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

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。我最近培育了在骨骼肌中特异性表达1A型（LGMD1A） 57型肌动素突变（TgT57I）的转基因小鼠。该转基因包括人肌动素cDNA和n端c-myc表位标签。三个独立的TgT57I小鼠系发生进行性肌原纤维病理（图1a，未发表的数据）。多块肌肉切片显示致密肌纤维斑块或聚集体的大小和数量随年龄增长而增加。超微结构分析显示边缘空泡、z型盘流和大片肌纤维紊乱（图1b，未发表数据）与人类患者相似。过表达人野生型肌动素cDNA的转基因小鼠未出现异常的肌肉病理。为了进一步表征TgT57I小鼠，我们进行了全肌肉生理学研究。EDL肌肉的质量减少33%，其横截面积减少30%，其最大比力减少23%。与大部分快速抽搐的EDL肌相反，TgT57I比目鱼肌生理保持正常；比目鱼肌也没有任何肌病。TgT57I小鼠肌肉群的进一步组织学分析显示，某些肌肉如股四头肌和肱三头肌大量聚集肌，而其他肌肉如胫骨前肌和膈肌则没有。同样，在LGMD1A中，MRI和ct扫描检测到的肌肉病理程度存在巨大差异。例如，扫描LGMD1A腿筋显示特定的累及和半膜的不对称损耗（未发表的数据）。我希望通过磁共振显微镜更彻底地评估TgT57I小鼠模型肌肉萎缩的模式和对称性。由于雄性近交系小鼠会出现非特异性管状聚集体病理，我建议对一只12个月大的雌性TgT57I小鼠进行分析。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 Three independent lines of TgT57I mice develop progressive myofibrillar pathology (fig. 1a, unpublished data).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analysis reveals rimmed vacuoles, Z-disc streaming, and large patches of myofibrillar disarray (fig. 1b, unpublished data) similar to those seen in human patients.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.