Predicting the sex of fish may be more important than it seems: “In aquaculture production, it allows determining the proportion of males and females in juvenile specimens, which can help to select the best individuals and increase production . And in conservation biology, it would allow us to better understand the demography of wild populations, to improve their management and to know the reproductive capacity of threatened species ” , explains Francesc Piferrer, research professor at the Institute of Marine Sciences, belonging to the Higher Research Council Scientific (CSIC). This expert has led an investigation whose result is a test capable of predicting whether a fish will be male or female with 89% reliability, as explained in the journal Epigenetics .
What experts have specifically looked for are epigenetic marks ; that is, the biochemical evidence of genetic expression – the activation and deactivation of genes – of DNA, influenced by the environment. And his object of study has been a most common species: the sea bass ( Dicentrarchus labrax ).
“This method had already been applied recently to determine the sex of a tree, the balsamic poplar ( Populus balsamifera ), but this is the first time it has been carried out with an animal,” explains Piferrer. “At the moment, it is useful for sex prediction in seabass and other similar species, but it could possibly be applied to other vertebrates with suitable adaptations.”
The authors of the research have focused on one of the key chemical alterations in epigenetics, technically known as cytosine methylation in a cytosine-guanine dinucleotide . The signatures of this change are found throughout the genome, both in genes and in the spaces between them, and can affect the numerous cytosine-guanine pairs – two of the four letters or nitrogenous bases that make up the vocabulary of the genome – containing a gene. As if it were a binary code, it is the combination of methylated or unmethylated pairs that make up the expression of genes, calculated at values between 0% and 100% .
Artificial intelligence renders its verdict
The researchers selected seven genes related to the sexual development of the fish and analyzed the methylation of their dinucleotides. The data was then fed into a model of machine learning , a type of artificial intelligence in which the algorithm learns by itself.
The study was carried out with samples obtained within the framework of the European project AQUAEXCEL, in which, in addition to the CSIC researchers, experts from the French Research Institute for the Exploitation of the Sea (IFREMER) and the National Research Institute have participated. Agronomic. The CSIC has already applied for a European patent for its new method .
“The identification of epigenetic marks is the subject of numerous investigations. For example, many cancer studies focus on the development of these types of marks , since they provide information not only for diagnosis, but also to predict certain tumors before they manifest. Currently, there is a great interest in the development of epigenetic marks, both in agricultural sciences and for the management of natural resources ”, concludes Piferrer.
More information: Anastasiadi D, Vandeputte M, Sánchez-Baizán N, Allal F, Piferrer F. Dynamic epimarks in sex-related genes predict gonad phenotype in seabass, a fish with mixed genetic and environmental sex determination. Epigenetics. Doi: 10.1080 / 15592294.2018.1529504
