Identification of the vitellogenin proteins in the newt Pleurodeles waltl (urodele amphibian)

Vitellogenin in the European cave salamander, Proteus anguinus: Its characterization and dynamics in a captive female as a basis for non-destructive sex identification

Vitellogenin (Vtg) is a precursor protein of egg yolk proteins in oviparous and ovoviviparous vertebrates. Except in a case of exposure to estrogenic endocrine disruptors, Vtg is a female-specific protein and could be used as a molecular marker for sex identification. This would be especially useful in the case of the endangered European cave salamander Proteus anguinus in which sexes are indistinguishable according to external morphology, which hinders the establishment of a successful captive breeding program. Here we describe the identification, partial characterization, and purification of Vtg from P. anguinus. Vtg was identified in the plasma of a vitellogenic proteus female with visible oocytes. The identification of this protein was accomplished by mass spectrometry analysis. Two-dimensional gel electrophoresis revealed proteus Vtg as a mix of 190 kDa isoforms with isoelectric points in the pH range 5.3-6.0. Vtg was purified from proteus blood by gel filtration followed by anion-exchange chromatography. Using specific staining of SDS-PAGE gels, the Vtg was found to be phosphorylated and lipidated. Unlike the case in some other aquatic vertebrates, in P. anguinus, Vtg was not present in detectable amounts in cutaneous mucus. Degradation of oocytes in the captive vitellogenic female was accompanied by simultaneous decrease of Vtg concentration. Over a period of 10 months, the concentration of Vtg dropped from maximal to sub-detectable. Our results show that Vtg is a promising molecular marker for sex identification and ovary maturation in P. anguinus, which could contribute to the development of a viable program for captive reproduction of this unique species.

Purification, characterization and expression of two vitellogenins in the Indian freshwater murrel Channa punctatus

The present study was undertaken to characterize different vitellogenins in Channa punctatus. Protein purification by gel chromatography followed by fast protein liquid chromatography (FPLC) revealed existence of two different Vg forms. Liquid chromatography tandem mass spectrophotometry (LC-MS/MS) suggested the existence of Vga and Vgb. Cloning of partial sequences of vga and vgb mRNA and phylogenetic analysis substantiated the existence of two vitellogenins. Real time PCR for vga and vgb genes from liver of estradiol-17β (E2) treated fish reveals difference in expression levels of transcripts of these two genes. vgb is expressed at lower dose of estradiol suggesting a higher sensitivity to estradiol. The present study thus proposes different regulatory control for the expression of these two genes and vgb as a superior biomarker than vga to assess exposure of C. punctatus to environmental estrogens.

Establishment of ELISA for murrel vitellogenin and choriogenin, as biomarkers of potential endocrine disruption

Vitellogenin (Vg) and choriogenin (Chg) are sensitive biomarkers for testing endocrine disruption in fish. Therefore, we have developed immunoassays for Vg and Chg in the Indian freshwater murrel, Channa punctatus. Vg is a known precursor of egg-yolk proteins, whereas Chg contributes to the formation of egg-envelope. Vg and Chg were induced in male murrel by administration of estradiol-17beta. Chg had an apparent native molecular mass of 180 kDa. It consisted of a single peptide with a molecular mass of 110 kDa, whereas native Vg protein (530 kDa) contained 175 kDa peptide. Highly specific polyclonal antibodies against purified plasma proteins, Vg and Chg, were employed for developing competitive enzyme linked immunosorbent assays (ELISAs). The sensitivity of Vg assay was 3.9 ng/mL (working range 15-500 ng/mL) and of Chg assay was 1.56 ng/mL (working range 6-200 ng/mL). The inter- and intra-assay variations were well within acceptable limits. The two antisera did not cross-react with male plasma proteins. Antiserum to Vg did not cross-react with Chg. Similarly, antiserum to Chg showed no correlation with Vg. Further, immunofluorescence and Western blotting confirmed the specificity of Vg and Chg antisera.

Relationship between estradiol-17 beta seasonal profile and annual vitellogenin content of liver, fat body, plasma, and ovary in the frog (Rana esculenta)

The seasonal plasma estradiol-17 beta (E2-17 beta) profile and annual vitellogenin content of liver, fat body, plasma, and ovary were investigated in Rana esculenta. Concomitant with the increase in E2-17 beta, vitellogenin peaked in liver, plasma, and ovary during autumn and winter, while it remained at a relatively high concentration in fat body during spring. In vitro experiments showed that E2-17 beta (10(-9) M) is ineffective in inducing vitellogenin production in fat body, but is effective in inducing vitellogenin production in liver. As fat bodies do not produce the vitellogenin they contain, we suggest that fat bodies are involved in the transfer of vitellogenin to the ovary.