Insulin-like growth factor I (somatomedin C) in goats during normal lactation and in response to somatotropin treatment

Comprehensive analysis on the regulation of differentially expressed of mRNA and ncRNA in different ovarian stages of ark shell Scapharca broughtonii

BACKGROUND

Ovarian development is an important prerequisite and basis for animal reproduction. In many vertebrates, it is regulated by multiple genes and influenced by sex steroid hormones and environmental factors. However, relative information is limited in shellfish. To explore the biological functions and molecular mechanisms of mRNA and non-coding RNA that regulate ovarian development in Scapharca broughtonii, we performed whole transcriptome sequencing analysis on ovaries at three developmental stages. Furthermore, the biological processes involved in the differential expression of mRNA and ncRNA were analyzed.

RESULTS

A total of 11,342 mRNAs, 6897 lncRNAs, 135 circRNAs, and 275 miRNAs were differentially expressed. By mapping the differentially expressed RNAs from the three developmental stages of Venn diagram, multiple groups of shared mRNAs and lncRNAs were found to be associated with ovarian development, with some mRNA and ncRNA functions associated with steroid hormone. In addition, we constructed and visualized the lncRNA/circRNA-miRNA-mRNA network based on ceRNA targeting relationships.

CONCLUSIONS

These findings may facilitate our further understanding the mRNA and ncRNAs roles in the regulation of shellfish reproduction.

Sex Reversal and Analyses of Possible Involvement of Sex Steroids in Scallop Gonadal Development in Newly Established Organ-Culture Systems

Many molluscs perform sex reversal, and sex hormones may be involved in the process. In adult scallops, Patinopecten yessoensis, gonadotropin releasing hormone and 17β-estradiol (E₂) are involved in male sexual maturation, however, little is known about the effects of E₂ and testosterone (T) on the gonadal differentiation in young scallops. In the present study, scallop gonadal development was analyzed to determine the sex reversal stage in Funka bay, and effects of E₂ and T were examined. In Funka bay, almost all scallops were male at month 12. Scallops equipped with ambiguous gonads were 61.1% at month 16 and disappeared at month 18. Therefore, sex reversal in Funka bay occurs at around month 16. For establishment of organ culture systems for bivalves, Manila clam gonads were cultured in 15% L-15 medium diluted with HBSS containing 10% KSR on agarose gel at 10°C, and the gonads survived for 14 days. Scallop gonads were also able to be cultured in 30% L15 medium diluted with ASW containing 10% KSR on agarose gel for seven days. At mature stage, Foxl2 and Tesk were predominantly expressed in ovary and testis, respectively. When scallop gonads at sex reversal stage were organ-cultured, sex steroid treatment decreased Tesk expression in the majority of scallop gonads at sex reversal stage. However, no obvious change in Foxl2 and Tesk expression was detected in mature gonads in response to either E₂ or T in culture, suggesting sex steroid treatment might affect gonadal development at sex reversal stage.

Reproduction-related genes in the pearl oyster genome

Molluscan reproduction has been a target of biological research because of the various reproductive strategies that have evolved in this phylum. It has also been studied for the development of fisheries technologies, particularly aquaculture. Although fundamental processes of reproduction in other phyla, such as vertebrates and arthropods, have been well studied, information on the molecular mechanisms of molluscan reproduction remains limited. The recently released draft genome of the pearl oyster Pinctada fucata provides a novel and powerful platform for obtaining structural information on the genes and proteins involved in bivalve reproduction. In the present study, we analyzed the pearl oyster draft genome to screen reproduction-related genes. Analysis was mainly conducted for genes reported from other molluscs for encoding orthologs of reproduction-related proteins in other phyla. The gene search in the P. fucata gene models (version 1.1) and genome assembly (version 1.0) were performed using Genome Browser and BLAST software. The obtained gene models were then BLASTP searched against a public database to confirm the best-hit sequences. As a result, more than 40 gene models were identified with high accuracy to encode reproduction-related genes reported for P. fucata and other molluscs. These include vasa, nanos, doublesex- and mab-3-related transcription factor, 5-hydroxytryptamine (5-HT) receptors, vitellogenin, estrogen receptor, and others. The set of reproduction-related genes of P. fucata identified in the present study constitute a new tool for research on bivalve reproduction at the molecular level.

Growth hormone increases Stat5 and Stat1 expression in lactating goat mammary gland: a specific effect compared to milking frequency

In ruminants, both milking frequency and exogenous GH treatment affect milk production. In a previous report, we showed that the modulation of milk yield due to variations in milking frequency and GH treatment was associated with variations in mammary cell numbers. The aim of this study was to clarify the different mechanisms governing the effects of GH treatment and milking frequency on signal transducer and activator of transcription (Stat) expression and activation, and on the expression of genes involved in mammary cell differentiation. Six Saanen goats in late lactation were milked once daily from one half-udder and thrice daily from the other half-udder for 23 days. At the same time, the goats were divided into two groups: GH-treated versus control group. After slaughter of the goats, soluble mammary proteins and RNA were extracted from half-udder samples. Levels of Stat5, Stat3 and Stat1 proteins and the Stat activation by phosphorylation were analysed by Western blot. The amounts of Stat5 protein and mRNA were significantly elevated by GH treatment in all half-udders (milked once or thrice daily). Positive Stat5 immunoreactivity was principally localised in the nuclei of epithelial cells, with heterogeneous intensity between cells. No significant changes in Stat5 protein phosphorylation levels were observed. Furthermore, GH significantly increased Stat1 protein levels, without modifying the level of Stat1 tyrosine phosphorylation, and tended to reduce the abundance of Stat3 protein. In contrast, milking frequency failed to modify Stat gene expression, protein level and phosphorylation. Using Northern blot, we showed that levels of kappa casein and prolactin receptor mRNA were not affected by the treatments. These observations suggest that GH probably acts specifically on mammary cells by regulating the expression of Stat1, 3 and 5. In contrast, milking frequency does not act through this regulatory pathway.

Increased Milk Yield in Transgenic Mice Expressing Insulin-like Growth Factor 1

Insulin-like growth factor 1 (IGF-1) mediates many of the actions of growth hormone. Overexpression of IGF-1 was reported to have endocrine and paracrine/autocrine effects on somatic growth in transgenic mice. To study the paracrine/autocrine effects of IGF-1 in mammary gland, transgenic mice were produced by pronuclear microinjection of a construct containing a bovine alpha-lactalbumin (alpha-LA) promoter linked to an ovine IGF-1 cNDA. This alpha-LA promoter has previously been shown to direct expression of a human factor VIII gene specifically to the mammary gland of transgenic mice. Three transgenic mouse lines were established as a result of microinjection of 398 embryos. Transgene expression was found in mammary gland at day 1 of lactation from these three lines. Progeny test were carried out by mating two transgenic males/one transgenic female to two nontransgenic females/one nontransgenic male. Mice from one line (line 1225) were all nonexpressors and the other (line 1372) failed to produce offspring. Milk yield was analyzed in the line 1137 that produced 10 mice, of which three were transgenic females and three nontransgenic females. All of the three transgenic females showed integration of the transgene and expressed transgene IGF-1 mRNA in the mammary gland. Milk yields from days 5, 10, and 15 of lactation were significant greater in transgenic expressors than in their nontransgenic littermates. Specifically, there is 17.9% increase in total milk yield from these three days for transgenics compared with nontransgenics. These results demonstrate that local overexpression of IGF-1 in transgenic mice is capable to stimulating milk yield during the first lactation.

Essential role of Ca2+ -dependent phospholipase A2 in estradiol-induced lysosome activation

The mechanism of lysosome activation by 17beta-estradiol has been studied in mussel blood cells. Cell treatment with estradiol induced a sustained increase of cytosolic free Ca2+ that was completely prevented by preincubating the cells with the Ca2+ chelator BAPTA-AM. Estradiol treatment was also followed by destabilization of the lysosomal membranes, as detected in terms of the lysosomes' increased permeability to neutral red. The effect of estradiol on lysosomes was almost completely prevented by preincubation with the inhibitor of cytosolic Ca2+ -dependent PLA2 (cPLA2), arachidonyl trifluoromethyl ketone (AACOCF3), and was significantly reduced by preincubation with BAPTA-AM. In contrast, it was virtually unaffected by preincubation with the inhibitor of Ca2+ -independent PLA2, (E)-6-(bromomethylene)tetrahydro-3-(1-naphtalenyl)-2H-pyran-2-one (BEL). The Ca2+ ionophore A-23187 yielded similar effects on [Ca2+](i) and lysosomes. Exposure to estradiol also resulted in cPLA2 translocation from cytosol to membranes, lysosome enlargement, and increased protein degradation. These results suggest that the destabilization of lysosomal membranes following cell exposure to estradiol occurs mainly through a Ca2+ -dependent mechanism involving activation of Ca2+ -dependent PLA2. This mechanism promotes lysosome fusion and catabolic activities and may mediate short-term estradiol effects.