MR AND MICRO-CT OF MYOFIBRILLAR PATHOLOGY IN MOUSE MODEL OF LGMD1A

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。我最近产生了转基因小鼠表达肢带型肌营养不良症1A型（LGMD 1A）thr 57 ile肌球蛋白突变（TgT 57 I），特别是在骨骼肌。转基因包括人肌球蛋白cDNA和N-末端c-myc表位标签。TgT 57 I小鼠的三个独立品系发展出进行性肌原纤维病理学（图1a，未发表的数据）。多块肌肉的切片显示致密肌原纤维斑块或聚集体的大小和数量随年龄增加。超微结构分析显示，边缘空泡、Z盘流和大片肌原纤维紊乱（图1b，未发表的数据）与人类患者中观察到的相似。过表达人野生型肌球蛋白cDNA的转基因小鼠没有出现异常的肌肉病理学。 为了进一步表征TgT 57 I小鼠，我们进行了全肌肉生理学。EDL肌肉的质量减少了33%，其横截面积减少了30%，其最大比力减少了23%。在很大程度上快速收缩的EDL肌肉，TgT 57 I比目鱼肌生理学保持正常;比目鱼肌也幸免于任何myopathology。TgT 57 I小鼠中肌肉群的进一步组织学分析揭示，某些肌肉如四头肌和三头肌大量聚集有肌聚集体，而其他肌肉如胫骨前肌和膈肌则没有。同样，在LGMD 1A中，通过MRI和CT扫描检测到的肌肉之间的病理程度存在巨大的差异。例如，LGMD 1A腘绳肌扫描显示半膜肌的特定受累和不对称消耗（未发表数据）。我希望通过磁共振显微镜更彻底地评估TgT 57 I小鼠模型中肌肉萎缩的模式和对称性。由于雄性近交系小鼠出现了严重的非特异性肾小管聚集体病理，因此我建议分析12个月大的雌性TgT 57 I小鼠。MicroCT和MRM成像将有助于对肌肉疾病小鼠模型中的肌肉群进行前所未有的完整评估。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. I have recently generated transgenic mice expressing the limb-girdle muscular dystrophy type 1A (LGMD1A) thr57ile myotilin mutation (TgT57I) specifically in skeletal muscle. The transgene includes the human myotilin cDNA and an N-terminal c-myc epitope tag. Three independent lines of TgT57I mice develop progressive myofibrillar pathology (fig. 1a, unpublished data). Sections of multiple muscles show an age-dependent increase in the size and number of dense myofibrillar plaques or aggregates. Ultrastructural analysis reveals rimmed vacuoles, Z-disc streaming, and large patches of myofibrillar disarray (fig. 1b, unpublished data) similar to those seen in human patients. Transgenic mice overexpressing the human wild-type myotilin cDNA develop no abnormal myopathology. To further characterize the TgT57I mice, we performed whole muscle physiology. The EDL muscle¿s mass is reduced by 33%, its cross-sectional area is reduced 30%, and its maximum specific force is reduced 23%. In contrast to the largely fast-twitch EDL muscle, TgT57I soleus muscle physiology remains normal; the soleus is also spared of any myopathology. Further histological analysis of muscle groups in TgT57I mice reveals that certain muscles such as quadriceps and triceps are heavily populated with myoaggregates while others such as tibialis anterior and diaphragm are spared. Similarly, in LGMD1A, there is tremendous variability in the degree of pathology between muscles detected by MRI and CT-scans. For example, scan of an LGMD1A hamstring shows specific involvement and assymetrical wasting of the semimembranosous (unpublished data). I wish to more thoroughly evaluate the pattern and symmetry of muscle wasting in the TgT57I mouse model by magnetic resoncance microscopy. Because male inbred mice develop a gross nonspecific tubular aggregate pathology, I propose to analyze a 12-month old female TgT57I mouse. MicroCT and MRM imaging will facilitate an unprecedentedly complete evaluation of muscle groups in a mouse model of muscle disease.