The role of LIN 9 in early mouse development
Final Report Abstract
We and others have identified the human MuvB complex as an important regulator of gene expression during the cell cycle. MuvB consists of a five-protein core-module that associates with additional proteins to either form the repressor DREAM complex or the activator complex Myb-MuvB (MMB). In quiescent cells MuvB binds to the E2F4 transcription factor and to p130, a protein that is related to the retinoblastoma tumor suppressor protein to form DREAM which contributes to the repression of E2F-regulated genes in G0/G. In S-phase binding to E2F4/p130 is lost and another transcription factor, B-MYB, is incorporated into the MuvB complex to form MMB which is essential for gene activation. To analyze the physiological function of MuvB in vivo we have targeted LIN9, a conserved core subunit of MuvB. We have analyzed the phenotype of these mice in and found that LIN9 is essential for early mouse embryonic development at the peri-implantation stage. Using a conditional allele of Lin9, we found that LIN9 is also required for viability of adult mice. Loss of Lin9 abolishes proliferation and leads to multiple defects in mitosis and cytokinesis because of its requirement for the expression of a large set of mitotic genes. To better understand the role of DREAM in early development we have investigated its function in mouse embryonic stem (ES) cells. To gain insights into the LIN9-dependent transcriptional program in ES cells, we have performed ChIP-on-chip experiments. Comparison with gene expression data obtained by microarray analysis revealed that MMB is a master regulation of genes whose products have important functions in mitosis and cytokinesis. Mitotic genes are often overexpressed in different types of cancers and their increased expression correlates with a poor prognosis for the patients. We therefore asked whether MMB contributes to the overexpression of mitotic genes in tumor cells and whether MMB or its downstream target genes could be novel targets for therapy. In a mouse model for lung tumorigenesis we could show that MMB contributes to K-RAS dependent lung tumorigenesis by activating mitotic genes. We also identified six mitotic kinesins and two microtuble associated proteins (PRC1 and CEP55) as direct targets of MMB in cancer cells. One of the key targets of MuvB, the mitotic kinesin KIF23, is also required for lung tumorigenesis as demonstrated by RNAi mediated depletion of KIF23 in vivo. In the final part of the project we focused on a novel target gene of LIN9, the actin- and microtubule binding protein GAS2L3. We found that GAS2L3 is expressed in mitosis and localizes to the midbody during cytokinesis. Depletion of GAS2L3 resulted in defects in cytokinesis and abscission. In vivo, mice deficient in Gas2l3 display defects in cardiomyocyte proliferation resulting in dilated cardiomyopathy and postnatal death of the animals. We are currently investigating the molecular function of GAS2L3 and MMB in cardiomyocytes.
Publications
- Lin9, a subunit of the mammalian DREAM complex, is essential for embryonic development, for survival of adult mice, and for tumor suppression. Mol Cell Biol 2010; 30:2896–908
Reichert N, Wurster S, Ulrich T, Schmitt K, Hauser S, Probst L, Götz R, Ceteci F, Moll R, Rapp U, Gaubatz S.
(See online at https://dx.doi.org/10.1128/MCB.00028-10) - LIN9, a Subunit of the DREAM Complex, Regulates Mitotic Gene Expression and Proliferation of Embryonic Stem Cells. PLoS ONE 2013; 8:e62882
Esterlechner J, Reichert N, Iltzsche F, Krause M, Finkernagel F, Gaubatz S
(See online at https://doi.org/10.1371/journal.pone.0062882) - An important role for Myb-MuvB and its target gene KIF23 in a mouse model of lung adenocarcinoma. Oncogene 2017
Iltzsche F, Simon K, Stopp S, Pattschull G, Francke S, Wolter P, Hauser S, Murphy DJ, García P, Rosenwald A, Gaubatz S
(See online at https://doi.org/10.1038/onc.2016.181) - Central spindle proteins and mitotic kinesins are direct transcriptional targets of MuvB, B-MYB and FOXM1 in breast cancer cell lines and are potential targets for therapy. Oncotarget 2017
Wolter P, Hanselmann S, Pattschull G, Schruf E, Gaubatz S
(See online at https://doi.org/10.18632/oncotarget.14466) - Deletion of Gas2l3 in mice leads to specific defects in cardiomyocyte cytokinesis during development. Proc Natl Acad Sci USA 2017; 114:8029–34
Stopp S, Gründl M, Fackler M, Malkmus J, Leone M, Naumann R, Frantz S, Wolf E, Eyss von B, Engel FB, Gaubatz S
(See online at https://doi.org/10.1073/pnas.1703406114)
