Ultrasound and MR Imaging of Mouse Brain Development.

基因工程小鼠目前正在开发用于大脑发育和广泛的神经发育疾病的体内研究。事实上，确定的突变小鼠对于确定受影响的遗传途径和解决发育性脑疾病的潜在细胞和分子基础至关重要。缺乏这些努力已经有效的体内成像方法，可用于研究神经发育障碍的小鼠模型，特别是在出生后早期阶段，当疾病首次出现时，大脑结构和功能的最大变化可能发生。因此，一个主要的挑战是开发和验证体内成像技术，可以检测和监测发育中小鼠大脑的大脑结构和功能的早期变化。我们已经建立了定量的，在体内锰（Mn）增强MRI（MEMRI）的方法来分析出生后早期的小鼠大脑，显示MEMRI提供了一个精致的敏感的方法，揭示多个核和轴突束在出生后早期的小鼠大脑。我们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接方面的实用性。这些新的发现指出了MEMRI在体内检测和定量分析发育中小鼠大脑功能回路的潜力。我们还发现，二价金属转运蛋白，DMT 1可以用作MEMRI的有效报告基因。我们现在建议开发和测试DMT 1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中的功能连接，从电路首次建立的关键新生儿阶段开始。我们将在中后脑（MHB）基因（En 1和En 2）和Fgf 17突变的小鼠中测试这种新的成像技术，这些基因具有小脑和中脑的形态和功能表型。最近的证据还表明，En和Fgf 17突变小鼠都有MHB电路缺陷。因此，我们将使用DMT 1-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Fgf 17突变小鼠中定义的核中的正常阶段依赖性MEMRI强度; 2）利用DMT 1遗传标记定义的核用于中脑和小脑回路的MEMRI分析;和3）使用DMT 1-MEMRI分析WT，En和Fgf 17突变小鼠之间功能回路的差异。这项研究具有很高的潜力，可以建立一种创新的、遗传控制的MEMRI形式，用于发育中小鼠大脑回路的体内分析，为分析各种神经发育障碍的小鼠模型提供关键的新工具，包括小脑发育不全综合征（例如，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.