Specifically, Lee's team found two mutations in the WNT1 gene -- one that caused early onset osteoporosis in the Swedish family, and one that caused a more severe form of osteogenesis imperfecta in the Asian family.
The study is one of four in the past two months alone that have identified various WNT1 mutations in families affected by osteogenesis imperfecta. "It's a hot topic right now," said Glorieux, who worked on one of those studies.
Together, the studies "underscore the importance of this protein in controlling bone formation," Lee said.
Both Lee and Glorieux said studying severe forms of brittle bone disease also gives insight into the common form of osteoporosis that affects many older adults.
In the United States, about 16 percent of women older than 50 have full-blown osteoporosis of the hip or lower spine, as do 4 percent of men, according to the U.S. Centers for Disease Control and Prevention. Many more -- including 61 percent of women -- have lower-than-normal bone mass in those areas.
The hope is to eventually develop new therapies for not only osteogenesis imperfecta, but also osteoporosis, Lee said. Knowing the specific WNT proteins involved in bone formation and maintenance gives researchers targets for new drug development, he explained.
Right now, the most common medications for osteoporosis are bisphosphonates, including brands such as Fosamax, Actonel and Boniva. Those drugs slow bone breakdown; unfortunately, they also put the brakes on bone formation, Lee said.
So researchers are trying to develop medications that would help build bone.
"If we can understand the mechanisms key to developing and maintaining bone mass, that opens potential therapeutic avenues," Glorieux said.
The Swedish family in this study had 10 members affected by a rare
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