Molecular cloning and sequence of retinoid X receptor in the green crab Carcinus maenas: a possible role in female reproduction

Abstract

Retinoid X receptor (RXR) belongs to an ancient superfamily of nuclear hormone receptors, and plays an important role in reproduction of vertebrates. However, the reproductive role of RXR has not been clarified in crustaceans. In this investigation, we first report the cloning of two alternative splice variants of RXR cDNA from green crab ovarian RNA. RXR mRNA levels were quantified in different vitellogenic stages of the crab hepatopancreas (HP) and ovary. The expression of RXR mRNA relative to the arginine kinase mRNA was significantly increased in the HP of vitellogenic crabs in a stage-dependent manner. The relative levels of RXR mRNA in the ovary were significantly lower in vitellogenic stage III crabs than in crabs in the other three stages. These data indicate that the HP and ovary of the crab are capable of expressing RXR, which may regulate, in part, vitellogenesis in the crab. We also examined the effects of methyl farnesoate (MF) and RXR-dsRNA treatments on vitellogenin and RXR gene expression. Vitellogenin and RXR mRNA levels in HP and ovarian fragments incubated in MF were significantly (P!0 . 001) higher than in control tissue fragments prepared from the same animal. Treatment of crabs with RXR-dsRNA significantly (P!0 . 001) reduced mRNA levels for RXR and for vitellogenin as well as MF levels in hemolymph. These results indicate that, MF and RXR form a complex (MF-RXR) directly and together stimulate ovarian development in these green crabs. This interaction of RXR, MF, and ovary development axis is a novel finding and is the first report to the best of our knowledge.

Ecdysone receptor in the mud crab Scylla paramamosain: a possible role in promoting ovarian development

“…Similarly, the injection of EcR-dsRNA into white leg shrimp Litopenaeus vannamei decreased the expression of ecdysteroid signaling response genes (Qian et al 2014). It has also been reported that in the shore crab C. maenas, the in vitro Rxr-dsRNA treatment of ovarian tissue led to significantly inhibited expression of both Rxr and Vg (Nagaraju et al 2011). In this study, the results of silencing experiments clearly indicated that the addition of EcR-dsRNA to the ovarian explants downregulated the expression of both SpEcR and SpVg, which occurred even when exogenous 20E was concurrently added.…”

Alternative splicing in the fiddler crab cognate ecdysteroid receptor: Variation in receptor isoform expression and DNA binding properties in response to hormone

“…In addition to the more common N-terminal domain RXR isoforms observed in insects and vertebrates, atypical isoforms arising through differential splicing in the RXR hinge and LBD domain have been identified in several brachyuran crabs (Chung et al, 1998a;Durica et al, 2002;Kim et al, 2005;Nagaraju et al, 2011;Techa and Chung, 2013), and in the hinge domain of the prawn, Marsupenaeus japonicus (Asazuma et al, 2007). In U. pugilator, sequencing studies and ribonuclease protection assays (RPA) have shown the existence of two regions of variability in UpRXR protein, differing in the inclusion or omission of a five amino acid sequence in the hinge region, and a 33 amino acid sequence in the LBD domain.…”

13-Cis-Retinoic Acid-Induced Hyperglycemia in the Fresh Water Edible Crab, Oziothelphusa Senex Senex is mediated by Triggering Release of Hyperglycemic Hormone from Eyestalks

“…The RAR isolated from the crab has been found to bear a close similarity to vertebrate RARs in the ligand-binding domain. To date, RXR was identified from the ovaries of C. pugilator, G. lateralis, M. japonicas, F. chinensis, C. maenas, Scylla serrata and Daphnia magna [32][33][34][35][36][37][38]. Recently, RXR has been also identified in the eyestalks of Callinectes sapidus [39] O. senex [40] and M. nipponence [41].…”

“…Recently, RXR has been also identified in the eyestalks of Callinectes sapidus [39] O. senex [40] and M. nipponence [41]. Reduction in mRNA levels for RXR and for vitellogenin in the crab, C. maenas after treatment with RXR dsRNA [36] and fluctuations in expression of RXR mRNA in ovaries during reproduction [30] suggests RA acts as reproductive hormone. RAs in crustaceans are also identified as morphogens involved in the limb bud regeneration and morphogenesis [13,14].…”

“…RXR has also been identified for which terpenoids can serve as ligands [42]. It was also established that RXR binds with ecdysteroid receptor (EcR) and form a heterodimer [36,42]. This RXR-EcR complex may bind with RA or ecdysteroid (EcD) or methyl farnesoate (MF) and form a heterotrimeric complex (RXR-EcR-RA/EcD/MF) thereby regulate a range of physiological facets in crustaceans.…”