RESUMO
The adenomatous polyposis coli (APC) gene is known to act as a tumor suppressor gene in both sporadic and hereditary colorectal cancer by negatively regulating WNT signaling. Familial adenomatous polyposis (FAP) patients develop intestinal polyps due to the presence of a single germline mutation in APC. The severity of the FAP phenotype is a function of the position of the APC mutation, indicating a complex role for APC that extends beyond the canonical WNT pathway. APC encodes a large protein with multiple functional domains, including an armadillo repeat domain that has been linked to protein-protein interactions. To determine the effect of the armadillo repeat domain on intestinal tumorigenesis, we generated a congenic mouse line (Apc ( Δ242 )) carrying a gene trap cassette between exons 7 and 8 of the murine Apc gene. Apc ( Δ242/+) mice express a truncated Apc product lacking the armadillo repeat domain as part of a fusion protein with ß-geo. Expression of the fusion product was confirmed by X-gal staining, ensuring that Apc ( Δ242 ) is not a null allele. In contrast, Apc ( Min/+) mice produce a truncated Apc product that contains an intact armadillo repeat domain. On the C57BL/6J background, Apc ( Δ242/+) mice develop more polyps than do Apc ( Min/+) mice along the entire length of the small intestine; however, polyps were significantly smaller in Apc ( Δ242/+) mice. In addition, polyp multiplicity in Apc ( Δ242/+) mice is affected by polymorphisms between inbred strains. These data suggest that the armadillo repeat domain of the Apc protein suppresses tumor initiation in the murine intestine while also promoting tumor growth.
Assuntos
Proteína da Polipose Adenomatosa do Colo/química , Polipose Adenomatosa do Colo , Genes APC , Polipose Adenomatosa do Colo/genética , Polipose Adenomatosa do Colo/metabolismo , Polipose Adenomatosa do Colo/patologia , Proteína da Polipose Adenomatosa do Colo/genética , Proteína da Polipose Adenomatosa do Colo/metabolismo , Alelos , Sequência de Aminoácidos , Animais , Proteínas do Domínio Armadillo/química , Proteínas do Domínio Armadillo/genética , Proteínas do Domínio Armadillo/metabolismo , Modelos Animais de Doenças , Fusão Gênica , Pólipos Intestinais/genética , Pólipos Intestinais/metabolismo , Pólipos Intestinais/patologia , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos C57BL , Reação em Cadeia da Polimerase , Estrutura Terciária de Proteína , Deleção de Sequência , Transdução de Sinais , beta-Galactosidase/genéticaRESUMO
We have isolated a Meis1a transgenic mouse line exhibiting recessive male-specific lethality and non-alcoholic fatty liver disease (NAFLD), which coincides with pubescence and is androgen-dependent. The phenotype is due to disruption of an endogenous locus, since other Meis1a transgenic lines do not exhibit these phenotypes. Necropsy analysis revealed hepatic microvesicular steatosis in pubescent male homozygous mice, which is absent in transgenic females. The transgene insertion site was localized to chromosome 1 and further refined by cloning the flanking regions. Sequence analysis shows that the integration site disrupts a putative metallo-beta-lactamase gene with a 21.3 kb deletion encompassing exons 5-7.