Annual Report 2020

Laboratory of Molecular Genetics

Haruna Takeda, Kotomi Sato

Introduction

 Inflammatory bowel diseases (IBD) increase the risk for colorectal cancer development. Previous exome sequencing studies have identified numerous genetic alterations including TP53 mutations in colitis-associated cancers (CAC); however, it is still challenging to identify genes which are specifically involved in CAC development simply from genomic data alone.

 To understand how CAC develops, we have taken a unique approach using Sleeping Beauty (SB) transposon mutagenesis. The SB mutagenesis screen is a powerful genetic tool for the genome-wide identification of cancer genes that are also mutated in human cancers. SB mutagenesis can also identify human cancer genes that were missed by genomic analyses because, for example, they are deregulated by epigenetic mechanisms.

Research activities

 We have generated compound mutant mice carrying active SB transposons in the intestinal and colonic epithelial cells, and treated the mice with dextran sodium sulfate (DSS) which can induce colitis. Mice developed more tumors and died earlier when treated with DSS. Analyses of transposon integration sites by our in-house bioinformatic pipeline have identified several candidate cancer genes that are likely to be involved in CAC development.

Future Prospects

 We will finish SB screens and perform functional validation for candidate cancer genes to identify novel CAC genes. In addition, we will establish colonic organoids derived from tumors and non-tumor tissues of IBD patients, and perform exome-sequencing and DNA methylation analyses. From these analyses, novel molecular mechanisms underlying CAC development will be elucidated.

List of papers published in 2020

Journal

1. Kazuhiro Murakami, Yumi Terakado, Kikue Saito, Yoshie Jomen, Haruna Takeda, Masanobu Oshima, Nick Barker. A genome-scale CRISPR screen reveals factors regulating Wnt-dependent renewal of mouse gastric epithelial cells. Proc Natl Acad Sci USA 118(4) 2021