Accelerated pseudogenization of trace amine‐associated receptor genes in primates

Abstract

Trace amines (TAs) in the mammalian brain have been investigated for four decades. Trace amine‐associated receptors (TAARs) were discovered during the search for receptors activated by TAs. TAARs are considered a second class of vertebrate olfactory receptors and successfully proliferated in conjunction with adaptation to living on the ground to detect carnivore odors. Thus, therian mammals have a high number of TAAR genes due to rapid species‐specific gene duplications. In primate lineages, however, their genomes have significantly smaller numbers of TAAR genes than do other mammals. To elucidate the evolutionary force driving these patterns, exhaustive data mining of TAAR genes was performed for 13 primate genomes (covering all four infraorders) and two nonprimate euarchontan genomes. This study identified a large number of pseudogenes in many of these primate genomes and thus investigated the pseudogenization event process for the TAAR repertoires. The degeneration of TAARs is likely associated with arboreal inhabitants reducing their exposure to carnivores, and this was accelerated by the change in the nose shape of haplorhines after their divergence from strepsirrhines. Arboreal life may have decreased the reliance on the chemosensing of predators, suggestive of leading to the depauperation of TAAR subfamilies. The evolutionary deterioration of TAARs in primates has been reestablished in recently derived primates due to high selection pressure and probably functional diversity.

Pattern of TAAR5 Expression in the Human Brain Based on Transcriptome Datasets Analysis

“…An evolutionary genetic survey demonstrated that TAAR5 is the most conserved TAAR subtype among all characterized mammalian species investigated so far [13]. Intriguingly, this receptor became the pseudogene in some primates [14] and its affinity for ligands varies in different species. For example, di-and trimethylamine display no agonistic activity for TAAR5 in most primates and cattle, but activate TAAR5 in mouse, rat, and dog [15].…”

Diversity in olfactory receptor repertoires is associated with dietary specialization in a genus of frugivorous bat

“…The fate of a gene duplicate includes several potential paths ( Hahn 2009 ; Teufel et al 2016 ; Yohe et al 2019b ). First, the duplicated gene may be completely redundant and not be expressed, and thus it could accumulate a deleterious mutation that may render it a pseudogene ( Eyun 2019 ). Second, one of the two copies may be released from purifying selection and accumulate new mutations that enable new function ( Pegueroles et al 2013 ).…”

Diversity in olfactory receptor repertoires is associated with dietary specialization in a genus of frugivorous bat

“…The fate of a gene duplicate includes one of several paths (Hahn 2009; Teufel et al 2016; Yohe et al 2019b). First, the duplicated gene may be completely redundant and not be expressed, and thus accumulate deleterious mutation that may render it a pseudogene (Eyun 2019). Second, one of the two copies may be released from purifying selection and accumulate new mutations that enable new function (Pegueroles et al 2013).…”