Molecular structure, expression, and functional role of Clec11a in skeletal biology and cancers.

C-type lectin domain family 11 member A (Clec11a), also known as stem cell growth factor (SCGF), C-type lectin superfamily member 3 (CLECSF3), or osteolectin was initially identified as a growth factor for hematopoietic progenitor cells. The human Clec11a gene encodes a polypeptide of 323 amino acids with characteristics of a secreted glycoprotein encompassing two integrin-binding motifs, RGD (Arg-Gly-Asp) and LDT (Leu-Asp-Thr), a putative leucine zipper domain, and a functional C-type lectin domain. It regulates hematopoietic differentiation and homeostasis and exhibits a protective effect against severe malarial anemia and lipotoxicity. Furthermore, Clec11a promotes the differentiation of mesenchymal progenitors into mature osteoblasts in vitro and plays an important role in the maintenance of adult skeleton age-related bone loss and fracture repair. Receptor ligand binding results in activation of downstream signaling cascades including glycogen synthase kinase 3 (GSK3), ß-catenin, and Wnt, resulting in the expression of osteoblast-related gene transcripts including Alp, Runx2, Lef1, and Axin2. In addition, Clec11a is also associated with the development of several cancers, including leukemia, multiple myeloma, and gastrointestinal tract tumors. To date, however, the mechanisms governing transcription regulation of the Clec11a gene are not known and remain to be uncovered. Understanding the function and mechanism of action of Clec11a will pave the way for the development of Clec11a as a novel therapeutic target for conditions such as cancer, anemia, and skeletal diseases.