An absence of Twist1 results in aberrant cardiac neural crest morphogenesis

Abstract

The basic helix-loop-helix transcription factor Twist1 plays an essential role in mesenchymal cell populations during embryonic development and in pathological disease. Remodeling of the cardiac outflow tract (OFT) into the functionally separate aortic arch and pulmonary trunk is dependent upon the dynamic, coordinated contribution of multiple mesenchymal cell populations. Here, we report that Twist1(-/-) mice exhibit OFTs that contain amorphic cellular nodules within their OFT endocardial cushions. The nodular mesenchyme expresses the related bHLH factors Hand1 and Hand2, but reduced levels of the normal cushion marker Periostin. Lineage mapping confirms that nodule cells are exclusively of cardiac neural crest origin (cNCC), and are not ectopic cardiomyocytes or smooth muscle cells. These studies also reveal a delay in cNCC colonization of the OFT cushions. Furthermore, these mapping studies uncover nodules in the pharyngeal arches, and identify Twist1(-/-) neural crest cell defects within the dorsal neural tube, which exhibits an expanded domain of Wnt1-Cre-lineage marked cells. Together, these data support a model where Twist1 is required both for proper cNCC delamination, and for emigration from the dorsal neural tube and along cNCC migration pathways. Within the Twist1(-/-) neural crest cell populations that do emigrate to the OFT, a Hand-expressing subpopulation displays defective maturation, tracking, and, presumably, cell-cell adhesion, further compromising cNCC morphogenesis.

SOX9 modulates the expression of key transcription factors required for heart valve development

“…When TWIST1 persists at later stages of valve development, it leads to increased mesenchyme proliferation, increased TBX20 expression, and primitive ECM (Chakraborty et al, 2010b). TWIST1 directly regulates Tbx20 (Lee and Yutzey, 2011), but, of note, Twist1-null hearts do not show a difference in Tbx20 levels in the AVC compared with WT (Vincentz et al, 2008). Interestingly, we found that TBX20 was downregulated in the Sox9 cKO AVC and that SOX9 occupied regulatory regions associated with TBX20.…”

“…TFs with the most reduced expression in Sox9 cKO valves were Twist1, Sox4 and Mecom. Similar to SOX9, these three TFs are highly expressed in the cardiac cushions and mutations in each of these factors cause major valve defects, resulting in embryonic fatality (Ya et al, 1998;Vincentz et al, 2008;Bard-Chapeau et al, 2014).…”

Preaxial polydactyly: interactions among ETV, TWIST1 and HAND2 control anterior-posterior patterning of the limb

“…Etv expression patterns overlap with Twist1 in several other developing tissues, such as the somites, cardiac mesenchyme, pharyngeal and branchial arches (Fuchtbauer, 1995;Chotteau-Lelievre et al, 2001;Brent and Tabin, 2004;Vincentz et al, 2008). Furthermore, the expression of both Etv and Twist1 is upregulated in breast cancer cells (Baert et al, 1997;Yang et al, 2004).…”

Hand1 phosphoregulation within the distal arch neural crest is essential for craniofacial morphogenesis

“…Digoxygenin (DiG)-labeled section and whole-mount ISHs were carried out as described (Barnes et al, 2011;Firulli et al, 2010;Vincentz et al, 2008). qRT-PCR was performed on a LightCycler 480II (Roche) using TaqMan primers (Life Technologies) recognizing the following transcripts: Fgf8, Spry1, Fgfr1, Etv5, Etv4, Shh, Ptch1, Gli1, Gli3 and Twist1.…”