Genetic and environmental influences on cortical mean diffusivity.
Genetic and environmental influences on cortical mean diffusivity.
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DOI：
10.1016/j.neuroimage.2016.11.032
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发表时间：
2017-02-01
期刊：
影响因子：
5.7
通讯作者：
Kremen WS
中科院分区：
文献类型：
--
作者：
Elman JA;Panizzon MS;Hagler DJ Jr;Fennema-Notestine C;Eyler LT;Gillespie NA;Neale MC;Lyons MJ;Franz CE;McEvoy LK;Dale AM;Kremen WS
磁共振成像（MRI）已成为早期检测年龄相关和神经病理脑变化的重要工具。最近的研究表明，扩散MRI扫描产生的皮层灰质平均扩散率（MD）的变化可能有助于检测阿尔茨海默病（AD）的早期影响，并且这些变化可能比标准结构MRI测量（如皮层厚度）相关的改变更早被检测到。因此，由于其潜在的临床相关性，我们研究了遗传和环境对中年男性皮质MD的影响，为这一测量的生物学相关性提供支持，并指导未来的基因关联研究。目前尚不清楚皮质MD的个体差异是否反映了其他MRI检测到的类似的神经解剖学变异性，或者是否捕获了独特的特征。例如，皮质MD的变异性可能反映了通常通过皮质厚度测量的形态学变异性。皮质MD在个体间的差异也可能源于贯穿皮质地幔的髓鞘纤维的破坏。因此，我们研究了遗传对皮质MD变异的影响是否与影响皮质带下皮层厚度和白质MD的影响相同或不同。单变量双胞胎分析表明，皮质MD在大多数大脑区域是可遗传的；区域遗传率估计的平均值从扣带皮层的0.38到枕叶皮层的0.66不等，与其他大脑MRI测量的遗传率一致。三变量分析发现，虽然皮质MD与其他两种测量方法之间存在一些共同的遗传变异，但这种重叠并不完全（即相关性在统计上与1不同）。大量不同的遗传变异影响皮质MD的个体间变异性；因此，该方法可为神经退行性疾病的进一步研究和基因关联研究提供参考。
Magnetic resonance imaging (MRI) has become an important tool in the early detection of age-related and neuropathological brain changes. Recent studies suggest that changes in mean diffusivity (MD) of cortical gray matter derived from diffusion MRI scans may be useful in detecting early effects of Alzheimer’s disease (AD), and that these changes may be detected earlier than alterations associated with standard structural MRI measures such as cortical thickness. Thus, due to its potential clinical relevance, we examined the genetic and environmental influences on cortical MD in middle-aged men to provide support for the biological relevance of this measure and to guide future gene association studies. It is not clear whether individual differences in cortical MD reflect neuroanatomical variability similarly detected by other MRI measures, or whether unique features are captured. For instance, variability in cortical MD may reflect morphological variability more commonly measured by cortical thickness. Differences among individuals in cortical MD may also arise from breakdowns in myelinated fibers running through the cortical mantle. Thus, we investigated whether genetic influences on variation in cortical MD are the same or different from those influencing cortical thickness and MD of white matter (WM) subjacent to the cortical ribbon. Univariate twin analyses indicated that cortical MD is heritable in the majority of brain regions; the average of regional heritability estimates ranged from 0.38 in the cingulate cortex to 0.66 in the occipital cortex, consistent with the heritability of other MRI measures of the brain. Trivariate analyses found that, while there was some shared genetic variance between cortical MD and each of the other two measures, this overlap was not complete (i.e., the correlation was statistically different from 1). A significant amount of distinct genetic variance influences inter-individual variability in cortical MD; therefore, this measure could be useful for further investigation in studies of neurodegenerative diseases and gene association studies.