Luma in Cardiac Function and Disease

描述(申请人提供)：真核细胞中的核膜(NE)将细胞核和细胞质隔开。NE由内核膜(INM)和外核膜(ONM)组成，内核膜和外核膜上排列着许多蛋白质，包括核骨架和细胞骨架(LINC)之间的连接复合体的蛋白质。几个LINC成员的突变会导致心肌病。Luma是INM中新发现的LINC复合体成员。在Luma中，丝氨酸358到亮氨酸(S358L)的单一氨基酸替换导致常染色体显性、完全穿透性心肌病。Luma与驻留在INM的LINC复合体的其他成员相互作用，包括Emerin、lamins和SUN2。亮度可能在Emerin定位中起作用，因为被RNA干扰去除亮度的HeLa细胞表现出Emerin定位的改变和Emerin水平的降低。LAMA的另一对配对LlamA/C直接与染色体相互作用，Lamin的突变导致染色体定位异常和基因表达的相关变化。上述结果使我们假设，Luma在心肌细胞核骨架和细胞骨架的完整性、染色体定位和基因表达中起着关键作用，并且Luma中的S358L突变会损害Luma功能的特定方面，从而导致心肌病。因此，我们的具体目标是：1)通过阐明Luma的亚细胞定位和相互作用伙伴，以及利用Luma的等位基因对心脏特异的Luma基因敲除小鼠模型进行详细的组织学和生理学分析，来表征Luma在发育和成年心肌细胞中的作用。2)通过对Luma S358L基因敲除小鼠模型的详细组织学和生理学分析，阐明Luma基因S358L突变所致心肌病的分子机制。3)利用人诱导多能干细胞(IPSC)和人胚胎干细胞(HESC)来源的Luma突变心肌细胞，研究Luma S358L突变对人心肌细胞功能的影响机制。

DESCRIPTION (provided by applicant): The nuclear envelope (NE) in eukaryotic cells separates nuclear and cytoplasmic compartments. The NE is comprised of an inner nuclear membrane (INM) and an outer nuclear membrane (ONM), which are lined with numerous proteins including those of the LInker-complex between the Nucleoskeleton and the Cytoskeleton (LINC). Mutations in several LINC members cause cardiomyopathies. Luma is a newly discovered member of the LINC complex in the INM. A single amino acid substitution of serine 358 to leucine (S358L) in Luma causes an autosomal-dominant, fully penetrant, cardiomyopathy. Luma interacts with other members of the LINC complex that reside in the INM, including Emerin, Lamins, and SUN2. Luma may play a role in Emerin localization, as HeLa cells depleted of Luma by RNA interference exhibit altered localization of Emerin and a reduction in Emerin levels. Another partner of Lama, LaminA/C directly interacts with chromosomes, and mutations in Lamin result in aberrant chromosome positioning and correlated changes in gene expression. The foregoing results have led us to the hypothesis that Luma plays a key role in cardiomyocyte nucleoskeletal and cytoskeletal integrity, chromosome positioning, and gene expression, and that the S358L mutation in Luma impairs specific aspects of Luma function to lead to cardiomyopathy. Accordingly, our Specific Aims are: 1) To characterize roles of Luma in developing and adult cardiomyocytes by elucidating Luma's subcellular localization and interaction partners, and by performing detailed histological and physiological analyses of cardiac specific Luma knockout mouse models utilizing a floxed allele of Luma. 2) To elucidate molecular mechanisms underlying cardiomyopathy consequent to the S358L mutation in Luma by detailed histological and physiological analyses of a Luma S358L knock-in mouse model. 3) To investigate mechanisms by which the Luma S358L mutation impacts human cardiomyocyte function, utilizing human induced pluripotent stem cell (iPSC) and human embryonic stem cell (hESC)-derived Luma- mutant cardiomyocytes.