The project supported by the Research Council of Finland aims to identify new disease-causing genes in families with early-onset osteoporosis. We use novel genetic methods to identify the underlying gene mutations in families with early-onset osteoporosis. When the gene defect is detected, we use cell-based studies and zebrafish and mouse models to study the mechanisms through which the gene mutation leads to osteoporosis. In addition, we perform extensive musculoskeletal evaluation, including bone and muscle biopsies, to establish the clinical and tissue-level consequences of the disease-causing gene variants. This study provides new information about inherited osteoporosis and helps us to improve diagnosis and treatment of osteoporosis and related bone disorders.