Mark Zoran joined the Department of Biology
faculty at Texas A&M University in January of 1992. He
is currently an Associate Professor of Biology and Neuroscience,
the Graduate Advisor for the Department of Biology, and
the Chair of the Interdisciplinary Faculty of Neuroscience.
Mark graduated from DePue High School (Illinois) in 1975.
He earned a B.A. in Biology (1979) from Augustana College,
Illinois, and an M.S. in Biological Sciences (1981) from
Illinois State University. In 1987, he received a Ph.D.
in Zoology (Neurobiology) from Iowa State University.
has studied the parental care behaviors of Cichlid fishes,
the neural pathways underlying rapid escape in aquatic
oligochaetes, and the developmental mechanisms governing
synapse formation between identified snail neurons.
His current research interests include developmental
relationships between electrical and chemical synapses
in regenerating nervous systems, molecular mechanisms
governing neural regeneration and morphallaxis, and
the cellular control of physiological rhythms in the
avian visual system (in collaboration with Dr. Vincent
Cassone). Mark teaches undergraduate courses in physiology
and neurobiology and graduate level courses in comparative
neurobiology and neural development.
laboratory studies cellular mechanisms governing the
formation of specific synaptic connections between neurons
and their targets. These mechanisms include cell-cell
recognition and target-dependent induction of the presynaptic
secretion machinery. Our studies investigate synapse
formation of identified motoneurons following nerve
injury in vivo and following isolation of neurons into
cell culture. Since the synapse is the site of most
interneuronal communication within the nervous system,
an understanding of the development, regeneration and
plasticity of these connections is crucial to an ultimate
appreciation of neural integration and brain function.
In our studies of synaptic specificity, we take advantage
of the accessibility of neurons within the buccal nervous
system of the American pond snail, Helisoma trivolvis.
focus of my research program investigates the role of
target-recognition and synaptic induction in the formation
of neuromuscular synapses. Using electrophysiological
techniques, we have found that identified buccal motoneurons
are selective in synapse formation and require contact
with appropriate muscle targets before acquiring secretory
competence. Action potential-regulated transmitter release
is elevated specifically at neuritic arbors in contact
with appropriate muscle targets and not at contacts
with inappropriate muscle targets. Image analyses of
presynaptic neuronal architecture revealed that appropriate,
but not novel, muscle targets elicit increased arborization
of neurites at sites of contact. The long-term goal
of these studies is to determine the signals and signaling
mechanisms associated with this selective synaptogenesis.
Blockage of activity-based cell-cell communication and
inhibition of RNA and protein synthesis disrupt target-dependent
induction of excitation-secretion coupling. Future studies
will investigate the specific molecular machinery expressed
during these crucial periods of synaptic contact. In
addition, electrical synaptic connections are also formed
by motoneurons in a robust, target-dependent fashion
in cell culture. Therefore, another exciting direction
my program has recently taken involves the cellular
mechanisms governing specificity of electrical synaptogenesis.
and J.C. Poyer. 1998. Temporal and spacial resolution
of Helisoma neuronal synapse formation. The Neuron in
Cell Culture. IBRO Handbook (Ed. L.W. Haynes),
John Wiley & Sons, Ltd., Sussex.
and M.J. Zoran. 1997. Serotonin-induced modulation
of excitability in an identified Helisoma neuron. J.
Exp. Biol. 200:1537-1548
and M.J. Zoran. 1996. Activity-dependent induction
of functional secretory properties at cultured neuromuscular
synapses of Helisoma. J. Neurophysiol. 76:2635-2643
M.J., B. Metts, and J.C. Poyer. 1996. Specific muscle
contacts induce increased transmitter release and neuritic
arborization in motoneuronal cultures. Dev. Biol.
and M.J. Zoran. 1996. Short-term and long-term
alterations in neuronal excitability during injury-induced
axonal regeneration in ganglia and cell culture. Invet.