This gene is localized at chromosome 2q37.3 (Perrin-Schmitt et al., 1997) and has 2 exons (Šošic et al., 2003).

TWIST2 DNA sequence contains 2 exons separated by a large intron, with the entire coding region located in exon 1 (Šošic et al., 2003). Two transcript variants encoding the same protein have been described: variant 1 of 1434 bp and variant 2 of 1186 bp. Both variants encode a same protein but have different 3 UTR ( NCBI).

No pseudogene of TWIST2 is known.

The TWIST2 gene encodes a 160 aminoacid protein with a predicted molecular weight of 19 kDa (Li et al., 1995; Lee et al., 2000; Gong and Li, 2002).
TWIST2 structure includes 2 nuclear localization signals at the N-terminus (aa 31-34, aa 49-53), a basic helix-loop-helix (bHLH) domain (aa 66-117) and a C-terminal TWIST box region (aa 141-160) (Gong and Li, 2002).
Post transcriptional phosphorylation at Ser55 is predicted for both human and rodent protein ( phosphosite). The bHLH domain includes highly conserved Thr and Ser residues whose posphorylation has been demonstrated to affect dimer formation and DNA binding affinity in other TWIST family members (Firulli et al., 2005; Firulli and Conway, 2008).

TWIST2 is involved in mesodermal patterning and in differentiation of multiple cell lineages including muscle, cartilage, osteogenic, adipogenic and myeloid cells (Lee et al., 2000; Gong and Li, 2002; Lee et al., 2003; Sharabi et al., 2008). In human embryonic tissues TWIST2 protein is detectable in early chondroblast cells in cartilage plate and surrounding mesenchymal cells, especially near the tip of the digits (Lee et al., 2000). In the skin, it is expressed early in the undifferentiated mesenchymal layer beneath the epidermis that will develop into dermis (Lee et al., 2000). TWIST2 is expressed in myeloid progenitors (Sharabi et al., 2008). In adult tissues, TWIST2 is expressed in the bone marrow (Ishikawa et al., 2013). A low level of expression has been reported in glands and tubules (Lee et al., 2000) as well as liver, muscle, pancreas, and adipose tissue (Pettersson et al., 2010). It should be pointed out that many antibodies used to detect the expression of TWIST proteins recognize both members of the family, making it hard to actually assess the specific contribution of each protein.

Nuclear in embryonic tissues, predominantly cytoplasmic in adult tissues (Lee et al., 2000).

TWIST2 is a transcription factor belonging to the bHLH (basic helix loop helix) family (Li et al., 1995; Lee et al., 2000). bHLH proteins form homo- or heterodimers with other bHLH family members and, as dimers, bind DNA through the bHLH domain at cis regulatory motifs, termed E-box (CANNTG), leading to either activation or inhibition of transcription (Murre et al., 1989; Franco et al., 2011b). The specificity of the dimers depends on several factors: partner choice, phosphorylation, other protein-protein interactions and spatial-temporal expression (Murre et al., 1989; Franco et al., 2011b). The partner choice depends mainly on the availability and on the phosphorylation status of the partner (Firulli and Conway, 2008).
TWIST2, similar to TWIST1, may also control gene expression by epigenetic modulation of the promoter: TWIST1-2 interacts with and recruits histone acetyl transferases/histone deacetylases to the promoter regulatory region, resulting in transcriptional repression through histone modification (Hamamori et al., 1999; Gong and Li, 2002; Lee et al., 2003).
Role in embryonic development
Murine Twist2 was identified through yeast-two-hybrid screen (Staudinger et al., 1993) and it was named Dermo1 for its expression pattern in the dermis of mouse embryo (Li et al., 1995). Dermo1 was later renamed Twist2 (Šošic et al., 2003) based on its high homology and overlapping expression pattern with Twist1 (Li et al., 1995; Lee et al., 2000; ŠoŠic et al., 2003). During mouse embryogenesis Twist2 displays a spatial expression pattern similar to Twist1, but temporally delayed (Li et al., 1995; Lee et al., 2000). Twist2 is expressed at a lower level in the sclerotome and dermatome of the somites, and in the limb buds at Day 10.5, and accumulates predominantly in the dermatome, prevertebrae, and the derivatives of the branchial arches by Day 13.5 (Li et al., 1995). As differentiation of prechondrial cells proceeds, Twist2 becomes restricted to the perichondrium (Li et al., 1995). In the dermis, expression increases continuously through Day 17.5, is detectable in newborns but is then downregulated in adult tissues (Li et al., 1995). An analogous role has been reported for Twist2 in avian limb outgrowth and patterning (Wade et al., 2012) as well as skin development (Scaal et al., 2001).
TWIST2 plays an important role in early bone development, acting as a negative regulator of osteoblast differentiation. Indeed, TWIST2 represses osteoblast maturation maintaining cells in a preosteoblast phenotype (Tamura and Noda, 1999; Lee et al., 2000) and it inhibits bone specific gene expression (Zhang et al., 2008). TWIST2 is involved in the modulation of the activity of Runx2, a master regulator of osteogenic program, both at the transcriptional level and at the protein level (Bialek et al., 2004; Zhang et al., 2008). By interacting with Runx2, TWIST2 inhibits the expression of Runx2 downstream targets, thus blocking the osteogenesis program (Lee et al., 2003). Runx2 can be downregulated by ERK, therefore ERK cooperates with TWIST2 in the inhibition of osteoblast differentiation (Nakamura et al., 2010). Insulin receptor signaling also controls osteoblast development by suppressing TWIST2 (Fulzele et al., 2010; Ulrich et al., 2013). In osteoblast TWIST2 physically interacts with ATF4 affecting its DNA binding function (Danciu et al., 2012). During cranial cell development TWIST2 is a mediator of Wnt signaling in specifying dermal cell fate and suppressing the cartilage cell fate (Tran et al., 2010).
TWIST2 is furthermore involved in the inhibition of muscle differentiation program acting as a transcriptional repressor of MyoD, the activation of which typically requires the binding of MEF2 (Gong and Li, 2002). TWIST2 needs histone deacetylases (HDAC) to exert Myo-MEF2 inhibition (Gong and Li, 2002). TWIST2 is also a critical regulator of adipose tissue homeostasis acting as a physical inhibitor of the transcription factor ADD1/SREBP1c, involved in adipocyte differentiation (Lee et al., 2003).
TWIST2 is required for normal corneal keratocyte proliferation and eyelid morphogenesis. Loss of TWIST2 leads to corneal thinning, due to early cessation of proliferation of corneal stromal progenitors, resulting in fewer mature stromal keratocytes for the production of the corneal matrix (Weaving et al., 2010).
In myeloid lineage development, TWIST2 inhibits the proliferation and the differentiation of granulocyte macrophage progenitors (Sharabi et al., 2008). TWIST2-null 129/Sv mice undergo almost normal embryonic development but die within the first two weeks after birth due to cachexia and high levels of proinflammatory cytokines (Šošic et al., 2003). However, the phenotype is influenced by genetic background. In fact TWIST2-null mice in the 129/C57 mixed background survive with only a mild disease and facial signs reminiscent of facial dermal dysplasia (Setleis syndrome), the human disease associated with germline TWIST2 inactivating mutations (Tukel et al., 2010).
Role in hematopoiesis and inflammation
TWIST2 is constitutionally expressed in myeloid progenitors where negatively controls myeloid lineage differentiation into macrophages, neutrophils and basophils (Sharabi et al., 2008). TWIST2 regulates the function of mature myeloid cells by promoting the expression of the anti-inflammatory cytokine interleukin-10 and inhibiting the production of pro-inflammatory cytokines interleukin-12 and interferon-γ (Sharabi et al., 2008). TWIST2 expression is also induced by NF-kB, as part of a negative feedback loop in which cytokines activate NF-kB and downstream activation of TWIST2 results in repression of NF-kB activation (Šošic et al., 2003).
In T lymphocytes and in immature thymocytes TWIST2 inhibits galectin-1-induced apoptosis, a process implicated in thymic negative selection (Koh et al., 2008; Koh et al., 2009; Merindol et al., 2014). TWIST2 prevents NF-kB mediated expression of galectin receptor (CD7), therefore inhibiting galectin1/CD7-mediated apoptosis (Koh et al., 2008; Koh et al., 2009; Merindol et al., 2014).
Role in apoptosis and senescence
TWIST2 antagonizes oncogene-induced cell failsafe programs, apoptosis and senescence. In a genetic screen for antiapoptotic proteins, TWIST2 was demonstrated to protect cells from Myc and E1A-induced apoptosis by modulating the ARF/MDM2/p53 pathway (Maestro et al., 1999).
TWIST2 overcomes oncogene-induced premature senescence by abrogating the transcription of p16Ink4A and p21Cip1, key regulators of the p53- and RB-dependent pathways (Ansieau et al., 2008).
Role in oxidative stress
TWIST2 participates in the control of reactive oxygen species (ROS) and in cellular response to oxidative stress. TWIST2 lowers the level of intracellular ROS and displays an antioxidant activity in several cell types. TWIST-driven inhibition of oxidative stress is involved in the protection of cells against c-Myc induced apoptosis (Floch et al., 2013).
Role in stemness (cancer stem cells)
TWIST2 mediates mesenchymal stem cell (MSC) self-renewal by maintaining the immature phenotype of human MSC and inhibiting osteogenesis and chondrogenesis (Isenmann et al., 2009). In mouse, the inhibition of MSC differentiation induced by fibroblast growth factor 2 (Fgf2) is strongly correlated with the upregulation of TWIST2 and Spry4 and with the suppression of Erk1/2 activation (Lai et al., 2011). TWIST2-expressing cells exhibit an increased expression of stem cell markers Bmi-1, Sox2, CD24, Nanog and an increased capacity of self-renewal (Liu et al., 2014).
Role in EMT
TWIST2 has been involved in epithelial-mesenchymal transition (EMT), a process by which cells lose epithelial characteristics and acquire a migratory, mesenchymal phenotype. EMT is associated with downregulation of epithelial markers, such as E-cadherin, and induction of mesenchymal markers, such as N-cadherin. EMT has an essential role in embryonic development and in the initial steps of tumor invasion and metastasis. Several bHLH transcription factors are involved in the regulation of EMT. TWIST2 has been implicated in EMT in several experimental models and cancer types (Tsuji et al., 2008; Katoh and Katoh, 2009; Ponnusamy et al., 2010; Fang et al., 2011; Akkari et al., 2012; Amatangelo et al., 2012; Salnikov et al., 2012; Shimoda et al., 2012; Mao et al., 2012; Mao et al., 2013; Teng and Li, 2014; Díaz-Martín et al., 2014). A dynamic interaction between EMT and stemness gene programs has been observed in prostate and bladder cancer cell experimental models (Celià-Terrassa et al., 2012).

TWIST genes are evolutionary conserved from jellyfish to human. Duplications and deletions of TWIST genes occurred during vertebrate evolution (Germanguz et al., 2007; Gitelman, 2007).
The human TWIST2 protein shares 98.8% amino acid identity to mouse and rat and 95% to chicken Twist2 (Lee et al., 2000).
Within the bHLH protein family, TWIST2 displays the highest level of sequence similarity with TWIST1. The two proteins are near identical in the C-terminal Helix-Loop-Helix (HLH) and TWIST BOX domains, while they display some divergence in the N-terminal region (Lee et al., 2000; Gong and Li, 2002; Barnes and Firulli, 2009).

TWIST2 nonsense mutations have been associated with Focal Facial Dermal Dyspasia type III (Setleis syndrome), a developmental defect characterized by bitemporal or pre auricolar facial dermal dysplasia (Tukel et al., 2010; Cervantes-Barragán et al., 2011; Franco et al., 2011a; Girisha et al., 2014).

Missense mutations have been found in endometrial cancer COSMIC