LOSS OF APC HETEROZYGOSITY AND ABNORMAL TISSUE BUILDING IN NASCENT INTESTINAL POLYPS IN MICE CARRYING A TRUNCATED APC GENE
LOSS OF APC HETEROZYGOSITY AND ABNORMAL TISSUE BUILDING IN NASCENT INTESTINAL POLYPS IN MICE CARRYING A TRUNCATED APC GENE
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DOI：
10.1073/pnas.92.10.4482
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发表时间：
1995-05-09
影响因子：
11.1
通讯作者：
TAKETO, M
中科院分区：
文献类型：
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作者：
OSHIMA, M;OSHIMA, H;TAKETO, M
APC（腺瘤性结肠息肉病）基因突变似乎不仅导致家族性腺瘤性息肉病，而且还导致许多散发性胃肠癌病例。利用小鼠胚胎干细胞中的同源重组，我们构建了含有编码aa 716 (Apc(Delta 716)) 截短产物的突变基因的小鼠，该基因的孟德尔遗传导致大多数纯合子小鼠在妊娠第8天之前在子宫内死亡。杂合子在整个肠道中形成多个息肉，主要在小肠。最早的息肉在出生后第三周出现多灶性，此后不断出现新的息肉。令人惊讶的是，每个新生息肉都由覆盖着一层正常绒毛上皮的微腺瘤组成。这些微腺瘤起源于单个隐窝，通过在邻近绒毛的内（乳腺）侧形成异常的外袋。我们通过剥离正常上皮，仔细解剖了新生息肉中的这种微腺瘤，并通过 PCR 确定了它们的基因型：所有微腺瘤都已经失去了野生型 Ape 等位基因，而突变型等位基因保持不变。这些结果表明，杂合性丧失以及绒毛内微腺瘤的形成是导致 Apc(Delta 716) 肠粘膜息肉病的原因。因此，截短的产物不太可能直接与野生型蛋白质相互作用并通过显性负性机制引起微腺瘤。
Mutations in the APC (adenomatous polyposis coli) gene appear to be responsible for not only familial adenomatous polyposis but also many sporadic cases of gastrointestinal cancers. Using homologous recombination in mouse embryonic stem cells, we constructed mice that contained a mutant gene encoding a product truncated at aa 716 (Apc(Delta 716)), Mendelian transmission of the gene caused most homozygous mice to die in utero before day 8 of gestation. The heterozygotes developed multiple polyps throughout the intestinal tract, mostly in the small intestine. The earliest polyps arose multifocally during the third week after birth, and new polyps continued to appear thereafter. Surprisingly, every nascent polyp consisted of a microadenoma covered with a layer of the normal villous epithelium. These microadenomas originated from single crypts by forming abnormal outpockets into the inner (lacteal) side of the neighboring villi. We carefully dissected such microadenomas from nascent polyps by peeling off the normal epithelium and determined their genotype by PCR: all microadenomas had already lost the wild-type Ape allele, whereas the mutant allele remained unchanged. These results indicate that loss of heterozygosity followed by formation of intravillous microadenomas is responsible for polyposis in Apc(Delta 716) intestinal mucosa. It is therefore unlikely that the truncated product interacts directly with the wild-type protein and causes the microadenomas by a dominant negative mechanism.