Mice with disrupted TGFbeta signaling have normal cerebella development, but exhibit facial dysmorphogenesis and strain-dependent deficits in their body wall

Mechanical stretch-induced endoplasmic reticulum stress, apoptosis and inflammation contribute to thoracic aortic aneurysm and dissection

Thoracic aortic aneurysm/dissection (TAAD) is characterized by excessive smooth muscle cell (SMC) loss, extracellular matrix (ECM) degradation and inflammation. In response to certain stimuli, endoplasmic reticulum (ER) stress is activated and regulates apoptosis and inflammation. Excessive apoptosis promotes aortic inflammation and degeneration, leading to TAAD. Therefore, we studied the role of ER stress in TAAD formation. A lysyl oxidase inhibitor, 3-aminopropionitrile fumarate (BAPN), was administrated to induce TAAD formation in mice, which showed significant SMC loss (α-SMA level). Excessive apoptosis (TUNEL staining) and ER stress (ATF4 and CHOP), along with inflammation, were present in TAAD samples from both mouse and human. Transcriptional profiling of SMCs after mechanical stress demonstrated the expression of genes for ER stress and inflammation. To explore the causal role of ER stress in initiating degenerative signalling events and TAAD, we treated wild-type (CHOP(+/+)) or CHOP(-/-) mice with BAPN and found that CHOP deficiency protected against TAAD formation and rupture, as well as reduction in α-SMA level. Both SMC apoptosis and inflammation were significantly reduced in CHOP(-/-) mice. Moreover, SMCs isolated from CHOP(-/-) mice were resistant to mechanical stress-induced apoptosis. Taken together, our results demonstrated that mechanical stress-induced ER stress promotes SMCs apoptosis, inflammation and degeneration, providing insight into TAAD formation and progression.

The interactions of TGF-beta signalling pathway and Jagged2/Notch1 pathway induce acanthosis in lingual epithelia

The aims of this study were to distinguish between the primary and secondary effects of TGF-β signalling disruption by Dox treatment in NTPDase2+ cells; and to investigate the interactions between TGF-β signalling and Jagged2/Notch1 pathway in regulating the expansion of tongue epithelia stem cells.Transgenic mice expressing rtTA from the mouse NTPDase2 promoter or K14 promoter were used to generate an inducible dominant negative TGF-β receptor type II (Tgfbr2) mutant model.Disruption of TGF-β signalling in NTPDase2+ cells initially inhibited the formation of filiform papillae but led to their regeneration over time. In contrast, disruption of TGF-β signalling induced proliferation of lingual epithelia in the middle tongue. We also observed the proliferation of lingual epithelia in the posterior tongue near the circumvallate papillae. Interactions among the TGF-β signalling pathways, Jagged2/Notch1 signalling pathways and epigenetic modifications regulate the expansion of lingual epithelial stem cells. Different molecular mechanisms are involved in the developmental regulation of lingual epithelia and filiform papillae, dependent on the location along the whole tongue. The fluctuating phenotype of tongue epithelia, over time, may be the combined effects of signalling pathways and epigenetic modifications.

Myocardial deletion of Smad4 using a novel α skeletal muscle actin Cre recombinase transgenic mouse causes misalignment of the cardiac outflow tract

SMAD4 acts as the converging point for TGFβ and BMP signaling in heart development. Here, we investigated the role of SMAD4 in heart development using a novel α skeletal muscle actin Cre recombinase (MuCre) transgenic mouse strain. Lineage tracing using MuCre/ROSA26^LacZ reporter mice indicated strong Cre-recombinase expression in developing and adult heart and skeletal muscles. In heart development, significant MuCre expression was noted at E11.5 in the atrial, ventricular, outflow tract and atrioventricular canal myocardium, but not in the endocardial cushions. MuCre-driven conditional deletion of Smad4 in mice caused double outlet right ventricle (DORV), ventricular septal defect (VSD), impaired trabeculation and thinning of ventricular myocardium, and mid-gestational embryonic lethality. In conclusion, MuCre mice effectively delete genes in both heart and skeletal muscles, thus enabling the discovery that myocardial Smad4 deletion causes misalignment of the outflow tract and DORV.