Investigating the Relationship Between Circadian Rhythm and Longevity in Mammals
A range of interesting research delves into the relevance of circadian rhythm to aging, from both (a) the perspective of how the regulation of circadian rhythm becomes dysfunctional with age, and (b) the evolutionary perspective of how differences in circadian rhythm may be relevant to differences in species life span. The research noted here falls into the second camp, looking at the evolution of genes that regulate circadian rhythm. The data is suggestive of the importance of circadian rhythm to the evolution of longevity in a species, but strangely, this importance is not universal across the varieties of mammal.
The relationship between genomic characteristics and species traits is of paramount importance for biology. We proposed a novel technique that allows one to determine the relationship between any genomic characteristic and species traits, such as maximal reported lifespan, the body weight of an adult animal, and the related longevity quotient. This technique is exemplified in the physiologically significant genes involved in regulating circadian rhythms, which change quite rapidly during evolution.
Regardless of devising this technique, the study of the genes that are critical for circadian rhythms is of interest on its own. For instance, we thoroughly examined the paralogous genes Fbxl21 and Fbxl3, which are involved in the regulation of circadian rhythms. We found out that the above-mentioned characteristic of the Fbxl21 gene correlates with the maximal reported lifespan and body weight only in two superorders of placental mammals, Euarchontoglires (the clades Euarchonta, Lagomorpha, and Rodentia) and Afrotheria. On the contrary, such a correlation is not observed in other superorders, such as Laurasiatheria and Xenarthra. The presence or absence of the correlation is confirmed statistically with a very high accuracy.
Thus for certain genes (such as Fbxl21), the accumulation of amino acid substitutions up to pseudogenization or gene loss, as well as the preference for certain amino acids in the encoded protein, is an effective way to achieve a significant phylogenetic change. The Fbxl21 gene and the species-specific maximal reported lifespan, together with body weight, are examples of such a phylogenetic change in Euarchontoglires and Afrotheria, which is also observed in relatively small taxonomic groups, as, for example, in anthropoid apes and the Cercopithecidae.