Date of Award

5-2013

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry

Advisor

Sharon Ashworth

Second Committee Member

Robert Gundersen

Third Committee Member

Mary Tyler

Abstract

Actin, which is present in all mammalian cells, provides the scaffolding for cell shape, forms protrusions for cell movement, and is a main component in the cellular structures necessary for cell division. Actin is present in a cell in two forms, monomeric G-actin and filamentous F-actin. Actin filaments are dynamic and are regulated by many actin-binding proteins, one such protein is cofilin. Cofilin binds to actin and causes actin severing or depolymerization, which increases the turnover of the filaments and leads to many vital cellular functions such as movement and division. When cell division and migration are disrupted an organism cannot properly develop and it die or be deformed.

Cardiovascular disease is the number one cause of death in the world and is often the result of malformations in the heart. Frequently the malformations will be asymptomatic until sudden death occurs. Zebrafish are an attractive model to study cardiovascular disease because their hearts develop and function similarly to human hearts. Zebrafish are small, transparent during development, inexpensive to maintain, and have external development that makes them ideal for studying cardiovascular diseases. Zebrafish have three cofilin isoforms, cofilin 1, cofilin 1-L, and cofilin 2. The genetic sequences for human and zebrafish cofilin 1 are extremely similar and share 75% sequence identity.

Other animal model systems have shown devastating effects on development when cofilin is knocked down. We proposed that when cofilin is knocked down in zebrafish their development would be disrupted and their cardiovascular system would not form or function properly. Cofilin expression was knocked down in the zebrafish using a morpholino injection. The zebrafish were then observed at key developmental time points. The zebrafish were evaluate for four parameters, cardiac looping, presence of pericardial edema, blood flow, and average heartbeat. Cofilin morphant zebrafish exhibited a wide range of cardiac deformities such as: partial looping of the heart, over or under twisting of the heart tube, extensive pericardial edema, erratic blood flow, and abnormal heartbeats. These studies demonstrated that cofilin was vital for the proper development of the cardiovascular system of zebrafish. The cofilin morphant zebrafish provided a practical approach to studying cardiovascular development and disease.

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