Strategies to overcome Meiotic Sex Chromosome Inactivation in the human malaria vector A. gambiae.
File(s)
Author(s)
Meacci, Dario
Type
Thesis
Abstract
Mosquito-borne diseases are responsible for around 700,000 deaths every year. Malaria alone is responsible for at least 400,000 deaths yearly, with the African continent accounting for more than 90% of those deaths. In recent years, new outbreaks of pathogens focused international attention on developing new methodologies to curb mosquito diffusion. Among those methodologies, the generation of genetically modified mosquitoes to reduce the size of vector populations seemed the most promising. The development of CRISPR systems has facilitated the engineering and application of several strategies to achieve a super-mendelian inheritance of desired genes, also known as gene drive.
A sex-distorter meiotic drive developed in A. gambiae allowed to heavily male-bias the vector progeny, lowering the population's reproductive capacity. To achieve the super-mendelian inheritance of this transgene, the solution would be to place it on the Y chromosome. Unfortunately, when placed on the Y, the sex-distorter gene is completely silenced. The silencing is attributed to Meiotic Sex Chromosome Inactivation (MSCI), an epigenetic silencing mechanism that is responsible for the silencing of the two sexual chromosomes during meiosis.
Here, I am testing different strategies to rescue the activity of this Y-linked gene. I am employing a nuclease-dead Cas9 to deliver an epigenetic activator on the target gene and testing Drosophila’s gypsy-retrotransposable elements as chromatin insulators.
Although the delivery of the epigenetic editor failed to increase the transcription levels of the Y-linked sex distorter gene, this study casts some light on the binding kinetics of the dCas9 during meiosis. Moreover, I discovered that the gypsy insulators were actually able to mildly increase the transcript levels of the transgene from the Y-chromosome, even if not high enough to produce a significant sex distortion. Finally, I discuss some ideas for future developments that might be promising for the final achievement of the Y-linked meiotic drive.
A sex-distorter meiotic drive developed in A. gambiae allowed to heavily male-bias the vector progeny, lowering the population's reproductive capacity. To achieve the super-mendelian inheritance of this transgene, the solution would be to place it on the Y chromosome. Unfortunately, when placed on the Y, the sex-distorter gene is completely silenced. The silencing is attributed to Meiotic Sex Chromosome Inactivation (MSCI), an epigenetic silencing mechanism that is responsible for the silencing of the two sexual chromosomes during meiosis.
Here, I am testing different strategies to rescue the activity of this Y-linked gene. I am employing a nuclease-dead Cas9 to deliver an epigenetic activator on the target gene and testing Drosophila’s gypsy-retrotransposable elements as chromatin insulators.
Although the delivery of the epigenetic editor failed to increase the transcription levels of the Y-linked sex distorter gene, this study casts some light on the binding kinetics of the dCas9 during meiosis. Moreover, I discovered that the gypsy insulators were actually able to mildly increase the transcript levels of the transgene from the Y-chromosome, even if not high enough to produce a significant sex distortion. Finally, I discuss some ideas for future developments that might be promising for the final achievement of the Y-linked meiotic drive.
Version
Open Access
Date Issued
2023-10-03
Date Awarded
01/01/2024
License URL
Advisor
Crisanti, Andrea
Fasulo, Barbara
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)