Sensitivity to Chronic Methamphetamine Administration and Withdrawal in Mice with Relaxin-3/RXFP3 Deficiency

Methamphetamine (METH) is a highly addictive psychostimulant, and cessation of use is associated with reduced monoamine signalling, and increased anxiety/depressive states. Neurons expressing the neuropeptide, relaxin-3 (RLN3), and its cognate receptor, RXFP3, constitute a putative ‘ascending arousal system’, which shares neuroanatomical and functional similarities with serotonin (5-HT)/dorsal raphe and noradrenaline (NA)/locus coeruleus monoamine systems. In light of possible synergistic roles of RLN3 and 5-HT/NA, endogenous RLN3/RXFP3 signalling may compensate for the temporary reduction in monoamine signalling associated with chronic METH withdrawal, which could alter the profile of ‘behavioural despair’, bodyweight reductions, and increases in anhedonia and anxiety-like behaviours observed following chronic METH administration. In studies to test this theory, Rln3 and Rxfp3 knockout (KO) mice and their wildtype (WT) littermates were injected once daily with saline or escalating doses of METH (2 mg/kg, i.p. on day 1, 4 mg/kg, i.p. on day 2 and 6 mg/kg, i.p. on day 3–10). WT and Rln3 and Rxfp3 KO mice displayed an equivalent sensitivity to behavioural despair (Porsolt swim) during the 2-day METH withdrawal and similar bodyweight reductions on day 3 of METH treatment. Furthermore, during a 3-week period after the cessation of chronic METH exposure, Rln3 KO, Rxfp3 KO and corresponding WT mice displayed similar behavioural responses in paradigms that measured anxiety (light/dark box, elevated plus maze), anhedonia (saccharin preference), and social interaction. These findings indicate that a whole-of-life deficiency in endogenous RLN3/RXFP3 signalling does not markedly alter behavioural sensitivity to chronic METH treatment or withdrawal, but leave open the possibility of a more significant interaction with global or localised manipulations of this peptide system in the adult brain.     

The evolution and possible role of two Sox8 genes during sex differentiation in Japanese flounder (Paralichthys olivaceus)

Sox8 genes, as members of the Sox family, have been studied widely in mammals. However, regulation of sox8 genes in teleosts has rarely been studied, and functional analysis of these genes in teleosts has rarely been performed. Here, two duplicates of sox8 genes were identified in Japanese flounder, Posox8a and Posox8b. The analysis of expression showed that Posox8a and Posox8b were expressed in Sertoli cells of the testis, indicating that they play important roles in development and functional maintenance of the testis. Positive selection and phylogenetic analysis found that both Posox8a and Posox8b underwent the purification selection during evolutionary and that sox8 was most likely to be the ancestor sox8a. These results suggested that both Posox8a and Posox8b had important biological functions after generation from three rounds of whole‐genome duplication in Japanese flounder. The functional differentiation of Posox8a and Posox8b was verified using cell transfection and dual‐luciferase reporter assays; Posox8a overexpression‐promoted 3β‐hydroxysteroid dehydrogenase expression and Posox8b overexpression‐promoted cytochrome P450 aromatase (cyp19a1; P450arom) expression. Finally, combined with Posox8a and Posox8b expression analysis from 30 to 100 days after hatch, we speculated that Posox8a and Posox8b might participate in the process of sex differentiation and gonadogenesis by regulating sex hormone biosynthesis in the Japanese flounder. Our study is the first to demonstrate the possible mechanism of Posox8a and Posox8b in Japanese flounder sex differentiation and gonadogenesis, laying a solid foundation for functional studies of sox8 genes in teleosts.     

SUMO E3 Ligases GmSIZ1a and GmSIZ1b regulate vegetative growth in soybean

SIZ1 is a small ubiquitin‐related modifier (SUMO) E3 ligase that mediates post‐translational SUMO modification of target proteins and thereby regulates developmental processes and hormonal and environmental stress responses in Arabidopsis. However, the role of SUMO E3 ligases in crop plants is largely unknown. Here, we identified and characterized two Glycine max (soybean) SUMO E3 ligases, GmSIZ1a and GmSIZ1b. Expression of GmSIZ1a and GmSIZ1b was induced in response to salicylic acid (SA), heat, and dehydration treatment, but not in response to cold, abscisic acid (ABA), and NaCl treatment. Although GmSIZ1a was expressed at higher levels than GmSIZ1b, both genes encoded proteins with SUMO E3 ligase activity in vivo. Heterologous expression of GmSIZ1a or GmSIZ1b rescued the mutant phenotype of Arabidopsis siz1‐2, including dwarfism, constitutively activated expression of pathogen‐related genes, and ABA‐sensitive seed germination. Simultaneous downregulation of GmSIZ1a and GmSIZ1b (GmSIZ1a/b) using RNA interference (RNAi)‐mediated gene silencing decreased heat shock‐induced SUMO conjugation in soybean. Moreover, GmSIZ1RNAi plants exhibited reduced plant height and leaf size. However, unlike Arabidopsis siz1‐2 mutant plants, flowering time and SA levels were not significantly altered in GmSIZ1RNAi plants. Taken together, our results indicate that GmSIZ1a and GmSIZ1b mediate SUMO modification and positively regulate vegetative growth in soybean.     

New transgenic reporters identify somatosensory neuron subtypes in larval zebrafish

To analyze somatosensory neuron diversity in larval zebrafish, we identified several enhancers from the zebrafish and pufferfish genomes and used them to create five new reporter transgenes. Sequential deletions of three of these enhancers identified small sequence elements sufficient to drive expression in zebrafish trigeminal and Rohon‐Beard (RB) neurons. One of these reporters, using the Fru.p2x3‐2 enhancer, highlighted a somatosensory neuron subtype that expressed both the p2rx3a and pkcα genes. Comparison with a previously described trpA1b reporter revealed that it highlighted the same neurons as the Fru.p2x3‐2 reporter. To determine whether neurons of this subtype possess characteristic peripheral branching morphologies or central axon projection patterns, we analyzed the morphology of single neurons. Surprisingly, although these analyses revealed diversity in peripheral axon branching and central axon projection, PKCα/p2rx3a/trpA1b‐expressing RB cells did not possess obvious characteristic morphological features, suggesting that even within this molecularly defined subtype, individual neurons may possess distinct properties. The new transgenes created in this study will be powerful tools for further characterizing the molecular, morphological, and developmental diversity of larval somatosensory neurons. © 2012 Wiley Periodicals, Inc., 2013     

Examination of relaxin and its receptors expression in pig gametes and embryos

Background  

Relaxin is a small peptide also known as pregnancy hormone in many mammals. It is synthesized by both male and female tissues, and its secretions are found in various body fluids such as plasma serum, ovarian follicular fluid, utero-oviduct secretions, and seminal plasma of many mammals, including pigs. However, the presence and effects of relaxin in porcine gametes and embryos are still not well-known. The purpose of this study was to assess the presence of relaxin and its receptors RXFP1 and RXFP2 in pig gametes and embryos.