Deficiency of Lrrk1 in mice causes a much higher BMD in the long bones and vertebrae than any other gene KO mouse lines that have been tested, which makes LRRK1 an attractive alternative drug target for the treatment of osteoporosis and osteoporotic fractures.4 The potential substrates in osteoclasts could be Csk, CLIP1, and Rac1/Cdc42 small GTPases. The gene discussed is LRRK1; the disease is osteoporosis.