COL1A1 and Osteopenia: However, we observed a more severe osteopenia in adult Pkd1Col1a1(3.6)-cKO compared to Oc-Cre or Dmp1-Cre-mediated Pkd1 deletion, which could result from the effects of Col1a1(3.6)-Cre to delete Pkd1 during embryogenesis or to the leakiness of this promoter leading to alterations in systemic factors that lead to secondary effects on bone.