Investigation of the two-hit hypotesis for Cerebral Cavernous malformations

描述(申请人提供)：脑海绵状畸形(CCM)是中枢神经系统的血管病变，由紧密堆积、粗大的毛细血管样血管组成。随着时间的推移，CCM病变从单个扩张的血管发展为复杂的多海绵状病变，并有出血的倾向，导致出血性中风。CCM可零星发生或遵循常染色体显性遗传模式。对于遗传性疾病，已经定位了三个座位，并鉴定了致病基因(CCM1、CCM2和CCM3)。虽然这些新的基因产物的功能已经开始被阐明，但它们对病变发生的影响或病变进展的机制还没有明确的联系。我推测CCM病变是由于第二位点体细胞突变导致CCM基因位点的分子纯合性所致。CCM病变发生的两次打击假说与散发性CCM和家族性CCM的反复观察差异是一致的；家族性CCM患者会发生多个病变，但单个病变几乎只在散发性病例中发生。在家族性和散发性视网膜母细胞瘤病例中，类似的发病模式导致了Knudson的两次打击模型的发展，在该模型中，肿瘤抑制基因的两个等位拷贝必须突变才能产生肿瘤形成。这个两次命中的假说对导致癌症发生的突变事件做出了具体的预测。我建议使用我们收集的存档组织样本来验证非癌症模型的这些预测；CCM的模型。两次打击假说预测，每一类CCM病变，那些在CCM1、CCM2或CCM3中有遗传突变的病变将在病变内显示与胚系突变双等位基因的体细胞突变。此外，两次打击假说预测，散发性CCM病变通常在其中一个CCM基因内含有两个不同的双等位体细胞突变。关于家族性病例中多个病变的分子遗传起源的两次命中假说的一个关键预测是，多个病变的出现是由于独立的体细胞突变事件。以下目标旨在使用临床相关的成熟人类CCM病变样本来全面研究两次击中假说。 1A.目的：探讨家族性CCM病例的两次打击假说。 1B.家族性CCM合并多发病变两次打击假说的验证 2.探讨散发性CCM的二次打击假说。 通过成功地完成这些目标，我打算更充分地了解CCM的潜在基础生物学，这是一种中风的遗传形式，以影响未来的基于生物的治疗。

DESCRIPTION (provided by applicant): Cerebral Cavernous Malformations (CCM) are vascular lesions of the central nervous system consisting of closely-packed, grossly-enlarged capillary-like vessels. CCM lesions develop through time from single dilated vessels into complex, multicavernous lesions and have a propensity for bleeding leading to hemorrhagic stroke. CCM may occur sporadically or follow an autosomal dominant pattern of inheritance. For the inherited condition, three loci have been mapped and the causative genes (CCM1, CCM2, and CCM3) have been identified. While the functions of these novel gene products have begun to be elucidated, there is no clear connection to their influence on lesion genesis or the mechanism for lesion progression. I hypothesize that CCM lesions arise due to a second-site somatic mutation leading to molecular homozygosity at the CCM gene locus. The two-hit hypothesis for CCM lesion genesis is consistent with the repeated observational difference between sporadic and familial CCM; multiple lesions develop in patients with familial CCM cases, but single lesions develop almost exclusively in sporadic cases. A similar pattern of incidence in familial and sporadic cases of retinoblastoma led to the development of a two-hit model by Knudson, in which both allelic copies of a tumor suppressor gene must be mutated to yield tumor formation. The two-hit hypothesis makes specific predictions for the mutational events leading to tumorogenesis in cancer. I propose to test these predictions for a non-cancer model; that of CCM using our collection of archived tissue samples. The two-hit hypothesis predicts that each class of CCM lesions, those with inherited mutations in CCM1, CCM2, or CCM3 will show somatic mutation within the lesion that is biallelic to the germline mutation. Additionally, the two-hit hypothesis predicts that sporadic CCM lesions will routinely harbor two distinct biallelic somatic mutations within one of the CCM genes. A key prediction of the two-hit hypothesis regarding the molecular genetic origins of multiple lesions in familial cases is that multiple lesions arise due to independent somatic mutational events. The following aims have been designed to comprehensively study the two-hit hypothesis using clinically-relevant mature human CCM lesion samples. 1a. To investigate the two-hit hypothesis in FAMILIAL cases of CCM. 1b. To validate the two-hit hypothesis in cases of familial CCM with MULTIPLE lesions 2. To investigate the two-hit hypothesis in SPORADIC cases of CCM. Through successful completion of these aims I intend to more fully understand the underlying fundamental biology of CCM, an inherited form of stroke, to impact future biologically-based therapy.