Estrogen modulates HNF-3beta mRNA levels in the developing chick oviduct

RNA-Seq reveals ACTH-induced steroid hormone pathway participating in goat adrenal gland response to castration

The content of androgen from adrenal is elevated under castration, and the mechanisms of compensatory secretion of adrenal androgen remain unknown. This study was designed to compare the transcript profiles between adrenals from noncastrated, orchiectomized and immunocastrated Yiling goats. Fifteen goats were randomly divided into three groups: pVAX-asd injection (control) group, pVAX-B2L-(G4S)3-kisspeptin-54-asd immunization (PBK-asd) group, and surgical castration (SC) group. Subsequently, serum was collected every two weeks after the initial immunization for hormone assays. At week 14 after immunization, adrenal glands were collected for transcriptome sequencing and qPCR. Serum testosterone concentration was significantly reduced in PBK-asd and SC group, demonstrating the effectiveness of castration. Both surgical and immunized castration resulted in adrenal hyperplasia, and thickness of adrenal cortex elevated. The specific genes involving castration were enriched in many pathways, including Steroid hormone biosynthesis pathway. The adrenocorticotropic hormone (ACTH), which promotes the production of adrenal steroids, and dehydroepiandrosterone (DHEA), a steroid hormone secreted by adrenal glands, both increased after castration. Further construction of co-expression network for transcription genes and traits (including adrenal weight and cortex thickness, ACTH and DHEA concentration) showed that the trait-related genes were enriched in multiple steroid-related pathways. These results showed that adrenal compensatory hyperplasia and androgen secretion caused by castration may involve in ACTH-induced steroid hormone synthesis.

Rapid Communication: MicroRNA co-expression network reveals apoptosis in the reproductive tract during molting in laying hens

The aim of this study was to determine the regulatory mechanisms of molting and recrudescence via studying the micro-RNA (miRNA) expression in the oviduct of laying hens. We performed a cDNA microarray analysis in the magnum tissue from the oviduct to identify the whole miRNA profiles through the molting and recrudescence periods. A total of 35 laying hens (47-wk-old) were divided into 7 groups (0 d: a control group; 6 and 12 d: 2 molting-period groups fed on a high-zinc diet; and 20, 25, 30, and 35 d: 4 recrudescence-period groups fed on a normal diet after a 12-d period on a high-zinc diet). An miRNA co-expression network (miRCN) was generated using the differentially expressed miRNA (DEM) according to the entire data integration. The significantly co-expressed miRNA ( = 111) were highly differentially expressed from 12 to 20 d, which was a transition period between molting and recrudescence, while their expression patterns were contrary to the estrogen changes. The targets of highly connected miRNA ( = 12) indicated the significant biological pathways and gene ontology (GO) terms, such as MAPK and Wnt signaling and magnesium-ion binding, which are associated with apoptotic activities. These results suggest that the miRNA of the miRCN might play a role in the apoptotic progression of the reproductive tract during molting.

Uncovering molecular events associated with the chemosuppressive effects of flaxseed: a microarray analysis of the laying hen model of ovarian cancer

Background

The laying hen model of spontaneous epithelial ovarian cancer (EOC) is unique in that it is the only model that enables observations of early events in disease progression and is therefore also uniquely suited for chemoprevention trials. Previous studies on the effect of dietary flaxseed in laying hens have revealed the potential for both amelioration and prevention of ovarian cancer. The objective of this study was to assess the effect of flaxseed on genes and pathways that are dysregulated in tumors. We have used a bioinformatics approach to identify these genes, followed by qPCR validation, immunohistochemical localization, and in situ hybridization to visualize expression in normal ovaries and tumors from animals fed a control diet or a diet containing 10% flaxseed.

Results

Bioinformatic analysis of ovarian tumors in hens led to the identification of a group of highly up-regulated genes that are involved in the embryonic process of branching morphogenesis. Expression of these genes coincides with expression of E-cadherin in the tumor epithelium. Levels of expression of these genes in tumors from flax-fed animals are reduced 40-60%. E-cadherin and miR200 are both up-regulated in tumors from control-fed hens, whereas their expression is decreased 60-75% in tumors from flax-fed hens. This does not appear to be due to an increase in ZEB1 as mRNA levels are increased five-fold in tumors, with no significant difference between control-fed and flax-fed hens.

Conclusions

We suggest that nutritional intervention with flaxseed targets the pathways regulating branching morphogenesis and thereby alters the progression of ovarian cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-709) contains supplementary material, which is available to authorized users.

The effect of estrogen compounds on human embryoid bodies

Human embryonic stem cells are derived from the inner cell mass of preimplantation embryo at the blastocyst stage and their differentiation occurs through an intermediate step involving the formation of embryoid bodies (EBs), which are aggregates of embryonic stem cells. The EBs seem to be a powerful tool for investigating the development of embryos, as they can mimic the initial stages of embryonic development. In this study, we aimed to investigate the effect of estrogen compounds on the proliferation and differentiation of short-term and long-term cultured EBs in vitro. For this study, 10-day-old (short-term cultured) and 30-day-old (long-term cultured) EBs were subjected to estradiol (E2), estriol (E3), selective estrogen receptor modulator (raloxifene [RLX]), bisphenol A, and 1,3,5-tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole for 7 days. To confirm the effects of estrogen treatment, ICI-182780 was added to the respective EBs for additional 7 days following estrogen treatment. Quantitative reverse transcription-polymerase chain reaction was performed to analyze the relative expression of differentiation marker genes representing the 3 germ layers. The expression of 7 marker genes, which included α-fetoprotein, hepatocyte nuclear factor (HNF)-3β, HNF-4α (endoderm), brachyury, cardiac actin ([cACT]; mesoderm), nestin (ectoderm), and Oct-4 (undifferentiated), was measured. Significantly, lower expression of HNF-4α in both short-term and long-term cultured EBs was observed after treatment of estrogen compounds compared to control. The expression of HNF-3β in short-term cultured EBs has been positively affected by E2, E3, and RLX. Regarding cACT, higher expression was observed after treatment of E2 (10(-7) mol/L) and E3 (10(-9) mol/L) in short-term cultured EBs, but opposite effects were demonstrated in long-term cultured EBs. The lower expressions of HNF-4α by E2 and RLX were negated by ICI-182780 treatment, although these findings were not statistically significant in E3-treated group. These findings suggest that estrogen compounds have effects on endodermal and mesodermal differentiation of human EBs.

Roles of hepatocyte nuclear factors (HNF) in the regulation of reproduction in teleosts

Hepatocyte nuclear factor (HNF) families are composed of liver-enriched transcription factors and upstream regulators of many liver-specific genes. HNF are involved in liver-specific gene expression, metabolism, development, cell growth and many cellular functions in the body. HNF genes can be activated or influenced by several hormones and insulin-like growth factors (IGF), and different combinations of the four HNF factors form a network in controlling the expression of liver-specific or liver-enriched genes. The functions of these factors and their interactions within the gonads of bony fishes, however, are not well understood, and the related literature is scant. Recently, several members of the HNF families have been detected in teleost gonads together with their downstream genes (IGF-I and IGF-II), suggesting that these HNF could be upregulated in vitro by steroid hormones. Thus, the hormone-HNF-IGF-gonad interaction may be an alternative axis in the reproductive mechanism that acts in concert with the conventional hypothalamus-pituitary-gonad pathway. This may help the early development and maturation of the gonad or gamete, sexual maturity or reversion and spawning-regulating mechanisms among fishes to be understood.

Steroid hormones (17β-estradiol and hydrocortisone) upregulate hepatocyte nuclear factor (HNF)-3β and insulin-like growth factors I and II expression in the gonads of tilapia (Oreochromis mossambicus) in vitro

Hepatocyte nuclear factors (HNF-1alpha, -1beta and -3beta) and insulin-like growth factors (IGF-I and -II), which are involved in liver-specific gene expression, metabolism, development and cell growth, have been found in the gonads of tilapia (Oreochromis mossambicus). However, the functions of these factors and how they interact within the gonads of bony fish are not understood. In the present study, we provided experimental evidence that the expression of HNF-3beta in the gonads of tilapia, but not HNF-1alpha and -1beta, was affected in vitro by 17beta-estradiol and hydrocortisone. Immunohistochemical staining confirmed that tilapia HNF-3beta was mainly found in the nuclei of hepatocytes, the follicular granulosa cells of the ovaries, and the interstitial cells of the testes of adult tilapia. Further data were gathered at various steroid concentrations (0.1, 1, 10, 100, and 1000 nM) over various culture intervals (6, 12, 18, 24, 30, and 36 h) and subjected to semi-quantitative RT-PCR analysis. The expression of downstream genes (IGF-I and -II) followed the same temporal patterns as HNF-3beta, albeit at decreased levels for 30 and 36 h culture intervals. Both hormones upregulated HNF-3beta mRNA expression at concentrations of 0.1-10 nM, and reached optimal physiological concentrations for induction of IGFs at 1-10 nM. The identity of the PCR fragments was concurrently verified by sequencing and PCR-Southern hybridization. We inferred that HNF-3beta and IGFs may play a regulatory role in tilapia gonads during oocyte maturation and spermatogenesis.

Establishment of a chick embryo model for analyzing liver development and a search for candidate genes

The liver plays a crucial role in metabolism. There is considerable interest in how the liver develops, as such knowledge could prove of importance in regenerative medicine. However, our understanding of liver development remains somewhat limited. We have developed a model system using the chick embryo that is cost effective and is easy to manipulate experimentally. We performed four fundamental studies: (i) construction of an atlas of the developing chick liver; (ii) identification of differentiation marker genes in the developing chick embryo; (iii) development of germ-layer specific electroporation; and (iv) establishment of organ culture from the developing chick liver. Using this system, we have been able to demonstrate the functions of candidate genes within a shorter period and in a more cost-effective manner. In parallel with the establishment of this system, we examined the expression patterns of genes known to be required for organ development in the developing chick embryo in order to identify genes also involved in liver development. To date, we have found sixteen genes that are expressed in the developing chick liver (GELD, genes expressed in liver development). This knowledge will be fundamental to the establishment of the basic technology for engineering liver tissue in the future.

Analysis of gene expression patterns in the developing chick liver

The chick embryo has been used widely for studying liver development. However, in the past 30 years, the usage has decreased markedly due to lack of appropriate marker genes for differentiation in the developing chick liver. To use the chick embryo for analyzing the molecular mechanism of liver development, we surveyed marker genes in the developing chick liver by examining the expression pattern of genes that are well-characterized in the developing mammalian liver. By whole-mount in situ hybridization, Fibrinogen-gamma (FIB) expression was first detected at stage 12, specifically in the anterior intestinal portal, and its liver-specific expression persisted in the later stages. Albumin (ALB) expression was first detected at stage 30, when the liver starts maturing. Cytokeratin 19 (CK19) was first detected at stage 37 in the ductal plate of the liver, and its expression continued in the intrahepatic bile ducts derived from the ductal plate. Hex, a transcription factor, is an additional marker of bile duct differentiation. Hence, FIB, ALB, and CK19 expression can be used to trace hepatic induction, maturation, and bile duct differentiation, respectively.

Signals from lateral plate mesoderm instruct endoderm toward a pancreatic fate

During embryonic development, organs arise along the gut tube as a series of buds in a stereotyped anterior-posterior (A-P) pattern. Using chick-quail chimeras and in vitro tissue recombination, we studied the interactions governing the induction and maintenance of endodermal organ identify focusing on the pancreas. Though several permissive signals in pancreatic development have been previously identified, here we provide evidence that lateral plate mesoderm sends instructive signals to the endoderm, signals that induce expression of the pancreatic genes Pdx1, p48, Nkx6.1, glucagon, and insulin. Moreover, this instructive signal directs cells to form ectopic insulin-positive islet-like clusters in endoderm that would otherwise form more rostral organs. Once generated, endocrine cells no longer require interaction with mesoderm, but nonendocrine cells continue to require permissive signals from the mesoderm. Stimulation of activin, BMP, or retinoic acid signaling is sufficient to induce Pdx1 expression in endoderm anterior to the pancreas. Lateral plate mesoderm appears to pattern the endoderm in a posterior-dominant fashion as first noted in the patterning of the neural tube at the same embryonic stage. These findings argue for a central role of the mesoderm in coordinating the A-P pattern of all three primary germ layers.

Hepatocyte nuclear factors-1alpha, -1beta, and -3beta expressed in the gonad of tilapia (Oreochromis mossambicus)

Hepatocyte nuclear factors (HNFs) are upstream regulators of many liver-specific genes and are involved in many cellular functions in the body, but their existence, expression, and function in gonads are still poorly understood. Here we report on the first cloning of partial cDNAs of HNF-1alpha and -1beta and full HNF-3beta cDNA from a tilapia (Oreochromis mossambicus) liver cDNA library. The deduced amino acid sequence of tilapia HNF-3beta has a 90 to 96% identity with those of other fishes (dwarf gourami, medaka, and zebrafish), 74% with mammals (human, rat, and mouse), and 82% with Xenopus. RT-PCR detected IGF-I and -II and HNF-1alpha, -1beta, and -3beta in both liver and gonads and the identity of the PCR fragments was confirmed by PCR hybridization. Immunoprecipitation and Western blotting also detected all three HNF proteins in both liver and gonads. Expression of HNFs in the gonads of the tilapia suggests that multi-HNFs may form a cascade to regulate gonadal physiology in the bony fish.

Estrogen opposes the apoptotic effects of bone morphogenetic protein 7 on tissue remodeling

Interactions between estrogen and growth factor signaling pathways at the level of gene expression play important roles in the function of reproductive tissues. For example, estrogen regulates transforming growth factor beta (TGFbeta) in the uterus during the proliferative phase of the mammalian reproductive cycle. Bone morphogenetic protein 7 (BMP-7), a member of the TGFbeta superfamily, is also involved in the development and function of reproductive tissues. However, relatively few studies have addressed the expression of BMP-7 in reproductive tissues, and the role of BMP-7 remains unclear. As part of an ongoing effort to understand how estrogen represses gene expression and to study its interactions with other signaling pathways, chick BMP-7 (cBMP-7) was cloned. cBMP-7 mRNA levels are repressed threefold within 8 h following estrogen treatment in the chick oviduct, an extremely estrogen-responsive reproductive tissue. This regulation occurs at the transcriptional level. Estrogen has a protective role in many tissues, and withdrawal from estrogen often leads to tissue regression; however, the mechanisms mediating regression of the oviduct remain unknown. Terminal transferase-mediated end-labeling and DNA laddering assays demonstrated that regression of the oviduct during estrogen withdrawal involves apoptosis, which is a novel observation. cBMP-7 mRNA levels during estrogen withdrawal increase concurrently with the apoptotic index of the oviduct. Furthermore, addition of purified BMP-7 induces apoptosis in primary oviduct cells. This report demonstrates that the function of BMP-7 in the oviduct involves the induction of apoptosis and that estrogen plays an important role in opposing this function.