Areas of Interest
We are pursuing three projects that extend from our interests
in the development of tissues and the innovative application of
light microscopy to biology: Developmental cell fusion,
Second-harmonic generation microscopy, and Genome-wide imaging
of C. elegans development.
Developmental cell fusion: Formation of multinucleate
syncytia (giant cells) is essential to the development and
regeneration of human skeletal muscle, and is key to
fertilization and the formation of various specialized cell
types in many species. Yet the mechanism by which fusing cells
recognize each other and merge their membranes is poorly
understood. We use genetics and microscopy in the nematode worm
C. elegans to study the mechanisms by which cells fuse during
this animal's development. Our recent studies of the unique
cell-fusion protein EFF-1 indicate that the molecular machinery
of cell fusion has been re-invented during evolution of
different cell types and divergent organisms. We are also
investigating the mechanism of mammalian myoblast fusion,
combining experimental tools developed specifically for that
system with our experience from the study of C. elegans syncytia.
Second-harmonic generation (SHG) imaging: We recently
discovered that thick myosin filaments in the actomyosin lattice
of striated muscle cells produce second-harmonic generation.
This non-linear optical effect produces bright contrast from the
endogenous unlabeled proteins themselves. The second harmonic
light can be imaged at high three-dimensional spatial resolution
on a microscope, yielding a digital profile of the arrangement
and internal structure of muscle fibers in live tissue. We are
applying SHG microscopy to the study of degenerative muscle
diseases and aging, as well as the process of myofibrillogenesis
in the differentiation of muscle cells.
Genome-wide imaging of C. elegans development: We are
working to develop a database of genome and proteome activity in
the developing nematode C. elegans. This tiny yet complex animal
is remarkable both for its transparency and the cell-by-cell
invariance its developmental program. We plan to use two
distinct fluorescence imaging technologies to record the
dynamics of expression and localization of GFP-tagged gene
products within live worms and embryos. The standardized digital
data produced by these instruments will then be correlated to
find genes and proteins that work coordinately in the formation
of specific cell types and tissues.
Lab Rotation Projects
Cell-cell fusion in mammalian and invertebrate development.
Muscle and connective tissue structure imaging. Genomic-scale
imaging of gene expression in embryogenesis.
Mohler WA, Shemer G, del Campo JJ, Valansi C, Opoku-Serebuoh,
Scranton V, Assaf N, White JG, and Podbilewicz B. 2002. The type
I membrane protein EFF-1 is essential for developmental cell
fusion. Dev. Cell. 2: 355-362.
Campagnola PJ, Millard AC, Terasaki M, Hoppe PE, Malone CJ,
and Mohler WA . 2002. Three-dimensional high-resolution
second-harmonic imaging of endogenous protein structural
proteins in biological tissues. Biophys. J. 82: 493-508.
Campagnola PJ, Clark HA, Mohler WA , Lewis A, and Loew LM.
2001. Second-harmonic imaging microscopy of living cells. J.
Biomed. Opt. 6: 277-286.
Skop AR, Bergmann D, Mohler WA , and White JG. 2001.
Completion of cytokinesis in C. elegans requires a brefeldin
A-sensitive membrane accumulation at the cleavage furrow apex.
Curr. Biol. 11: 735-746.
Heid PJ, Raich WB, Smith R, Mohler WA , Simokat K, Gendreau
SB, Rothman JH, and Hardin J. 2001. The zinc finger protein
DIE-1 is required for late events during epithelial cell
rearrangement in C. elegans. Dev. Biol. 236: 165-180.
Hoier EF, Mohler WA , Kim SK, Hajnal A. 2000. The
Caenorhabditis elegans APC-related gene apr-1 is required for
epithelial cell migration and Hox gene expression. Genes Dev,
Mohler WA and Squirrell JM. 2000. Multiphoton imaging of
embryonic development. In: Imaging Neurons: A Laboratory Manual.
Yuste R, Lanni F, Konnerth A. eds. Cold Spring Harbor Laboratory
Press, Cold Spring Harbor, NY.
Charlton CA, Mohler WA , Blau HM. 2000. Neural cell adhesion
molecule (NCAM) and myoblast fusion. Dev Biol, 221:112-119.