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Zeng Z, Xu X, Wang Q, Zhang Z, Meng P, Huo X. Maternal exposure to atmospheric PM 2.5 and fetal brain development: Associations with BAI1 methylation and thyroid hormones. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 308:119665. [PMID: 35738517 DOI: 10.1016/j.envpol.2022.119665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 06/13/2022] [Accepted: 06/18/2022] [Indexed: 02/05/2023]
Abstract
Maternal exposure to atmospheric fine particulate matter (PM2.5) during pregnancy is associated with adverse fetal development, including abnormal brain development. However, the underlying mechanisms and influencing factors remain uncertain. This study investigated the roles of DNA methylation in genes involving neurodevelopment and thyroid hormones (THs) in fetal brain development after maternal exposure to PM2.5 from e-waste. Among 939 healthy pregnant women recruited from June 2011 to September 2012, 101 e-waste-exposed and 103 reference mother-infant pairs (204 pairs totally) were included. Annual ground-level PM2.5 concentrations over e-waste-exposed area (116.38°E, 23.29°N) and reference area (116.67°E, 23.34°N) in 2011, 2012 were obtained by estimates and maternal exposure was evaluated by calculating individual chronic daily intakes (CDIs) of PM2.5. Methylation and THs including thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) level were measured in umbilical cord blood collected shortly after delivery. We found higher ground-level PM2.5 concentrations led to greater individual CDI of PM2.5 in e-waste-exposed pregnant women. After adjustment for gender and birth BMI, significant mediation effects on the adverse associations of maternal PM2.5 exposure with birth head circumference were observed for methylations at positions +13 and + 32 (respectively mediated proportion of 9.8% and 5.3%, P < 0.05 and P < 0.01) in the brain-specific angiogenesis inhibitor 1 (BAI1) gene, but not for methylations in the catenin cadherin-associated protein, alpha 2 (CTNNA2) gene. BAI1 (position +13) methylation was also significantly correlated with FT3 levels (rs = -0.156, P = 0.032), although maternal CDI of PM2.5 was positively associated with higher odds of abnormal TSH levels (OR = 5.03, 95% CI: 1.00, 25.20, P = 0.05) rather than FT3 levels. Our findings suggest that methylation (likely linked to THs) in neonates may play mediation roles associated with abnormal brain development risk due to maternal exposure to atmospheric PM2.5 from e-waste.
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Affiliation(s)
- Zhijun Zeng
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 511443, Guangdong, China
| | - Xijin Xu
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou, 515041, Guangdong, China; Department of Cell Biology and Genetics, Shantou University Medical College, Shantou, 515041, Guangdong, China
| | - Qihua Wang
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 511443, Guangdong, China
| | - Zhuxia Zhang
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 511443, Guangdong, China
| | - Peipei Meng
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 511443, Guangdong, China
| | - Xia Huo
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 511443, Guangdong, China.
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Jin T, Wang R, Peng S, Liu X, Zhang H, He X, Teng W, Teng X. Developmental Hypothyroidism Influences the Development of the Entorhinal-Dentate Gyrus Pathway of Rat Offspring. Endocrinol Metab (Seoul) 2022; 37:290-302. [PMID: 35390249 PMCID: PMC9081305 DOI: 10.3803/enm.2021.1343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 01/21/2022] [Accepted: 02/10/2022] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Developmental hypothyroidism impairs learning and memory in offspring, which depend on extensive neuronal circuits in the entorhinal cortex, together with the hippocampus and neocortex. The entorhinal-dentate gyrus pathway is the main entrance of memory circuits. We investigated whether developmental hypothyroidism impaired the morphological development of the entorhinal-dentate gyrus pathway. METHODS We examined the structure and function of the entorhinal-dentate gyrus pathway in response to developmental hypothyroidism induced using 2-mercapto-1-methylimidazole. RESULTS 1,1´-Dioctadecyl-3,3,3´,3´-tetramethylindocarbocyanine perchlorate tract tracing indicated that entorhinal axons showed delayed growth in reaching the outer molecular layer of the dentate gyrus at postnatal days 2 and 4 in hypothyroid conditions. The proportion of fibers in the outer molecular layer was significantly smaller in the hypothyroid group than in the euthyroid group at postnatal day 4. At postnatal day 10, the pathway showed a layer-specific distribution in the outer molecular layer, similar to the euthyroid group. However, the projected area of entorhinal axons was smaller in the hypothyroid group than in the euthyroid group. An electrophysiological examination showed that hypothyroidism impaired the long-term potentiation of the perforant and the cornu ammonis 3-cornu ammonis 1 pathways. Many repulsive axon guidance molecules were involved in the formation of the entorhinaldentate gyrus pathway. The hypothyroid group had higher levels of erythropoietin-producing hepatocyte ligand A3 and semaphorin 3A than the euthyroid group. CONCLUSION We demonstrated that developmental hypothyroidism might influence the development of the entorhinal-dentate gyrus pathway, contributing to impaired long-term potentiation. These findings improve our understanding of neural mechanisms for memory function.
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Affiliation(s)
- Ting Jin
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
- Department of Endocrinology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ranran Wang
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
- Department of Endocrinology, Chifeng College Affiliated Hospital, Chifeng, China
| | - Shiqiao Peng
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Xin Liu
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Hanyi Zhang
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Xue He
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Weiping Teng
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Xiaochun Teng
- Department of Endocrinology and Metabolism, Institute of Endocrinology, National Health Commission Key Laboratory of Thyroid Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China
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Abstract
Astrocytes, initially described as merely support cells, are now known as a heterogeneous population of cells actively involved in a variety of biological functions such as: neuronal migration and differentiation; regulation of cerebral blood flow; metabolic control of extracellular potassium concentration; and modulation of synapse formation and elimination; among others. Cerebellar glial cells have been shown to play a significant role in proliferation, differentiation, migration, and synaptogenesis. However, less evidence is available about the role of neuron-astrocyte interactions during cerebellar development and their impact on diseases of the cerebellum. In this review, we will focus on the mechanisms underlying cellular interactions, specifically neuron-astrocyte interactions, during cerebellar development, function, and disease. We will discuss how cerebellar glia, astrocytes, and Bergmann glia play a fundamental role in several steps of cerebellar development, such as granule cell migration, axonal growth, neuronal differentiation, and synapse formation, and in diseases associated with the cerebellum. We will focus on how astrocytes and thyroid hormones impact cerebellar development. Furthermore, we will provide evidence of how growth factors secreted by glial cells, such as epidermal growth factor and transforming growth factors, control cerebellar organogenesis. Finally, we will argue that glia are a key mediator of cerebellar development and that identification of molecules and pathways involved in neuron-glia interactions may contribute to a better understanding of cerebellar development and associated disorders.
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Fanibunda SE, Desouza LA, Kapoor R, Vaidya RA, Vaidya VA. Thyroid Hormone Regulation of Adult Neurogenesis. VITAMINS AND HORMONES 2018; 106:211-251. [DOI: 10.1016/bs.vh.2017.04.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Moog NK, Entringer S, Heim C, Wadhwa PD, Kathmann N, Buss C. Influence of maternal thyroid hormones during gestation on fetal brain development. Neuroscience 2017; 342:68-100. [PMID: 26434624 PMCID: PMC4819012 DOI: 10.1016/j.neuroscience.2015.09.070] [Citation(s) in RCA: 221] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/22/2015] [Accepted: 09/25/2015] [Indexed: 01/09/2023]
Abstract
Thyroid hormones (THs) play an obligatory role in many fundamental processes underlying brain development and maturation. The developing embryo/fetus is dependent on maternal supply of TH. The fetal thyroid gland does not commence TH synthesis until mid gestation, and the adverse consequences of severe maternal TH deficiency on offspring neurodevelopment are well established. Recent evidence suggests that even more moderate forms of maternal thyroid dysfunction, particularly during early gestation, may have a long-lasting influence on child cognitive development and risk of neurodevelopmental disorders. Moreover, these observed alterations appear to be largely irreversible after birth. It is, therefore, important to gain a better understanding of the role of maternal thyroid dysfunction on offspring neurodevelopment in terms of the nature, magnitude, time-specificity, and context-specificity of its effects. With respect to the issue of context specificity, it is possible that maternal stress and stress-related biological processes during pregnancy may modulate maternal thyroid function. The possibility of an interaction between the thyroid and stress systems in the context of fetal brain development has, however, not been addressed to date. We begin this review with a brief overview of TH biology during pregnancy and a summary of the literature on its effect on the developing brain. Next, we consider and discuss whether and how processes related to maternal stress and stress biology may interact with and modify the effects of maternal thyroid function on offspring brain development. We synthesize several research areas and identify important knowledge gaps that may warrant further study. The scientific and public health relevance of this review relates to achieving a better understanding of the timing, mechanisms and contexts of thyroid programing of brain development, with implications for early identification of risk, primary prevention and intervention.
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Affiliation(s)
- N K Moog
- Department of Medical Psychology, Charité University Medicine Berlin, Luisenstrasse 57, 10117 Berlin, Germany
| | - S Entringer
- Department of Medical Psychology, Charité University Medicine Berlin, Luisenstrasse 57, 10117 Berlin, Germany; University of California, Irvine, Development, Health, and Disease Research Program, 333 The City Drive West, Suite 1200, Orange, CA 92868, USA; Department of Pediatrics, University of California, Irvine, School of Medicine, 505 South Main Street, Suite 525, Orange, CA 92868, USA
| | - C Heim
- Department of Medical Psychology, Charité University Medicine Berlin, Luisenstrasse 57, 10117 Berlin, Germany; Department of Biobehavioral Health, Pennsylvania State University, College of Health and Human Development, 219 Biobehavioral Health Building, University Park, PA 16802, USA
| | - P D Wadhwa
- University of California, Irvine, Development, Health, and Disease Research Program, 333 The City Drive West, Suite 1200, Orange, CA 92868, USA; Department of Pediatrics, University of California, Irvine, School of Medicine, 505 South Main Street, Suite 525, Orange, CA 92868, USA; Department of Psychiatry and Human Behavior, University of California, Irvine, School of Medicine, 3117 Gillespie Neuroscience Research Facility, 837 Health Sciences Drive, Irvine, CA 92697, USA; Department of Obstetrics and Gynecology, University of California, Irvine, School of Medicine, 3117 Gillespie Neuroscience Research Facility, 837 Health Sciences Drive, Irvine, CA 92697, USA; Department of Epidemiology, University of California, Irvine, School of Medicine, 3117 Gillespie Neuroscience Research Facility, 837 Health Sciences Drive, Irvine, CA 92697, USA
| | - N Kathmann
- Department of Clinical Psychology, Humboldt-Universität zu Berlin, Rudower Chaussee 18, 12489 Berlin, Germany
| | - C Buss
- Department of Medical Psychology, Charité University Medicine Berlin, Luisenstrasse 57, 10117 Berlin, Germany; University of California, Irvine, Development, Health, and Disease Research Program, 333 The City Drive West, Suite 1200, Orange, CA 92868, USA; Department of Pediatrics, University of California, Irvine, School of Medicine, 505 South Main Street, Suite 525, Orange, CA 92868, USA.
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Günbey E, Karlı R, Gökosmanoğlu F, Düzgün B, Ayhan E, Atmaca H, Ünal R. Evaluation of olfactory function in adults with primary hypothyroidism. Int Forum Allergy Rhinol 2015; 5:919-22. [DOI: 10.1002/alr.21565] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/26/2015] [Accepted: 05/05/2015] [Indexed: 12/23/2022]
Affiliation(s)
- Emre Günbey
- Department of Otorhinolaryngology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
| | - Rıfat Karlı
- Department of Otorhinolaryngology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
| | - Feyzi Gökosmanoğlu
- Department of Endocrinology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
| | - Berkan Düzgün
- Department of Otorhinolaryngology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
| | - Emre Ayhan
- Department of Otorhinolaryngology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
| | - Hulusi Atmaca
- Department of Endocrinology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
| | - Recep Ünal
- Department of Otorhinolaryngology; Ondokuz Mayıs University School of Medicine; Samsun Turkey
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Kapoor R, Fanibunda SE, Desouza LA, Guha SK, Vaidya VA. Perspectives on thyroid hormone action in adult neurogenesis. J Neurochem 2015; 133:599-616. [DOI: 10.1111/jnc.13093] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 02/18/2015] [Accepted: 02/24/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Richa Kapoor
- Department of Biological Sciences; Tata Institute of Fundamental Research; Mumbai India
| | - Sashaina E. Fanibunda
- Department of Biological Sciences; Tata Institute of Fundamental Research; Mumbai India
| | - Lynette A. Desouza
- Department of Biological Sciences; Tata Institute of Fundamental Research; Mumbai India
| | - Suman K. Guha
- Department of Biological Sciences; Tata Institute of Fundamental Research; Mumbai India
| | - Vidita A. Vaidya
- Department of Biological Sciences; Tata Institute of Fundamental Research; Mumbai India
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Autoinflammatory grey matter lesions in humans: cortical encephalitis, clinical disorders, experimental models. Curr Opin Neurol 2012; 25:349-57. [PMID: 22543404 DOI: 10.1097/wco.0b013e3283534a8a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
PURPOSE OF REVIEW In recent years, evidence has accumulated that grey matter abnormalities are common in many inflammatory central nervous system (CNS) disorders, such as multiple sclerosis (MS), which is by far the most frequent autoimmune-mediated CNS disease. RECENT FINDINGS A recent study described comprehensively the pathology of grey matter lesions in early MS. In this study, cortical demyelination together with inflammation was frequently observed in early MS cases. This study and others serve as a basis for a model of the development of cortical MS lesions in which several consecutive events may be involved. After the activation of T cells, which may open the blood-brain barrier, the humoral immune system may mediate the inflammatory process. The inflammation may become chronic through the involvement of activated glial cells and the persistence of immune cells in the meninges.Apart from MS, other grey matter CNS disorders exist in which antibodies against neuronal structures contribute to pathophysiological events such as in limbic encephalitis. Humoral and adaptive immunity mediates the pathophysiology of Rasmussen encephalitis. SUMMARY This review focuses on the difference between inflammatory grey matter and white matter lesions. New insights into inflammatory grey matter lesions in MS and other CNS inflammatory processes such as limbic encephalitis are discussed.
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Jahagirdar V, Zoeller TR, Tighe DP, Wagner CK. Maternal hypothyroidism decreases progesterone receptor expression in the cortical subplate of foetal rat brain. J Neuroendocrinol 2012; 24:1126-34. [PMID: 22435967 DOI: 10.1111/j.1365-2826.2012.02318.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Steroid hormones exert profound effects on the development of brain areas controlling complex cognitive function in adulthood. One class, progestins, may contribute by acting on the progestin receptor (PR), which is transiently expressed in a critical layer of developing cortex: the subplate. PR expression in the subplate coincides with the establishment of ongoing cortical connectivity and may play an important organisational role. Identification of the factor(s) that regulate the precise timing of PR expression within subplate may help elucidate the function of PR. Thyroid hormone may interact with hormone response elements within the PR gene. The present study examined the effects of maternal hypothyroidism on levels of PR immunoreactivity (PR-IR) within the foetal subplate. Pregnant rats were made hypothyroid by the administration of methimazole and potassium perchlorate in drinking water. Maternal hypothyroidism significantly decreased PR-IR within the foetal subplate. Using the incorporation of 5-bromo-2'-deoxyuridine (BrDU) during subplate cell neurogenesis (embryonic day 13.5) to determine subplate cell survival in hypothyroid animals, we found that decreases in PR-IR cannot be attributed to significant subplate cell loss but are more likely the result of altered PR expression. Gestational thyroxine replacement to hypothyroid dams prevented the decrease in PR-IR within the subplate. These results identify thyroid hormone as a potential factor in the regulation of PR expression in the developing brain. These results are consistent with the idea that endocrine cross-talk between progesterone and thyroid hormone may be one mechanism by which maternal hypothyroidism alters normal cortical development.
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Affiliation(s)
- V Jahagirdar
- Department of Psychology and Center for Neuroscience Research, University at Albany, Albany, NY 12222, USA
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Wang Y, Zhong J, Xu H, Wei W, Dong J, Yu F, Wang Y, Gong J, Shan Z, Teng W, Chen J. Perinatal iodine deficiency and hypothyroidism increase cell apoptosis and alter doublecortin and reelin protein expressions in rat cerebellum. Arch Med Res 2012; 43:255-64. [PMID: 22595232 DOI: 10.1016/j.arcmed.2012.05.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 04/20/2012] [Indexed: 11/19/2022]
Abstract
BACKGROUND AND AIMS Adequate thyroid hormone is critical for cerebellar development. Developmental hypothyroidism induced by iodine deficiency during the perinatal period results in permanent impairments of cerebellar development with an unclear mechanism. In the present study we investigated effects of perinatal iodine deficiency and hypothyroidism on cerebellar cell apoptosis, doublecortin (Dcx) and reelin. Apoptosis is an essential part of neural development. Dcx and reelin are two important molecules involved in neuronal migration, structure, and development in cerebellum. METHODS Two developmental rat models were created by administering dam rats with either iodine-deficient diet or propylthiouracil (PTU, 5 ppm or 15 ppm)-added drinking water from gestational day (GD) 6 until postnatal day (PND) 28. TUNEL assay and protein levels of Dcx and reelin in cerebella were assessed on PND14, 21 and 28. RESULTS Apoptotic cells were increased in the iodine-deficient and PTU-treated rats. Dcx protein levels in the cerebella of iodine-deficient and PTU-treated rats were significantly downregulated on PND14. Interestingly, iodine deficiency and PTU treatment upregulated the levels of Dcx protein on PND21 and 28. Reelin expressions in iodine-deficient and PTU-treated rats were significantly decreased on PND14 and 21. On PND28, reelin expressions of three treated groups were still lower than control group, although without significant difference. CONCLUSIONS These findings may implicate alterations in cell apoptosis and levels of Dcx and reelin in the impairments of cerebellar development induced by developmental iodine deficiency and hypothyroidism.
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Affiliation(s)
- Yi Wang
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, PR China
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Wang Y, Zhong J, Wei W, Gong J, Dong J, Yu F, Wang Y, Chen J. Developmental iodine deficiency and hypothyroidism impair neural development, upregulate caveolin-1, and downregulate synaptotagmin-1 in the rat cerebellum. Biol Trace Elem Res 2011; 144:1039-49. [PMID: 21611807 DOI: 10.1007/s12011-011-9089-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 05/16/2011] [Indexed: 01/30/2023]
Abstract
Adequate thyroid hormone is critical for cerebellar development. Developmental hypothyroidism induced by iodine deficiency during gestation and postnatal period results in permanent impairments of cerebellar development with an unclear mechanism. In the present study, we implicate cerebellar caveolin-1 and synaptotagmin-1, the two important molecules involved in neuronal development, in developmental iodine deficiency, and in developmental hypothyroidism. Two developmental rat models were created by administrating dam rats with either iodine-deficient diet or propylthiouracil (PTU, 5 or 15 ppm)-added drinking water from gestational day 6 till postnatal day (PN) 28. Nissl staining and the levels of caveolin-1 and synaptotagmin-1 in cerebella were assessed on PN28 and PN42. The results show that the numbers of Purkinje cells were reduced in the iodine-deficient and PTU-treated rats. The upregulation of caveolin-1 and the downregulation of synaptotagmin-1 were observed in both iodine-deficient and PTU-treated rats. These findings may implicate decreases in the number of Purkinje cells and the alterations in the levels of caveolin-1 and synaptotagmin-1 in the impairments of cerebellar development induced by developmental iodine deficiency and hypothyroidism.
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Affiliation(s)
- Yi Wang
- Department of Occupational and Environmental Health, School of Public Health, China Medical University, 92 North 2nd Road, Shenyang, 110001, People's Republic of China
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Desouza LA, Sathanoori M, Kapoor R, Rajadhyaksha N, Gonzalez LE, Kottmann AH, Tole S, Vaidya VA. Thyroid hormone regulates the expression of the sonic hedgehog signaling pathway in the embryonic and adult Mammalian brain. Endocrinology 2011; 152:1989-2000. [PMID: 21363934 PMCID: PMC3179409 DOI: 10.1210/en.2010-1396] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Thyroid hormone is important for development and plasticity in the immature and adult mammalian brain. Several thyroid hormone-responsive genes are regulated during specific developmental time windows, with relatively few influenced across the lifespan. We provide novel evidence that thyroid hormone regulates expression of the key developmental morphogen sonic hedgehog (Shh), and its coreceptors patched (Ptc) and smoothened (Smo), in the early embryonic and adult forebrain. Maternal hypo- and hyperthyroidism bidirectionally influenced Shh mRNA in embryonic forebrain signaling centers at stages before fetal thyroid hormone synthesis. Further, Smo and Ptc expression were significantly decreased in the forebrain of embryos derived from hypothyroid dams. Adult-onset thyroid hormone perturbations also regulated expression of the Shh pathway bidirectionally, with a significant induction of Shh, Ptc, and Smo after hyperthyroidism and a decline in Smo expression in the hypothyroid brain. Short-term T₃ administration resulted in a significant induction of cortical Shh mRNA expression and also enhanced reporter gene expression in Shh(+/LacZ) mice. Further, acute T₃ treatment of cortical neuronal cultures resulted in a rapid and significant increase in Shh mRNA, suggesting direct effects. Chromatin immunoprecipitation assays performed on adult neocortex indicated enhanced histone acetylation at the Shh promoter after acute T₃ administration, providing further support that Shh is a thyroid hormone-responsive gene. Our results indicate that maternal and adult-onset perturbations of euthyroid status cause robust and region-specific changes in the Shh pathway in the embryonic and adult forebrain, implicating Shh as a possible mechanistic link for specific neurodevelopmental effects of thyroid hormone.
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Affiliation(s)
- Lynette A Desouza
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India.
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Koromilas C, Liapi C, Schulpis KH, Kalafatakis K, Zarros A, Tsakiris S. Structural and functional alterations in the hippocampus due to hypothyroidism. Metab Brain Dis 2010; 25:339-54. [PMID: 20886273 DOI: 10.1007/s11011-010-9208-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 07/02/2010] [Indexed: 12/23/2022]
Abstract
Thyroid hormones (THs) exert a broad spectrum of effects on the central nervous system (CNS). Hypothyroidism, especially during CNS development, can lead to structural and functional changes (mostly resulting in mental retardation). The hippocampus is considered as one of the most important CNS structures, while the investigation and understanding of its direct and indirect interactions with the THs could provide crucial information on the neurobiological basis of the (frequently-faced in clinical practice) hypothyroidism-induced mental retardation and neurobehavioral dysfunction. THs-deficiency during the fetal and/or the neonatal period produces deleterious effects for neural growth and development (such as reduced synaptic connectivity, delayed myelination, disturbed neuronal migration, deranged axonal projections, decreased synaptogenesis and alterations in neurotransmitters' levels). On the other hand, the adult-onset thyroid dysfunction is usually associated with neurological and behavioural abnormalities. In both cases, genomic and proteomic changes seem to occur. The aim of this review is to provide an up-to-date synopsis of the available knowledge regarding the aforementioned alterations that take place in the hippocampus due to fetal-, neonatal- or adult-onset hypothyroidism.
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Affiliation(s)
- Christos Koromilas
- Department of Pharmacology, Medical School, National & Kapodistrian University of Athens, Athens, Greece
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Tachi N, Hashimoto Y, Nawa M, Matsuoka M. TAG-1 is an inhibitor of TGFbeta2-induced neuronal death via amyloid beta precursor protein. Biochem Biophys Res Commun 2010; 394:119-25. [PMID: 20184861 DOI: 10.1016/j.bbrc.2010.02.127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 02/19/2010] [Indexed: 12/26/2022]
Abstract
Our earlier studies indicated that TGFbeta2-induced neuronal cell death by binding to the extracellular domain of amyloid beta precursor protein (APP) on the cell surface and by triggering an intracellular death signal pathway, mediated by a heterotrimeric G protein Go, Rac1/cdc42, ASK1, JNK, NADPH oxidase, and caspases in this order. Recently, transient axonal glycoprotein-1 (TAG-1), a glycophosphatidylinositol-linked protein, was identified as another natural ligand of APP. TAG-1 increases APP intracellular domain release and triggers FE65-dependent transcriptional activity in a gamma-secretase-dependent manner by binding to APP. In this study, we show that TAG-1 inhibits TGFbeta2-mediated neuronal cell death via APP by attenuating the binding of TGFbeta2 to APP in a gamma-secretase-independent manner. TAG-1 is expressed in murine hippocampal neurons at 8 weeks of age, but its expression is reduced at 8 and 20 months. These findings suggest that an age-related reduction of TAG-1 expression may predispose neurons to cell death, induced by the binding of TGFbeta2 to APP. This mechanism may contribute to the onset and the progression of Alzheimer's disease-relevant neuronal cell death.
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Affiliation(s)
- Nobuyuki Tachi
- Department of Pharmacology, Tokyo Medical University, 6-1-1 Shinjuku, Tokyo 160-8402, Japan
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15
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The gray aspects of white matter disease in multiple sclerosis. Proc Natl Acad Sci U S A 2009; 106:8083-4. [PMID: 19451620 DOI: 10.1073/pnas.0903377106] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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16
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Contactin-2/TAG-1-directed autoimmunity is identified in multiple sclerosis patients and mediates gray matter pathology in animals. Proc Natl Acad Sci U S A 2009; 106:8302-7. [PMID: 19416878 DOI: 10.1073/pnas.0901496106] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Gray matter pathology is increasingly recognized as an important feature of multiple sclerosis (MS), but the nature of the immune response that targets the gray matter is poorly understood. Starting with a proteomics approach, we identified contactin-2/transiently expressed axonal glycoprotein 1 (TAG-1) as a candidate autoantigen recognized by both autoantibodies and T helper (Th) 1/Th17 T cells in MS patients. Contactin-2 and its rat homologue, TAG-1, are expressed by various neuronal populations and sequestered in the juxtaparanodal domain of myelinated axons both at the axonal and myelin sides. The pathogenic significance of these autoimmune responses was then explored in experimental autoimmune encephalitis models in the rat. Adoptive transfer of TAG-1-specific T cells induced encephalitis characterized by a preferential inflammation of gray matter of the spinal cord and cortex. Cotransfer of TAG-1-specific T cells with a myelin oligodendrocyte glycoprotein-specific mAb generated focal perivascular demyelinating lesions in the cortex and extensive demyelination in spinal cord gray and white matter. This study identifies contactin-2 as an autoantigen targeted by T cells and autoantibodies in MS. Our findings suggest that a contactin-2-specific T-cell response contributes to the development of gray matter pathology.
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17
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Zikova M, Corlett A, Bendova Z, Pajer P, Bartunek P. DISP3, a sterol-sensing domain-containing protein that links thyroid hormone action and cholesterol metabolism. Mol Endocrinol 2009; 23:520-8. [PMID: 19179482 DOI: 10.1210/me.2008-0271] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In the body, the brain is the most cholesterol-rich organ. Despite this, remarkably little is known about the mechanisms in the brain that regulate cholesterol homeostasis. Due to the blood-brain barrier, plasma lipoproteins are unable to traverse, and instead cholesterol must be synthesized de novo from within the central nervous system. Thyroid hormone receptors, activated in response to thyroid hormone (T(3)), are known to modulate the level of serum cholesterol via complex regulatory pathways. By screening for T(3)-regulated genes we have identified Disp3, a sterol-sensing domain-containing protein that is related to the Dispatched family of proteins. Analysis by RT-PCR and immunohistochemistry demonstrated that DISP3 is predominately expressed in specific cell types of the brain, retina, and testis. Using the model of hyperthyroidism in vivo, we observed the modulation of Disp3 expression in the retina. Furthermore, in vitro analysis of Disp3 expression in cells treated with T(3) revealed both positive and negative regulation. DISP3 localizes within the endoplasmic reticulum and was further found to colocalize with cholesterol. Ectopic expression of DISP3 in fibroblasts resulted in elevated cholesterol levels combined with an altered cholesterol distribution. Given that DISP3 is highly expressed in Purkinje cells, hippocampal neurons, and retinal ganglion cells and that its overexpression results in increased cholesterol levels, it is tempting to postulate that DISP3 may contribute to cholesterol homeostasis in neural cell types. Taken together, we propose that DISP3 represents a new molecular link between thyroid hormone and cholesterol metabolism.
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Affiliation(s)
- Martina Zikova
- Department of Cell Differentiation, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
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18
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Structural requirement of TAG-1 for retinal ganglion cell axons and myelin in the mouse optic nerve. J Neurosci 2008; 28:7624-36. [PMID: 18650339 DOI: 10.1523/jneurosci.1103-08.2008] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
White matter axons organize into fascicles that grow over long distances and traverse very diverse environments. The molecular mechanisms preserving this structure of white matter axonal tracts are not well known. Here, we used the optic nerve as a model and investigated the role of TAG-1, a cell adhesion molecule expressed by retinal axons. TAG-1 was first expressed in the embryonic retinal ganglion cells (RGCs) and later in the postnatal myelin-forming cells in the optic nerve. We describe the consequences of genetic loss of Tag-1 on the developing and adult retinogeniculate tract. Tag-1-null embryos display anomalies in the caliber of RGC axons, associated with an abnormal organization of the astroglial network in the optic nerve. The contralateral projections in the lateral geniculate nucleus are expanded postnatally. In the adult, Tag-1-null mice show a loss of RGC axons, with persistent abnormalities of axonal caliber and additional cytoskeleton and myelination defects. Therefore, TAG-1 is an essential regulator of the structure of RGC axons and their surrounding glial cells in the optic nerve.
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19
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Mörtl M, Sonderegger P, Diederichs K, Welte W. The crystal structure of the ligand-binding module of human TAG-1 suggests a new mode of homophilic interaction. Protein Sci 2007; 16:2174-83. [PMID: 17766378 PMCID: PMC2204121 DOI: 10.1110/ps.072802707] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Human TAG-1 is a neural cell adhesion molecule that is crucial for the development of the nervous system during embryogenesis. It consists of six immunoglobulin-like and four fibronectin III-like domains and is anchored to the membrane by glycosylphosphatidylinositol. Herein we present the crystal structure of the four N-terminal immunoglobulin-like domains of TAG-1 (TAG-1(Ig1-4)), known to be important in heterophilic and homophilic macromolecular interactions. The contacts of neighboring molecules within the crystal were investigated. A comparison with the structure of the chicken ortholog resulted in an alternative mode for the molecular mechanism of homophilic TAG-1 interaction. This mode of TAG-1 homophilic interaction is based on dimer formation rather than formation of a molecular zipper as proposed for the chicken ortholog.
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Affiliation(s)
- Mario Mörtl
- University of Konstanz, Department of Biology, Konstanz, Germany
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20
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Goodman JH, Gilbert ME. Modest thyroid hormone insufficiency during development induces a cellular malformation in the corpus callosum: a model of cortical dysplasia. Endocrinology 2007; 148:2593-7. [PMID: 17317780 DOI: 10.1210/en.2006-1276] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
There is a growing body of evidence that subtle decreases in maternal thyroid hormone during gestation can impact fetal brain development. The present study examined the impact of graded levels of thyroid hormone insufficiency on brain development in rodents. Maternal thyroid hormone insufficiency was induced by exposing timed-pregnant dams to propylthiouracil (PTU) at doses of 0, 1, 2, 3, and 10 ppm in the drinking water from gestational d 6 through weaning on postnatal d 30. An examination of Nissl-stained sections of the brains from developmentally hypothyroid offspring killed on postnatal d 23 revealed the presence of a heretofore unreported bilateral cellular malformation, a heterotopia, positioned within the white matter of the corpus callosum of both hemispheres. Immunohistochemical techniques were used to determine that this heterotopia primarily consists of neurons born between gestational d 17-19 and exhibits a dose-dependent increase in size with decreases in thyroid hormone levels. Importantly, this structural abnormality is evident at modest levels of maternal thyroid hormone insufficiency ( approximately 45% reductions in T(4) with no change in T(3)), persists in adult offspring despite a return to normal hormonal status, and is dramatically reduced in size with prenatal thyroid hormone replacement. Developmental exposure to methimazole, another goitrogen, also induced formation of this heterotopia. Whereas the long-term consequence of this cortical malformation on brain function remains to be determined, the presence of the heterotopia underscores the critical role thyroid hormone plays in brain development during the prenatal period and provides a new model in which to study mechanisms of cortical development and cortical dysplasia.
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Affiliation(s)
- Jeffrey H Goodman
- Center for Neural Recovery and Rehabilitation Research, Helen Hayes Hospital, West Haverstraw, NY 10993, USA.
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21
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Farahvar A, Darwish NH, Sladek S, Meisami E. Marked recovery of functional metabolic activity and laminar volumes in the rat hippocampus and dentate gyrus following postnatal hypothyroid growth retardation: A quantitative cytochrome oxidase study. Exp Neurol 2007; 204:556-68. [PMID: 17307164 DOI: 10.1016/j.expneurol.2006.12.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 12/06/2006] [Accepted: 12/14/2006] [Indexed: 11/24/2022]
Abstract
Similar to cretinism in human children, absence or deficiency of thyroid hormones in rats and mice during early postnatal development results in marked retardation of brain development along with behavioral and cognitive deficits. Less is known about brain recovery from postnatal hypothyroidism. [Farahvar, A., Meisami, E., 2007. Novel two-dimensional morphometric maps and quantitative analysis reveal marked growth and structural recovery of the rat hippocampal regions from early hypothyroid retardation. Experimental Neurology.] found, by means of morphometric maps, that surface areas of hippocampal cortex and its CA1-CA4 regions which were significantly reduced in developing hypothyroid rats, show nearly complete growth recovery upon restoration of thyroid function. Here we explore the ability of hippocampal synapse-rich neuronal fiber layers to show recovery from early hypothyroid growth retardation. Rat pups were made hypothyroid from birth to day 25 (weaning) or up to young adulthood (day 90) by a treatment with the reversible goitrogen, PTU (n-propylthiouracil), in the drinking water. Recovery was induced by withdrawal of PTU at weaning and analysis of cytochrome oxidase (CytOx)-stained serial sections of the hippocampus and dentate gyrus at the ages of 25 and 90 days. CytOx stains the synapse-rich fiber layers of the hippocampal formation (HCF). Volumetric growth of molecular layer, stratum oriens and radiatum and dentate hilar region showed complete or nearly complete recovery from marked and significant growth retardation induced by early postnatal hypothyroidism. Also the reduced CytOx staining intensity in the hypothyroid rat HCF layers showed marked recovery following hormonal restoration. Results indicate remarkable growth plasticity of the HCF and ability of the synapse-rich fiber layers to show complete recovery of metabolic and functional neural activity from deleterious effects of early hypothyroidism. Mitochondrial CytOx is highly localized to the synapse-rich fiber layers of the HCF and its activity and histochemical staining intensity correlates positively with functional metabolic activity of neural tissue. Thus hippocampus and dentate gyrus neuronal fiber layers and their oxidative activity show remarkable ability to recover from the postnatal hypothyroid growth retardation. The results indicate that some brain regions are less vulnerable to early developmental insults and can recover.
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Affiliation(s)
- Arash Farahvar
- Department of Molecular and Integrative Physiology, University of Illinois, 524 Burrill Hall, 407 S. Goodwin Avenue, Urbana, IL 61801, USA
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22
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Farahvar A, Meisami E. Novel two-dimensional morphometric maps and quantitative analysis reveal marked growth and structural recovery of the rat hippocampal regions from early hypothyroid retardation. Exp Neurol 2007; 204:541-55. [PMID: 17261283 PMCID: PMC1924968 DOI: 10.1016/j.expneurol.2006.10.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Accepted: 10/23/2006] [Indexed: 11/30/2022]
Abstract
Effects of postnatal hypothyroidism and recovery from this condition on regional growth of the rat hippocampus (HC) were studied using two-dimensional (2D) foldout, morphometric maps of HC and its constituent CA1-CA4 regions. The maps were derived from unfolding serial coronal sections of the rat forebrain, consisting of the entire rostrocaudal extent of HC pyramidal cell layer in the normal control and hypothyroid weanling (P25, postnatal day 25) and young adult (P90) male rats, as well as animals allowed to recover from hypothyroid-induced growth retardation at weaning. The maps revealed novel views of HC regions for assessment of topological relationships and measurement of surface areas of the HC cortical sheet (pyramidal cell layer). In normal control P90 rats, the unfolded HC on each side extended 4 times more laterally than rostrocaudally; total HC surface area was about 40 mm(2), compared to 30 mm(2) in the weanling, indicating 35% growth from P25 to P90; CA1 took up 52% of the total HC surface area, followed by CA3 (31%) and CA2 and CA4, 8% each. Hypothyroidism resulted in significant (p<0.01) 11% and 20% reductions in the HC surface area in P25 and P90 rats, respectively; CA1 and CA4 regions suffered the most reductions while CA3 and CA2 regions the least. Recovering rats examined at P90 exhibited remarkable growth plasticity and recovery in HC regions, as evident by their near normal HC cortical surface area values, compared to age-matched controls. The 2D maps also revealed growth deficits in all HC regions of the hypothyroid rats; recovery in these parameters occurred across all dimensions, although the anterior-posterior growth was more severely affected than the mediolateral one. These results are confirmed and extended by volumetric analysis of laminar volumes of HC regions presented in a companion paper [Farahvar, A., Darwish, N., Sladek, S., Meisami, E., in press. Marked recovery of functional metabolic activity and laminar volumes in the rat hippocampus and dentate gyrus following postnatal hypothyroid growth retardation: a quantitative cytochrome oxidase study. Exp. Neurol.]. These results imply that HC regions, in contrast to whole brain, possess exceptional growth plasticity, as shown by ability to dramatically recover from early hypothyroid retardation; also 2D morphometric maps are useful tools to visualize complex and convoluted regional sheet of HC cortex and depict quantitative aspects of growth in normal and experimental conditions.
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Affiliation(s)
- Arash Farahvar
- Department of Molecular and Integrative Physiology, Medical Scholars Program, University of Illinois, 407 S. Goodwin Avenue, Urbana-Champaign, IL 61801, USA
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23
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Kirk AB. Environmental perchlorate: why it matters. Anal Chim Acta 2006; 567:4-12. [PMID: 17723372 DOI: 10.1016/j.aca.2006.03.047] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Revised: 03/09/2006] [Accepted: 03/12/2006] [Indexed: 12/30/2022]
Abstract
The only known mechanism of toxicity for perchlorate is interference with iodide uptake at the sodium-iodide symporter (NIS). The NIS translocates iodide across basolateral membranes to the thyroid gland so it can be used to form thyroid hormones (TH). NIS is also expressed in the mammary gland during lactation, so that iodide can be transferred from a mother to her child. Without adequate iodide, an infant cannot produce sufficient TH to meet its developmental needs. Effects expected from perchlorate are those that would be seen in conditions of hypothyroidism or hypothyroxinemia. The probability of a permanent adverse effect is greatest during early life, as successful neurodevelopment is TH-dependent. Study of perchlorate risk is complicated by a number of factors including thyroid status of the mother during gestation, thyroid status of the fetus, maternal and infant iodine intake, and exposure of each to other TH-disrupting chemicals. Perhaps the greatest standing issue, and the issue most relevant to the field of analytical chemistry, is the simple fact that human exposure has not been quantified. This review will summarize perchlorate's potential to adversely affect neurodevelopment. Whether current environmental exposures to perchlorate contribute to neuro-impairment is unknown. Risks posed by perchlorate must be considered in conjunction with iodine intake.
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Affiliation(s)
- Andrea B Kirk
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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24
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Mihrshahi R. The corpus callosum as an evolutionary innovation. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2006; 306:8-17. [PMID: 16116611 DOI: 10.1002/jez.b.21067] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The corpus callosum (CC) is the major interhemispheric fibre bundle in the eutherian brain and has been described as a true evolutionary innovation. This paper reviews the current literature with regard to functional, developmental and genetic concepts that may help elucidate the evolutionary origin of this structure. It has been suggested that the CC arose in the eutherian brain as a more direct and, therefore, more effective system for the interhemispheric integration of topographically organized sensory cortices than the anterior commissure (AC) and hippocampal commissure (HC) already present in nonplacental mammals. It can also be argued, however, that the ability of the CC to integrate the newly evolving motor cortices of placental mammals may have played a role in the evolutionary fixation of this structure. Investigations into the developmental mechanism involved in the formation of the CC and their underlying patterns of gene expression make it possible to formulate a tentative hypothesis about the evolutionary origin of this commissure. This paper suggests that changes in the developmental patterns of the expression of certain regulatory genes may have allowed a first group of callosal pioneering axons to cross the cortical midline. These pioneering fibres may have used the axons of the HC to find their way across the midline. Additional callosal fibres may then have fasciculated with these pioneers. Once the CC had formed in this way, more complex systems of axonal guidance may have evolved over time, thus enabling a gradual increase in the size and complexity of the CC.
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Affiliation(s)
- Robin Mihrshahi
- Department of Biological Sciences, Macquarie University, Sydney, North Ryde 2109, Australia.
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Poguet AL, Legrand C, Feng X, Yen PM, Meltzer P, Samarut J, Flamant F. Microarray analysis of knockout mice identifies cyclin D2 as a possible mediator for the action of thyroid hormone during the postnatal development of the cerebellum. Dev Biol 2003; 254:188-99. [PMID: 12591240 DOI: 10.1016/s0012-1606(02)00039-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thyroid hormone is a major regulator of postnatal brain development, but the precise molecular mechanisms underlying its action in this organ remain poorly understood. We used microarray analysis to identify new target genes in brain. Thyroid hormone treatment of hypothyroid Pax8(-/-) knockout mice, which lack thyroid follicular cells, had a very limited global effect on brain transcripts. This analysis mainly identified cyclin D2 as a new thyroid hormone target gene in the cerebellum of hypothyroid mice. Thyroid hormone receptor (TRalpha and/or TRbeta) knockout mice studies provided further genetic evidence that cyclin D2 is likely to mediate the antiapoptotic effect exerted by thyroid hormone on the cerebellum external granular layer neuroblasts but that this transcriptional activation is not directly exerted by the thyroid hormone receptors.
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Affiliation(s)
- Anne-Lise Poguet
- Laboratoire de Biologie Moléculaire et Cellulaire de l'Ecole Normale Supérieure de Lyon UMR CNRS 5665 LA INRA913, 46 Allée d'ltalie 69364 Lyon CEDEX07France
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26
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Abstract
1. In addition to its role in cellular metabolic activity, thyroid hormone (TH) is critically involved in growth, development, and function of the central nervous system. In the brain, as in other structures, TH is described to exert its major action by the binding of L-3,5,3'-triiodothyronine (T3), considered as the bioactive form of the hormone, to nuclear thyroid hormone receptors (TR) that function as ligand-dependent transcription factors. 2. The transcription of numerous brain genes was indeed shown to be positively or negatively regulated by TH, turning these TR-mediated effects one explanation for the physiological effects of TH. In this context, the knowledge from TR-knockout studies provides some surprising results, since neonatal hypothyroidism is associated to more significant abnormalities than is TR deficiency. Some (nonexclusive) hypotheses include a permissive effect of TH, allowing derepression of unliganded-TR effects and non-TR-mediated effects of the hormone, further emphasizing the importance of a controlled accessibility of neural cells to TH. 3. On the other hand, T3 was demonstrated to directly act not only on neuronal but also on glial cells proliferation and differentiation, contributing to the harmonious development of the brain. Interestingly, in addition to these direct actions on neuronal and glial cells, several lines of evidence, notably developped in our laboratory, point out the role of thyroid hormone in neuronal-glial interactions.
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Affiliation(s)
- Sandra König
- Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21949-590, Rio de Janeiro, Brazil
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