Faculty Sponsor: Ruth Johnson, Biology Department.
Live Poster Session: Zoom Link Goes Here
Gillian Churchland
Gillian Churchland is a rising junior at Wesleyan University double majoring in Biology and Mathematics. She’s from New York City, but is happiest somewhere she can hike, climb, swim, or mountain bike. This is Gillian’s second semester working in the Johnson lab, and she’s very interested in cell biology and the molecular mechanisms that create complex tissues, organs, and behavior.
Abstract:
In the Drosophila pupal eye, cells organize to form repeating hexagonal units called ommatidia. However, the exact mechanisms that lead to this precise patterning are not fully understood. Nuclear shape, size, and depth is unique across different cell types within the eye, suggesting that the nucleus is a major factor in determining overall cell shape. The nucleus is tethered to the cell’s cytoskeleton via the LINC protein complex, which attaches to nuclear Lamins on the inner nuclear membrane. However, when one of the LINC proteins, klarsicht, was removed from the developing pupae via RNAi, nuclei became untethered from the cytoskeleton. We show that untethered nuclei in primary pigment cells of the ommatidia have profound shape and positional changes, which in turn impacts cell shape. Specifically, untethered nuclei became less round, longer, and thinner, adopting a distinctive crescent shape. Their perimeters increased, as did their area and aspect ratio (length/width). Additionally, 83.15% of untethered nuclei migrated significantly upwards or downwards, compared to only 3.5% of nuclei in control cells. This movement had no pattern; nuclei were not more likely to move up than down, and neighboring nuclei did not have the same behavior. Nuclear movement was also quantified by calculating the angle between primary pigment cells, cone cells, and nuclei, where a larger angle represented a more displaced nucleus. Untethered nuclei moved 29.02° more on average than tethered nuclei. Furthermore, corresponding primary pigment cells had smaller areas and smaller perimeters. The nucleus was also significantly larger with respect to the cell, as calculated by dividing the area of the nucleus by the area of the cell. Our results demonstrate that the connection between the nuclei and the cytoskeleton is vital for establishing proper nuclei position and structure, which in turn impacts cell shape. However, the 2D shape of primary cells remained mostly intact, indicating that the cell can compensate for a larger, misshapen, and displaced nucleus and still retain its original structure.