Designer Nodal/BMP2 Chimeras Mimic Nodal Signaling, Promote Chondrogenesis, and Reveal a BMP2-like Structure

Abstract

Background: Nodal is a TGF- superfamily member that plays important roles in development and diseases but is difficult to produce for biochemical studies. Results: Nodal promotes chondrogenesis, and Nodal/bone morphogenetic protein 2 chimeras function indistinguishably from Nodal but have BMP2-like structure. Conclusion: Nodal/BMP2 chimeras can substitute for Nodal in functional and structural studies. Significance: Nodal/BMP2 chimeras have therapeutic potential. Nodal, a member of the TGF- superfamily, plays an important role in vertebrate and invertebrate early development. The biochemical study of Nodal and its signaling pathway has been a challenge, mainly because of difficulties in producing the protein in sufficient quantities. We have developed a library of stable, chemically refoldable Nodal/BMP2 chimeric ligands (NB2 library). Three chimeras, named NB250, NB260, and NB264, show Nodal-like signaling properties including dependence on the co-receptor Cripto and activation of the Smad2 pathway. NB250, like Nodal, alters heart looping during the establishment of embryonic left-right asymmetry, and both NB250 and NB260, as well as Nodal, induce chondrogenic differentiation of human adipose-derived stem cells. This Nodal-induced differentiation is shown to be more efficient than BPM2-induced differentiation. Interestingly, the crystal structure of NB250 shows a backbone scaffold similar to that of BMP2. Our results show that these chimeric ligands may have therapeutic implications in cartilage injuries.