Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Biology and Biomedical Sciences: Developmental, Regenerative and Stem Cell Biology


English (en)

Date of Award

Spring 4-30-2014

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Douglas L Chalker


As part of its sexual development, the ciliate Tetrahymena thermophila establishes a differentiated somatic genome called the macronucleus. A key aspect of this differentiation is the genome-wide removal of transposon-like and other repetitive elements. This process, referred to DNA rearrangement, involves RNAi-directed formation of subnuclear heterochromatic foci. Many of the factors necessary to direct the DNA rearrangement machinery to proper loci have been discovered, but less is known about how these subnuclear heterochromatic foci are formed. My thesis work focuses on identification and investigation of factors important for the formation of these subnuclear structures which are referred to as DNA elimination foci. Lia4, a chromoshadow domain protein, is required for DNA rearrangement and formation of DNA elimination foci indicating a crucial role in organizing the developing macronucleus and de novo formation of higher order heterochromatin (Chapter 2). Hpl1, Hpl2, and Hpl4 are components of DNA elimination foci suggesting they have a role in macronuclear differentiation (Chapter 3). Hpl2 is essential for production of viable progeny, yet dispensable for DNA rearrangement indicating that components of DNA elimination foci are involved in other critical process during macronuclear differentiation (Chapter 4).


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