Postdoctoral Positions are available in two NIH funded project areas:
I. Saccharomyces cerevisiae Pathogenesis and Quantitative Genetics (one
We are developing the model eukaryote S. cerevisiae as a model for
the pathogenic fungi and as a microbial model for quantitative genetics.
Quantitative genetics is the study of polygenic traits. Since most of the
phenotypic variation in natural populations is polygenic, quantitative
genetics is fundamentally important. Quantitative traits have been most
extensively studied in higher eukaryotes. However, detailed genetic and
molecular analysis in higher eukaryotes is quite difficult compared to
microbial systems. We will use the simplicity/genetic manipulability of S.
cerevisiae and whole genome analysis (1, 2, 3) to dissect the ability to
grow at high temperatures -- high temperature growth is both a quantitative
trait and a virulence trait (4, 5).
With respect to fungal pathogenesis S. cerevisiae is not only a
model eukaryote, this species is also a close relative of many pathogenic
fungi and is an emerging opportunistic pathogen in its own right.
Quantitative genetics is highly relevant to fungal pathogenesis because the
phenotypic differences between the avirulent S. cerevisiae laboratory
strain genetic background and the virulent S. cerevisiae clinical isolates
are quantitative in nature, e.g. the ability to grow at high temperatures.
In addition to aiding our understanding of quantitative genetics and fungal
pathogenesis, our genetic analysis will help us understand the evolution of
a harmless saprophyte into an emerging opportunistic pathogen.
II. Saccharomyces cerevisiae Phase Variation (one position).
S. cerevisiae phase variation, which is distinct from pseudohyphal
formation, MAT switching, Ty elements & silencing, is a novel eukaryotic
microbial model for cellular differentiation and gene regulation. Phase
variation, which has been extensively characterized in bacteria, involves
the regulation of gene expression through reversible DNA sequence changes
(reviewed in Trends in Genetics 8:422-427, Adv. Microb. Ecol. 13:263-300,
Curr. Biol. 4:24-33, Micro. Mol. Biol. Rev. 61:281-294); specific genes are
phase variable and specific regions of these genes are highly mutable. One
of the most common mechanisms of bacterial phase variation involves changes
in simple repetitive sequences -- similar to a number of human genetic
Clinical S. cerevisiae isolates undergo phase variation at multiple
loci with each phase variable locus having distinct phenotypic effects on,
for example, the utilization of novel carbon sources and on gene
expression. This work will be a detailed characterization of phase
variation including (i) the mechanism of phase variation at each locus and
(ii) the regulation by phase variable gene products of gene expression.
This work will use whole genome analysis to clone the phase variable loci
(1) and examine phase variable gene expression (2, 3).
1.) Winzeler, E.A., D. Richards, A. Conway, A.L. Goldstein, S. Kalman, M.J.
McCullough, J.H. McCusker, D.A. Stevens, L. Wodicka, D.J. Lockhart, and
R.W. Davis. 1998. Direct allelic variation scanning of the yeast genome.
2.) Lashkari, D.A., J.L. DeRisi, J.H. McCusker, A.F. Namath, C. Gentile, S.
Hwang, P.O. Brown, and R.W. Davis. 1997. Yeast micro-arrays for genome wide
parallel genetic and gene expression analysis. PNAS 94:13057-13062.
3.) Lashkari, D.A., J.H. McCusker, and R.W. Davis. 1997. Whole genome
analysis: experimental access to all genome sequenced segments through
larger scale efficient oligonucleotide synthesis and PCR. PNAS 94:8945-8947.
4.) McCusker, J.H., K.V. Clemons, D.A. Stevens, and R.W. Davis. 1994.
Saccharomyces cerevisiae virulence phenotype as determined in CD-1 mice is
associated with the ability to grow at 42ºC and form pseudohyphae. Infec.
5.) McCusker, J.H., K.V. Clemons, D.A. Stevens, and R.W. Davis. 1994.
Genetic characterization of pathogenic Saccharomyces cerevisiae isolates.
Extensive molecular biology expertise is required and yeast/fungal
genetics experience is highly desirable. The start date is flexible.
Salary funding is available on the grant. It is extremely unlikely that an
offer will be made without an interview. Therefore, while others are
welcome to apply, because of interview travel cost considerations only
candidates in North America or, possibly, Western Europe are likely to be
interviewed. Duke University is an AA/EOE. Send curriculum vitae as
e-mail text (ABSOLUTELY NO ATTACHMENTS OR ENCLOSURES) with contact
information for three references to:
Dr. John H. McCusker
Dept. of Microbiology, 3020
Duke University Medical Center
Durham, NC 27710
e-mail: mccusker at abacus.mc.duke.edu
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