The present invention provides an animal model which overexpresses
regucalcin, a calcium-binding protein that is inherently expressed in the
liver and the like of the higher animal, and which is characterized by a
showing of bone pathology typified by osteoporosis. When regucalcin
expression is lowered, it induces other physiological abnormalities. In
the present invention, cDNA encoding the full length of regucalcin
protein was cloned from a rat liver cDNA library, ORF was cut out, and
introduced into an expression vector (pCXN2). The pCXN2 gene expression
vector containing ORF cDNA was microinjected into the male pronucleus of
a fertilized egg of rat which was subsequently transplanted into the
uterine tube of a host rat to generate transgenic rats homozygous for
regucalcin. The transgenic rats are characterized by remarkable bone
pathology, morphologically as well as biochemically, and by significant
suppression of body weight gain, and are therefore useful for screening
of preventive and therapeutic agents related to bone diseases.