with different Cre drivers, we have defined the topographies of XCI mosaicism for multiple CNS cell types and of retinal vascular dysfunction in a model of Norrie disease. Depending on cell type, fluctuations in the XCI mosaic are observed over a wide range of spatial scales, from neighboring cells to left versus right sides of the body. These data imply a major role for XCI in generating female-specific, genetically directed, stochastic diversity in eutherian mammals on spatial scales that would be predicted to affect CNS function within and between individuals.
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Affiliation(s)
- Hao Wu
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Junjie Luo
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Huimin Yu
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Amir Rattner
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alisa Mo
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Yanshu Wang
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Philip M Smallwood
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Bracha Erlanger
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Sarah J Wheelan
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Division of Biostatistics and Bioinformatics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jeremy Nathans
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Hitzemann R, Bottomly D, Iancu O, Buck K, Wilmot B, Mooney M, Searles R, Zheng C, Belknap J, Crabbe J, McWeeney S. The genetics of gene expression in complex mouse crosses as a tool to study the molecular underpinnings of behavior traits. Mamm Genome 2013; 25:12-22. [PMID: 24374554 PMCID: PMC3916704 DOI: 10.1007/s00335-013-9495-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 11/25/2013] [Indexed: 02/06/2023]
Abstract
Complex Mus musculus crosses provide increased resolution to examine the relationships between gene expression and behavior. While the advantages are clear, there are numerous analytical and technological concerns that arise from the increased genetic complexity that must be considered. Each of these issues is discussed, providing an initial framework for complex cross study design and planning.
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Affiliation(s)
- Robert Hitzemann
- Portland Alcohol Research Center, Veterans Affairs Medical Center, Portland, 97239, OR, USA
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Ullmann JFP, Watson C, Janke AL, Kurniawan ND, Reutens DC. A segmentation protocol and MRI atlas of the C57BL/6J mouse neocortex. Neuroimage 2013; 78:196-203. [PMID: 23587687 DOI: 10.1016/j.neuroimage.2013.04.008] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 03/26/2013] [Accepted: 04/05/2013] [Indexed: 10/27/2022] Open
Abstract
The neocortex is the largest component of the mammalian cerebral cortex. It integrates sensory inputs with experiences and memory to produce sophisticated responses to an organism's internal and external environment. While areal patterning of the mouse neocortex has been mapped using histological techniques, the neocortex has not been comprehensively segmented in magnetic resonance images. This study presents a method for systematic segmentation of the C57BL/6J mouse neocortex. We created a minimum deformation atlas, which was hierarchically segmented into 74 neocortical and cortical-related regions, making it the most detailed atlas of the mouse neocortex currently available. In addition, we provide mean volumes and relative intensities for each structure as well as a nomenclature comparison between the two most cited histological atlases of the mouse brain. This MR atlas is available for download, and it should enable researchers to perform automated segmentation in genetic models of cortical disorders.
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Affiliation(s)
- Jeremy F P Ullmann
- Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia.
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Talishinsky A, Rosen GD. Systems genetics of the lateral septal nucleus in mouse: heritability, genetic control, and covariation with behavioral and morphological traits. PLoS One 2012; 7:e44236. [PMID: 22952935 PMCID: PMC3432065 DOI: 10.1371/journal.pone.0044236] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 07/30/2012] [Indexed: 11/19/2022] Open
Abstract
The lateral septum has strong efferent projections to hypothalamic and midbrain regions, and has been associated with modulation of social behavior, anxiety, fear conditioning, memory-related behaviors, and the mesolimbic reward pathways. Understanding natural variation of lateral septal anatomy and function, as well as its genetic modulation, may provide important insights into individual differences in these evolutionarily important functions. Here we address these issues by using efficient and unbiased stereological probes to estimate the volume of the lateral septum in the BXD line of recombinant inbred mice. Lateral septum volume is a highly variable trait, with a 2.5-fold difference among animals. We find that this trait covaries with a number of behavioral and physiological phenotypes, many of which have already been associated with behaviors modulated by the lateral septum, such as spatial learning, anxiety, and reward-seeking. Heritability of lateral septal volume is moderate (h(2) = 0.52), and much of the heritable variation is caused by a locus on the distal portion of chromosome (Chr) 1. Composite interval analysis identified a secondary interval on Chr 2 that works additively with the Chr 1 locus to increase lateral septum volume. Using bioinformatic resources, we identified plausible candidate genes in both intervals that may influence the volume of this key nucleus, as well as associated behaviors.
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Affiliation(s)
- Alexander Talishinsky
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Glenn D. Rosen
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
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Han L, Itoh K, Yaoi T, Moriwaki S, Kato S, Nakamura K, Fushiki S. Prenatal and Lactational Exposure to Bisphenol A in Mice Alters Expression of Genes Involved in Cortical Barrel Development without Morphological Changes. Acta Histochem Cytochem 2011; 44:25-33. [PMID: 21448315 PMCID: PMC3061449 DOI: 10.1267/ahc.10042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 01/05/2011] [Indexed: 01/01/2023] Open
Abstract
It has been reported that premature infants in neonatal intensive care units are exposed to a high rate of bisphenol A (BPA), an endocrine disrupting chemical. Our previous studies demonstrated that corticothalamic projection was disrupted by prenatal exposure to BPA, which persisted even in adult mice. We therefore analyzed whether prenatal and lactational exposure to low doses of BPA affected the formation of the cortical barrel, the barreloid of the thalamus, and the barrelette of the brainstem in terms of the histology and the expression of genes involved in the barrel development. Pregnant mice were injected subcutaneously with 20 µg/kg of BPA daily from embryonic day 0 (E0) to postnatal 3 weeks (P3W), while the control mice received a vehicle alone. The barrel, barreloid and barrelette of the adult mice were examined by cytochrome C oxidase (COX) staining. There were no significant differences in the total and septal areas and the patterning of the posterior medial barrel subfield (PMBSF), barreloid and barrelette, between the BPA-exposure and control groups in the adult mice. The developmental study at postnatal day 1 (PD1), PD4 and PD8 revealed that the cortical barrel vaguely appeared at PD4 and completely formed at PD8 in both groups. The expression pattern of some genes was spatiotemporally altered depending on the sex and the treatment. These results suggest that the trigeminal projection and the thalamic relay to the cortical barrel were spared after prenatal and lactational exposure to low doses of BPA, although prenatal exposure to BPA was previously shown to disrupt the corticothalamic projection.
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Affiliation(s)
- Longzhe Han
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
| | - Kyoko Itoh
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
| | - Takeshi Yaoi
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
| | - Sanzo Moriwaki
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
| | - Shingo Kato
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
| | - Keiko Nakamura
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
| | - Shinji Fushiki
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine
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Xie N, Yang Q, Chappell TD, Li CX, Waters RS. Prenatal alcohol exposure reduces the size of the forelimb representation in motor cortex in rat: an intracortical microstimulation (ICMS) mapping study. Alcohol 2010; 44:185-94. [PMID: 20083368 DOI: 10.1016/j.alcohol.2009.10.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 10/24/2009] [Accepted: 10/24/2009] [Indexed: 11/16/2022]
Abstract
Children with fetal alcohol spectrum disorder (FASD) often exhibit sensorimotor dysfunctions that include deficits in motor coordination and fine motor control. Although the underlying causes for these motor abnormalities are unknown, they likely involve interactions between sensory and motor systems. Rodent animal models have been used to study the effects of prenatal alcohol exposure (PAE) on skilled reaching and on the development and organization of somatosensory barrel field cortex. To this end, PAE delayed the development of somatosensory cortex, reduced the size of whisker and forelimb representations in somatosensory barrel field cortex, and delayed acquisition time to learn a skilled reaching task. However, whether PAE also affects the motor cortex (MI) remains to be determined. In the present study, we investigated the effect of PAE on the size of the forelimb representation in rat MI, thresholds for activation, and the overlap between motor and sensory cortical forelimb maps in sensorimotor cortex. Pregnant Sprague-Dawley rats were assigned to alcohol (Alc), pair-fed (PF), and chow-fed (CF) groups on gestation day 1 (GD1). Rats in the Alc group (n=4) were chronically intubated daily with binge doses of alcohol (6g/kg body weight) from GD1 to GD20 that resulted in averaged blood alcohol levels measured on GD10 (mean=191.5+/-41.9mg/dL) and on GD17 (mean=247.0+/-72.4mg/dL). PF (n=2) and CF (n=3) groups of pregnant rats served as controls. The effect of PAE on the various dependent measures was obtained from multiple male offspring from each dam within treatment groups, and litter means were compared between the groups from alcohol-treated and control (Ct: CF and PF) dams. At approximately 8 weeks of age, rats were anesthetized with ketamine/xylazine and the skull opened over sensorimotor cortex. A tungsten microelectrode was then inserted into the depths of layer V and intracortical microstimulation was used to deliver trains of pulses to evoke muscle contractions and/or movements; maximum stimulating < or =100microA. When a motor response was observed, the threshold for movement was measured and the motor receptive field projected to the cortical surface to serve as representative point for that location. A motor map for the forelimb representation was generated by systematically stimulating at adjacent sites until current thresholds reached the maximum and/or motor responses were no longer evoked. The major findings in this study were as follows: (1) PAE significantly reduced the area of the forelimb representation in the Alc offspring (6.01mm(2), standard error of the mean=+/-0.278) compared with the Ct offspring (8.03mm(2)+/-0.586), (2) PAE did not significantly reduce the averaged threshold for activation of movements between groups, (3) PAE significantly reduced the percent overlap (Alc=31.1%, Ct=55.4%) between the forelimb representation in sensory and motor cortices, and (4) no significant differences were observed in averaged body weight, hemisphere weight, or age of animal between treatment groups. These findings suggest that the effects of PAE are not restricted to somatosensory barrel field cortex but also involve the MI and may underlie deficits in motor control and sensorimotor integration observed among children with FASD.
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Affiliation(s)
- Ni Xie
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, 38163, USA
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Abstract
PURPOSE OF REVIEW Advances in magnetic resonance microscopy (MRM) make it practical to map gene variants responsible for structural variation in brains of many species, including mice and humans. We review results of a systematic genetic analysis of MRM data using as a case study a family of well characterized lines of mice. RECENT ADVANCES MRM has matured to the point that we can generate high contrast, high-resolution images even for species as small as a mouse, with a brain merely 1/3000th the size of humans. We generated 21.5-micron data sets for a diverse panel of BXD mouse strains to gauge the extent of genetic variation, and as a prelude to comprehensive genetic and genomic analyses. Here we review MRM capabilities and image segmentation methods; heritability of brain variation; covariation of the sizes of brain regions; and correlations between MRM and classical histological data sets. SUMMARY The combination of high throughput MRM and genomics will improve our understanding of the genetic basis of structure-function correlations. Sophisticated mouse models will be critical in converting correlations into mechanisms and in determining genetic and epigenetic causes of differences in disease susceptibility.
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Aggarwal M, Zhang J, Miller MI, Sidman RL, Mori S. Magnetic resonance imaging and micro-computed tomography combined atlas of developing and adult mouse brains for stereotaxic surgery. Neuroscience 2009; 162:1339-50. [PMID: 19490934 PMCID: PMC2723180 DOI: 10.1016/j.neuroscience.2009.05.070] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 05/26/2009] [Accepted: 05/27/2009] [Indexed: 01/05/2023]
Abstract
Stereotaxic atlases of the mouse brain are important in neuroscience research for targeting of specific internal brain structures during surgical operations. The effectiveness of stereotaxic surgery depends on accurate mapping of the brain structures relative to landmarks on the skull. During postnatal development in the mouse, rapid growth-related changes in the brain occur concurrently with growth of bony plates at the cranial sutures, therefore adult mouse brain atlases cannot be used to precisely guide stereotaxis in developing brains. In this study, three-dimensional stereotaxic atlases of C57BL/6J mouse brains at six postnatal developmental stages: postnatal day (P) 7, P14, P21, P28, P63 and in adults (P140-P160) were developed, using diffusion tensor imaging (DTI) and micro-computed tomography (CT). At present, most widely-used stereotaxic atlases of the mouse brain are based on histology, but the anatomical fidelity of ex vivo atlases to in vivo mouse brains has not been evaluated previously. To account for ex vivo tissue distortion due to fixation as well as individual variability in the brain, we developed a population-averaged in vivo magnetic resonance imaging adult mouse brain stereotaxic atlas, and a distortion-corrected DTI atlas was generated by nonlinearly warping ex vivo data to the population-averaged in vivo atlas. These atlas resources were developed and made available through a new software user-interface with the objective of improving the accuracy of targeting brain structures during stereotaxic surgery in developing and adult C57BL/6J mouse brains.
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Affiliation(s)
- Manisha Aggarwal
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jiangyang Zhang
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Michael I. Miller
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Richard L. Sidman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Susumu Mori
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Gaglani SM, Lu L, Williams RW, Rosen GD. The genetic control of neocortex volume and covariation with neocortical gene expression in mice. BMC Neurosci 2009; 10:44. [PMID: 19426526 PMCID: PMC2685397 DOI: 10.1186/1471-2202-10-44] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Accepted: 05/09/2009] [Indexed: 11/10/2022] Open
Abstract
Background The size of the cerebral cortex varies widely within human populations, and a large portion of this variance is modulated by genetic factors. The discovery and characterization of these genes and their variants can contribute to an understanding of individual differences in brain development, behavior, and disease susceptibility. Here we use unbiased stereological techniques to map quantitative trait loci (QTLs) that modulate the volume of neocortex. Results We estimated volumes bilaterally in an expanded set of BXD recombinant inbred strains (n = 56 strains and 223 animals) taken from the Mouse Brain Library . We generated matched microarray data for the cerebral cortex in the same large panel of strains and in parental neonates to efficiently nominate and evaluate candidate genes. Volume of the neocortex varies widely, and is a heritable trait. Genome-wide mapping of this trait revealed two QTLs – one on chromosome (Chr) 6 at 88 ± 5 Mb and another at Chr 11 (41 ± 8 Mb). We generated both neonatal and adult neocortical gene expression databases using microarray technology. Using these databases in combination with other bioinformatic tools we have identified positional candidates on these QTL intervals. Conclusion This study is the first to use the expanded set of BXD strains to map neocortical volume, and we found that normal variation of this trait is, at least in part, genetically modulated. These results provide a baseline from which to assess the genetic contribution to regional variation in neocortical volume, as well as other neuroanatomic phenotypes that may contribute to variation in regional volume, such as proliferation, death, and number and packing density of neurons
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Affiliation(s)
- Shiv M Gaglani
- Department of Neurology, Division of Behavioral Neurology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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O'Leary DD, Sahara S. Genetic regulation of arealization of the neocortex. Curr Opin Neurobiol 2008; 18:90-100. [PMID: 18524571 DOI: 10.1016/j.conb.2008.05.011] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Revised: 05/13/2008] [Accepted: 05/15/2008] [Indexed: 12/18/2022]
Abstract
Arealization of the neocortex is controlled by a regulatory hierarchy beginning with morphogens secreted from patterning centers positioned at the perimeter of the dorsal telencephalon. These morphogens act in part to establish within cortical progenitors the differential expression of transcription factors that specify their area identity, which is inherited by their neuronal progeny, providing the genetic framework for area patterning. The two patterning centers most directly implicated in arealization are the commissural plate, which expresses fibroblast growth factors, and the cortical hem, which expresses bone morphogenetic proteins and vertebrate orthologs of Drosophila wingless, the Wnts. A third, albeit putative, patterning center is the antihem, identified by its expression of multiple signaling molecules. We describe recent findings on roles for these patterning centers in arealization. We also present the most recent evidence on functions of the four transcription factors, Emx2, COUP-TFI, Pax6, and Sp8, thus far implicated in arealization. We also describe screens for candidate target genes of these transcription factors, or other genes potentially involved in arealization. We conclude with an assessment of a forward genetics approach for identifying genes involved in determining area size based in part on quantitative trait locus mapping, and the implications for significant differences between individuals in area size on behavioral performance.
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Affiliation(s)
- Dennis Dm O'Leary
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA 92037, USA.
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