Ultrasound and MR Imaging of Mouse Brain Development.

目前正在开发基因工程小鼠，用于大脑发育和一系列神经发育疾病的体内研究。事实上，明确的突变小鼠对于确定受影响的遗传途径和解决发育性大脑疾病的潜在细胞和分子基础至关重要。这些努力一直缺乏有效的体内成像方法，可以用于研究神经发育障碍的小鼠模型，特别是在疾病首次出现的出生后早期阶段，大脑结构和功能可能发生最大的变化。因此，一个主要的挑战是开发和验证体内成像技术，该技术可以检测和监测发育中的小鼠大脑结构和功能的早期变化。我们已经建立了定量的在体锰(Mn)增强磁共振成像(MEMRI)方法来分析出生后早期的小鼠大脑，表明MEMRI为揭示出生后早期小鼠脑内的多个核团和轴索提供了一种非常敏感的方法。我们的实验室和其他实验室的结果已经证明了MEMRI在评估神经活动和连通性方面的实用性。这些新的发现现在指出了MEMRI在体内检测和定量分析发育中的小鼠大脑功能回路的潜力。我们还发现二价金属转运蛋白DMT1可以作为MEMRI的有效报告基因。我们现在建议开发和测试DMT1表达与MEMRI的组合，以提供一种精确的体内方法来分析小鼠大脑的功能连接，从电路首次建立的关键新生阶段开始。我们将在中后脑(MHB)基因积聚(EN1和EN2)和Fgf17突变的小鼠身上测试这项新的成像技术，这些基因具有形态和功能的小脑和中脑表型。最近的证据还表明，en和Fgf17突变小鼠在MHb回路中都存在缺陷。因此，我们将使用DMT1-MEMRI来研究这些小鼠在出生后大脑发育的关键时期的MHB电路。该项目的具体目标是：1)确定野生型(WT)、EN和Fgf17突变小鼠定义的核中正常阶段依赖的MEMRI强度；2)利用DMT1对定义的核进行基因标记，用于中脑和小脑回路的MEMRI分析；以及3)使用DMT1-MEMRI分析WT、EN和Fgf17突变小鼠在功能电路方面的差异。这项研究具有很高的潜力，可以建立一种创新的、由基因控制的MEMRI形式，用于在体分析发育中的小鼠大脑电路，为分析各种神经发育障碍的小鼠模型提供关键的新工具，这些疾病包括小脑发育不良综合征(如Joubert和Dandy-Walker综合征)、自闭症谱系障碍和精神分裂症。

Genetically-engineered mice are currently being developed for in vivo studies of brain development and a wide range of neurodevelopmental diseases. Indeed, defined mutant mice have been critical for identifying the affected genetic pathways and addressing the underlying cellular and molecular basis of developmental brain diseases. Lacking in these efforts have been effective in vivo imaging methods that can be used to study mouse models of neurodevelopmental disorders, especially during early postnatal stages when disease is first manifested, and the greatest changes in brain structure and function are likely to occur. A major challenge is therefore to develop and validate in vivo imaging techniques that can detect and monitor early changes in brain structure and function in the developing mouse brain. We have established quantitative, in vivo manganese (Mn)-enhanced MRI (MEMRI) approaches for analyzing the early postnatal mouse brain, showing that MEMRI provides an exquisitely sensitive method for revealing multiple nuclei and axonal tracts in the early postnatal mouse brain. Results from our laboratory and others have already proven the utility of MEMRI for assessing neural activity and connectivity. These new findings now point to the potential of MEMRI for in vivo detection and quantitative analysis of functional circuits in the developing mouse brain. We have also discovered that the Divalent Metal Transporter, DMT1 can be utilized as an effective reporter gene for MEMRI. We now propose to develop and test a combination of DMT1 expression with MEMRI to provide a precise in vivo approach to analyze functional connectivity in the mouse brain, starting from critical neonatal stages when the circuitry is first established. We will test this new imaging technology in mice with mutations in the mid-hindbrain (MHB) genes engrailed (En1 and En2) and Fgf17, which have morphological and functional cerebellum and midbrain phenotypes. Recent evidence also suggests that both En and Fgf17 mutant mice have defects in MHB circuitry. We will therefore use DMT1-MEMRI to study MHB circuitry in these mice during the critical postnatal period of brain development. The specific aims of the project are: 1) Determine the normal stage-dependent MEMRI intensities in defined nuclei in wildtype (WT), En and Fgf17 mutant mice; 2) Utilize DMT1 to genetically label defined nuclei for MEMRI analysis of midbrain and cerebellar circuits; and 3) Analyze differences in functional circuitry between WT, En and Fgf17 mouse mutants using DMT1-MEMRI. This research has high potential to establish an innovative, genetically-controlled form of MEMRI for in vivo analysis of circuits in the developing mouse brain, providing critical new tools for analyzing mouse models of a wide variety of neurodevelopmental disorders, including cerebellum hypoplasia syndromes (e.g., Joubert and Dandy-Walker syndromes), autism spectrum disorders, and schizophrenia.