Tbx2 and Tbx3 Act Downstream of Shh to Maintain Canonical Wnt Signaling during Branching Morphogenesis of the Murine Lung

Abstract

Numerous signals drive the proliferative expansion of the distal endoderm and the underlying mesenchyme during lung branching morphogenesis, but little is known about how these signals are integrated. Here, we show by analysis of conditional double mutants that the two T-box transcription factor genes Tbx2 and Tbx3 act together in the lung mesenchyme to maintain branching morphogenesis. Expression of both genes depends on epithelially derived Shh signaling, with additional modulation by Bmp, Wnt, and Tgfβ signaling. Genetic rescue experiments reveal that Tbx2 and Tbx3 function downstream of Shh to maintain pro-proliferative mesenchymal Wnt signaling, in part by direct repression of the Wnt antagonists Frzb and Shisa3. In combination with our previous finding that Tbx2 and Tbx3 repress the cell-cycle inhibitors Cdkn1a and Cdkn1b, we conclude that Tbx2 and Tbx3 maintain proliferation of the lung mesenchyme by way of at least two molecular mechanisms: regulating cell-cycle regulation and integrating the activity of multiple signaling pathways.

A de novo 2.2 Mb recurrent 17q23.1q23.2 deletion unmasks novel putative regulatory non-coding SNVs associated with lethal lung hypoplasia and pulmonary hypertension: a case report

“…TBX2 and TBX4 are essential for normal development, including proper lung organogenesis [37]. Dysregulation of these genes in mice leads to a reduction of lung branching [47,48], supporting the notion that 17q23.1q23.2 CNV deletions, detected in our newborn and other patients, are causative for their lethal lung phenotypes. Although SNVs and CNVs involving TBX4 confer a risk of lung disease, the heterogeneity of clinical features associated with TBX4 abnormalities suggests that they are not sufficient to lead to specific phenotypes and that lung phenotype cannot be explained by TBX4 haploinsufficiency alone.…”

Epithelial heparan sulfate regulates Sonic Hedgehog signaling in lung development

“…These results indicate that non-canonical WNT signaling was overall normal in Ext1 f/f ; Shh cre lungs. To test whether the decreased canonical WNT signaling accounted for some of the branching phenotype, we treated lung explants with LiCl at 10mM, a previously used dose that could efficiently activate canonical WNT signaling in explant culture system [ 37 ].However, LiCl treatment was insufficient to rescue the branching defects of mutant lung explants( S7L–S7S Fig ). These findings indicate that epithelial HS directly or indirectly modulates canonical WNT signaling in developing lung, however, the reduction of canonical WNT signaling may only play a minor role in branching or synergize with other dysregulated signaling pathways to contribute to some aspects of the developmental defects of Ext1 mutant lungs.…”

“…Sense riboprobes transcribed by T3 RNA polymerase were used as negative control. ISH on paraffin sections was performed as previously described [ 37 ]. Whole mount in situ hybridization was carried out using an optimized protocol [ 71 ].…”

IRF2BP2-deficient microglia block the anxiolytic effect of enhanced postnatal care

“…Both canonical and non-canonical Wnt signalling are important for synaptic plasticity and CNS development 48 . Overall, EPC appears to suppress non-canonical Wnt signalling in WT mice (with reduced levels of Wnt6 49 ) and increase canonical Wnt signalling (with reduced expression of known inhibitors of canonical Wnt signalling: Cdh1 50 , Itgbl1 51 , Shisa3 52 , Trabd2b 53 , Emilin1 54 , and Plac8 55 ). Wnt6 has been tied to schizophrenia and mood disorders 56 .…”