Disease relevance of Msx2

• A ternary complex of necdin, MAGE-D1, and Msx2 was formed in vitro, and an endogenous complex containing these three proteins was detected in differentiating embryonal carcinoma cells [1].
• We provide evidence that targeted infection in ovo using adenovirus containing Msx2 and a reporter molecule indicative of translation can induce apoptosis in either even- or odd-numbered rhombomeres [2].
• We provide evidence indicating that the lack of interdigital cell death and associated syndactyly is related to an absence of interdigital cells marked by expression of Fgfr2 and Msx2 [3].
• In addition, cotransfection studies in ROS 17/2.8 osteosarcoma cells using an Msx2 expression vector showed that Msx2 inhibits a COL1A1 promoter-chloramphenicol acetyltransferase construct [4].
• In the second, a mouse model of the human disease craniosynostosis, Boston type, has been created by misregulation of the Msx2 gene product [5].

High impact information on Msx2

• Most Msx2-mutant phenotypes, including calvarial defects, are enhanced by genetic combination with Msx1 loss of function, indicating that Msx gene dosage can modify expression of the PFM phenotype [6].
• Consistent with phenotypes associated with PFM, Msx2-mutant mice also display defective tooth, hair follicle and mammary gland development, and seizures, the latter accompanied by abnormal development of the cerebellum [6].
• Msx2-/- mice also have defects in endochondral bone formation [6].
• Msx2 deficiency in mice causes pleiotropic defects in bone growth and ectodermal organ formation [6].
• Our results provide a developmental basis for PFM and demonstrate that Msx2 is essential at multiple sites during organogenesis [6].

Chemical compound and disease context of Msx2

• We demonstrated previously that individuals affected with an autosomal dominant disorder of skull morphogenesis (craniosynostosis, Boston type) bear a mutated form of Msx2 in which a histidine is substituted for a highly conserved proline in position 7 of the N-terminal arm of the homeodomain (p148h) [7].

Biological context of Msx2

• To better understand Msx2 actions on osteogenesis versus adipogenesis, mechanistic studies were extended to C3H10T1/2 mesenchymal cells [8].
• MINT, the Msx2 interacting nuclear matrix target, enhances Runx2-dependent activation of the osteocalcin fibroblast growth factor response element [9].
• Msx2 abrogates Runx2-MINT OCFRE activation, and MINT-directed RNA interference reduces endogenous OC expression [9].
• However, Msx1 and Msx2 expression was unchanged in these transgenic mice, implying that induction of these genes is not essential for mediating BMP-induced interdigital apoptosis in mice [10].
• Thus, deregulated Msx2 gene expression may be a plausible genetic mechanism by which the autosomal dominant form of congenital microphthalmia may arise [11].

Anatomical context of Msx2

• Conversely, stable, forced Msx2 expression in MC3T3-E1 cells prevented osteoblast differentiation and matrix mineralization [12].
• Our findings indicate that Msx2 plays a central role in preventing ligaments and tendons from mineralizing [12].
• In addition, Msx2 was downregulated in a symptom- and calcification-dependent manner at the affected region in patients with ossification of the posterior longitudinal ligament [12].
• Reverse transcription-PCR and in situ hybridization demonstrated that Msx2 expression is higher in periodontal ligament and tendon cells than in osteoblasts [12].
• Msx1 and Msx2 were expressed in the sutural mesenchyme and the dura mater [13].

Associations of Msx2 with chemical compounds

• Of the three sutures studied, the coronal suture exhibited the greatest increase in Msx2 expression and was the most likely to undergo obliteration and fusion [14].
• The effect of Msx2 overexpression on retinal cell proliferation was assayed by bromodeoxyuridine (BrdU) incorporation and immunohistochemical staining [11].
• Regardless of cholesterol content, high fat diets induced mineralization of the proximal aorta (assessed by von Kossa staining) and promoted aortic expression of Msx2 and Msx1, genes encoding homeodomain transcription factors that regulate mineralization and osseous differentiation programs in the developing skull [15].
• By contrast, GST-Msx2 has no effect on calcitriol-regulated DNA-protein interactions at the VDRE [16].
• Finally, Msx2-/- uteri were found to exhibit abnormal water trafficking upon DES exposure, demonstrating the importance of Msx2 in tissue responsiveness to estrogen exposure [17].

Physical interactions of Msx2

• Necdin interacts with the Msx2 homeodomain protein via MAGE-D1 to promote myogenic differentiation of C2C12 cells [1].
• In addition, YY1 bound specifically to three YY1 binding sites on the proximal promoter of Msx2 that accounted for this transactivation [18].
• In support of this hypothesis, we found that Msx2 and Dlx5 can bind to the B-TAAT site as well as to a fragment containing the D- and E-TAAT sites in the Msx2 AER enhancer sequences [19].
• Functional antagonism between Msx2 and CCAAT/enhancer-binding protein alpha in regulating the mouse amelogenin gene expression is mediated by protein-protein interaction [20].

Regulatory relationships of Msx2

• In chromatin immunoprecipitation assays, Msx2 selectively inhibits Runx2 binding to OC chromatin [9].
• Bmp4 was expressed in the apical mesenchyme and Msx2 in the root sheath [21].
• Interestingly the expression of Msx2 was induced by bone morphogenetic protein 2 treatment in Runx2-deficient mesenchymal cells [22].
• Smad4 and beta-catenin co-activators functionally interact with lymphoid-enhancing factor to regulate graded expression of Msx2 [23].
• Introduction of Msx2 induced alkaline phosphatase activity in C3H10T1/2 and C2C12 cells and promoted the calcification of murine primary osteoblasts [22].

Other interactions of Msx2

• These results are consistent with functional redundancy between Msx1 and Msx2 in dental mesenchyme and support a model whereby Msx and Dlx genes function in parallel within the dental mesenchyme during tooth initiation [24].
• To better understand Msx2 regulation of the OCFRE, we have studied functional interactions between MINT and Runx2, a master regulator of osteoblast differentiation [9].
• Msx2 expression continued in the epithelial cell rests of Malassez, and the nearby cementoblasts intensely expressed Bmp3, which may regulate some functions of the fragmented epithelium [21].
• BMP-2 treatment completely blocked myotube formation and transiently induced expression of Cbfa1 and the bone-related homeodomain protein Msx-2 concomitant with loss of the myoblast phenotype [25].
• In this study, we have localized the ossification defect in ch mutants to the calvarial mesenchyme, which lacks the expression of transcription factors Msx2 and Alx4 [26].

Analytical, diagnostic and therapeutic context of Msx2

• In both fetal and neonatal digits, we find that both Msx1 and Msx2 are expressed during regeneration, but not during wound healing associated with proximal amputations where no regenerative response is observed [27].
• We show that Msx2, a homeodomain protein, binds to this motif; however, Northern blot analysis revealed that Msx2 mRNA is present in undifferentiated bone cells but not in fully differentiated osteoblasts [4].
• Protein-protein interaction between Msx2 and C/EBPalpha is identified with co-immunoprecipitation analyses [20].
• Electrophoresis mobility shift assays demonstrate that Msx2 interferes with the binding of C/EBPalpha to its cognate site in the mouse amelogenin minimal promoter, although Msx2 itself does not bind to the same promoter fragment [20].
• Western blot analysis of fractionated cell extracts reveals that mature approximately 110 kDa (N-terminal) and approximately 250 kDa (C-terminal) MINT protein fragments accumulate in chromatin and nuclear matrix fractions, cosegregating with Msx2 and topoisomerase II [28].

References