The present invention discloses heterodimers comprising endoglin-Fc and ALK1-Fc, or heterodimers comprising endoglin-Fc and ALK2-Fc. The Fc domains can include amino acid mutations that promote heterodimer formation. In certain aspects, the disclosure provides heteromeric polypeptide complexes comprising a co-receptor of the TGF-beta superfamily and an extracellular domain of a type I serine/threonine kinase receptor of the TGF-beta superfamily, an extracellular domain of a type II serine/threonine kinase receptor of the TGF-beta superfamily, or an additional co-receptor of the TGF-beta superfamily. In some embodiments, the disclosure provides heteromultimers comprising a ligand-domain of one or more co-receptor selected from: endoglin, Cripto-1, Cryptic, Cryptic family protein IB, CRIM1, CRIM2, BAMBI, BMPER, RGM-A, RGM-B, hemojuvelin, betaglycan, and MuSK. In some embodimnents, the disclosure provides soluble heteromultimers comprising a ligand-domain of a co-receptor and a ligand- binding domain of a type II receptor selected from: ActRIIA, ActRIIB. TGFBRII, BMPRII, and MISRII. In some embodiments, the disclosure provides soluble heteromultimers comprising a ligand-domain of a co-receptor and a ligand-binding domain of a type I receptor selected from: ALK1, ALK2, ALK3, ALK4, ALK5, ALK6, and ALK7. In certain aspects, such TGF-beta superfamily heteromultimers may be used to regulate (promote or inhibit) growth of tissues or cells including, for example, bone and hematopoietic lineages, including red blood cells.La présente invention concerne des hétérodimères comprenant endogline-Fc et ALKl-Fc, ou des hétérodimères comprenant endogline-Fc et ALK2-Fc. Les domaines Fc peuvent comprendre des mutations d'acide aminé qui favorisent la formation d'hétérodimères. Dans certains aspects, l'invention concerne des complexes de polypeptide hétéromères comprenant un co-récepteur de la superfamille TGF-bêta et un domaine extracellulaire d'un récepteur de sérine/thréonine kinase d
