Tgif1 and Tgif2 Regulate Axial Patterning in Mouse

Abstract

Tgif1 and Tgif2 are transcriptional repressors that inhibit the transcriptional response to transforming growth factor β signaling, and can repress gene expression by direct binding to DNA. Loss of function mutations in TGIF1 are associated with holoprosencephaly (HPE) in humans. In mice, embryos lacking both Tgif1 and Tgif2 fail to complete gastrulation, and conditional double null embryos that survive past gastrulation have HPE and do not survive past mid-gestation. Here we show that in mice of a relatively pure C57BL/6 strain background, loss of Tgif1 alone results in defective axial patterning and altered expression of Hoxc6. The primary defects in Tgif1 null embryos are the presence of extra ribs on the C7 vertebra, consistent with a posterior transformation phenotype. In addition we observed defective cervical vertebrae, primarily C1-C5, in both adult mice and embryos that lacked Tgif1. The combination of Tgif1 and Tgif2 mutations increases the severity and penetrance of the posterior transformation phenotype, without altering the type of defects seen. Similarly, exposure of Tgif1 mutant embryos to retinoic acid at E8.5 increased the severity and penetrance of the Tgif1 phenotype. This suggests that Tgif1 and Tgif2 regulate axial patterning and that reduced TGIF function sensitizes embryos to the effects of retinoic acid.

The protein kinase C super‐family member PKN is regulated by mTOR and influences differentiation during prostate cancer progression

“…Alexafluor 488, 546, and 647 secondary antibodies were from Thermo Fisher Scientific. Whole‐mount in situ hybridization was performed on embryos with digoxigenin‐labeled riboprobes, as described . β‐galactosidase staining was carried out as described.…”

“…Whole-mount in situ hybridization was performed on embryos with digoxigenin-labeled riboprobes, as described. 28 β-galactosidase staining was carried out as described 29 . Whole mount images were captured on a Leica MZ16 stereomicroscope and QImaging 5.0 RTV digital camera.…”

Functions of TGIF homeodomain proteins and their roles in normal brain development and holoprosencephaly

“…Primary fibroblasts from Tgif1 null embryos have gene expression changes and proliferation defects in vitro , that were partly dependent on altered TGFß signaling (Mar & Hoodless, 2006; Zerlanko et al, 2012). Increased sensitivity of Tgif1 mutant embryos to retinoic acid-induced teratogenecity was also observed, resulting in a higher frequency of exencephaly in exposed Tgif1 null embryos and more severe defects in the axial skeleton (Bartholin et al, 2006; Melhuish et al, 2016). Overall, these studies suggest that Tgif1 has multiple effects in mouse development, some of which may be attributable to the TGFß or retinoic acid pathways, but do not reveal any strong link to HPE.…”

“…Since Tgif1 and Tgif2 in mice appear to have largely overlapping functions during embryonic development (Melhuish, Taniguchi, & Wotton, 2016; Powers et al, 2010; Taniguchi, Anderson, Sutherland, & Wotton, 2012), TGIF2 represents a reasonable candidate gene that, when mutated, might cooperate with a TGIF1 mutation in driving the HPE phenotype. However, there is as yet no evidence for HPE-associated mutations in the human TGIF2 gene.…”

“…Given the teratogenic effects of retinoic acids and their link to HPE-like phenotypes (Lanoue et al, 1997; Sulik, Dehart, Rogers, & Chernoff, 1995), the possibility that reduced TGIF levels result in increased retinoid responsive gene expression has been of some interest. There is some evidence for increased sensitivity of Tgif1 null mouse embryos to in utero exposure to retinoic acid, but not for increased HPE-like phenotypes specifically (Bartholin et al, 2006; Melhuish et al, 2016).…”