Quintyne, Nicholas

FAU's Office of Undergraduate Research and Inquiry hosts an annual symposium where students engaged in undergraduate research may present their findings either through a poster presentation or an oral presentation.

Methamphetamine (METH) is addictive and associated with a high rate of relapse. One relapse trigger is re-experiencing drug-associated contextual associations. Therefore it is possible that, by targeting METH-associated contextual memories, drug seeking behavior can be inhibited. Recent evidence has suggested that memory formation relies on actin polymerization, which allows dendritic spines to undergo structural and functional plasticity, key components of memory. To see if actin polymerization could be a target for the extinction of METH seeking memories we inhibited actin polymerization in animals that had been trained in either METH or food associated conditioned place preference. Pretest inhibition of actin cycling in the basolateral amygdala complex produced immediate and persistent extinction of METH seeking behavior. Additionally, inhibiting actin polymerization 24hrs before testing disrupted seeking behavior for METH but not food. These results indicate that METH-associated memories are selectively vulnerable to disruption through inhibition of actin dynamics.

Dysfunction of GABAB-receptor (GABAB-R)-mediated synaptic transmission underlies various nervous system disorders including epilepsy, depression, schizophrenia, and addiction. Currently, only one GABAB-R orthosteric ligand is in clinical use. However, side effects such as sedation, tolerance, and motor impairment limit its use. A dissociation of the therapeutic effects from the side effects may be achievable with drugs enhancing the endogenous physiological cellular response. The development of GABAB-R allosteric modulators has provided new modes of efficacy that may facilitate the development of novel therapeutic agents. In the present study, we investigated the effects of novel, newly synthesized GABAB-R allosteric ligands using a HEK-293 cell line stably expressing human GABAB1(b)/human GABAB(2) subunits using a cell-based cAMP HTRF assay. One compound was identified and characterized as a potential novel GABAB-R positive allosteric modulator (PAM), and will be subjected to further in vitro and in vivo analyses.

Mitosis is the separation of duplicated chromosomes into two daughter cells
in order to create viable offspring. There are many checks in mitosis to ensure the
inherited chromosome number is correct. Sometimes, these checkpoints are
overcome and daughter cells inherit defects which can lead to cancer. One defect is
the appearance of lagging chromosomes, the result of inaccurate chromosomal
separation which leads to incorrect chromosome number termed aneuploidy.
Aneuploidy is one of the defining traits of cancerous cells. The potential mechanism
of lagging chromosomes in the cancerous cell line UPCI:OSCC070 is investigated in
this study. siRNA-induced knockdown of KIFC1, a protein that is involved in the
centrosomal clustering to prevent multipolar spindles, was used in the cells.
Examining both levels of knockdown and time of exposure, we saw that the loss of
KIFC1 led to a significant increase in lagging chromosomes, indicating this protein
is critical to proper mitotic progression.

Dynactin is a multisubunit protein complex required for proper functioning of the microtubule motor, cytoplasmic dynein. Dynactin serves as a processivity factor for the motor as well as a cargo adaptor, allowing dynein to function in a wide array of cellular processes. Additionally, dynactin serves as a microtubule anchor. The p150Glued subunit of dynactin is of particular importance to these processes, as it possesses dynactin’s microtubule binding sequences, termed the CAP-Gly and Basic domains. These domains have differential affinities for microtubules, with CAP-Gly binding to microtubules with a higher affinity than Basic. By testing a set of shRNA plasmids with antisense sequences to the untranslated region of p150Glued we have found effective knockdown of the protein in COS-7 cells; future researchers can then introduce plasmids for p150Glued lacking either the CAP-Gly or Basic domains, or both, potentially showing a differential effect on anchoring, dependent upon which domain is present.

Formation of multipolar spindles is closely linked to increased genomic instability and tumor progression. Centrosome hyperamplification is insufficient to initiate this mitotic defect, centrosome coalescence must be interrupted. Studies have indicated that cytoplasmic dynein is a key factor in preventing multipolarity, and overexpression of the NuMA protein is sufficient to mislocalize dynein from the spindle and abrogate the coalescence machinery. Because the mechanism by which NuMA can inhibit dynein is unclear, we are purifying NuMA to use in in vitro studies, to better understand how NuMA blocks dynein activity. Purifying NuMA from recombinant sources has not been successful; therefore we are utilizing a native source. We are using the oral cancer cell line UPCI:SCC078 as the source because it has nine copies of the NUMA1 gene. With modifications to the protocols used previously, our goal is to yield sufficient quantities of NuMA for biochemical analysis with purified NuMA.

Dynactin, a multisubunit protein complex, serves as a processivity factor and cargo adaptor for the microtubule motor cytoplasmic dynein. Together, these proteins permit mitotic progression, intracellular trafficking, and endomembrane organization. Dynactin also independently anchors microtubules at the centrosome during interphase. In this study, we use shRNAs to knock down expression of the p24, p27, p62, and Arp1 subunits of dynactin to determine those components’ roles in anchoring. Recent work has shown p62’s importance to dynactin integrity (Yeh et al., 2012), and we confirm that its loss disrupts microtubule organization. The peripheral p27 and binding partner p25 seem to contribute to membrane selectivity and have little effect on dynactin structure and anchoring. We find that an intact dynactin complex is necessary to maintain microtubule organization via the anchoring complex. While not directly bound to microtubules, these subunits provide crucial structural support to facilitate interactions among dynactin and other centrosomal anchoring components.

As tumors generate, there is a progression in genomic instability derived from chromosomal rearrangement and instability. Often, these manifest themselves as defects in mitosis, frequently as lagging chromosomes, multipolar spindles, and anaphase bridges. Lagging chromosomes are the result of inaccurate chromosomal division in mitosis, thus jeopardizing the genome of an organism’s offspring; they derive from several errors, such as failure of a chromosome to attach to the mitotic spindle. The goal of this project has been to characterize the mechanisms of lagging chromosomes in the cancer cell line UPCI:SCC103. Our laboratory’s work has shown that treatment with certain carcinogens increase the rate of mitotic defect. To further our understanding these defects, we are monitoring the progression of lagging chromosomes in UPCI:SCC103 cells with live cell analysis, using GFP-tagged histone H2B to track their appearance and fate, so to distinguish between the possible causes and resolutions of this mitotic defect.