Senior Honors Projects, 2010-current

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Award

Spring 2018

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Biology

Advisor(s)

Terrie K. Rife

Timothy Bloss

Corey Cleland

Kate Trammell

Abstract

A hallmark of Alzheimer’s Disease (AD) is the aggregation of hyperphosphorylated tau protein into neurofibrillary tangles. Tau localizes to both the cytoplasm and the nucleus of neuronal cells; however, its nuclear role has not been fully defined. Tau has recently been shown to bind to purine-pyrimidine (R/Y) repeats in DNA and stabilize them into Z-DNA. Evidence from our lab suggests that the binding of tau to R/Y repeats causes transcriptional changes of the NOS1 gene. Six major isoforms of tau exist in neurons. These isoforms fall into two groups, denoted as 3R tau and 4R tau, and are found at an equal ratio in healthy whole-cell extracts. During AD progression, an imbalance of 3R and 4R tau occurs, along with changes in NOS1 expression and a buildup of Z-DNA in severe AD patients. Based on studies of mouse tau and our lab’s previous work, we hypothesized that the 3R and 4R tau would be found in equal ratios in the nucleus of normal human cells, and that tau would bind to the NOS1 R/Y repeat. To test these hypotheses, western blotting of nuclear proteins from human neuroblastoma cells (SK-N-MC) and antibodies for specific tau isoforms were used to examine which isoforms were found in SK-N-MC cells. Additionally, electrophoretic mobility shift assays (EMSAs) were developed to better understand tau’s ability to bind R/Y repeats using the R/Y repeat from the NOS1 gene. The western blots showed that the 3R isoform of tau predominates in SK-N-MC cells, that similar tau isoforms are present in the nuclear, cytoplasmic, and chromatin- bound fractions, and that a majority of nuclear tau exists bound to DNA. Our EMSAs showed that some nuclear protein binds the NOS1 R/Y repeat, this protein has not been identified. Future experiments will use western blotting to characterize nuclear tau in other cell lines, continue improving our EMSAs, and identify the NOS1 R/Y repeat binding protein.

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