Foxa2 minimal notochord enhancer element mediates Cre expression in the node and notochord

摘要

The Cre/loxP system is facilitates excision of DNA sequences locatedbetween two loxP sites by the Cre recombinase (Cre) of Bacteriophage P1.Generation of different tissue-specific Cre transgenic mice, which can beused for conditional gene inactivation in specific tissues, is an ideal tool forstudying gene function in different tissues in mice.The winged-helix transcription factor, Foxa2, is essential for developmentof the node and notochord. In mouse, Foxa2 expression is observed in thenode, notochord, floor plate and gut epithelium during development.In order to facilitate genetic studies of notochord development, we have useda 520 bp element (mNE) upstream of the Foxa2 gene, which directs specificexpression in the node and notochord to generate a mouse line, mNE-Cre, inwhich the Cre gene was placed under the regulatory control of the mNE andlinked to an IRES-lacZ reporter. Staining for b-galactocidase (b-gal) activityrevealed that the Cre transgene was expressed from E7.5 to E9.5 specificallyin the notochord. Moreover, crossing of the mNE-Cre transgenic mice withthe loxP mouse reporter line, Z/EG, resulted in enhanced green fluorescentprotein (EGFP) signal specifically in the node and notochord from E8.0 toE9.5. The mNE-Cre mice have been used to conditionally inactivateSmoothened (Smo) in the notochord, and preliminary data revealed that lossof both alleles of Smo in the notochord resulted in embryonic lethality. ThemNE-Cre transgenic mice are therefore a useful resource for conditionalgene manipulation in the notochord in mice.