RSPO2 and Osteopenia: This phenotype may be consistent with the Wnt10b-null mouse model in which the growth rate and bone mass are normal at 1 month of age, but progressive osteopenia develops thereafter.34 A potential role for Rspo2 in the repression of osteoclastogenesis will need to be investigated further in studies that activate osteoclast activity, such as ovariectomy.