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.
ExperimentName: Targeted disruption of Lrp5 in mice
NonHumanModel: Mus musculus
GeneAlteration: Model animals were subjected to targeted disruption of Lrp5 by inserting an IRES-LacZ-Neomycin cassette to replace the region encoding the extracellar domain, starting at amino acid 373.
ModelPhenotype: HP:0004349 (Reduced bone mineral density), HP:0410280 (Pediatric onset), decreased osteoblast proliferation, HP:0007968 (Remnants of the hyaloid vascular system), failure of macrophage-mediated endothelial cell apoptosis
HumanPhenotype: HP:0000939 (Osteoporosis), HP:0011463 (Childhood onset), HP:0000541 (Retinal detachment), HP:0007968 (Remnants of the hyaloid vascular system), HP:0008046 (Abnormal retinal vascular morphology), HP:0000618 (Blindness), HP:0001249 (Intellectual disability), HP:0020110 (Bone fracture), HP:0000938 (Osteopenia), HP:0000926 (Platyspondyly)
ModelEvidence: Model animals subjected to targeted disruption of Lrp5 resembled human patients in that they exhibited reduced bone mineral density in the post-natal stage (Figs. S2, 3A), decreased osteoblast proliferation (Fig. 4), delayed ossification (Fig. 5), and remnants of the hyaloid vascular system due to failure of macrophage-mediated endothelial cell apoptosis (Fig. 8).
ModelVariant: The model features disruption of the wild-type Lrp5 gene, but not a mutation equivalent to a human variant.