Cienciaes.com: More conflict than love

2020-03-04 11:15:22

One of the most curious genetic mechanisms that reflect the eternal conflict between the two sexes is genetic imprinting. Imprinting is the phenomenon by which, although we inherit one copy of all our genes from the mother and another copy from the father, some of those genes will work exclusively or mainly from the chromosome inherited from only one of the parents, and not from the other. other. Thus, there are genes that work only from one of the chromosomes inherited from the mother. The same genes inherited from the father do not work, they are silenced. There are also genes that only work from one of the chromosomes inherited from the father, and the same genes inherited from the maternal chromosome are, on this occasion, those that are silenced.

The genes that undergo the phenomenon of genetic imprinting have not been “chosen” randomly during evolution but arise from the conflict between the sexes. Parents of mammals have a biological interest in their offspring growing as much as possible from the mother’s organism, which maintains them and from which they extract nutrients for such growth during pregnancy and lactation. In this way, their offspring will probably be more successful when it comes to reproducing. However, mothers have a conflicting interest in stopping excessive growth in their offspring, which could leave them exhausted and unable to reproduce again with other males. In this context, it would be advantageous for males to take control of genes that stimulate growth and advantageous for females to take control of genes that curb excessive growth. This is, in effect, what has happened throughout evolution.

Some genes with particular imprint are those that produce the so-called micro-ARNs, abbreviated as miRNAs. miRNAs are short fragments of ribonucleic acid that possess a sequence of “letters” complementary to that of a ARN messenger produced by one or another gene, and which is necessary for the production of the protein whose information is encoded in the gene. The miRNAs bind to the ARN messengers, render them useless and lead to their destruction. In this way, the operation of a gene controlled by the father and that produces a beneficial protein for the transmission of his genes can be counteracted by another gene, the one that produces the miRNA, whose operation is controlled by the mother.

In this connection, a team of researchers from the Massachusetts Institute of Technology has very recently made an interesting discovery. By studying a group of genes that produce more than thirty maternally imprinted miRNAs, that is, they function from the chromosome inherited from the mother, they identify two paternally imprinted genes that are the targets of their activity. These genes are not involved in growth or in the control of nutrients, but rather, pay attention, they affect synaptic transmission and neuronal functioning. Synaptic transmission controls, as is well known, very important aspects of behavior and life. It can, for example, affect the sensation of hunger and thus modulate the demands of newborns during the lactation period.

The researchers indicate that there are other groups of genes that produce miRNAs, with similar characteristics, which could also affect the development of the nervous system and the establishment of synapses in certain brain areas.

Reference:
Whipple et al., 2020, Imprinted Maternally Expressed microRNAs Antagonize Paternally Driven Gene Programs in Neurons. Molecular Cell 78, 1–11 April 2, 2020 Published by Elsevier Inc.

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