Apoptosis in Laminin alpha2-Deficient Muscle Pathology

描述(申请人提供)：先天性肌营养不良通常是由于肌纤维周围基底膜中层粘连蛋白a2(Merosin)表达不足引起的。Merosin缺陷型先天性肌营养不良症(MCMD)的特征是出生后不久就出现严重的肌肉无力，但改善不够明显，无法进行正常的步行运动。Dy突变的小鼠也缺乏正常的层粘连蛋白U2的表达，为该病提供了一个实验模型。像dyw菌株这样的严重突变株经历了肌肉纤维的退化和再生，但这些纤维在涉及细胞凋亡的过程中死亡。最终，老鼠会在4个月内死亡。我们发现，肌肉特异性过表达细胞凋亡抑制物(Bcl2)可以显着延长DYW小鼠的存活时间，改善断奶后的生长，从而表明对肌肉细胞特异性细胞死亡的调控对疾病的进展具有显着的影响。此外，我们发现，缺乏bax(一种相关的促凋亡蛋白)的d/v动物表现出更长的寿命和生长，并伴随着与层粘连蛋白A2缺乏的髓鞘形成缺陷相关的后肢瘫痪减轻。通过实验进一步探讨Bcl2和Bax在层粘连蛋白A2缺乏的肌肉病理过程中的作用，并确定它们在疾病早期和晚期对细胞凋亡、再生和生存的影响。我们还将研究其他凋亡调节分子的表达，特别是FLIPL、ARC、XIAP和APAF-1，在正常和层粘连蛋白A2缺陷的肌肉细胞中。这些蛋白质的表达将在体内进行实验改变，以确定它们是否可以调节层粘连蛋白U2缺陷肌肉的生存，以及是否可以通过改变它们的水平来调节不同阶段的疾病进展。这些结果将进一步加深我们对层粘连蛋白a2缺陷性肌肉变性过程中细胞凋亡过程的控制机制的理解，并可能确定可以作为治疗干预治疗人类mcmd的靶点的途径。

DESCRIPTION (provided by applicant): Congenital muscular dystrophy is often caused by deficiency in laminin a2 (merosin) expression in the basement membrane surrounding muscle fibers. Merosin-deficient congenital muscular dystrophy (MCMD) is characterized by severe muscle weakness shortly after birth that does not improve significantly enough to allow normal ambulatory motion. The dy mutant mouse lines also lack normal laminin u2 expression and provide an experimental models for this disease. Severe mutants such as the dyw strain undergo muscle fiber degeneration followed by regeneration, but these fibers die in a process involving apoptosis. Ultimately mice die within 4 months of age. We have found that muscle specific overexpression of Bcl-2 (an inhibitor of apoptosis) can significantly prolong the survival dyw mice and improve post-weaning growth thus indicating that regulation of the cell death specifically in muscle cells has a dramatic effect on this disease progression. Additionally, we find that d/v animals deficient in Bax, a related pro-apoptotic protein, exhibit even greater longevity and growth along with reduced hind limb paralysis associated with laminin a2- deficient myelination defects. Experiments are proposed to further explore the role of Bcl-2 and Bax in the progression of laminin a2-deficient muscle pathology and determine their effects on apoptosis, regeneration and survival at both early and later stages of disease. We will also examine expression of other apoptotic regulatory molecules, specifically FLIPL, ARC, XIAP, and Apaf-1, in normal and laminin a2-deficient muscle cells. Expression of these proteins will be experimentally altered in vivo to determine whether or not they can regulate the survival of laminin u2-deficient muscle and if disease progression can be modulated at different stages by altering their levels. These results will further our understanding of mechanisms controlling the apoptotic process during laminin a2-deficient muscle degeneration and possibly identify pathways that could serve as targets for therapeutic intervention in the treatment of human MCMD.