New DNA modification ‘signature’ found in zebrafish


Researchers on the Garvan Institute of Medical Analysis have uncovered a brand new type of DNA modification within the genome of zebrafish, a vertebrate animal that shares an evolutionary ancestor with people ~400 million years in the past.

Dr Ozren Bogdanovic and his group found that unusually excessive ranges of DNA repeats of the sequence ‘TGCT’ within the zebrafish genome endure a modification known as methylation, which can change the form or exercise of the encompassing DNA. The research, revealed in Nucleic Acids Research and performed in collaboration with the Queen Mary College of London, may result in the event of latest experimental fashions for learning how DNA modifications influence human improvement and illness.

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Picture credit score: Dr Kate Patterson

“We’ve revealed a new form of DNA methylation in zebrafish at TGCT repeats, and crucially, the enzyme that makes the modification,” says Dr Bogdanovic, who heads the Developmental Epigenomics Lab at Garvan and Senior Analysis Fellow on the College of Biotechnology and Biomolecular Sciences, UNSW Sydney. “These findings open the field to new possibilities in studying the epigenome – the additional layer of instructions on DNA that change how genes are read – and understand how it may be clinically relevant.”

Hidden signatures

All species which have DNA – from vegetation to people – additionally modify it by attaching molecules known as methyl teams.

“DNA methylation is vital to cellular function, as it controls which genes are turned on and off,” explains the primary writer of the paper, PhD scholar Sam Ross. “This is why the cells in our body can carry out vastly different functions, despite having almost identical DNA.”

There are 4 ‘base’ letters that make-up DNA – C, G, T and A. Invertebrates, methylation happens largely the place the letter G follows a C (‘CG’), however there are some exceptions. One instance is methylation at non-CG websites in human mind cells, aberrations of which have been linked to Rett Syndrome, a genetic dysfunction that impairs progress, motion and speech in kids.

To research non-CG methylation additional, the researchers performed complete profiling of the zebrafish genome, a vertebrate organism that could be a distant evolutionary relative of people and shares 70% of our genes, which makes it a helpful mannequin for learning the consequences of human genes.

The group found that methylation occurred the place the sequence ‘TGCT’ appeared a number of instances, shut collectively.

“We were fascinated to see that methylation levels at TGCT repeats were higher than any non-CG methylation previously observed in the majority of adult vertebrate tissues,” says Dr Bogdanovic. “Further, this methylation was present at high levels in the sperm and egg, absent in the fertilised egg, and then appeared again in the growing embryo, reaching its highest levels in adult tissues such as the brain and gonads. While we are yet to reveal how this modification changes gene expression, we believe TGCT methylation to be linked to the ‘awakening’ of the embryonic genome in zebrafish.”

New potential for learning illness

The researchers additional revealed that the enzyme Dnmt3ba was liable for methylating the TGCT repeats within the zebrafish genome.

“While it’s unclear if a similar modification occurs in animals more broadly, our discovery in zebrafish is significant, because it means we can start to selectively manipulate this atypical form of methylation in a model organism. It means we can change the levels of Dnmt3ba to see what happens when we remove just one form of methylation, but not another,” says Dr Bogdanovic.

“This could greatly facilitate our understanding of how changes in atypical methylation patterns affect specific tissues such as the brain, to gain further insights into the molecular mechanisms of neurodevelopmental disorders,” says Dr Bogdanovic.

“We hope that our findings will help us develop new experimental models that can be used to study epigenetics in a way that has not been possible thus far.”

Supply: Garvan Institute

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