ISSN:1080-4013    

DOI:10.1002/mrdd.20081

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractMental retardation affects 2 to 3% of the US population. It is defined by broad criteria, including significantly subaverage intelligence, onset by age 18, and impaired function in a group of adaptive skills. A myriad of genetic and environmental causes have been described, but for approximately half of individuals diagnosed with mental retardation the molecular basis remains unknown. Genomic microarrays, also called array comparative genomic hybridization (array CGH), represent one of several novel technologies that allow the detection of chromosomal abnormalities, such as microdeletions and microduplications, in a rapid, high throughput fashion from genomic DNA samples. In one early application of this technology, genomic microarrays have been used to characterize the extent of chromosomal changes in a group of patients diagnosed with one particular type of disorder that causes mental retardation, such as deletion 1p36 syndrome. In another application, DNA samples from individuals with idiopathic mental retardation have been assayed to scan the entire genome in attempts to identify chromosomal changes. Genomic microarrays offer both a genome‐wide perspective of chromosomal aberrations as well as higher resolution (to the level of approximately one megabase) compared to alternative available technologies. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;11:279

ISSN:1080-4013    

DOI:10.1002/mrdd.20082

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractDrosophila melanogasteris emerging as a valuable genetic model system for the study of mental retardation (MR). MR genes are remarkably similar between humans and fruit flies. Cognitive behavioral assays can detect reductions in learning and memory in flies with mutations in MR genes. Neuroanatomical methods, including some at single‐neuron resolution, are helping to reveal the cellular bases of faulty brain development caused by MR gene mutations.Drosophila fragile X mental retardation 1(dfmr1) is the fly counterpart of the human gene whose malfunction causes fragile X syndrome. Research on the fly gene is leading the field in molecular mechanisms of the gene product's biological function and in pharmacological rescue of brain and behavioral phenotypes. Future work holds the promise of using genetic pathway analysis and primary neuronal culture methods inDrosophilaas tools for drug discovery for a wide range of MR and related disorders. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;11:286

ISSN:1080-4013    

DOI:10.1002/mrdd.20083

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractThe human and mouse genome projects elucidated the sequence and position map of innumerous genes expressed in the central nervous system (CNS), advancing our ability to manipulate these sequences and create models to investigate regulation of gene expression and function. In this article, we reviewed gene targeting methodologies with emphasis on applications to CNS development and neurodevelopmental disorders. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;11:295

ISSN:1080-4013    

DOI:10.1002/mrdd.20084

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractStudies on human patients and animal models of disease have shown that disruptions in prenatal and early postnatal brain development are a root cause of mental retardation. Since proper brain development is achieved by a strict spatiotemporal control of neurogenesis, cell migration, and patterning of synapses, abnormalities in one or more of these events during prenatal development can lead to cognitive dysfunction after birth. Many of underlying causes of mental retardation must therefore be studied in developing brains. To aid in this research, live imaging using laser scanning microscopy (LSM) has recently allowed neuroscientists to delve deeply into the complex three‐dimensional environment of the living brain to record dynamic cellular events over time. This review will highlight recent examples of how LSM is being applied to elucidate both normal and abnormal cortical development. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;11:303

ISSN:1080-4013    

DOI:10.1002/mrdd.20088

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractNew knowledge of the perceptual, discriminative, and memory capabilities of very young infants has opened the door to further evaluation of these abilities in infants who have risk factors for cognitive impairments. A neurophysiologic technique that has been very useful in this regard is the recording of event‐related potentials (ERPs). The event‐related potential (ERP) technique is widely used by cognitive neuroscientists to study cognitive abilities such as discrimination, attention, and memory. This method has many attractive attributes for use in infants and children as it is relatively inexpensive, does not require sedation, has excellent temporal resolution, and can be used to evaluate early cognitive development in preverbal infants with limited behavioral repertories. In healthy infants and children, ERPs have been used to gain a further understanding of early cognitive development and the effect of experience on brain function. Recently, ERPs have been used to elucidate atypical memory development in infants of diabetic mothers, difficulties with perception and discrimination of speech sounds in infants at risk for dyslexia, and multiple areas of cognitive differences in extremely premature infants. Atypical findings seen in high‐risk infants have correlated with later cognitive outcomes, but the sensitivity and specificity of the technique has not been studied, and thus evaluation of individual infants is not possible at this time. With further research, this technique may be very useful in identifying children with cognitive deficits during infancy. Because even young infants can be examined with ERPs, this technique is likely to be helpful in the development of focused early intervention programs used to improve cognitive function in high‐risk infants and toddlers. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;

ISSN:1080-4013    

DOI:10.1002/mrdd.20085

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractPositron emission tomography (PET) is a technique that enables imaging of the distribution of radiolabeled tracers designed to track biochemical and molecular processes in the body after intravenous injection or inhalation. New strategies for the use of radiolabeled tracers hold potential for imaging gene expression in the brain during development and following interventions. In addition, PET may be key in identifying the physiological consequences of gene mutations associated with mental retardation. The development of high spatial resolution microPET scanners for imaging of rodents provides a means for longitudinal study of transgenic mouse models of genetic disorders associated with mental retardation. In this review, we describe PET methodology, illustrate how PET can be used to delineate biochemical changes during brain development, and provide examples of how PET has been applied to study brain glucose metabolism in Rett syndrome, serotonin synthesis in autism, and GABAAreceptors in Angelman's syndrome and Prader–Willi syndrome. Future application of PET scanning in the study of mental retardation might include measurements of brain protein synthesis in fragile X syndrome and tuberous sclerosis complex, two common conditions associated with mental retardation in which cellular mechanisms involve dysregulation of protein synthesis. Mental retardation results in life‐long disability, and application of new PET technologies holds promise for a better understanding of the biological underpinnings of mental retardation, with the potential to uncover new treatment options. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;11:3

ISSN:1080-4013    

DOI:10.1002/mrdd.20086

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractStudying the biological mechanisms underlying mental retardation and developmental disabilities (MR/DD) is a very complex task. This is due to the wide heterogeneity of etiologies and pathways that lead to MR/DD. Breakthroughs in genetics and molecular biology and the development of sophisticated brain imaging techniques during the last decades have facilitated the emergence of a field called Behavioral Neurogenetics. Behavioral Neurogenetics focuses on studying genetic diseases with known etiologies that are manifested by unique cognitive and behavioral phenotypes. In this review, we describe the principles of magnetic resonance imaging (MRI) techniques, including structural MRI, functional MRI, and diffusion tensor imaging (DTI), and how they are implemented in the study of Williams (WS), velocardiofacial (VCFS), and fragile X (FXS) syndromes. From WS we learn that dorsal stream abnormalities can be associated with visuospatial deficits; VCFS is a model for exploring the molecular and brain pathways that lead to psychiatric disorders for which subjects with MR/DD are at increased risk; and finally, findings from multimodal imaging techniques show that aberrant frontal–striatal connections are implicated in the executive function and attentional deficits of subjects with FXS. By deciphering the molecular pathways and brain structure and function associated with cognitive deficits, we will gain a better understanding of the pathophysiology of MR/DD, which will eventually make possible more specific treatments for this population. © 2005 Wiley‐Liss, Inc. MRDD Research Reviews 2005;11:331

ISSN:1080-4013    

DOI:10.1002/mrdd.20089

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY

摘要:

AbstractAs researchers have examined the so‐called “behavioral phenotypes” of different genetic mental retardation conditions, the measurement of behavior becomes increasingly important. From earlier, more global examinations of noteworthy behaviors or profiles, recent researchers have moved from reliance on a single, all‐encompassing questionnaire to more multimethod, multireporter approaches. This paper summarizes strengths and weaknesses in utilizing parent‐report questionnaires and checklists; psychiatric nosology and specific psychiatric questionnaires; observational studies; reports from individuals with mental retardation themselves; profile analyses of psychometric test and subtest scores; and “grouping” analyses of items (factor analysis) and people (cluster analysis). Although we advocate a mixture of approaches to behavioral assessment, in future work researchers will require more theoretically driven methods for studying behavior, greater acknowledgment that the child's behavior is simply one event in ongoing interactions–transactions with other people, and more attention to age‐related changes in behavioral phenotypes. © 2005 Wiley‐Liss, Inc. MRDD Research Rev

ISSN:1080-4013    

DOI:10.1002/mrdd.20087

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2005

数据来源: WILEY