The human brain is the most amazing self-assembling machine in the
world. Our interest is in understanding how the 100 billion neurons and
100 billion glia that compose our brains are able to acquire the
necessary shapes and make the necessary cell-cell contacts to give rise
to human consciousness.
To identify the basis of neuronal shape and connectivity at a
fundamental level, we have turned to the simple model system of the
roundworm C. elegans, a nematode whose entire nervous system
contains only 302 neurons. Remarkably, each of these neurons acquires
the same shape and makes the same cell-cell contacts in every
individual. Thus, because this nervous system is "genetically
hard-wired," it is straightforward to isolate mutants that disrupt
wiring and then to identify the relevant genes.
We have focused, for a start, on the major sense organ of C. elegans,
called the amphid. The amphid contains 12 sensory neurons ensheathed by
two glial cells. The neurons extend unbranched dendrites to the tip of
the nose. We have characterized an unusual mechanism by which these
dendrites extend, and have identified a pair of secreted matrix
proteins--similar to those involved in sperm-egg adhesion--which are
required to define the contact site at the nose where the dendrites
attach. In ongoing work, we seek to characterize the mechanism by which
the amphid contact site is specified, as well as how distinct contact
sites at the nose tip are specified to collectively determine the
sensory anatomy of this simple organism.
By identifying how neurons get their shapes and make the right contacts
in this model system, we aim to establish an intellectual framework
that will help us understand how our own brain's far more complex
anatomy is encoded.
About Maxwell G. Heiman
Max Heiman received a BS in Biology from Yale University in 1997,
studying homeobox gene regulation in the laboratory of Frank Ruddle. In
2003, he received a PhD in Biochemistry from the University of
California, San Francisco. There, he worked in the laboratory of Peter
Walter and identified factors that regulate cell-cell fusion, using
yeast mating as a model genetic system. He then conducted postdoctoral
studies at Rockefeller University in the laboratory of Shai Shaham,
using C. elegans as a model system in which to characterize neuronal and glial development.
Heiman's general interests are in the self-assembly of complex
biological structures, ranging in scale from extracellular matrix
fibrils to the complete nervous system. He has been a fellow of the
Howard Hughes Medical Institute and the Jane Coffin Childs Fund.