Characterizing the Nuclear Function of the Cell Adhesion Molecule Fat and Chromatin Regulation by the Inner Nuclear Membrane Protein Speg

Tissue growth, pattern formation and cell metabolism are fundamental to animal development. Coordination of these aspects requires elegant signal transduction systems. In Drosophila, fat (ft) encodes an enormous atypical cadherin that is important for such coordination. Ft functions at the cell surface, regulating tissue growth through the Hippo pathway and Planar Cell Polarity (PCP) tissue patterning. Ft also enters mitochondria to regulate mitochondrial function and metabolic state. However, the coordination of Ft’s functions remains largely unknown. In the first part of my thesis, I present surprising results suggesting that Ft can be cleaved to release an intracellular fragment, which translocates into the nucleus. In the nucleus, Ft is associated with chromatin. Using DamID-microarray, a DNA binding site mapping technique, I showed that Ft binds to specific genomic loci in vivo. Through ChIP-seq, I characterized the genome-wide DNA binding profile of Ft in vivo. ChIP-seq results suggested that nuclear Ft binds mostly open chromatin. Interestingly, the ChIP-seq profile of Ft is highly correlated with that of the Hippo pathway transcription cofactor Yki. Overall, I propose that nuclear translocation of Ft is a novel mechanism by which Ft exerts function. In the second part of my thesis, I focused on Speg, an inner nuclear membrane protein essential for germ cell development. Although the nuclear envelope and lamina have been implicated in chromosome organization and gene regulation, the role of Speg is unknown. Using DamID, I found that Speg is specifically associated with repressive chromatin in vitro and the Speg-associated genes are clustered. Using ATAC-seq chromatin accessibility assay and mRNA-seq in vivo, I found that chromatin accessibility is affected and some affected regions correlate with gene expression changes in speg mutants. Overall, I propose that speg is important for the regulation of chromosome organization and gene transcription.

Department dc:contributor.department

Molecular and Medical Genetics

Year dc:date.issued

2018

Author dc:creator

• Kuok, Chi Kin

Advisor dc:contributor.advisor

• McNeill, Helen

• DamID
• Fat
• nuclear envelope
• nucleus
• Speg (CG9723)
• the Hippo pathway

Handle dc:identifier.uri

http://hdl.handle.net/1807/89648

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/89648