26 February
2007
American scientists have identified
a new form of the brittle bone disorder osteogenesis
imperfecta and have determined the genetic defect that
underlies it.
Osteogenesis imperfecta (OI) is a
disorder characterised by bones that break easily and is
caused by mutations in the gene encoding the protein type
I collagen. The classical form of OI is a dominant
disease, meaning that a mutation in only one copy of the
type I collagen gene is sufficient to cause the disease.
Joan Marini and colleagues from the
US National Institute of Child Health and Human
Development <http://www.nichd.nih.gov/>
in Maryland have now identified a new recessive form of
the disease, in which mutations of both copies of a gene
are required.
Predicting that some forms of OI
might be caused by altered forms of proteins that
interact with and modify type I collagen, the authors
sequenced the gene encoding an enzyme called P3H1 in five
individuals with severe or lethal abnormal bone
development.
Mutations that either significantly
reduced or eliminated the amount of P3H1 were found in
all five individuals. P3H1 chemically modifies a single
amino acid in type I collagen, which presumably
facilitates folding and promotes stability.
This recessive form of OI has
features that overlap with those of classical OI, but is
also characterised by distinctive features.
The study will appear in the March
issue of Nature Genetics <http://www.nature.com/ng/>
Source: Australian
Life Scientist Online: by
Kate McDonald 26-Feb-2007
