The gene that gives you extra-dense bones
THROUGHOUT your lifetime, your bones are continually broken down and replaced through a process called restoration. Any time old bone is broken down faster than new bone can be generated, net bone loss occurs.
Boss loss can lead to osteopenia, which is characterised by low bone density and strength, eventually leading to osteoporosis. Besides diet, rumour has it that bone density can be affected by your genetics. Is this fact or fiction?
In 1994, a man survived without broken bones or fractures following a car crash. His doctors discovered that he had unusually dense bones; eight times denser than the average for a man his age. His radiologist referred him to Karl Insogna, director of the Yale Bone Centre in Connecticut.
Six years later, Insogna overheard a fellow physician mention his encounter with a family with unusually high bone mass. The two physicians became partners and traced the family tree, eventually linking the man from the car crash to this family. The duo noted that each member of the family had dense bones and unusually square jaws, but otherwise quite normal skeletons.
Insogna’s team studied the family, eventually zeroing in on a region of chromosome 11 that was likely linked to this enhanced quality.
In New York, Matthew Warman, who directed the Orthopedic Research Laboratories at the Boston Children’s Hospital, found mutations that disabled the LRP5 gene in children with osteoporosis pseudoglima syndrome (brittle bone disease). His team at Case Western Reserve University were also studying chromosome 11.
Eventually, the team found a gene mutation that hyperactivates the LRP5 gene, resulting in extra-dense bones.
In Nebraska, Mark Johnson and his colleagues at the Osteoporosis Research Centre of Creighton University also discovered the same mutation while studying a family with unusually dense bones. They identified 21 family members ranging from three to 93 years old who had this condition, all of whom had never broken a bone in their lives.
In more recent research, scientists are hoping to use these findings to discover ways to prevent and treat osteoporosis. One of the challenges present is how this mutation behaves as a single-gene disorder, meaning it may not be present in all members of families with high bone density and thus reducing the pool from which researchers can find viable research subjects.