Targeted Disruption of Tgif, the Mouse Ortholog of a Human Holoprosencephaly Gene, Does Not Result in Holoprosencephaly in Mice

Abstract

5′-TG-3′-interacting factor or transforming growth factor beta (TGF-β)-induced factor (TGIF) belongs to a family of evolutionarily conserved proteins that are characterized by an atypical three-amino-acid loop extension homeodomain. In vitro studies have implicated TGIF as a transcriptional repressor and corepressor in retinoid and TGF-β signaling pathways that regulate several important biological processes. Heterozygous nonsense and missense mutations of the human TGIF gene have been associated with holoprosencephaly, the most common congenital malformation of the forebrain. In mice, Tgif mRNA is expressed ubiquitously in the ventricular neuroepithelium at embryonic day 10.5 (E10.5) but displays a medial to lateral gradient in the developing cerebral cortex at E12.5. The expression quickly declines by E14.5. The spatiotemporal expression profile of Tgif is consistent with its involvement in midline forebrain development. To better understand the function of Tgif in forebrain patterning and proliferation in vivo, we generated mice lacking Tgif by targeted deletion of exons 2 and 3, which encode 98% of the amino acids. Tgif^−/− mice had no detectable Tgif protein by Western blotting. Surprisingly, however, these mice were viable and fertile. In addition, there were no discernible derangements in any of the major organ systems, including the forebrain. Overall our results point to a possible functional redundancy of Tgif, potentially provided by the closely related Tgif2.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/.

ACKNOWLEDGMENTS

This work was supported in part by National Institute of Neurological Disorders and Stroke grant R01NS032457 to C.A.W. and by National Cancer Institute grant R24CA83034, a shared resource to Beth Israel Deaconess Medical Center administered by Daniel G. Tenen. C.A.W. is an Investigator of the Howard Hughes Medical Institute. J.S. is a Stuart H. Q. & Victoria Quan Fellow.

We thank members of the Walsh laboratory for their input throughout the course of this project, Clifford Tabin for the mouse Shh cDNA plasmid, Susan Dymecki for the FLP deleter mice, Margaret Thompson for the 129 genomic library, Urs Berger for the help with the ISH, Roderick Bronson for consultation on histology, Susanne White for help with histology, and Massachusetts General Hospital Gene Targeting Core for ES cell work and microinjections.