Title

Cell Size regulation by a New Cell Cycle checkpoint: Characterization of clinically relevant Tuberin mutants

Streaming Media

Type of Proposal

Oral presentation

Start Date

31-3-2017 2:00 PM

End Date

31-3-2017 3:20 PM

Faculty

Faculty of Science

Faculty Sponsor

Dr. Lisa Porter

Abstract

Tuberous sclerosis (TS) is a multi-system genetic disease caused by the growth of benign tumours primarily in the brain, kidneys, heart, eyes, lungs, and skin. TS has particularly severe consequences on the central nervous system, resulting in seizures, developmental delay and behavioral problems. This disorder affects around 1.5 million individuals worldwide and occurs by a mutation in one of two genes; TSC1 or TSC2. The TSC2 gene encodes for the protein Tuberin, a tumour suppressor protein well known for it’s ability to regulated cell growth and the cell cycle. Altered levels of Tuberin and mutations in this protein have been found in several cancers, including medulloblastoma and skin cancer. We have established that Tuberin binds and regulates the G2/M cyclin, Cyclin B1 (CycB1) creating a new G2/M checkpoint. Our results show that the Tuberin/CycB1 interaction regulates cell size and this regulation is nutrient dependent. Several mutations responsible for TS are present in the CycB1 binding domain located in the N-terminal domain of Tuberin. It is our hypothesis that these mutations can affect the Tuberin/CycB1 interaction and result in dysregulation of cell proliferation and cell size. Using site-directed mutagenesis we constructed six TSC2 mutants to study the phenotypes in HEK293 and NIH3T3 cells. We have demonstrated that one mutation, Tuberin-C698Y, has lower affinity for CycB1 binding and presents a nuclear localization instead of the usual cytoplasmic localization of the wild type complex. We are focusing on this mutation to determine the full range of consequences of abrogating this interaction. Importantly, we are inserting the Tuberin-C698Y mutation into the HEK293 cells genome through the CRISPR-Cas9 system to determine the endogenous significance of this specific change. The phenotype of these cells will be studied by immunofluorescence and flow cytometry techniques. Patients with specific TSC2 mutations develop TS and have an increased chance of select cancers. Having a better understanding of how specific changes in this large protein alters fundamental cell biology such as cell proliferation and cell size can ultimately help to effectively treat patients with these specific mutations.

Share

COinS
 
Mar 31st, 2:00 PM Mar 31st, 3:20 PM

Cell Size regulation by a New Cell Cycle checkpoint: Characterization of clinically relevant Tuberin mutants

Tuberous sclerosis (TS) is a multi-system genetic disease caused by the growth of benign tumours primarily in the brain, kidneys, heart, eyes, lungs, and skin. TS has particularly severe consequences on the central nervous system, resulting in seizures, developmental delay and behavioral problems. This disorder affects around 1.5 million individuals worldwide and occurs by a mutation in one of two genes; TSC1 or TSC2. The TSC2 gene encodes for the protein Tuberin, a tumour suppressor protein well known for it’s ability to regulated cell growth and the cell cycle. Altered levels of Tuberin and mutations in this protein have been found in several cancers, including medulloblastoma and skin cancer. We have established that Tuberin binds and regulates the G2/M cyclin, Cyclin B1 (CycB1) creating a new G2/M checkpoint. Our results show that the Tuberin/CycB1 interaction regulates cell size and this regulation is nutrient dependent. Several mutations responsible for TS are present in the CycB1 binding domain located in the N-terminal domain of Tuberin. It is our hypothesis that these mutations can affect the Tuberin/CycB1 interaction and result in dysregulation of cell proliferation and cell size. Using site-directed mutagenesis we constructed six TSC2 mutants to study the phenotypes in HEK293 and NIH3T3 cells. We have demonstrated that one mutation, Tuberin-C698Y, has lower affinity for CycB1 binding and presents a nuclear localization instead of the usual cytoplasmic localization of the wild type complex. We are focusing on this mutation to determine the full range of consequences of abrogating this interaction. Importantly, we are inserting the Tuberin-C698Y mutation into the HEK293 cells genome through the CRISPR-Cas9 system to determine the endogenous significance of this specific change. The phenotype of these cells will be studied by immunofluorescence and flow cytometry techniques. Patients with specific TSC2 mutations develop TS and have an increased chance of select cancers. Having a better understanding of how specific changes in this large protein alters fundamental cell biology such as cell proliferation and cell size can ultimately help to effectively treat patients with these specific mutations.