Biology ETDs

Publication Date

Spring 4-15-2019

Abstract

Properly executed cell division is crucial to development, maintenance, and longevity of multicellular organisms. Defects in both symmetric and asymmetric divisions can lead to improper developmental patterning, as well as genomic instability, disruption of tissue homeostasis, and cancer. Our research focuses on how regulators orchestrate proper cell divisions. Mushroom Body Defect (Mud) is one such regulator, and here we describe how Mud is regulated via the Hippo signaling pathway kinase Warts (Wts), showing Wts phosphorylates Mud to enhance interaction with the polarity protein Partner of Inscuteable, promoting spindle orientation activity. We next focus on another regulator, Shortstop (Shot), describing a role for Shot in cell divisions, with both tissue culture and in vivoDrosophilaepithelial models showing spindle assembly, spindle misalignment, and chromosome migration defects in Shot knockdowns (KDs). These activities are mediated not only through traditional Shot roles in stabilization of spindle MTs through crosslinks to actin, but also through direct interaction of Shot to dynein activator subunit actin-related protein 1 (Arp1). We hypothesize Shot interaction with Arp1 functions to crosslink it to spindle MTs, facilitating MT motor protein Dynein activity, promoting its activities in cell division. Live cell imaging experiments show defects in cell division timing under Shot KD conditions, implicating involvement of the spindle assembly checkpoint (SAC). Inhibition of SAC components under Shot KD conditions leading to timing rescue. Shot loss in vivoleads increases in apoptosis, in line with previous findings linking mitotic regulators to cell death. Previous studies implicated induction of the jun-N-kinase (JNK) apoptotic pathway under spindle regulator KD, but Shot KD apoptosis likely does not utilize JNK. When Shot KD-induced apoptosis is inhibited, tumorigenic-like conditions result, underscoring the importance of Shot as a key component in development and maintenance of multicellular organisms. Shot KD-induced apoptosis is likely mediated via p53 and the DNA damage response (DDR), with DNA double strand breaks occurring in Shot KD, and additionally enhanced when coupled to SAC inhibition. Finally, we utilize mRNA sequencing (RNAseq) to describe Shot KD-induced genes involved in DDR, highlighting a distinct mechanism to mitigate loss of a key oriented cell division regulator.

Language

English

Keywords

Oriented Cell Division, Tissue Development, Drosophila, Shortstop, Mushroom Body Defect, Apoptosis

Document Type

Dissertation

Degree Name

Biology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

Christopher A. Johnston

Second Committee Member

Richard M. Cripps

Third Committee Member

Stephen A. Stricker

Fourth Committee Member

Helen J. Hathaway

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