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Faculty
Alexander Lichtler
Associate Professor of
Genetics and Developmental Biology
lichtler@nso1.uchc.edu
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. |
