Periodic Reporting for period 1 - PREMETAZOAEPIGENOME (The role of genome regulation in the origin of animals)
Reporting period: 2017-09-01 to 2019-08-31
The particular focus of PREMETAZOAEPIGENOME was understanding the regulation of the genome in these unicellular relatives of animals. In animals, the expression of genes in time and space – the process that is regulated by complex mechanisms that involves networks of transcription factors as well as histone posttranslational modification. This regulatory complexity enables cell differentiation into multiple cell types. In contrast, the regulation of the genome in well-studied unicellular organisms was shown to be much less complex. Thus, the aim of the PREMETAZOAEPIGENOME was to investigate the genome regulation in a clade of close unicellular relatives of animals called ichthyosporeans.
In this project, we have successfully established one of the ichthyosporeans, Sphaeroforma arctica, as a tractable experimental organism. We have successfully characterized its life cycle in the laboratory, we have obtained a better version of its genome, and we have characterized the gene expression changes during its life cycle. These results will in the future enable us to understand how its genome is regulated, and whether it has some of the regulatory complexity seen in animals.
To begin to study the genome regulation in ichthyosporeans, I then analyzed gene expression throughout the entire cell cycle, making use of the protocols for synchronization. We found that there is a highly coordinated transacriptional regulation in the last stage of the cycle, where Sphaeroforma arctica cells undergo a coordinated transition into a transiently multicellular state. Furthermore, combining with a bioinformatics analysis, we found that this transiently multinucleated state involves upregulation of homologs of animal cell adhesion molecules. This discovery pointed out that multicellularity in animals and ichtyosporeans might have a common cell adhesion mechanism. The results of this study, which involved several collaborators and also included a comprehensive cell biological analysis of this transiently multicellular state using advanced microscopy, as well as re-sequencing of the entire genome of Sphaeroforma arctica, will soon be published.
Finally, to get insight into genome regulatory mechanisms, which was the initial main aim of PREMETAZOAEPIGENOME, we have, with Alfonso Mendaña Gomez, a MSc student in the lab, established and optimized protocols for the genomic assays, in both Sphaeroforma arctica and Creolimax fragrantissima. Establishment of these protocols is the first step towards the investigation of genome regulatory mechanisms.