Description
This year, iGEM bordeaux 2017 aims to study the alternative splicing of the unc-60 gene in C. elegans. This gene can be spliced differently and two isoforms can be generated : UNC-60A, a non muscular isoform and UNC-60B, a muscular isoform. Thus, identity of cell depends on these two proteins and that is why our project focuses on the splicing of unc-60 which generate the muscular isoform. Our goal is to control this splicing by light activation through a mechanism known in Neurospora crassa (Fungi) or, alternatively, by chemical activation also known in N. crassa.
The alternative splicing of this gene is regulated by the SUP-12's RRM (RNA Recognition Motif) domain, a region of the protein which binds to the unc-60 pre-RNA, to induce, with ASD-2, the muscular isoform. Thus the cell becomes a muscular cell. The "Stargate WCC" project aims to control alternative splicing of unc-60 by SUP-12 protein. For this purpose, our team uses a photo-inducible system, the White Collar system which exists naturally in N. crassa in which it regulates the circadian rhythm according to the light level. Indeed, two proteins, White Collar 1 and 2, fit together in order to form a complex : the White Collar Complex or WCC, activated by a conformational change in response to light. Then this WCC modified and activated binds to circadian genes promoters in the aim of inducing FRQ proteins. In the worm, the WCC will be implied into neural cell to activate SUP-12 protein, regulate the alternative splicing of unc-60 and generate a muscle cell instead of a neural cell.
Alternatively, Q system can be used. Indeed this is a system whose repressible binary expression system was established in Drosophila and mammalian cells based on regulatory genes from N. crassa. This system uses a transcriptional activator QF which binds on the QUAS promoter to induce the expression of target gene. Activation by QF can be suppressed by a transcriptional repressor called QS which binds on QF. Also, suppresion of QS activity can be realised by the nontoxic small molecule quinic acid which interfere QS and QF interaction. It can be difficult to “turn off” or “turn down” gene expression by direct promoter fusion while QS expression and quinic acid effect can be an efficient approach to inhibate or activate gene expression. On the contrary, with the regulator role of quinic acid, the Q system can “turn on” gene expression at any desired time point and combines spatial and temporal control.
In conclusion, the "Stargate WCC" project is intended to control alternative splicing via different regulating mechanisms involving a logical gate that inspired us the project name. For this purpose, our team decided to focus on gene expression in muscular cell in order to control cell differentiation. This experimental procedure strives to give necessary tools in biomedical research especially in the regeneration of members. In fact, this tool could be used in research connected to stem cells therapy, Bioprinting or research in genetic diseases like Duchenne muscular dystrophy or amyotrophic lateral sclerosis. Therefore, multiple prospects open up to "Stargate WCC" project.
