RESUMO
BACKGROUND & AIMS: ELF3, a member of the ETS transcription factor family, has been shown to transactivate the transforming growth factor beta type II receptor (TGF-betaRII) promoter. Previously we showed that Elf3-null mice have a defect in the small intestine caused by a failure of small intestinal epithelial cells to differentiate and that these cells produced significantly lower levels of Tgf-betaRII. To prove that the defect observed in Elf3-null mice resulted from the lack of Elf3-dependent activation of Tgf-betaRII expression, we performed a genetic rescue. METHODS: We generated transgenic mice that express human TGF-betaRII specifically in the intestinal epithelium under the control of the mouse A33 antigen promoter. Mice expressing the A33-TGF-betaRII transgene were mated with Elf3(+/-) mice, and double heterozygous offspring harboring both the transgene and one mutant Elf3 allele were intercrossed. RESULTS: The resultant A33-TGF-betaRII transgenic Elf3(-/-) pups displayed normal small intestinal morphology, while the characteristic abnormality was retained in all Elf3(-/-) mice that did not express the transgene. This phenotypic rescue shows for the first time in vivo that a single gene, Elf3, is the critical upstream regulator of Tgf-betaRII in mouse small intestinal epithelium. CONCLUSIONS: This has important implications for our understanding of tissue-specific gene regulation and further strengthens the potential clinical connection between ELF3 and colorectal cancer involving transforming growth factor beta insensitivity.
Assuntos
Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica no Desenvolvimento , Células Caliciformes/fisiologia , Intestino Delgado/citologia , Glicoproteínas de Membrana/genética , RNA/genética , Receptores de Fatores de Crescimento Transformadores beta/genética , Fatores de Transcrição/genética , Animais , Proteínas de Ligação a DNA/deficiência , Feminino , Células Caliciformes/citologia , Imuno-Histoquímica , Intestino Delgado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Transgênicos , Fenótipo , Regiões Promotoras Genéticas , Proteínas Serina-Treonina Quinases , Receptor do Fator de Crescimento Transformador beta Tipo II , Receptores de Fatores de Crescimento Transformadores beta/biossíntese , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/deficiência , Ativação TranscricionalRESUMO
BACKGROUND & AIMS: The mammalian small intestine is lined by a highly specialized epithelium that functions in the digestion and absorption of nutrients. The molecular mechanisms that direct intestinal epithelial cell morphogenesis and terminal differentiation are poorly understood. We have previously identified Elf3 (E74-like factor-3) as a member of the ETS transcription factor family strongly expressed in small intestinal epithelium. The aim of this study is to investigate the biological roles of Elf3 in vivo. METHODS: Mice with a null mutation of Elf3 were generated through targeted gene disruption. Characterization of intestinal development was performed by histologic and immunohistochemical techniques. RESULTS: Targeted disruption of Elf3 resulted in fetal lethality of about 30% at around embryonic day 11.5. Seventy percent of the Elf3-deficent progeny were born and displayed severe alterations of tissue architecture in the small intestine, manifested by poor villus formation and abnormal morphogenesis and terminal differentiation of absorptive enterocytes and mucus-secreting goblet cells. Crypt cell proliferation, however, appeared intact in Elf3-deficient mice.Elf3-deficient enterocytes express markedly reduced levels of the transforming growth factor beta type II receptor (TGF-beta RII), an inducer of intestinal epithelial differentiation. CONCLUSIONS: Elf3 is an important regulator of morphogenesis and terminal differentiation of epithelial cell lineages in the small intestine.
