College of Arts and Sciences
DEPARTMENT OF BIOLOGY
2011 BIOLOGY HONORS STUDENTS
Congratulations to All!
Mathew Wajda, Mallory Romanovitch, Katherine St. Denis, Nathan Hicks,
Charles Hackett and Dr. Jim Vigoreaux
Charles S. Hackett received the George Perkins Marsh Award in
Ecology/Evolution
This award is presented to a student doing outstanding academic performance and excellence in
research in Biology. Mr. Charles Hackett’s Honors project on neural stem cell transplantation in
treatment of an animal model of Multiple Sclerosis will lead to two important journal papers. He
plans a career in medicine and medical research.
The title of his thesis is: "Modulating neural stem cell Fas expression in EAE"
ABSTRACT
MS is a chronic debilitating disease characterized by multifocal lesions of the white matter and a
variable clinical course. MS commonly presents first as a relapsing-remitting disease and later
progresses to a state of chronic neurodegeneration with white matter loss and cognitive decline.
Neural stem/progenitor cell (NPC) transplantation holds significant promise as a novel treatment
strategy for MS. Although studies have shown that NPC transplantation is beneficial in the
established animal model of MS (experimental autoimmune encephalomyelitis or EAE); it is
unclear whether NPCs have the ability to integrate into the host CNS and replace lost cells or if
their main mechanism of action is via bystander support of resident tissue. Using the EAE model
and a mutant strain of NPCs (lpr), we investigated the effects of altering the Fas system in NPC
transplantation therapy. Understanding the mechanisms by which NPCs exert beneficial effects
as well as exploring methods of increasing post-transplantation survival and differentiation is
critical to advancing this treatment strategy. We show the transplantation of NPCs into EAE
mice ameliorates clinical symptoms with greater efficacy than sham treatments regardless of cell
type (wt or lpr). Mice treated with NPC transplantation via retro-orbital injections showed
significantly decreased inflammatory infiltrates and clinical scoring (indicative of increased
treatment efficacy) at the acute time point with similar findings observed at the chronic time
point. As minimal numbers of NPCs enter the CNS and these cells do not express terminal
differentiation markers, our results suggest NPCs mainly exert their effects via bystander and
peripheral immunomodulation as opposed to direct cell replacement.
____________________________________________________________________________
Nathan D. Hicks received the Joan M. Herbers Award in Biology
This award is presented to a student doing outstanding academic performance and excellence in
research in Biology. Mr. Hicks’s Honors project on the genetics of malaria will lead to two
important journal papers. He plans a career in medicine and medical research.
The title of his thesis is: The Dynamics of Clonal Diversity Within Infections of the Lizard
Malaria Parasite, Plasmodium mexicanum
ABSTRACT
Infections of Plasmodium spp., the malaria parasites, can exist within their vertebrate hosts as
either a genetically uniform population of asexually dividing clones, or a mixture of genetically
distinct clonal populations. Multiple-clone infections open the possibility of interactions
between parasite clonal populations in addition to the complex interactions that can occur
between parasite and host. These interactions could potentially influence both the ecology of
malaria infections and thus disease traits, as well as the evolution of traits such as virulence,
transmission biology, and sex ratio. A number of studies in human malaria as well as model
malaria systems have addressed the role of clonal diversity on the ecology and evolution of
malaria; however, there remain many questions about the generation, maintenance, and influence
of clonal diversity within infections. My project addresses two such questions in Plasmodium
mexicanum, a malaria parasite of the western fence lizard, Sceloporus occidentalis.
First, I ask if there is variation among clones for efficiency of establishment in the blood. That
is, can some clones achieve a greater relative representation in the blood than their proportion
when transferred from another host? I initiated experimental infections containing two clones
inoculated in equal proportions, as well as corresponding single clone infections for each clones
used. These infections were followed for 50 or 60 days post-inoculation and the relative
proportion of each clone was determined over time. In general, there was little evidence of
variation in establishment efficiency of clones, excepting one clone which appeared to have a
competitive advantage at first sampling in the blood. If there is low variation in establishment
efficiency and a low degree of change in relative proportions over time, then the stability of
clones in the transition through the vector will be a critical next step in understanding how the
relative proportion of a clone within an infection translates into fitness, or subsequent
transmission into new hosts.
Second, I ask what are the dynamics of clonal diversity in natural, free-ranging infections of P.
mexicanum. I selected infected lizards from two mark-and-recapture studies, the first of which
was performed over two summers in 1996 and 1997 by Dr. Rebecca Eisen and the second of
which I performed over a single summer in 2010. Blood samples collected at the time of capture
were subjected to PCR of two polymorphic microsatellite markers and assessed for the number
of clones and relative proportion of clones at all time points. In general, there was a high level of
stability in clonal diversity, where most infections contained the same clone(s) through up to two
transmission seasons, and mixed-clone infections that did change, either through addition of a
novel clone or loss of an existing clone, were not radically altered in which clone dominated the
infection. That is, changes in clonal identity in infections always involved minor clones which
did not displace the major clone in the infection. This finding indicates that super-infection by
novel clones into established infections may rarely be a profitable strategy for a clone and that
once multiple-clone infections are established they could potentially cycle through a number of
subsequent hosts with little change in the overall clonal diversity.
I conclude by noting the significance of general stability of number of clones and their relative
proportion over time in infections of Plasmodium mexicanum.
____________________________________________________________________________
Mallory P. Romanovitch received the Paul A. Moody Award in Biology
This award is presented to a student doing outstanding academic performance and excellence in
research in Biology. Ms. Romanovitch’s Honors project is determining the function of an
important cell membrane receptor. She begins her masters degree research next year in the
Department of Biology.
The title of her thesis is: Localization of the L-glutamate Receptor in Paramecium tetraurelia and
its Association with a Glycine-Binding Protein
ABSTRACT
Glutamate is the primary excitatory neurotransmitter in the mammalian central nervous system,
and an attractant for Paramecium tetraurelia, a unicellular ciliated protozoan. When L-glutamate
binds to the P.tetraurelia surface receptors, the membrane hyperpolarizes and causes the cell to
swim smoothly and fast. This behavioral change in a L-glutamate concentration gradient causes
populations of cells to accumulate by a biased random walk. A protein with homology to a rat
glutamate binding protein of an NMDA-receptor-like complex is believed to be the receptor for
L-glutamate in P.tetraurelia because down regulation of this protein by RNAi showed a decrease
in L-glutamate chemoresponse. In this work, the sequence for pGluR1 was ligated into the
plasmid pPXV with a C-terminal Flag-tag. Cilia, cell body membranes and whole cell lysates
were analyzed by Western Blots with antibodies for the Flag tag was performed to determine the
receptor localization. Immuno-blotting and enhanced chemical luminescence were performed on
the Western blots. Four proteins homologous to the rat glycine-binding protein of the NMDAreceptor-like complex were found in the P.tetraurelia genome. Since NMDA receptors require
the binding of a co-agonist for receptor activation, glycine was used in T-mazes to observe
whether there is an effect of glycine on L-glutamate chemoresponse.
___________________________________________________________________________________
Katherine M. St. Denis received the Kurt Milton Pickett Award
This award is presented to a student doing outstanding academic performance and excellence in
research in Biology. Ms. St. Denis is a McNair Scholar and has already published her research
on the genetics of malaria. She has been accepted into the Ph.D. program at the University of
Pennsylvania.
The title of her thesis is: "Genetic Variation of a Malaria Parasite, Plasmodium mexicanum, Over
Space and Time".
ABSTRACT
Molecular genetic data are highly useful in determining diversity within and among species and
examining patterns of evolutionary change. I first used such data to examine the question of
what defines a species of malaria parasite. I found that for Plasmodium mexicanum, a malaria
parasite of western fence lizards, Sceloporus occidentalis, there was no variation in cytochrome
b, a coding gene, for 150+ infections from three distinct sites in northern California. Driven by
this initial study, I then focused on genetic changes over time within that well-defined parasite
species. Coevolution of parasites and their hosts has long been theorized to cause rapid
evolutionary change in both, a hypothesis that has not been tested for malaria parasites,
important pathogens of both humans and wildlife. I tested this hypothesis for P. mexicanum at a
single study site in northern California. I had two main goals for this thesis: to test and perfect
protocols for extracting DNA from stained blood smears on slides, and to assess genetic changes
for four microsatellite markers in P. mexicanum over a 33-year period. I sought to answer the
question, what primarily drives evolutionary change within a single population of a malaria
parasite species? I determined from the data that the most likely cause of changes in P.
mexicanum at the site under study is drift. Although selection cannot be eliminated as a
possibility, it seems less likely. Allele frequency changes based on analysis using the Shannon
information index and prevalence data from 1978 to the present were compared. My results
indicate that there was an association between sudden drops in prevalence and allele frequency
changes, with relatively stable allele frequencies for a long period when the population was
stable, and rapid changes in the years immediately following a crash of the parasite population.
Another somewhat unusual observation was the incidence of genetic similarities between the
earliest and most recent years under study. This could just be coincidental, and thus still
indicative of drift. A second, albeit less likely, explanation is that the loci used in this study are
linked to coding markers under strong selection, and that the observed pattern indicates that the
parasite changed in response to environmental pressures (the very same that would have resulted
in a population crash) and then returned to a similar genetic nature as that of the late 1970’s as
the population began to recover.
___________________________________________________________________________
Mathew P. Wajda received the Bernd Heinrich Award in
Physiology or Evolution
This award is presented to a student doing outstanding academic performance and excellence in
research in Biology. Mr. Wajda conducted research on the function of flight muscles on the
mating behavior of fruit flies. He plans to attend medical school.
Mathew is doing upper level research entitled "The Functional Role of Flight Muscle In Male
Drosophila Courtship Song"
The title of his thesis is: “The Effects of Muscle Protein Mutations on Courtship Song in
Drosophila”
ABSTRACT
While previous studies have shown that indirect flight muscles (IFM), the major power
producing muscles for flight, are neurally activated during song, the precise role of the flight
musculature in courtship has not been investigated. It is also understood that courtship song
plays a role in the species recognition during courtship rituals and that some elements of the
mating song are subject to sexual selection. This research aims to determine if flight muscle and
Drosophila courtship behaviors are integrally connected to courtship song. We studied transgenic
Drosophila melanogaster strains expressing mutant myosin regulatory light chain (Dmlc2)
proteins missing the N-terminal region (Dmlc2Δ2-46), two key phosphorylation sites
(Dmlc2S66,67A), or both (Dmlc2Δ2-46;S66,67A). Analysis of mating song parameters revealed that the
courtship song in these strains is altered in ways not predicted from information about the
mutations’ effect on flight mechanics. These results suggest that the contractile mechanism
underlying flight and courtship song are different. Given these data, and the understanding that
each observed courtship behavior is important, we examined the transgenic strains’ courtship
behavior for compensatory behavioral changes in these mating song defective Dmlc2 mutants.
Our results suggest that the Dmlc2+ control transgenic strain performs normal courtship behavior
whereas the three transgenic mutant strains (Dmlc2Δ2-46, Dmlc2S66,67A, and Dmlc2Δ2-46;S66,67A)
move more slowly throughout the courtship rituals, while still achieving mating success. We
propose that Dmlc2 plays an essential role in the courtship song distinct from its role in flight.
Dmlc2 may also play a role, albeit a less significant one, in other courtship behaviors.