The IMIM Evolutionary Genome Group, in cooperation with the UPF department of experimental sciences and health, have identified the genes that differentiate mammals from other animals, i.e., the genes that are found only in mammals. To do this, the researchers designed a set of programs that made it possible to compare the already sequenced genome of 68 mammals. These include Homo sapiens, as well as other primates and representatives of the main orders of this class of animals, including the Iberian lynx.

The data obtained were used to create a catalogue of genes exclusive to mammals - some 6000 families of genes. At the same time, the genes were assigned a possible age of origin based on the species in which they appear. The researchers also tried to discover what it is that these genes do, using expression data (RNA sequencing) for different tissues in order to see where and to what extent they were expressed, as well as proteomic data to determine whether they are translated, i.e., whether they produce proteins.  These are genes without counterparts outside of the group of mammals, i.e., they are not present in other hairless species. In humans, they are estimated to represent 2.5% of the genes that code for proteins.

New shorter but active genes

Some of these genes have a de novo origin; that is, they are not the result of the duplication of existing genes. De novo genes are important for acquiring new functions during evolution, as was shown in a prior study, also led by Dr. Mar Albà, an IMIM ICREA researcher and coordinator of the Evolutionary Genomics Group (Origins of de novo genes in human and chimpanzee, published in Plos Genetics). The new study has therefore managed to identify the function of some of these genes, linked to how skin is structured and why it is different from that of, say, reptiles, as well as others that play a role in the mammary glands that distinguish mammals. Antimicrobial peptides have also been identified that play a role in defending the body against pathogens. The researchers also point out that the genes they have found are short and are normally only expressed in one or a few types of tissue.

Studies of this kind help us to understand how new genes are formed as part of evolution and whether they play an important role in the adaptation of organisms to their environment. Cataloguing the genes in mammals is the first step to understanding what their functions are and brings us closer to defining a set of pieces that arose at the base of their evolution and are common to all of them or some of their subgroups.

Reference article

Villanueva-Cañas, J.L., Ruiz-Orera, J., Agea, M.I., Gallo, M., Andreu, D. & Albà, M.M. (2017). New Genes and Functional Innovation in Mammals. Genome Biology and Evolution, 9, 1886–1900