Pathogenesis of Laminin-alpha2 Deficiency

描述(申请人提供)：层粘连蛋白-ot2缺乏症的发病机制。人类LAMA2基因的突变导致第一组先天性肌营养不良症(CMD 1)，这是一种毁灭性的儿童隐性疾病。LAMA2编码层粘连蛋白-c-β2，这是一种在骨骼肌中含量丰富的细胞外蛋白质。拟议中的实验将测试有关层粘连蛋白-C_2丢失如何导致CMD1严重神经肌肉功能障碍的假说。对于AIMS 1和AIMS 2，我们将研究细胞凋亡在CMD1发病机制中的作用。在培养中，层粘连蛋白-cz2缺陷的肌管是不稳定的，并通过抗凋亡蛋白Bcl-2抑制的过程死亡。然而，尚不清楚细胞凋亡是否在体内CMD1神经肌肉功能丧失中起重要作用。拟议中的实验将确定层粘连蛋白-C_2缺乏的小鼠的疾病如何受到Bcl-2家族成员的靶向改变的影响。 对于目标3，我们将确定肌肉干细胞功能是否在CMD 1中发生改变。出生后的肌肉中含有多能干细胞，但还没有研究检查这些最近在患病肌肉中发现的干细胞。我们将测试层粘连蛋白-β2缺乏激活这些稀有细胞的增殖和改变分化能力的可能性。对于目标4，我们将确定在受影响的组织中是否发生了不适当的重新进入细胞周期。不适当的细胞周期可导致正常的有丝分裂后细胞死亡，包括神经元和肌纤维。我们假设，层粘连蛋白-cz2缺乏改变了信号传递，导致细胞周期的失调。为了验证这一假设，我们将确定是否在层粘连蛋白-cβ2缺陷细胞中不适当地诱导了细胞周期调节因子。这些结果将增加我们对CMD 1发病机制的理解，并可能为治疗提供新的途径，可能是基于抑制细胞凋亡、干细胞修复或细胞周期抑制。

DESCRIPTION (provided by applicant): Pathogenesis of laminin-ot2-deficiency. Mutations in the human LAMA2 gene cause congenital muscular dystrophy, group 1 (CMD 1), a devastating, recessive disease of childhood. LAMA2 encodes laminin-c Beta 2, an extracellular protein that is abundant in skeletal muscle. The proposed experiments will test hypotheses about how loss of laminin-c_2 leads to the severe neuromuscular dysfunction in CMD1. For Aims 1 & 2, we will examine the role of apoptosis in CMD1 pathogenesis. In culture, laminin-cz2-deficient myotubes are unstable and die by a process that is inhibited by the antiapoptosis protein Bcl-2. It is not known, however, whether apoptosis is important in the loss of CMD1 neuromuscular function in vivo. The proposed experiments willdetermine how disease in laminin-c_2-deficient mice is affected by targeted alterations of Bcl-2 family members. For Aim 3, we will determine if muscle stem cell function is altered in CMD 1. Postnatal muscle contains multipotent stem cells, but no studies have examined these recently identified stem cells in diseased muscle. We will test the possibility that laminin- Beta 2-deficiency activates proliferation and alters the differentiation capability of these rare cells. For Aim 4, we will determine if inappropriate re-entry into the cell cycle occurs in affected tissue. Inappropriate cell cycling can lead to death of normally post-mitotic cells including neurons and myofibers. We hypothesize that laminin-cz2-deficiency alters signal transmission resulting in dysregulation of the cell cycle. To test this hypothesis, we will determine if cell cycle regulators are inappropriately induced in laminin-c beta 2-deficient cells. The results will increase our understanding of CMD 1 pathogenesis and could suggest new routes to therapy, perhaps based on apoptosis inhibition, stem cell repair, or cell cycle inhibition.