Evolutionary Fate of the Androgen Receptor−Signaling Pathway in Ray-Finned Fishes with a Special Focus on Cichlids

Abstract

The emergence of the steroid system is coupled to the evolution of multicellular animals. In vertebrates in particular, the steroid receptor repertoire has been shaped by genome duplications characteristic to this lineage. Here, we investigate for the first time the composition of the androgen receptor–signaling pathway in ray-finned fish genomes by focusing in particular on duplicates that emerged from the teleost-specific whole-genome duplication. We trace lineage- and species-specific duplications and gene losses for the genomic and nongenomic pathway of androgen signaling and subsequently investigate the sequence evolution of these genes. In one particular fish lineage, the cichlids, we find evidence for differing selection pressures acting on teleost-specific whole-genome duplication paralogs at a derived evolutionary stage. We then look into the expression of these duplicated genes in four cichlid species from Lake Tanganyika indicating, once more, rapid changes in expression patterns in closely related fish species. We focus on a particular case, the cichlid specific duplication of the rac1 GTPase, which shows possible signs of a neofunctionalization event.

Effects of parental care on resource allocation into immune defense and buccal microbiota in mouthbrooding cichlid fishes*

“…) and possibly subjected to neo‐functionalization after duplication (Lorin et al. ). Two genes, MHC 1 alpha and fam60a , differentiated in their expression between BPMB males and females.…”

“…On the other hand, androgens are known to act as immune suppressors (Slater et al 1995) and may thus negatively impact the expression of immune genes in females of MMB species. In cichlids, the expression of ara has been proposed to be tissue-and speciesspecific, yet independent from sex (Böhne et al 2014) and possibly subjected to neo-functionalization after duplication (Lorin et al 2015). Two genes, MHC 1 alpha and fam60a, differentiated in their expression between BPMB males and females.…”

Testosterone and dihydrotestosterone levels in the transition zone correlate with prostate volume

“…Steroid hormones and steroid hormone receptors appeared very early in the evolution of animals. Testosterone (T), dihydrotestosterone (DHT), and androgen receptor (AR) evolved in early vertebrates, more than 400 million years ago . The main adrenal androgen, dehydroepiandrosterone sulfate (DHEAS), which intermediates in the biosynthesis of T, appeared even earlier, probably in invertebrates …”

An evaluation of the endocrine disruptive potential of crude oil water accommodated fractions and crude oil contaminated surface water to freshwater organisms using in vitro and in vivo approaches

“…Amphibians and most other vertebrates have a single aromatase coding gene (cyp19a1), whereas teleosts have 2, cyp19a1a and cyp19a1b, expressed predominantly in the ovary and brain, respectively [47]. Similarly, teleosts have 2 androgen receptor genes, ar1 and ar2, whereas other vertebrates including amphibians have only 1 [49]. The different aromatase and androgen receptor genes evaluated among species in the present study were therefore the result of genetic differences among the species studied.…”