Retinoid metabolism in invertebrates: When evolution meets endocrine disruption

Molecular Basis for Vitamin A Uptake and Storage in Vertebrates

“…Although certain retinoid metabolites characteristic for the metabolic pathways involved in maintaining retinoid homeostasis can be found in early metazoans, the key genes that encode LRAT, RBP, and STRA6 are absent in invertebrate genes [98,99]. The reported presence of REs in tissues of sponges and two gastropods species can instead be attributed to the activity of DGAT1 orthologues [100,101,102].…”

Input overload: Contributions of retinoic acid signaling feedback mechanisms to heart development and teratogenesis

“…Currently, we do not understand many aspects of the conserved feedback, including its evolutionary origin. From an evolutionary perspective, in silico genomic studies and functional studies in mollusks support the hypothesis that retinoic acid (RA) signaling is an ancient molecular pathway that predates the origins of the bilaterian body plan (Albalat, ; Andre et al, ). Therefore, it would be particularly interesting if the mechanisms underlying RA feedback regulation were ancient, predating the common bilaterian ancestor.…”

“…Therefore, it would be particularly interesting if the mechanisms underlying RA feedback regulation were ancient, predating the common bilaterian ancestor. While the intracellular production and degradation components are predicted to be conserved in protostomes and invertebrate deuterostomes (Albalat, ; Albalat and Canestro, ; Andre et al, ), if RA signaling regulates the expression of these genes in a manner similar to that found in vertebrates has not been examined. However, it is known that RA positively regulates Cyp26 expression in chordate Ciona , but does not significantly affect Aldh1a expression (Ishibashi et al, ), suggesting that at least the positive regulation of Cyp26 by RA predates a common chordate ancestor.…”

The cycling gonad: retinoic‐acid synthesis and degradation patterns during adult zebrafish Danio rerio oogenesis

“…To promote meiosis, RA regulates the expression of genes coding for several proteins of the meiotic machinery, via the transcription factors retinoic acid and retinoid x receptors (RAR, RXR) (Bowles et al, ; Koubova et al, ; Rodriguez‐Mari et al, ). RA is, in fact, a potent metabolite, derived from retinol and participates in distinct processes such as morphogenesis, development and reproduction (Blomhoff & Blomhoff, ;Theodosiou et al, ; Andre et al, ). The biosynthesis of active retinoids includes a two‐step oxidation cascade leading to signal transduction (Theodosiou et al, ; Andre et al, ): an initial retinol‐to‐retinal conversion, carried out by retinol dehydrogenases (Rdhs), followed by a retinal‐to‐retinoic acid reaction catalysed by retinal dehydrogenases (Aldhs) (Yoshida et al, ; Canestro et al, ; Farjo et al, ; Kumar et al, ; Sandell et al, ).…”

“…RA is, in fact, a potent metabolite, derived from retinol and participates in distinct processes such as morphogenesis, development and reproduction (Blomhoff & Blomhoff, ;Theodosiou et al, ; Andre et al, ). The biosynthesis of active retinoids includes a two‐step oxidation cascade leading to signal transduction (Theodosiou et al, ; Andre et al, ): an initial retinol‐to‐retinal conversion, carried out by retinol dehydrogenases (Rdhs), followed by a retinal‐to‐retinoic acid reaction catalysed by retinal dehydrogenases (Aldhs) (Yoshida et al, ; Canestro et al, ; Farjo et al, ; Kumar et al, ; Sandell et al, ). Members of the cytochrome P450 family (CYP26s) carry out an additional oxidative inactivation step (Ray et al, ; White et al, ).…”