Article
Version 1
Preserved in Portico This version is not peer-reviewed
Steroid Receptors and Vertebrate Evolution
Version 1
: Received: 28 January 2019 / Approved: 30 January 2019 / Online: 30 January 2019 (12:56:43 CET)
Version 2 : Received: 29 March 2019 / Approved: 1 April 2019 / Online: 1 April 2019 (13:50:13 CEST)
Version 2 : Received: 29 March 2019 / Approved: 1 April 2019 / Online: 1 April 2019 (13:50:13 CEST)
A peer-reviewed article of this Preprint also exists.
Abstract
Considering that life on earth evolved about 3.7 billion years ago, vertebrates are young, appearing in the fossil record during the Cambrian explosion about 542 to 515 million years ago. Results from sequence analyses of genomes from bacteria, yeast, plants, invertebrates and vertebrates indicate that receptors for adrenal steroids (aldosterone, cortisol), and sex steroids (estrogen, progesterone, testosterone) also are young, with receptors for estrogens and 3-ketosteroids first appearing in basal chordates (cephalochordates: amphioxus), which are close ancestors of vertebrates. An ancestral progesterone receptor and an ancestral corticoid receptor, the common ancestor of the glucocorticoid and mineralocorticoid receptors, evolved in jawless vertebrates (cyclostomes: lampreys, hagfish). This was followed by evolution of an androgen receptor and distinct glucocorticoid and mineralocorticoid receptors in cartilaginous fishes (gnathostomes: sharks). Adrenal and sex steroid receptors are not found in echinoderms: and hemichordates, which are ancestors in the lineage of cephalochordates and vertebrates. The presence of steroid receptors in vertebrates, in which these steroid receptors act as master switches to regulate differentiation, development, reproduction, immune responses, electrolyte homeostasis and stress responses, argues for an important role for steroid receptors in the evolutionary success of vertebrates, considering that the human genome contains about 22,000 genes, which is not much larger than genomes of invertebrates, such as Caenorhabditis elegans (~18,000 genes) and Drosophila (~14,000 genes).
Keywords
Steroids, Vertebrate Evolution, Ancestral Estrogen, Cambrian, Snowball Earth
Subject
Biology and Life Sciences, Anatomy and Physiology
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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