Ancestral functions of genes regulated by imprinting in mammals - Testing the hypothesis that grb10 has a role in growth regulation in zebrafish

Genomic imprinting is a form of epigenetic regulation that governs a group of genes in placental mammals and angiosperms. Methylation of one gene copy within the egg or sperm causes silencing of one parental allele and results in monoallelic expression from either the maternal or paternal allele. This process has been extensively studied in mammals, especially mice, but little is known about the evolution of genomic imprinting and the role of these genes outside of species that are regulated by imprinting mechanisms, which likely reflects the ancestral functions of these genes (before mammals and imprinting arose).
The evolution of genomic imprinting has been debated since it was first discovered around 35 years ago. The strongest theory to date suggests that genomic imprinting evolved to act on genes that already have established roles in regulating growth in development, known as the parental conflict hypothesis. To date, only IGF2 and IGF2R have been confirmed to have conserved roles regarding growth regulation and development across imprinted and non-imprinted species, out of over 150 imprinted genes.
This project will use zebrafish as a model to look at the conserved gene GRB10, an imprinted gene in mammals, to investigate if this has a growth regulatory role in developing zebrafish, a non-imprinted species. This will look to test the current hypothesis for the evolution of genomic imprinting. Other roles that have been associated with imprinted genes alongside growth regulation will be considered. For GRB10, this could be a role relating to insulin signalling in development. Alongside this, currently available literature will be searched to investigate what is known about other imprinted genes in various species. This may identify other candidate genes that are conserved in zebrafish for potential functional testing.
Methods may include but are not limited to:
- Mutant zebrafish grb10a/grb10b lines will be used to investigate the role that these genes have in development as well as CRISPR KO zebrafish lines which will be generated to help determine gene function and characterise regulatory elements
- Phenotypic evaluation using microscopy
- Measurement and comparison of body parameters
- In situ hybridisation using lineage specific markers
- Bioinformatic methods including sequence alignments and online tools including a variety of publicly available databases to evaluate and gather information about what is known about other imprinted genes in imprinted species vs. non-imprinted species
Exploring the evolutionary origins of genes that are regulated by imprinting will help to clarify why genomic imprinting evolved and whether this group of genes are involved in regulating development or if they have a broader or different purpose in health and disease. Imprinting disorders result in severe developmental disorders as well as having links to other issues including some cancers and diabetes. This research will help improve our understanding of genomic imprinting and will help us understand why this can go wrong and potentially help us learn how to prevent or treat these problems in the future. Overall, this will improve our understanding of this area of human health and disease.