Areas of Interest
My laboratory's research is focused on the molecules that
regulate the differentiation of osteoblasts, which are the cells
responsible for bone formation. We are using the a1 Type I
collagen (Col1a1) promoter, which is very highly expressed in
osteoblasts, as a model system for these studies. By studying
promoter-reporter constructs in transgenic mice, we identified a
homeodomain protein binding site which is necessary for high
level expression of the gene. We are currently studying four
proteins which bind to this site, Msx2, Dlx5 , Prx1 and Prx2.
Although knockout and overexpression studies in mice have
suggested that these proteins play a role in skeletal
development, the precise mechanistic description of this role is
difficult because these proteins are expressed in many cell
types during development. My laboratory has focused on
development and exploitation of retroviral vectors which allow
studies of protein and promoter function in primary osteoblasts
derived directly from chick embryos or mice, which more closely
mimic cells in intact animals than immortalized osteoblastic
cell lines. Our results led us to propose a model for the role
of Msx2 in skull development, in which Msx2 inhibits osteoblast
differentiation yet causes more rapid bone growth. This model
explains the results obtained from overexpression and knockout
studies. Our ongoing studies on Dlx5, Prx1 and Prx2 are leading
to similar insights. Dlx5 stongly stimulates osteoblast
differentiation, while Prx1 and 2 may be inhibitors. A second
area of research is focused on developing retrovirus vectors and
techniques for gene therapy of bone. We have developed a vector
in which the Col1a1 promoter drives expression of a marker gene
specifically in osteoblasts of transgenic mice, which has
previously proved difficult because of the inactivation of
retroviruses in embryonic stem cells. We are also developing
methods for re-introducing engineered osteoblast precursers into
the bone. Thus we hope to be able to treat mouse models of human
diseases, and eventually to contribute to treatment of human
diseases such as osteoporosis.
Lab Rotation Projects
We are focusing on bone and tooth biology. The specific
aspects that we are currently studying are the regulation of
osteoblast and odontoblast differentiation by homeobox genes of
Dlx and Msx families. We use a variety of techniques for these
studies, including ectopic expression of these proteins in
primary cell cultures using retrovirus or lentivirus vectors,
inhibition of expression of genes using lentivirus
vector-delivered siRNA, and studies on standard or conditional
knockouts of these genes. We also
have long standing interests in studying the regulation of the
type I collagen gene in osteoblasts using transgenic mice, and
the development of methods for gene therapy of bone diseases
such as osteoporosis or osteogenesis imperfecta. We have
recently developed techniques for manipulation of bacterial
artificial chromosomes using homologous recombination, which we
believe will be valuable in these studies. Rotation projects
will be selected by the student from among these various
projects.
Selected Publications
Tadic, T., Dodig, M., Ercig, I., Marijanovic, I., Mina, M.,
Kalajzic, Z., Velonis, D., Kronenberg, M.S., Kosher, R.A.,
Ferrari, D. and Lichtler, A.C. Overexpression of Dlx5 in chicken
calvarial cells accelerates osteoblastic differentiation J. Bone
Miner. Res 17:1008-1014 2002.
Kalajzic, I., Stover, M. L., Liu, P., Kalajzic, Z., Rowe, D.
W. and Lichtler, A. C. Use of vsv-g pseudotyped retroviral
vectors to target murine osteoprogenitor cells. Virology
284:37-45, 2001
Stover, M.L., Wang, C-K.L., McKinstry, M.B., Kalajzic, I.,
Gronowicz, G., Clark, S.H., Rowe, D.W. and Lichtler, A.C.
Bone-directed expresion of Col1a1 promoter-driven
self-inactivating retroviral vector in bone marrow cells and
transgenic mice. Mol. Ther. 3:543-550, 2001.
Liu, P., Kalajzic, I., Stover, M.L., Rowe, D.W. and Lichtler,
A.C. 2001. Human bone marrow stromal cells are efficiently
transduced by vesicular stomatitis virus-pseudotyped
retrovectors without affecting subsequent osteoblastic
differentiation. Bone 29:331-335. |
