Most traits in animal science are complex traits, i.e. influenced by many genes in interaction with the environment. How can we understand and predict these traits? The International Journal of Molecular Science publishes a special issue this year on the topic: Exploring the Genotype–Phenotype Map to Explain Complex Traits. Researchers from Wageningen University & Research Animal Breeding and Genomics (WUR-ABG) have been invited to prepare a manuscript for this special issue.
The genome (DNA) of an animal contains all genes that regulate all processes in life. To do so the genes has to become active. While mutations in the DNA can change the functioning of a gene, for most complex traits the expression levels of the genes are more important. The expression of genes is regulated at multiple stages: (1) epigenomics: the DNA can be methylated (methyl groups are added to the DNA molecule) at specific places that inactivates the expression of genes – and several other regulatory mechanisms regulate the activation of the genes as well; (2) transcriptomics: the first step in the activation is to copy the DNA code into RNA, which can be done in different amounts; (3) proteomics: the RNA code is translated into proteins – which need to fold properly, and post-translation modifications can be important for activation of the function of the protein; (4) metabolomics: the metabolism of the cell produces numerous metabolites that affect many complex traits directly, or even are the complex traits themselves.
Each of these steps are called endophenotypes, in contrast with the externally visible phenotype of the complex trait. In the review paper WUR-ABG researchers describe how all these endophenotypes can be studied, how the contribution of each endophenotype to the complex traits can be determined, and how integration of all the endophenotypes can lead to understanding and prediction of the complex traits.