MOUSE MODELS OF EARLY INTESTINAL NEOPLASIA

描述：(改编自调查人员的摘要) 干细胞异常增殖(分裂数和克隆数 扩张)可能是一个主要的风险因素，如果不是早期的 肠道肿瘤发生的最早表现。然而，干细胞 很难研究，因为它们的数量少，很难研究 在数量更多的终末分化的上皮中进行鉴定 细胞。这项提议将重点放在小鼠的肠道干细胞上 缺乏DNA错配修复(MMR)。MMR的缺乏导致 突变率增加约100倍，这增加了 两种互补办法的可行性。第一，茎的数量 细胞分裂可以从基因上从细胞的积累来估计 微卫星(MS)座位的体细胞突变。突变只能 在干细胞中积累，因为所有其他细胞在几天内就会消失。 因此，所有的上皮细胞本质上都反映了 干细胞，而这又应该是干细胞数量的函数 组织。初步数据显示，肠道MS基因座、AS 通过计算机模拟预测，随着时间的推移逐渐变得多变 年龄。第二，突变的频率和其他神秘的模式 干细胞扩增将从原位损失中扣除 突变引起的内源性组织学标志物(LacZ)。越大 在有缺陷的环境中预期的自发突变数量 MMR应该会提高这种成熟的组织学的效率 技术。干细胞分裂的数量及其模式 在Pms2基因发生生殖系突变的小鼠身上将观察到扩张， MLH1，或APC，以及饮食(限制高脂肪/低钙和卡路里) 这会增加或减少肿瘤的发生率。这些研究 将决定目前干细胞中的隐蔽变化 分割率或扩张模式与 肠道肿瘤。

DESCRIPTION: (adapted from the investigator's abstract) Abnormal stem cell proliferation (numbers of divisions and clonal expansion) is likely a major risk factor and an early if not the earliest manifestation of intestinal tumorigenesis. However, stem cells are difficult to study since they are small in number and hard to identify among the more numerous terminally differentiated epithelial cells. This proposal will focus on the intestinal stem cells of mice deficient in DNA mismatch repair (MMR). The lack of MMR results in approximately 100-fold increases in mutation rates which increases the feasibility of two complementary approaches. First, the number of stem cell divisions can be estimated genetically from the accumulation of somatic mutations in microsatellite (MS) loci. Mutations can only accumulate in stem cells since all other cells are lost within days. Therefore, all epithelial cells essentially reflect the genotypes of the stem cells, which in turn should be a function of the numbers of their divisions. Preliminary data demonstrate that intestinal MS loci, as predicted by computer simulations, become progressively polymprphic with age. Second, frequencies of mutation and patterns of otherwise occult stem cell expansions will be deducted from the in situ loss of endogenous histologic markers (lacZ) due to mutation. The greater numbers of spontaneous mutations expected in the setting of deficient MMR should increase the efficiency of this well established histological technique. The numbers of stem cell divisions and their patterns of expansion will be observed in mice with germline mutations in Pms2, Mlh1, or Apc, and on diets (high fat/low calcium and calorie restricted) which increase or decrease the frequencies of neoplasia. These studies will determine whether currently occult alterations in stem cell division rates or in patterns of expansion are associated with intestinal neoplasia.