FSHD Syndrome: DNA Repeats, Methylation, & Chromatin

描述(申请人提供)：筋膜肩周型肌营养不良症 FSHD是一种罕见的常染色体显性遗传综合征，由一些 1的亚端粒区(4q35)中的复杂重复序列(D4Z4)的拷贝 4号染色体的同源物。在4q35，这个3.3kb重复序列的拷贝数为 多态的。未受影响的个体在每个等位基因上有11到95个拷贝 4q35。相比之下，超过90%的FSHD患者在 这些等位基因4q亚端粒区中的一个。它已经被许多人提出 研究人员认为，正常情况下，这个区域是异色的，但当 D4Z4的串联拷贝数少于10，该区域失去其浓缩的 染色质结构，这种异染色染色化的损失，依次是 假想在受累肌肉中诱导不适当的基因表达 细胞。然而，目前还没有关于染色质研究的报道。 正常细胞或FSHD细胞在此区域的结构。 在计划的研究中，免疫化学、细胞化学和免疫细胞化学 将使用各种方法来检查该区域是否确实是异染色体 以及当它含有FSHD时是否会失去异色结构 删除。正常成肌细胞培养和淋巴母细胞样细胞系 将对个人和FSHD患者进行研究。这些实验将包括 异染色质1β蛋白的组蛋白乙酰化和结合分析 D4Z4染色质区域。另外，我们将确定这一地区是否 在正常细胞中后期复制，异染色质就是这种情况。 与提出的该区域的异色性一致，它具有 最近的研究表明，该重复序列高度甲基化。预赛 将扩大对D4Z4重复序列甲基化的研究，以检查 该重复序列在含有缺失的染色体中不再发生高甲基化 4在FSHD细胞中。最近的研究表明，来自另一种基因的细胞 综合征、ICF(一种DNA甲基转移酶缺乏症)和染色体不稳定 综合症)，在这个重复序列中甲基化不足。因为异常低甲基化 能否有利于染色体重排，将ICF细胞株与正常细胞系进行比较 关于这一地区重新安排的频率。拟议的研究 有助于阐明神秘的FSHD综合征的分子病因学。

DESCRIPTION (provided by applicant): Fascioscapulohumeral muscular dystrophy (FSHD) is an unusual autosomal dominant syndrome caused by the loss of some copies of a complex repeat (D4Z4) in a subtelomeric region (4q35) of one chromosome 4 homologue. The number of copies of this 3.3-kb repeat at 4q35 is polymorphic. Unaffected individuals have 11 to about 95 copies on each allelic 4q35. In contrast, more than 90% of FSHD patients have less than 10 copies at one of these allelic 4q subtelomeric regions. It has been proposed by many investigators that normally this region is heterochromatic but that when the number of tandem copies of D4Z4 is less than 10, the region loses its condensed chromatin structure, This loss of heterochroma-tinization, in turn, is hypothesized to induce inappropriate gene expression in the affected muscle cells. However, there have been no reports about studies of the chromatin structure in this region for normal or FSHD cells. In the planned research, immunochemical, cytochemical, and immunocytochemical methods will be used to examine whether this region is indeed heterochromatic and whether it loses the heterochromatic structure when it contains the FSHD deletion. Myoblast cultures and lymphoblastoid cell lines from normal individuals and FSHD patients will be studied. These experiments will include analysis of histone acetylation and binding of heterochromatin 1 beta protein to the D4Z4 chromatin region. Also, we will determine whether this region is late-replicating in normal cells, as is the case for heterochromatin. Consistent with the proposed heterochromatic nature of this region, it has recently been shown that this repeat is highly methylated. The preliminary study of methylation of the D4Z4 repeat will be expanded to examine whether this repeat is no longer hypermethylated in the deletion-containing chromosome 4 in FSHD cells. It has recently been shown that cells from another genetic syndrome, ICF (a DNA methyltransferase-deficiency and chromosome instability syndrome), are undermethylated in this repeat. Because abnormal hypomethylation can favor chromosome rearrangements, ICF and normal cell lines will be compared for the frequency of rearrangements in this region. The proposed research should help elucidate the molecular etiology of the enigmatic FSHD syndrome.