Elucidating mechanisms involved in Lamin B1 mediated demyelination

 描述（由申请方提供）：常染色体显性脑白质营养不良（ADLD）是一种致死性、进行性成人发病疾病，其特征为自主神经和运动功能障碍，伴有广泛的CNS脱髓鞘。我们以前已经表明，ADLD是由核纤层蛋白B1基因的重复引起的，核纤层蛋白B1的表达增加是疾病过程的基础。在真核细胞中，核纤层蛋白B1是核纤层的主要组成部分，核纤层是一种与内核膜相邻的纤维网。核纤层维持细胞核的结构完整性，并在基本细胞过程中发挥作用，包括转录、DNA复制、DNA修复和表观遗传调控。我们最近已经证明，少突胶质细胞特异性过度表达核纤层蛋白B1的转基因（TG）小鼠表现出严重的空泡脱髓鞘的脊髓，导致年龄依赖性退行性表型联想到ADLD。TG脊髓表现出负责脂质合成的多个基因的表达显著减少，包括关键的脂肪生成转录因子SREBP 1和2。这伴随着脊髓少突胶质细胞中抑制性组蛋白标记H3 K9 me 3和H3 K27 me 3的整体增加。由于髓鞘由~70%的脂质组成，脂质合成的缺陷可导致严重的脱髓鞘。与我们的基因表达数据一致，我们观察到脊髓白色物质特异性的富含髓鞘的脂质显著减少。我们的研究结果确定脂质合成缺陷作为一个主要组成部分的脱髓鞘引起的核纤层蛋白B1过度表达，并提出了一种新的核纤层蛋白B1和脂质代谢之间的联系。虽然脂质失调提供了一个令人信服的框架来解释在转基因小鼠中观察到的脱髓鞘，连接核纤层蛋白B1的过度表达和少突胶质细胞中的脂质合成的机制是未知的，该建议旨在确定这些途径。我们将检验核纤层蛋白B1调节抑制性组蛋白标记以下调特定靶基因表达的假设，并检查核纤层蛋白B1在少突胶质细胞中的过度表达是否会导致可能影响少突胶质细胞功能的特定途径失调。我们还将确定调节核纤层蛋白B1水平如何影响疾病表型。我们提出的实验将阐明连接核纤层蛋白B1过表达，脂质失调和脱髓鞘表型的机制，结果将是关键的ADLD的治疗途径的识别。此外，他们还将深入了解少突胶质细胞功能的基本生物学，这可能有助于理解其他常见的脱髓鞘疾病，如多发性硬化症。

 DESCRIPTION (provided by applicant): Autosomal Dominant Leukodystrophy (ADLD) is a fatal, progressive adult-onset disease characterized by autonomic and motor dysfunction with widespread CNS demyelination. We have previously shown that ADLD is caused by duplications of the lamin b1 gene and that increased expression of lamin B1 underlies the disease process. In eukaryotic cells, lamin B1 is a major constituent of the nuclear lamina, a fibrous meshwork adjacent to the inner nuclear membrane. The nuclear lamina maintains the structural integrity of the nucleus and has roles in essential cellular processes including transcription, DNA replication, DNA repair, and epigenetic regulation. We have recently demonstrated that transgenic (TG) mice with oligodendrocyte specific over-expression of lamin B1 exhibit severe vacuolar demyelination of the spinal cord that result in age dependent degenerative phenotypes reminiscent of ADLD. TG spinal cords showed dramatic reductions in the expression of multiple genes responsible for lipid synthesis, including the critical lipogenic transcription factors, SREBP1 and 2. This was accompanied by global increases in the repressive histone marks H3K9me3 and H3K27me3 in spinal cord oligodendrocytes. As myelin is made up of ~70% lipids, defects of lipid synthesis can result in severe demyelination. Consistent with our gene expression data, we observed a significant reduction of myelin enriched lipids that were specific to the spinal cord white matter. Our results identify lipid synthesis defects as a major component of the demyelination caused by lamin B1 over-expression and suggests a novel link between lamin B1 and lipid metabolism. While lipid dysregulation provides a cogent framework for explaining the demyelination observed in the transgenic mice, the mechanisms linking lamin B1 over-expression and lipid synthesis in oligodendrocytes are unknown and this proposal aims at identifying these pathways. We will test the hypothesis that lamin B1 modulates repressive histone marks to down regulate expression of specific target genes and examine whether lamin B1 over expression in oligodendrocytes results in the dysregulation of specific pathways that may impact oligodendrocyte function. We will also determine how modulating lamin B1 levels impacts the disease phenotype. The experiments that we have proposed will elucidate mechanisms linking lamin B1 over-expression, lipid dysregulation and the demyelination phenotype, results that will be critical in the identification of therapeutic pathways for ADLD. In addition, they will also provide insights into the basic biology of oligodendrocyte function that may help in understanding other common demyelinating diseases such as Multiple Sclerosis.