251
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Molloy CA, Keddache M, Martin LJ. Evidence for linkage on 21q and 7q in a subset of autism characterized by developmental regression. Mol Psychiatry 2005; 10:741-6. [PMID: 15940295 DOI: 10.1038/sj.mp.4001691] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Autism is a pervasive developmental disorder with a strong genetic component. While candidate regions of the genome have been identified, location of genes conferring susceptibility to autism has been hindered by the heterogeneity within this clinically defined disorder, and the likely contribution of many genes of weak effect. Subsetting samples on the basis of distinct, nondiagnostic clinical features has been recommended to decrease sample heterogeneity. In this study, linkage analysis was performed on a subset of families in the database of the Autism Genetic Resource Exchange (AGRE). This set of autism-affected relative pairs (n=34) was also concordant for a history of developmental regression as measured by the Autism Diagnostic Interview-Revised (ADI-R). In this sample, a maximum multipoint LOD score of 3.4 under the dominant mode of inheritance and an NPL score of 3.0 (P=1.3 x 10(-3)) were observed on chromosome 21 near D21S1437. On chromosome 7 near D7S483 a LOD score of 2.0 under the dominant mode of inheritance and an NPL score of 3.7 (P=7.9 x 10(-5)) were observed. Genetic elements in these regions of 21q and 7q are likely to confer susceptibility to autism or modify the disease presentation in a subgroup of children characterized by a history of developmental regression.
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Affiliation(s)
- C A Molloy
- Center for Epidemiology and Biostatistics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Department of Pediatrics, Cincinnati, OH 45229-3039, USA.
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252
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Cobos I, Calcagnotto ME, Vilaythong AJ, Thwin MT, Noebels JL, Baraban SC, Rubenstein JLR. Mice lacking Dlx1 show subtype-specific loss of interneurons, reduced inhibition and epilepsy. Nat Neurosci 2005; 8:1059-68. [PMID: 16007083 DOI: 10.1038/nn1499] [Citation(s) in RCA: 386] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Accepted: 06/13/2005] [Indexed: 11/08/2022]
Abstract
Dlx homeodomain transcription factors are essential during embryonic development for the production of forebrain GABAergic interneurons. Here we show that Dlx1 is also required for regulating the functional longevity of cortical and hippocampal interneurons in the adult brain. We demonstrate preferential Dlx1 expression in a subset of cortical and hippocampal interneurons which, in postnatal Dlx1 mutants, show a time-dependent reduction in number. This reduction preferentially affects calretinin(+) (bipolar cells) and somatostatin(+) subtypes (for example, bitufted cells), whereas parvalbumin(+) subpopulations (basket cells and chandelier cells) seem to be unaffected. Cell transplantation analysis demonstrates that interneuron loss reflects cell-autonomous functions of Dlx1. The decrease in the number of interneurons was associated with a reduction of GABA-mediated inhibitory postsynaptic current in neocortex and hippocampus in vitro and cortical dysrhythmia in vivo. Dlx1 mutant mice show generalized electrographic seizures and histological evidence of seizure-induced reorganization, linking the Dlx1 mutation to delayed-onset epilepsy associated with interneuron loss.
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Affiliation(s)
- Inma Cobos
- Nina Ireland Laboratory of Developmental Neurobiology, Department of Psychiatry, University of California San Francisco, San Francisco, California 94158, USA.
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253
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Redcay E, Courchesne E. When is the brain enlarged in autism? A meta-analysis of all brain size reports. Biol Psychiatry 2005; 58:1-9. [PMID: 15935993 DOI: 10.1016/j.biopsych.2005.03.026] [Citation(s) in RCA: 381] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 02/17/2005] [Accepted: 03/16/2005] [Indexed: 11/15/2022]
Abstract
BACKGROUND Multiple studies have reported increased brain size in autism, while others have found no difference from normal. These conflicting results may be due to a lack of accounting for age-related changes in brain enlargement, use of small sample sizes, or differences in data acquisition methods. METHODS Reports of autism head circumference (HC), magnetic resonance imaging (MRI), and post-mortem brain weight (BW) that met specific criteria were identified and analyzed. Percent difference from normal values (%Diff) and standardized mean differences (SMD) were calculated to compare brain size across studies and measurement methods. Curve fitting, analysis of variance, and heterogeneity analyses were applied to assay the effects of age and measurement type on reported brain size in autism. RESULTS A fitted curve of HC and MRI %Diff values from 15 studies revealed a largely consistent pattern of brain size changes. Specifically, brain size in autism was slightly reduced at birth, dramatically increased within the first year of life, but then plateaued so that by adulthood the majority of cases were within normal range. Analysis of variance of MRI and post-mortem %Diff values by age group (young child, older child, adult) and measurement type (MRI, BW) revealed a significant main effect of both age and measurement type, with the youngest ages (2-5) showing the greatest deviation from normal. Random effects heterogeneity analysis revealed a significant effect of age on HC and MRI SMD. CONCLUSIONS These findings reveal a period of pathological brain growth and arrest in autism that is largely restricted to the first years of life, before the typical age of clinical identification. Study of the older autistic brain, thus, reflects the outcome, rather than the process, of pathology. Future research focusing on this early process of brain pathology will likely be critical to elucidate the etiology of autism.
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Affiliation(s)
- Elizabeth Redcay
- Department of Psychology, University of California, San Diego, USA.
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254
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Abstract
Advances in defining mechanisms of cortical development have been paralleled in recent years by an intense interest in translating these findings into greater insight of both childhood- and adult-onset cognitive and mental health disorders of developmental etiology. Successful integration of basic and clinical findings have been applied to monogenic disorders. The greater challenge lies in studying cortical development in the context of gene x environment interactions, which underlie the pathogenesis of the most common neurodevelopmental disorders. This can occur through an improved delineation of pathophysiological characteristics unique to specific complex disorders and the application of this information to the refinement of the most relevant model systems.
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Affiliation(s)
- Pat Levitt
- Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37203, USA.
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255
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Pozas E, Ibáñez CF. GDNF and GFRalpha1 promote differentiation and tangential migration of cortical GABAergic neurons. Neuron 2005; 45:701-13. [PMID: 15748846 DOI: 10.1016/j.neuron.2005.01.043] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Revised: 11/05/2004] [Accepted: 01/27/2005] [Indexed: 12/17/2022]
Abstract
Cortical GABAergic neurons are generated in the ventral telencephalon and migrate dorsally into the cortex following a tangential path. GDNF signaling via GFRalpha1 was found to promote the differentiation of ventral precursors into GABAergic cells, enhancing their neuronal morphology and motility. GDNF stimulated axonal growth in cortical GABAergic neurons and acted as a potent chemoattractant of GABAergic cells. These effects required GFRalpha1 but neither RET nor NCAM, the two transmembrane signaling receptors known for GDNF. Mutant mice lacking GDNF or GFRalpha1, but neither RET nor NCAM, showed reduced numbers of GABAergic cells in the cerebral cortex and hippocampus. We conclude that one of the normal functions of GDNF signaling via GFRalpha1 in the developing brain is to promote the differentiation and migration of cortical GABAergic neurons. The lack of involvement of RET or NCAM in these processes suggests the existence of additional transmembrane effectors for GDNF.
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Affiliation(s)
- Esther Pozas
- Division of Molecular Neurobiology, Department of Neuroscience, Karolinska Institute, S-17177 Stockholm, Sweden.
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256
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Abstract
Autism is a complex, behaviorally defined, developmental brain disorder with an estimated prevalence of 1 in 1,000. It is now clear that autism is not a disease, but a syndrome with a strong genetic component. The etiology of autism is poorly defined both at the cellular and the molecular levels. Based on the fact that seizure activity is frequently associated with autism and that abnormal evoked potentials have been observed in autistic individuals in response to tasks that require attention, several investigators have recently proposed that autism might be caused by an imbalance between excitation and inhibition in key neural systems including the cortex. Despite considerable ongoing effort toward the identification of chromosome regions affected in autism and the characterization of many potential gene candidates, only a few genes have been reproducibly shown to display specific mutations that segregate with autism, likely because of the complex polygenic nature of this syndrome. Among those, several candidate genes have been shown to control the early patterning and/or the late synaptic maturation of specific neuronal subpopulations controlling the balance between excitation and inhibition in the developing cortex and cerebellum. In the present article, we review our current understanding of the developmental mechanisms patterning the balance between excitation and inhibition in the context of the neurobiology of autism.
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MESH Headings
- Autistic Disorder/genetics
- Autistic Disorder/metabolism
- Autistic Disorder/physiopathology
- Brain/abnormalities
- Brain/metabolism
- Brain/physiopathology
- Brain Stem/abnormalities
- Brain Stem/metabolism
- Brain Stem/physiopathology
- Cerebellum/abnormalities
- Cerebellum/metabolism
- Cerebellum/physiopathology
- Chromosomes, Human, Pair 15/genetics
- Chromosomes, Human, Pair 16/genetics
- Chromosomes, Human, Pair 17/genetics
- Chromosomes, Human, Pair 19/genetics
- Chromosomes, Human, Pair 20/genetics
- Gene Expression/genetics
- Genetic Markers
- Glutamic Acid/metabolism
- Humans
- Magnetic Resonance Imaging
- gamma-Aminobutyric Acid/metabolism
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Affiliation(s)
- Franck Polleux
- Department of Pharmacology-Neuroscience Center, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA.
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257
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Ponten H, Sönniksen K, Abrahamsson T, Waters N, Gustafsson B, Hanse E, Groc L. Behavioral and neurochemical repercussions of hippocampal network activity blockade during the neonatal period. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 155:81-6. [PMID: 15763278 DOI: 10.1016/j.devbrainres.2004.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 12/21/2004] [Accepted: 12/22/2004] [Indexed: 11/17/2022]
Abstract
Early destruction of the ventral hippocampus from postnatal day 7 (P7) has been shown to induce behavioral alterations in post-pubertal rats, similar to those observed in models for schizophrenia. Using a single injection of tetanus toxin into the ventral hippocampus at P1, we tested the consequences of an early neonatal activity deprivation (<P7) on behavioral and neurochemical parameters of pre- and post-pubertal rats. We found no significant differences in either behavioral or biochemical pattern, indicating that an early neonate neural activity blockade does not induce behavioral alterations in pre- and post-puberty rats.
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Affiliation(s)
- Henrik Ponten
- Department of Pharmacology, Göteborg University, Sweden
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258
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Mataga N, Mizuguchi Y, Hensch TK. Experience-dependent pruning of dendritic spines in visual cortex by tissue plasminogen activator. Neuron 2005; 44:1031-41. [PMID: 15603745 DOI: 10.1016/j.neuron.2004.11.028] [Citation(s) in RCA: 294] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2004] [Revised: 09/13/2004] [Accepted: 10/19/2004] [Indexed: 11/27/2022]
Abstract
Sensory experience physically rewires the brain in early postnatal life through unknown processes. Here, we identify a robust anatomical consequence of monocular deprivation (MD) in layer II/III of visual cortex that corresponds to the rapid, functional loss of responsiveness preceding any changes in axonal input. Protrusions on pyramidal cell apical dendrites increased steadily after eye opening, but were transiently lost through competitive mechanisms after brief MD only during the physiological critical period. Proteolysis by tissue-type plasminogen activator (tPA) conversely declined with age and increased with MD only in young mice. Targeted disruption of tPA release or its upstream regulation by glutamic acid decarboxylase (GAD65) prevented MD-induced spine loss that was pharmacologically rescued concomitant with critical period plasticity. An extracellular mechanism for structural remodeling that is limited to the binocular zone upon proper detection of competing inputs thus links early sensory experience to visual function.
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Affiliation(s)
- Nobuko Mataga
- Laboratory for Neuronal Circuit Development, Institute of Physical and Chemical Research (RIKEN), Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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259
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Davies W, Isles AR, Wilkinson LS. Imprinted gene expression in the brain. Neurosci Biobehav Rev 2005; 29:421-30. [PMID: 15820547 DOI: 10.1016/j.neubiorev.2004.11.007] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Revised: 11/18/2004] [Accepted: 11/18/2004] [Indexed: 11/28/2022]
Abstract
In normal mammals, autosomal genes are present in duplicate (i.e. two alleles), one inherited from the father, and one from the mother. For the majority of genes both alleles are transcribed (or expressed) equally. However, for a small subset of genes, known as imprinted genes, only one allele is expressed in a parent-of-origin dependent manner (note that the 'imprint' here refers to the epigenetic mechanism through which one allele is silenced, and is completely unrelated to classical 'filial imprinting' manifest at the behavioural level). Thus, for some imprinted genes expression is only (or predominantly) seen from the paternally inherited allele, whilst for the remainder, expression is only observed from the maternally inherited allele. Early work on this class of genes highlighted their importance in gross developmental and growth phenotypes. Recent studies in mouse models and humans have emphasised their contribution to brain function and behaviour. In this article, we review the literature concerning the expression of imprinted genes in the brain. In particular, we attempt to define emerging organisation themes, especially in terms of the direction of imprinting (i.e. maternal or paternal expression). We also emphasise the likely role of imprinted genes in neurodevelopment. We end by pointing out that, so far as discerning the precise functions of imprinted genes in the brain is concerned, there are currently more questions than answers; ranging from the extent to which imprinted genes might contribute to common mental disorders, to wider issues related to how easily the new data on brain may be accommodated within the dominant theory regarding the origins and maintenance of imprinting, which pits the maternal and paternal genomes against each other in an evolutionary battle of the sexes.
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Affiliation(s)
- William Davies
- Neurobiology and Developmental Genetics Programmes, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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260
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Dykens EM, Sutcliffe JS, Levitt P. Autism and 15q11-q13 disorders: Behavioral, genetic, and pathophysiological issues. ACTA ACUST UNITED AC 2005; 10:284-91. [PMID: 15666333 DOI: 10.1002/mrdd.20042] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
New insights into biological factors that underlie autism may be gained by comparing autism to other neurodevelopmental disorders that have autistic features and relatively well-delineated genetic etiologies or neurobiological findings. This review moves beyond global diagnoses of autism and instead uses an endophenotypic approach to compare specific clusters of autistic symptomatology to features of chromosome 15q11-q13 disorders. Paternally or maternally derived deficiencies of 15q11-q13 result in Prader-Willi or Angelman syndromes, and we first use a global approach to review potential autism susceptibility genes in the 15q11-q13 region. We then use a more trait-based approach to suggest possible ties between specific phenotypic characteristics of autism and Prader-Willi syndrome, namely savant-like skills. We conclude with insights from pathophysiological studies that implicate altered development of specific neuron types and circuits in the cerebral cortex as part of the pathophysiological processes associated with autism and mental retardation.
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Affiliation(s)
- Elisabeth M Dykens
- Department of Psychology and Human Development, Vanderbilt Kennedy Center for Research on Human Development, 230 Appleton Place, Peabody Box 40, Nashville, TN 37203, USA.
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261
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Eagleson KL, Bonnin A, Levitt P. Region- and age-specific deficits in γ-aminobutyric acidergic neuron development in the telencephalon of theuPAR-/- mouse. J Comp Neurol 2005; 489:449-66. [PMID: 16025458 DOI: 10.1002/cne.20647] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We have previously shown that in adult mice with a null mutation in the urokinase-type plasminogen activator receptor (uPAR) gene, maintained on a C57BL/6J/129Sv background, there is a selective loss of GABAergic interneurons in anterior cingulate and parietal cortex, with the parvalbumin-expressing subpopulation preferentially affected. Here, we performed a more detailed anatomical analysis of uPAR(-/-) mutation on the congenic C57BL/6J background. With glutamic acid decarboxylase-67 and gamma-aminobutyric acid (GABA) immunostaining, there is a similar region-selective loss of cortical interneurons in the congenic uPAR(-/-) mice from the earliest age examined (P21). In contrast, the loss of parvalbumin-immunoreactive cells is observed only in adult cortex, and the extent of this loss is less than in the mixed background. Moreover, earlier in development, although there are normal numbers of parvalbumin cells in the uPAR(-/-) cortex, fewer cells coexpress GABA, suggesting that the parvalbumin subpopulation migrates appropriately to the cortex, but does not differentiate normally. Among the other forebrain regions examined, only the adult hippocampus shows a loss of GABAergic interneurons, although the somatostatin, rather than the parvalbumin, subpopulation contributes to this loss. The data suggest that uPAR function is necessary for the normal development of a subpopulation of GABAergic neurons in the telencephalon. It is likely that the late-onset parvalbumin phenotype is due to the effects of an altered local environment on selectively vulnerable neurons and that the extent of this loss is strain dependent. Thus, an interplay between complex genetic factors and the environment may influence the phenotypic impact of the uPAR mutation both pre- and postnatally.
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Affiliation(s)
- Kathie L Eagleson
- Vanderbilt Kennedy Center for Research on Human Development; Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, USA.
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262
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Legaz I, Olmos L, Real MA, Guirado S, Dávila JC, Medina L. Development of neurons and fibers containing calcium binding proteins in the pallial amygdala of mouse, with special emphasis on those of the basolateral amygdalar complex. J Comp Neurol 2005; 488:492-513. [PMID: 15973681 DOI: 10.1002/cne.20608] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We studied the development of neurons and fibers containing calbindin, calretinin, and parvalbumin in the mouse pallial amygdala, with special emphasis on those of the basolateral amygdalar complex. Numerous calbindin-immunoreactive (CB+) cells were observed in the incipient basolateral amygdalar complex and cortical amygdalar area from E13.5. At E16.5, CB+ cells became more abundant in the lateral and basolateral nuclei than in the basomedial nucleus, showing a pattern very similar to that of gamma-aminobutyric acid (GABA)ergic neurons. Many CB+ cells observed in the pallial amygdala appeared to originate in the anterior entopeduncular area/ganglionic eminences of the subpallium. The density of CB+ cells gradually increased in the pallial amygdala until the first postnatal week and appeared to decrease later, coinciding with the postnatal appearance of parvalbumin cells and raising the possibility of a partial phenotypic shift. Calretinin (CR) immunoreactivity could be observed in a few cells and fibers in the pallial amygdala at E14.5, and by E16.5 it became a good marker of the different nuclei of the basolateral amygdalar complex. Numerous CB+ and CR+ varicosities, part of which have an intrinsic origin, were observed in the basolateral amygdalar complex from E16.5, and some surrounded unstained perikarya and/or processes before birth, indicating an early formation of inhibitory networks. Each calcium binding protein showed a distinct spatiotemporal expression pattern of development in the mouse pallial amygdala. Any alteration in the development of neurons and fibers containing calcium binding proteins of the pallial amygdala may result in important disorders of emotional and social behavior.
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Affiliation(s)
- Isabel Legaz
- Department of Human Anatomy, Faculty of Medicine, University of Murcia, 30100 Murcia, Spain
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