Conserved and species-specific chromatin remodeling and regulatory dynamics during mouse and chicken limb bud development.

Chromatin remodeling and genomic alterations impact spatio-temporal regulation of gene expression, which is central to embryonic development. The analysis of mouse and chicken limb development provides important insights into the morphoregulatory mechanisms, however little is known about the regulatory differences underlying their morphological divergence. Here, we identify the underlying shared and species-specific epigenomic and genomic variations. In mouse forelimb buds, we observe striking synchrony between the temporal dynamics of chromatin accessibility and gene expression, while their divergence in chicken wing buds uncovers species-specific regulatory heterochrony. In silico mapping of transcription factor binding sites and computational footprinting establishes the developmental time-restricted transcription factor-DNA interactions. Finally, the construction of target gene networks for HAND2 and GLI3 transcriptional regulators reveals both conserved and species-specific interactions. Our analysis reveals the impact of genome evolution on the regulatory interactions orchestrating vertebrate limb bud morphogenesis and provides a molecular framework for comparative Evo-Devo studies.

The microtubule-associated protein PRC1 is a potential therapeutic target for lung cancer.

In this study, we investigated whether proteins that are involved in cytokinesis are potential targets for therapy of lung cancer. We find that the microtubule-associated protein PRC1 (protein required for cytokinesis 1), which plays a key role in organizing anti-parallel microtubule in the central spindle in cytokinesis, is overexpressed in lung cancer cell lines compared to normal cells. Increased expression of PRC1 is correlated with a poor prognosis of human lung adenocarcinoma patients. Lentiviral delivered, inducible RNAi of PRC1 demonstrated that proliferation of lung cancer cell lines strongly depends on PRC1. Significantly, we also show that PRC1 is required for tumorigenesis in vivo using a mouse model for non-small cell lung cancer driven by oncogenic K-RAS and loss of p53. When PRC1 is depleted by in vivo RNA interference, lung tumor formation is significantly reduced. Although PRC1 has been suggested to regulate Wnt/ß-catenin signaling in cancer cells, we find no evidence for a role of PRC1 in this pathway in lung cancer. Instead, we show that the depletion of PRC1 results in a strong increase in bi- and multinuclear cells due to defects in cytokinesis. This ultimately leads to apoptosis and senescence. Together these data establish PRC1 as a potential target for therapy of lung cancer.

Deletion of Gas2l3 in mice leads to specific defects in cardiomyocyte cytokinesis during development.

GAS2L3 is a recently identified cytoskeleton-associated protein that interacts with actin filaments and tubulin. The in vivo function of GAS2L3 in mammals remains unknown. Here, we show that mice deficient in GAS2L3 die shortly after birth because of heart failure. Mammalian cardiomyocytes lose the ability to proliferate shortly after birth, and further increase in cardiac mass is achieved by hypertrophy. The proliferation arrest of cardiomyocytes is accompanied by binucleation through incomplete cytokinesis. We observed that GAS2L3 deficiency leads to inhibition of cardiomyocyte proliferation and to cardiomyocyte hypertrophy during embryonic development. Cardiomyocyte-specific deletion of GAS2L3 confirmed that the phenotype results from the loss of GAS2L3 in cardiomyocytes. Cardiomyocytes from Gas2l3-deficient mice exhibit increased expression of a p53-transcriptional program including the cell cycle inhibitor p21. Furthermore, loss of GAS2L3 results in premature binucleation of cardiomyocytes accompanied by unresolved midbody structures. Together these results suggest that GAS2L3 plays a specific role in cardiomyocyte cytokinesis and proliferation during heart development.