CLONING AND DEVELOPMENTAL EXPRESSION OF LFB3 HNF1-BETA TRANSCRIPTION FACTOR IN XENOPUS-LAEVIS/

We have cloned the Xenopus laevis homologue of the LFB3/HNF1 beta tran scription factor. RNase protection and in situ hybridisation experimen ts show that XLFB3 transcription starts in the gastrulating endoderm a t stage 10.5 (mid-gastrula). At later stages, XLFB3 transcripts within the endoderm are restricted to mid- and hindgut and to their derivati ve organs and tissues. XLFB3 is also expressed in the neuroectoderm an d in the pronephros anlage. XLFB3 is not expressed in the rostral part of all three germ layers, with coincident anterior borders that are s hifted anteriorly by treatment of developing embryos with retinoic aci d. XLFB3 is a useful marker of early endoderm differentiation and its expression pattern along the antero-posterior axis, as well as the res ponse to retinoic acid treatment, suggests a role in early morphogenes is.