Research for the pathogenesis of oculopharyngeal muscular dystrophya -establish an animal model

常染色体显性眼咽肌营养不良症（OPMD）是一种迟发性疾病，临床表现为进行性上睑下垂、吞咽困难和肢体无力，以及骨骼肌纤维中独特的核内内含物。该疾病是由聚(a)结合蛋白核1 （PABPN1; PABP2）中10-丙氨酸延伸至12-17个丙氨酸残基引起的。虽然PABPN1是OPMD内含物的主要成分，但该病的确切病因尚不清楚。为了阐明hPABPN1的分子机制并为治疗试验建立一个有用的模型，我们培育了表达hPABPN1的转基因小鼠。表达正常hPABPN1并具有10-丙氨酸延伸的转基因小鼠系未表现出肌病变化，而表达高水平扩增hPABPN1并具有13-丙氨酸延伸的转基因小鼠系表现出明显的肌病表型，尤其是在老年时。后一种小鼠的病理研究发现核内包涵体由聚集的突变体hPABPN1产物组成。此外，在退行性纤维周围可见一些TUNEL阳性核，坏死肌纤维病变处可见一簇TUNEL阳性核。有趣的是，肌病改变的程度在眼睑和咽肌更为突出。此外，疲劳试验显示，四肢肌肉无力明显。核包涵体似乎随着年龄的增长而逐渐发育，至少在1周龄后，在模型小鼠肌肉中。我们通过表达突变的PABPN1建立了第一个转基因小鼠OPMD模型，我们的模型小鼠在肌纤维活力方面表现出更显著的改变。

Autosomal dominant oculopharyngeal muscular dystrophy (OPMD) is a late-onset disorder characterized clinically by progressive ptosis, dysphagia, and limb weakness, and by unique intranuclear inclusions in the skeletal muscle fibers. The disease is caused by the expansion of a 10-alanine stretch to 12-17 alanine residues in the poly(A)-binding protein, nuclear 1 (PABPN1 ; PABP2). While PABPN1 is a major component of the inclusions in OPMD, the exact cause of the disease is unknown. To elucidate the molecular mechanism and to construct a useful model for therapeutic trials, we have generated transgenic mice expressing the hPABPN1. Transgenic mice lines expressing a normal hPABPN1 with 10-alanine stretch did not reveal myopathic changes, whereas lines expressing high-levels of expanded hPABPN1 with a 13-alanine stretch showed an apparent myopathy phenotype, especially in old age. Pathological studies in the latter mice disclosed intranuclear inclusions consisting of aggregated mutant hPABPN1 product. Furthermore, some TUNEL positive nuclei were shown around degenerating fibers and a cluster of it in the lesion in necrotic muscle fibers. Interestingly, the degree of myopathic changes was more prominent in the eyelid and pharyngeal muscles. Further, muscle weakness in the limbs was apparent as shown by the fatigability test. Nuclear inclusions seemed to develop gradually with aging, at least after 1 week of age, in model mouse muscles. We established the first transgenic mouse model of OPMD by expressing mutated PABPN1, and our model mice appear to have more dramatic alternations in myofiber viability.