Ivan Borisovich Lobov

Bio: Ivan Borisovich Lobov is an academic researcher from University of Cincinnati. The author has contributed to research in topics: Wnt signaling pathway & LRP5. The author has an hindex of 1, co-authored 1 publications receiving 1068 citations.

Cbfa1-independent decrease in osteoblast proliferation, osteopenia, and persistent embryonic eye vascularization in mice deficient in Lrp5, a Wnt coreceptor

Abstract: The low-density lipoprotein receptor-related protein (Lrp)-5 functions as a Wnt coreceptor. Here we show that mice with a targeted disruption of Lrp5 develop a low bone mass phenotype. In vivo and in vitro analyses indicate that this phenotype becomes evident postnatally, and demonstrate that it is secondary to decreased osteoblast proliferation and function in a Cbfa1-independent manner. Lrp5 is expressed in osteoblasts and is required for optimal Wnt signaling in osteoblasts. In addition, Lrp5-deficient mice display persistent embryonic eye vascularization due to a failure of macrophage-induced endothelial cell apoptosis. These results implicate Wnt proteins in the postnatal control of vascular regression and bone formation, two functions affected in many diseases. Moreover, these features recapitulate human osteoporosis-pseudoglioma syndrome, caused by LRP5 inactivation.

WNT signaling in bone homeostasis and disease: from human mutations to treatments

Abstract: Low bone mass and strength lead to fragility fractures, for example, in elderly individuals affected by osteoporosis or children with osteogenesis imperfecta. A decade ago, rare human mutations affecting bone negatively (osteoporosis-pseudoglioma syndrome) or positively (high-bone mass phenotype, sclerosteosis and Van Buchem disease) have been identified and found to all reside in components of the canonical WNT signaling machinery. Mouse genetics confirmed the importance of canonical Wnt signaling in the regulation of bone homeostasis, with activation of the pathway leading to increased, and inhibition leading to decreased, bone mass and strength. The importance of WNT signaling for bone has also been highlighted since then in the general population in numerous genome-wide association studies. The pathway is now the target for therapeutic intervention to restore bone strength in millions of patients at risk for fracture. This paper reviews our current understanding of the mechanisms by which WNT signalng regulates bone homeostasis.

Secreted antagonists of the Wnt signalling pathway

Abstract: The extracellular antagonists of the Wnt signalling pathway can be divided into two broad classes. Both classes of molecule prevent ligand-receptor interactions, but by different mechanisms: members of the first class, which include the sFRP (secreted Frizzled-related protein) family, WIF (Wnt inhibitory factor)-1 and Cerberus, primarily bind to Wnt proteins; the second class comprises certain members of the Dickkopf (Dkk) family, which bind to one subunit of the Wnt receptor complex. In addition, there are other protein interactions that contribute to Wnt antagonist function. Moreover, certain sFRPs and Dkks do not antagonise Wnt function, which suggests that these families have as-yet-undiscovered functions.