Luma in Cardiac Function and Disease

描述（由申请人提供）：真核细胞的核膜（NE）将细胞核和细胞质分隔开。NE由内核膜（INM）和外核膜（ONM）组成，其内衬有许多蛋白质，包括核骨架和细胞骨架之间的连接体复合物（LINC）的蛋白质。几个LINC成员的突变导致心肌病。Luma是INM中LINC复合体的新成员。在Luma中丝氨酸358到亮氨酸（S358 L）的单个氨基酸取代引起常染色体显性的、完全渗透的心肌病。Luma与位于INM中的LINC复合物的其他成员相互作用，包括Emerin，Lamins和SUN 2。Luma可能在Emerin定位中发挥作用，因为通过RNA干扰耗尽Luma的HeLa细胞表现出Emerin定位的改变和Emerin水平的降低。LaminA/C是Lama的另一个伴侣，它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完整性、染色体定位和基因表达中起关键作用，并且Luma中的S358 L突变损害Luma功能的特定方面以导致心肌病。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伴侣，并通过利用Luma的floxed等位基因对心脏特异性Luma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 S358 L基因敲入小鼠模型的详细组织学和生理学分析，阐明Luma S358 L突变导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）衍生的Luma突变心肌细胞，研究Luma S358 L突变影响人心肌细胞功能的机制。

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.