Serial analysis of gene expression in mouse uterus at the implantation site

Influence of conceptus presence and preovulatory estradiol exposure on uterine gene transcripts and proteins around maternal recognition of pregnancy in beef cattle

The uterine environment must provide sufficient endocrine conditions and nutrients for pregnancy maintenance and conceptus survival. The objective of this study was to determine the effects of preovulatory estradiol and conceptus presence on uterine transcripts and uterine luminal fluid (ULF) proteins. Beef cows/heifers were synchronized and artificially inseminated (d 0). Uteri were flushed (d 16); conceptuses and endometrial biopsies were collected. Total cellular RNA was extracted from endometrium for RNA sequencing and RT-PCR validation. There were two independent ULF pools made for each of the following groups: highE2/conceptus, highE2/noconceptus, lowE2/conceptus, and lowE2/noconceptus that were analyzed using the 2D LC-MS/MS based iTRAQ method. There were 64 differentially expressed genes (DEGs) and 77 differentially expressed proteins (DEPs) in common among the highE2/conceptus vs highE2/noconceptus and lowE2/conceptus vs lowE2/noconceptus groups. In summary, the interaction between preovulatory estradiol and the conceptus induces the expression of genes, proteins, and pathways necessary for pregnancy.

NR4A1 Affects Endometrial Receptivity by Participating in Mesenchymal-Epithelial Transition of Endometrial Stromal Cells

Decidualization is a substantive differentiation process experienced by endometrium to prepare for pregnancy. During this process, the endometrial stromal cells are transformed to endometrial epithelial cells. The receptivity of endometrium is necessary for the decidualization and successful implantation of endometrium, while the main hormones coordinating this process are estrogen and progesterone (P). In our study, the immunofluorescence, qPCR, and western blot experiments were conducted on different types of clinical endometrial tissue samples. The experimental results show that in the endometrium of normal subjects during the luteal phase, the protein level and serum P4 level of the orphan nuclear receptor NR4A1 messenger RNA were all significantly higher than those of patients with endometriosis or primary infertility, and the two levels presented positive correlation. Through decidualization induction of the human endometrial stromal cells (hESCs) cultured in vitro and additional P treatment, the results of chromatin immunoprecipitation and other experiments show that the P treatment could upregulate the expression of NR4A1 in hESCs, and this process was mediated under the direct effect of progesterone receptor (PR) and NR4A1. When the NR4A1 in hESCs was silenced, the promotion of hESC proliferation by P was inhibited. P and overexpressed NR4A1 increased the expression of epithelial cell marker in decidual hESCs, and qPCR showed that NR4A1's response to P was earlier than that of the epithelial cell marker. The results of spheroid adhesion assay show that the silent NR4A1 had reduced the adhesion of decidual hESCs induced in vitro to embryo. To sum it up, NR4A1 participated in the decidualization process by responding to the P regulation via and by promoting the hESCs' mesenchymal-epithelial transition, so as to further influence the receptivity of endometrium.

Cell-Cell Communication at the Embryo Implantation Site of Mouse Uterus Revealed by Single-Cell Analysis

As a crucial step for human reproduction, embryo implantation is a low-efficiency process. Despite rapid advances in recent years, the molecular mechanism underlying embryo implantation remains poorly understood. Here, we used the mouse as an animal model and generated a single-cell transcriptomic atlas of embryo implantation sites. By analyzing inter-implantation sites of the uterus as control, we were able to identify global gene expression changes associated with embryo implantation in each cell type. Additionally, we predicted signaling interactions between uterine luminal epithelial cells and mural trophectoderm of blastocysts, which represent the key mechanism of embryo implantation. We also predicted signaling interactions between uterine epithelial-stromal crosstalk at implantation sites, which are crucial for post-implantation development. Our data provide a valuable resource for deciphering the molecular mechanism underlying embryo implantation.

MicroRNAs in Small Extracellular Vesicles Indicate Successful Embryo Implantation during Early Pregnancy

Synchronous communication between the developing embryo and the receptive endometrium is crucial for embryo implantation. Thus, uterine receptivity evaluation is vital in managing recurrent implantation failure (RIF). The potential roles of small extracellular vesicle (sEV) miRNAs in pregnancy have been widely studied. However, the systematic study of sEVs derived from endometrium and its cargos during the implantation stage have not yet been reported. In this study, we isolated endometrium-derived sEVs from the mouse endometrium on D2 (pre-receptive phase), D4 (receptive phase), and D5 (implantation) of pregnancy. Herein, we reveal that multivesicular bodies (MVBs) in the endometrium increase in number during the window of implantation (WOI). Moreover, our findings indicate that CD63, a well-known sEV marker, is expressed in the luminal and glandular epithelium of mouse endometrium. The sEV miRNA expression profiles indicated that miR-34c-5p, miR-210, miR-369-5p, miR-30b, and miR-582-5p are enriched during WOI. Further, we integrated the RIF’s database analysis results and found out that miR-34c-5p regulates growth arrest specific 1 (GAS1) for normal embryo implantation. Notably, miR-34c-5p is downregulated during implantation but upregulated in sEVs. An implication of this is the possibility that sEVs miR-34c-5p could be used to evaluate uterine states. In conclusion, these findings suggest that the endometrium derived-sEV miRNAs are potential biomarkers in determining the appropriate period for embryo implantation. This study also has several important implications for future practice, including therapy of infertility.

Association of Polymorphisms in Candidate Genes with the Litter Size in Two Sheep Breeds

Hu sheep and Small-tailed Han sheep are the most widely raised and most famous maternal sheep breeds in China, which are known for precocious puberty, perennial oestrus and high fecundity (1-6 lambs each parity). Therefore, it is crucial to increase litter size of these two breeds for intensive sheep industry. The objective of this study was to identify potential genetic markers linked with sheep litter size located at ten genes. This study collected blood sample of 537 Hu sheep and 420 Small-tailed Han sheep with litter size of first parity. The average litter sizes in Hu sheep and Small-tailed Han sheep were 2.21 and 1.93. DNA-pooling sequencing method was used for detecting the potential single nucleotide polymorphisms (SNPs) in ten genes related to follicle development and female reproduction. SNPscan® was used for individually genotyping. As a result, a total of 78 putative SNPs in nine out of ten candidate genes (except NOG) were identified. In total, 50 SNPs were successfully genotyped in Hu sheep and Small-tailed Han sheep. After quality control, a total of 42 SNPs in Hu sheep and 44 SNPs in Small-tailed Han sheep were finally used for further analysis. Association analysis revealed that nine SNPs within six genes (KIT: g.70199073A>G, KITLG: g.124520653G>C, ADAMTS1: g.127753565T>C, ADAMTS1: g.127754640G>T, NCOA1: g.31928165C>T, NCOA1: g.32140565G>A, LIFR: g.35862868C>T, LIFR: g.35862947G>T and NGF: g.91795933T>C) were significantly associated with litter size in Hu sheep or Small-tailed Han sheep. A combined haplotypes analysis of the two loci (LIFR: g.35862868C>T and LIFR: g.35862947G>T) revealed that H2H3 (CTTT) combined haplotypes had the largest litter size than the rest combined haplotypes and more than those with either mutation alone in Small-tailed Han sheep. Taken together, our study suggests that nine significant SNPs in six genes can be served as useful genetic markers for MAS in sheep.

Fatty Acid Desaturase 3 (FADS3) Is a Specific ∆13-Desaturase of Ruminant trans-Vaccenic Acid

In mammalian species, the Fatty Acid Desaturase (FADS) gene cluster includes FADS1 (∆5-desaturase), FADS2 (∆6-desaturase), and a third gene member, named FADS3. According to its high degree of nucleotide sequence homology with both FADS1and FADS2, FADS3 was promptly suspected by researchers in the field to code for a new mammalian membrane-bound fatty acid desaturase. However, no catalytic activity was attributed to the FADS3 protein for a decade, until the rat FADS3 protein was shown in vitro to be able to catalyze the unexpected ∆13-desaturation of trans-vaccenic acid, producing the trans11,cis13-conjugated linoleic acid isomer. This review summarizes the recent investigations establishing the FADS3 enzyme as a reliable mammalian trans-vaccenate ∆13-desaturase in vivo and tries to identify further unresolved issues that need to be addressed.

FOXO3a is essential for murine endometrial decidualization through cell apoptosis during early pregnancy

Embryo implantation is essential for normal pregnancy, and the process of decidualization is critical for embryo implantation. However, the mechanism of decidualization during early pregnancy is still unknown. Forkhead box O3a (FOXO3a) is the most important functional transcription factor of the forkhead box family and is a highly conserved transcription factor of apoptosis-related genes. In the mouse uterus, FOXO3a was found to be expressed regularly from Days 1-7 of early pregnancy. Upon further exploration, it was found that FOXO3a was expressed at significantly higher levels at the implantation site than at the interimplantation site on Days 5-7 of pregnancy. Under artificial decidualization, FOXO3a was highly expressed in the first and second decidual zones. After decidualization, the expression of FOXO3a was significantly increased both in vivo and vitro. In primary stromal cells, apoptosis was reduced by decreased expression of FOXO3a after inducing decidualization. Moreover, when FOXO3a-small interfering RNA was transfected into the uteri of mice, the expression of decidualization- and apoptosis-related factors was impaired. Thus, FOXO3a might play an important role in decidualization during early pregnancy, and cell apoptosis might be one of pathways for FOXO3a-regulated decidualization.

Fads3 modulates docosahexaenoic acid in liver and brain

Fatty acid desaturase 3 (FADS3) is the third member of the FADS gene cluster. FADS1 and FADS2 code for enzymes required for highly unsaturated fatty acid (HUFA) biosynthesis, but FADS3 function remains elusive. We generated the first Fads3 knockout (KO) mouse with an aim to characterize its metabolic phenotype and clues to in vivo function. All mice (wild type (WT) and KO) were fed facility rodent chow devoid of HUFA. No differences in overt phenotypes (survival, fertility, growth rate) were observed. Docosahexaenoic acid (DHA, 22:6n-3) levels in the brain of postnatal day 1 (P1) KO mice were lower than the WT (P < 0.05). The ratio of docosapentaenoic acid (DPA, 22:5n-3) to DHA in P1 KO liver was higher than in WT suggesting lower desaturase activity. Concomitantly, 20:4n-6 was lower but its elongation product 22:4n-6 was greater in the liver of P1 KO mice. P1 KO liver Fads1 and Fads2 mRNA levels were significantly downregulated whereas expression levels of elongation of very long chain 2 (Elovl2) and Elovl5 genes were upregulated compared to age-matched WT. No Δ13-desaturation of vaccenic acid was observed in liver or heart in WT mice expressing FADS3 as was reported in vitro. Taken together, the fatty acid compositional results suggest that Fads3 enhances liver-mediated 22:6n-3 synthesis to support brain 22:6n-3 accretion before and during the brain growth spurt.

Transgelin-2: A potential oncogenic factor

Actin-binding proteins are proteins that could bind to actin or actin fibers. As a member of actin-binding proteins, Transgelin-2 is expressed in smooth muscle cells and non-smooth muscle cells, and its gene, TAGLN2, is differently expressed in all cells and tissues. The deregulation of Transgelin-2 is considered to be correlated with progression of many kinds of diseases, especially the development of malignant tumors, such as invasion, metastasis, and resistance, yet the function and mechanism of action of Transgelin-2 remain elusive. Therefore, we reviewed the basic characteristics and function of Transgelin-2 and its biological role in various types of diseases in order to provide the theoretical basis for further research and new perspectives on cancer development.

Expression of mmu-miR-96 in the endometrium during early pregnancy and its regulatory effects on stromal cell apoptosis via Bcl2

Decidualization of endometrial stromal cells is an important feature of implantation and pregnancy. The molecular mechanism underlying decidualization remains unclear, particularly regarding the microRNA (miRNA/miR) regulation of this process. The present study revealed the temporal and spatial distribution of mmu-miR-96 in the mouse uterus during early pregnancy by reverse transcription-quantitative polymerase chain reaction and in situ hybridization. In addition, primary stromal cells were isolated from the mouse uterus and used to explore the role of mmu-miR-96 in decidualization. The results demonstrated that mmu-miR-96 was highly expressed in stromal cells during pregnancy, and was upregulated at implantation sites. In addition, mmu-miR-96 was strongly expressed during decidualization, which indicates that it may serve a role in the decidualization of stromal cells. Based on existing reports, mmu-miR-96 participates in apoptosis; therefore the present study investigated its effects on the apoptosis of primary endometrial stromal cells. The results indicated that overexpression of mmu-miR-96 may induce apoptosis of stromal cells. In further studies regarding the underlying mechanism, the target genes of mmu-miR-96 were screened by bioinformatics analysis, and it was confirmed that B-cell lymphoma 2, an anti-apoptotic gene, was the target of mmu-miR-96, as determined using a reporter gene assay. In conclusion, the present study suggested that mmu-miR-96 participates in the decidualization of endometrial stromal cells in mice, thereby serving a key role in pregnancy.

Gene profiling the window of implantation: Microarray analyses from human and rodent models

Poor uterine receptivity leads to implantation defects or failure. Identification of uterine molecules crucial to uterine receptivity and/or embryo implantation provides the opportunity to design a diagnostic screening toolkit for uterine receptivity or targeted drug discovery for treating implantation-based infertility. In this regard, gene-profiling studies performed in humans and rodents have identified numerous genes involved in the transcriptional regulation of uterine receptivity and embryo implantation. In this article, we compared available uterine microarray datasets collected during the time of uterine receptivity and implantation in humans, mice and hamsters to uncover conserved gene sets. We also compared the transcriptome signature of women with unexplained infertility (UIF) and recurrent implantation failure (RIF) to gain insight into genes potentially dysregulated during endometrial receptivity or embryo implantation. Among numerous differentially expressed genes, few were revealed that might have molecular diagnostic screening potential for identifying the uterine receptive state during the time of implantation. Finally, functional annotation of gene sets uncovered altered uterine apoptosis or cell adhesion pathways in women with UIF and RIF, respectively. These conserved or divergent gene sets provide insights into the uterine receptive state for supporting blastocyst implantation.

Alternative splicing generates novel Fads3 transcript in mice

Fads3 is the third member of the fatty acid desaturase gene cluster; with at least eight evolutionarily conserved alternative transcripts (AT), having no clearly established function as are known for FADS2 and FADS1. Here we present identification of a novel Fads3 transcript in mice (Fads3AT9), characterize Fads3AT9 expression in mouse tissues and evaluate correlations with metabolite profiles. Total RNA obtained from mouse tissues is reverse-transcribed into cDNA and used as template for PCR reactions. Tissue fatty acids were extracted and quantified by gas chromatography. Sequencing analysis revealed complete absence of exon 2 resulting in an open reading frame of 1239 bp, encoding a putative protein of 412 aa with loss of 37 aa compared to classical Fads3 (Fads3CS). FADS3AT9 retains all the conserved regions characteristic of front end desaturase (cytochrome b5 domain and three histidine repeats). Both Fads3CS and Fads3AT9 are ubiquitously expressed in 11 mouse tissues. Fads3AT9 abundance was greater than Fads3CS in pancreas, liver, spleen, brown adipose tissue and thymus. Fads3CS expression is low in pancreas while Fads3AT9 is over ten-fold greater abundance. The eicosanoid precursor fatty acid 20:4n - 6, the immediate desaturation product of the Fads1 coded Δ5-desaturase, was highest in pancreas where Fads3CS is low. Changes in expression patterns and fatty acid profiles suggest that Fads3AT9 may play a role in the regulation and/or biosynthesis of long chain polyunsaturated fatty acids from precursors.

Identification of gene expression changes in rabbit uterus during embryo implantation

Embryo implantation in the rabbit is unique in that a typical fusion type of implantation is employed, in which trophoblast cells adhere and fuse to the apical surface of uterine epithelial cells. In the present study, we analyzed global gene expression changes in the rabbit uterus during embryo implantation by using RNA-seq. We identified a total of 536 differentially expressed genes (fold change >2 and adjusted p-value <0.01), of which 266 genes were down-regulated and 270 genes were up-regulated at the implantation site compared to the inter-implantation site. Functional clustering revealed that cell adhesion is among top ranked enriched terms from both gene ontology and pathway analysis, highlighting the importance of cell adhesion during embryo implantation in rabbits. Through gene network analysis, we prioritized 9 genes using the hub gene method. Our study provides a valuable resource for in-depth understanding of the mechanism underlying embryo implantation in rabbits.

Fatty Acid Desaturases, Polyunsaturated Fatty Acid Regulation, and Biotechnological Advances

Polyunsaturated fatty acids (PUFAs) are considered to be critical nutrients to regulate human health and development, and numerous fatty acid desaturases play key roles in synthesizing PUFAs. Given the lack of delta-12 and -15 desaturases and the low levels of conversion to PUFAs, humans must consume some omega-3 and omega-6 fatty acids in their diet. Many studies on fatty acid desaturases as well as PUFAs have shown that fatty acid desaturase genes are closely related to different human physiological conditions. Since the first front-end desaturases from cyanobacteria were cloned, numerous desaturase genes have been identified and animals and plants have been genetically engineered to produce PUFAs such as eicosapentaenoic acid and docosahexaenoic acid. Recently, a biotechnological approach has been used to develop clinical treatments for human physiological conditions, including cancers and neurogenetic disorders. Thus, understanding the functions and regulation of PUFAs associated with human health and development by using biotechnology may facilitate the engineering of more advanced PUFA production and provide new insights into the complexity of fatty acid metabolism.

Expression of DROSHA in the Uterus of Mice in Early Pregnancy and Its Potential Significance During Embryo Implantation

Previous studies have shown that microRNAs are involved in the process of implantation. They play an important role in cell growth and proliferation. DROSHA is the microRNA-processing enzyme and is required for the maturation of microRNAs. However, its expression and function during early pregnancy in mice still remain unclear. In the present study, we analyzed the expression pattern of DROSHA in the mouse uterus during early pregnancy, pseudopregnancy, artificially induced decidualization, and in the ovariectomized mouse uterus using real-time quantitative polymerase chain reaction, Western blotting analyses, and immunohistochemistry. We found that DROSHA was spatiotemporally expressed in decidualizing stromal cells during early pregnancy and in pseudopregnant mice in which decidualization was artificially induced. In the ovariectomized mouse uterus, the expression of DROSHA was upregulated after progesterone treatment. In a stromal cell culture model, the expression of DROSHA gradually increased with the progression of stromal decidualization. Taken together, our findings suggest that DROSHA is involved in stromal decidualization and may play an important role in embryo implantation in mice.

Expression of KRAS in the endometrium of early pregnant mice and its effect during embryo implantation

This study investigated the expression pattern of Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) in the endometrium of early-stage pregnant mice and its function during embryo implantation. The expression of KRAS was measured at the mRNA level using real-time polymerase chain reaction (PCR) and at the protein level using immunohistochemistry and western blotting. The expressions of KRAS mRNA and protein were not significantly different in the endometrium of pseudopregnant and early-stage pregnant mice. However, the immunohistochemistry results showed that KRAS was highly expressed in the decidualizing stromal cells on days 5-7 of mouse pregnancy and was enhanced in the epithelial cells as pregnancy progressed. The expression of KRAS protein was higher after the stromal cell was artificially decidualized in vivo and in vitro. Stromal cell proliferation was attenuated after down-regulating KRAS expression. After silencing KRAS in the mouse uterus, the embryo implantation rate was significantly reduced (P < 0.005). We speculate that KRAS may regulate the stromal cell proliferation and differentiation progress and then affect the embryo implantation process. This study reveals that KRAS plays an important role in regulating the embryo implantation process.

MicroRNA-451 plays a role in murine embryo implantation through targeting Ankrd46, as implicated by a microarray-based analysis

OBJECTIVE

To determine the potential microRNA (miRNA) regulators of embryo implantation, as a continuation of genomic and proteomic research.

DESIGN

Laboratory animal research.

SETTING

University hospital laboratory.

ANIMAL(S)

Adult healthy female C57BL6/J mice (age 6-8 weeks, nonfertile, weighing 18-20 g each).

INTERVENTION(S)

Female mice were mated naturally with fertile males to produce pregnancy. Luminal epithelium was collected by laser-capture microdissection during the implantation period. Mouse models of pseudopregnancy, delayed implantation, and artificial decidualization were established.

MAIN OUTCOME MEASURE(S)

The miRNA profile in luminal epithelium was clarified by microarray analysis and validated by real-time reverse transcription polymerase chain reaction (qRT-PCR) in a series of models. Target genes were predicted and confirmed by luciferase activity assay. The role of miRNA in implantation was examined by loss-of-function and gain-of-function of miRNA in vitro and in vivo.

RESULT(S)

A total of 29 and 15 miRNAs were up- and down-regulated, respectively, during the implantation period; 11 of these miRNAs were validated by qRT-PCR. The profile of miR-451 was clarified in a series of models. A dual-luciferase activity assay showed that Ankrd46 was a target gene of miR-451. Loss-of-function by LV-miR-451 sponge or miR-451 inhibitor led to a reduced number of embryo implantations, but had little effect on fertilization.

CONCLUSION(S)

miR-451 was specifically up-regulated during the implantation period, and it may play a major role in embryo implantation by targeting Ankrd46.

Cross-species transcriptomic approach reveals genes in hamster implantation sites

The mouse model has greatly contributed to understanding molecular mechanisms involved in the regulation of progesterone (P4) plus estrogen (E)-dependent blastocyst implantation process. However, little is known about contributory molecular mechanisms of the P4-only-dependent blastocyst implantation process that occurs in species such as hamsters, guineapigs, rabbits, pigs, rhesus monkeys, and perhaps humans. We used the hamster as a model of P4-only-dependent blastocyst implantation and carried out cross-species microarray (CSM) analyses to reveal differentially expressed genes at the blastocyst implantation site (BIS), in order to advance the understanding of molecular mechanisms of implantation. Upregulation of 112 genes and downregulation of 77 genes at the BIS were identified using a mouse microarray platform, while use of the human microarray revealed 62 up- and 38 down-regulated genes at the BIS. Excitingly, a sizable number of genes (30 up- and 11 down-regulated genes) were identified as a shared pool by both CSMs. Real-time RT-PCR and in situ hybridization validated the expression patterns of several up- and down-regulated genes identified by both CSMs at the hamster and mouse BIS to demonstrate the merit of CSM findings across species, in addition to revealing genes specific to hamsters. Functional annotation analysis found that genes involved in the spliceosome, proteasome, and ubiquination pathways are enriched at the hamster BIS, while genes associated with tight junction, SAPK/JNK signaling, and PPARα/RXRα signalings are repressed at the BIS. Overall, this study provides a pool of genes and evidence of their participation in up- and down-regulated cellular functions/pathways at the hamster BIS.

The LIF-mediated molecular signature regulating murine embryo implantation

The establishment of a receptive uterus is the prime requirement for embryo implantation. In mice, the E2-induced cytokine leukemia inhibitory factor (LIF) is essential in switching the uterine luminal epithelium (LE) from a nonreceptive to a receptive state. Here we define the LIF-mediated switch using array analysis and informatics to identify LIF-induced changes in gene expression and annotated signaling pathways specific to the LE. We compare gene expression profiles at 0, 1, 3, and 6 h, following LIF treatment. During the first hour, the JAK-STAT signaling pathway is activated and the expression of 54 genes declines, primarily affecting LE cytoskeletal and chromatin organization as well as a transient reduction in the progesterone, TGFbetaR1, and ACVR1 receptors. Simultaneously 256 genes increase expression, of which 42 are transcription factors, including Sox, Kfl, Hes, Hey, and Hox families. Within 3 h, the expression of 3987 genes belonging to more than 25 biological process pathways was altered. We confirmed the mRNA and protein distribution of key genes from 10 pathways, including the Igf-1, Vegf, Toll-like receptors, actin cytoskeleton, ephrin, integrins, TGFbeta, Wnt, and Notch pathways. These data identify novel LIF-activated pathways in the LE and define the molecular basis between the refractory and receptive uterine phases. More broadly, these findings highlight the staggering capacity of a single cytokine to induce a dynamic and complex network of changes in a simple epithelium essential to mammalian reproduction and provide a basis for identifying new routes to regulating female reproduction.

MiR-133b regulates the expression of the Actin protein TAGLN2 during oocyte growth and maturation: a potential target for infertility therapy

Infertility is an area of increasing in life science research. Although follicular maturation disorders and anovulation are the primary causations of infertility, its molecular mechanism is not well understood. Recent research has shown that microRNAs (miRNAs) might play an important role in the regulation of ovarian follicle development and maturation. In this study, the expression of miRNAs in metaphase I (MI) oocytes treated with or without insulin-like growth factor 1 (IGF-1) was observed by microRNA microarray analysis. Results show that 145 miRNAs were up-regulated and 200 miRNAs were down-regulated in MI oocytes after IGF-1 treatment. MiR-133b, which was up-regulated more than 30-fold, was chosen for further research. As a potential target of miR133b, transgelin 2 (TAGLN2) gene was down-regulated, at both transcription and translation levels, in miR-133b- over-expressed 293T cells, but TAGLN2 was up-regulated when the expression of miR-133b was inhibited. Furthermore, the expression level of TAGLN2 in the ovaries of 8-week- old mice was higher than that observed in 4-week-old mice. Immunofluorescence experiments showed that TAGLN2 was located in the cytoplasm. In general, our results indicate that miR-133b may play important roles in the growth and maturation of oocytes by regulating its potential target, TAGLN2, at both transcription and translation levels. Therefore, our research provides a potential new target for infertility therapy.

Crystallin αB acts as a molecular guard in mouse decidualization: regulation and function during early pregnancy

Although decidualization is crucial for the establishment of successful pregnancy, the molecular mechanism underlying decidualization remains poorly understood. Crystallin αB (CryAB), a small heat shock protein (sHSP), is up-regulated and phosphorylated in mouse decidua. In mouse primary endometrial stromal cells, CryAB is induced upon progesterone treatment via HIF1α. In addition, CryAB is strongly phosphorylated through the p38-MAPK pathway under stress or during in vitro decidualization. Knockdown of CryAB results in the increase of apoptosis of stromal cells and inhibits decidualization under oxidative or inflammatory stress. Our data indicate that CryAB protects decidualization against stress conditions.

The differential expression of microRNAs between implantation sites and interimplantation sites in early pregnancy in mice and their potential functions

Embryo implantation is a complex process that involves synchronized crosstalk between a receptive endometrium and a functional blastocyst. It can take place only during the window of implantation, a period when a series of changes in gene expression occur in the endometrium to accept the embryo. As modulators of gene expression, microRNAs (miRNAs) have been identified as regulators of embryo implantation. To better understand how miRNAs regulate implantation and the related molecular mechanisms, we compared the expression profiles of miRNAs and messenger RNAs between implantation sites (IMs) and inter-IMs in the endometrium of pregnant mice on day 5 by microarrays. The results showed that compared with inter-IMs, 30 miRNAs were upregulated and 42 miRNAs (>2-fold) were downregulated at the IMs. By combining the results of the microarray experiments, we found that 20 upregulated pathways and 14 downregulated pathways might be subject to miRNA regulation at IMs. We also found that some miRNAs and their targets may play a key role in implantation.

Unsaturated fatty acids, desaturases, and human health

With the increasing concern for health and nutrition, dietary fat has attracted considerable attention. The composition of fatty acids in a diet is important since they are associated with major diseases, such as cancers, diabetes, and cardiovascular disease. The biosynthesis of unsaturated fatty acids (UFA) requires the expression of dietary fat-associated genes, such as SCD, FADS1, FADS2, and FADS3, which encode a variety of desaturases, to catalyze the addition of a double bond in a fatty acid chain. Recent studies using new molecular techniques and genomics, as well as clinical trials have shown that these genes and UFA are closely related to physiological conditions and chronic diseases; it was found that the existence of alternative transcripts of the desaturase genes and desaturase isoforms might affect human health and lipid metabolism in different ways. In this review, we provide an overview of UFA and desaturases associated with human health and nutrition. Moreover, recent findings of UFA, desaturases, and their associated genes in human systems are discussed. Consequently, this review may help elucidate the complicated physiology of UFA in human health and diseases.

Costimulatory molecule CD28 participates in the process of embryo implantation in mice

Embryo implantation is a complex process requiring reciprocal interactions between implantation-competent blastocysts and receptive uteri. Accumulating literatures have indicated that T cells are involved in this process. The first signal mediated by T-cell receptor/CD3 complex and the second signal delivered by costimulatory molecules are essential for the differentiation of T cell into an effector cell. Expression and function of CD28, an important costimulatory molecule, during early pregnancy in mice is still unclear. In the present study, we investigated the expression pattern of CD28 in mouse uterus during early pregnancy and pseudopregnancy by real-time quantitative polymerase chain reaction, Western blotting, in situ hybridization, and immunohistochemistry (IHC). We found that injection of the uterine horn with CD28 antisense oligodeoxynucleotides leads to a decreased number of implantation sites. The expression pattern of CD3 protein examined by IHC is similar to that of CD28. These findings suggest that CD28 participates in the process of embryo implantation in mice, which might play its role through delivering the second costimulatory signal.

Cell-specific transcriptional profiling reveals candidate mechanisms regulating development and function of uterine epithelia in mice

All mammalian uteri have luminal (LE) and glandular epithelia (GE) in their endometrium. The LE mediates uterine receptivity and blastocyst attachment for implantation, and the GE synthesize and secrete or transport bioactive substances involved in blastocyst implantation, uterine receptivity, and stromal cell decidualization. However, the mechanisms governing uterine epithelial development after birth and their function in the adult are not fully understood. Here, comprehensive microarray analysis was conducted on LE and GE isolated by laser capture microdissection from uteri on Postnatal Day 10 (PD 10) and day of pseudopregnancy (DOPP) 2.5 and 3.5. This data was integrated with analysis of uteri from gland-containing control and aglandular progesterone-induced uterine gland knockout mice from PD 10 and DOPP 3.5. Many genes were expressed in both epithelia, but there was greater expression of genes in the LE than in the GE. In the neonate, GE-expressed genes were enriched for morphogenesis, development, migration, and retinoic acid signaling. In the adult, LE-expressed genes were enriched for metabolic processes and steroid biosynthesis, whereas retinoid signaling, tight junction, extracellular matrix, and regulation of kinase activity were enriched in the GE. The transcriptome differences in the epithelia support the idea that each cell type has a distinct and complementary function in the uterus. The candidate genes and regulatory networks identified here provide a framework to discover new mechanisms regulating development of epithelia in the postnatal uterus and their functions in early pregnancy.

Dietary arachidonic acid and docosahexaenoic acid regulate liver fatty acid desaturase (FADS) alternative transcript expression in suckling piglets

Molecular regulation of fatty acid desaturase (Fads) gene expression by dietary arachidonic acid (ARA) and docosahexaenoic acid (DHA) during early post-natal period, when the demand for long chain polyunsaturated fatty acids (LC-PUFA) is very high, has not been well defined. The objective of the current study was to determine regulation of liver Fads1, Fads2 and Fads3 classical (CS) and alternative transcripts (AT) expression by dietary ARA and DHA, within the physiological range present in human breast milk, in suckling piglets. Piglets were fed one of six milk replacer formula diets (formula-reared groups, FR) with varying ARA and DHA content from days 3-28 of age. The ARA/DHA levels of the six formula diets were as follows (% total fatty acid, FA/FA): (A1) 0.1/1.0; (A2) 0.53/1.0; (A3-D3) 0.69/1.0; (A4) 1.1/1.0; (D2) 0.67/0.62; and (D1) 0.66/0.33. The control maternal-reared (MR) group remained with the dam. Fads1 expression was not significantly different between FR and MR groups. Fads2 expression was down-regulated significantly in diets with 1:1 ratio of ARA:DHA, compared to MR. Fads2 AT1 expression was highly correlated to Fads2 expression. Fads3 AT7 was the only Fads3 transcript sensitive to dietary LC-PUFA intake and was up-regulated in the formula diets with lowest ARA and DHA contents compared to MR. Thus, the present study provides evidence that the proportion of dietary ARA:DHA is a significant determinant of Fads2 expression and LC-PUFA metabolism during the early postnatal period. Further, the data suggest that Fads3 AT7 may have functional significance when dietary supply of ARA and DHA are low during early development.

Progesterone regulation of Na/K-ATPase β1 subunit expression in the mouse uterus during the peri-implantation period

Luminal closure and embryo apposition are essential for blastocyst attachment during early pregnancy. In our preliminary microarray results (unpublished data), sodium-potassium adenosine triphosphatase (Na/K-ATPase) β1 (Atp1b1) was highly expressed in mouse uterus on Days 3 and 4 of pregnancy. However, expression and regulation of Atp1b1 in the mammalian uterus during early pregnancy are unknown. Using in situ hybridization, a strong level of Atp1b1 mRNA was detected in luminal epithelial cells on Days 3 and 4 of pregnancy (Day 1 = day of vaginal plug). The expression pattern of FXYD domain-containing ion transport regulator 4 (Fxyd4) was similar to that of Atp1b1. Real-time reverse transcription polymerase chain reaction confirmed the high expression level of Atp1b1 mRNA. Compared with Day 1, the mRNA level of Atp1b1 on Days 3 and 4 increased by 3.5 ± 0.5 and 4.5 ± 0.5 fold, respectively. When the embryo invaded through epithelial cells into the maternal stromal compartment on day 5, Atp1b1 expression decreased to a basal level. Progesterone stimulated Atp1b1 expression by 2.8 ± 1 fold compared with oil in ovariectomized mice at 24 hours after treatment. Expression of Atp1b1 was further upregulated to 4 ± 0.4 fold by estrogen and progesterone. Based on time-course study, progesterone rapidly induced Atp1b1 expression at 6 and 12 hours (13.7 ± 0.5 and 16.6 ± 1.4, respectively); furthermore, this upregulation was blocked by RU486 (progesterone receptor antagonist). Transcription activity of the Atp1b1 promoter was (Day 1 = day of vaginal plug) stimulated by CCAAT/enhancer binding protein beta (Cebpb). In conclusion, Atp1b1 was highly expressed in luminal epithelium during peri-implantation and upregulated by progesterone.

Dietary long-chain polyunsaturated fatty acids upregulate expression of FADS3 transcripts

The fatty acid desaturase (FADS) gene family at 11q12-13.1 includes FADS1 and FADS2, both known to mediate biosynthesis of omega-3 and omega-6 long-chain polyunsaturated fatty acids (LCPUFA). FADS3 is a putative desaturase due to its sequence similarity with FADS1 and FADS2, but its function is unknown. We have previously described 7 FADS3 alternative transcripts (AT) and 1 FADS2 AT conserved across multiple species. This study examined the effect of dietary LCPUFA levels on liver FADS gene expression in vivo and in vitro, evaluated by qRT-PCR. Fourteen baboon neonates were randomized to three diet groups for their first 12 weeks of life, C: Control, no LCPUFA, L: 0.33% docosahexaenoic acid (DHA)/0.67% arachidonic acid (ARA) (w/w); and L3: 1.00% DHA/0.67% ARA (w/w). Liver FADS1 and both FADS2 transcripts were downregulated by at least 50% in the L3 group compared to controls. In contrast, FADS3 AT were upregulated (L3 > C), with four transcripts significantly upregulated by 40% or more. However, there was no evidence for a shift in liver fatty acids to coincide with increased FADS3 expression. Significant upregulation of FADS3 AT was also observed in human liver-derived HepG2 cells after DHA or ARA treatment. The PPARγ antagonist GW9662 prevented FADS3 upregulation, while downregulation of FADS1 and FADS2 was unaffected. Thus, FADS3 AT were directly upregulated by LCPUFA by a PPARγ-dependent mechanism unrelated to regulation of other desaturases. This opposing pattern and mechanism of regulation suggests a dissimilar function for FADS3 AT compared to other FADS gene products.

Cystathionine β-synthase deficiency causes infertility by impairing decidualization and gene expression networks in uterus implantation sites

Hyperhomocysteinemia has been reported in human reproduction as a risk factor for early pregnancy loss, preeclampsia, and congenital birth defects like spina bifida. Female infertility was also observed in cystathionine beta synthase-deficient mice ( Cbs-KO) as an animal model for severe hyperhomocysteinemia. The aim for the present research was to elucidate the time-point of pregnancy loss and to pinpoint gene and cellular changes involved in the underlying pathological mechanism. By mating 90-day-old wild-type and Cbs-KO female mice with their homologous male partners, we found that pregnancy loss in Cbs-KO occurred between the 8th and 12th gestation day during placenta formation. DNA microarrays were carried out on uterus from implantation and interimplantation samples obtained on day 8. The results allowed us to select genes potentially involved in embryo death; these were individually confirmed by RT-qPCR, and their expressions were also followed throughout pregnancy. We found that changes in expression of Calb1, Ttr, Expi, Inmt, Spink3, Rpgrip1, Krt15, Mt-4, Gzmc, Gzmb, Tdo2, and Afp were important for pregnancy success, since a different regulation in Cbs-KO mice was found. Also, differences in relationships among selected genes were observed, indicating a dysregulation of these genes in Cbs-KO females. In conclusion, our data provide more information on the gene expression cascade and its timely regulated process required for a successful pregnancy. In addition, we unveil new potential avenues to explore further investigations in pregnancy loss.

Junctional adhesion molecule 2 mediates the interaction between hatched blastocyst and luminal epithelium: induction by progesterone and LIF

Background

Junctional adhesion molecule 2 (Jam2) is a member of the JAM superfamily. JAMs are localized at intercellular contacts and participated in the assembly and maintenance of junctions, and control of cell permeability. Because Jam2 is highly expressed in the luminal epithelium on day 4 of pregnancy, this study was to determine whether Jam2 plays a role in uterine receptivity and blastocyst attachment in mouse uterus.

Methodology/Principal Findings

Jam2 is highly expressed in the uterine luminal epithelium on days 3 and 4 of pregnancy. Progesterone induces Jam2 expression in ovariectomized mice, which is blocked by progesterone antagonist RU486. Jam2 expression on day 4 of pregnancy is also inhibited by RU486 treatment. Leukemia inhibitory factor (LIF) up-regulates Jam2 protein in isolated luminal epithelium from day 4 uterus, which is blocked by S3I-201, a cell-permeable inhibitor for Stat3 phosphorylation. Under adhesion assay, recombinant Jam2 protein increases the rate of blastocyst adhesion. Both soluble recombinant Jam2 and Jam3 can reverse this process.

Conclusion

Jam2 is highly expressed in the luminal epithelium of receptive uterus and up-regulated by progesterone and LIF via tyrosine phosphorylation of Stat3. Jam2 may play a role in the interaction between hatched blastocyst and receptive uterus.

Progesterone and DNA damage encourage uterine cell proliferation and decidualization through up-regulating ribonucleotide reductase 2 expression during early pregnancy in mice

Embryo implantation into the maternal uterus is a crucial step for the successful establishment of mammalian pregnancy. Following the attachment of embryo to the uterine luminal epithelium, uterine stromal cells undergo steroid hormone-dependent decidualization, which is characterized by stromal cell proliferation and differentiation. The mechanisms underlying steroid hormone-induced stromal cell proliferation and differentiation during decidualization are still poorly understood. Ribonucleotide reductase, consisting of two subunits (RRM1 and RRM2), is a rate-limiting enzyme in deoxynucleotide production for DNA synthesis and plays an important role in cell proliferation and tumorgenicity. Based on our microarray analysis, Rrm2 expression was significantly higher at implantation sites compared with interimplantation sites in mouse uterus. However, the expression, regulation, and function of RRM2 in mouse uterus during embryo implantation and decidualization are still unknown. Here we show that although both RRM1 and RRM2 expression are markedly induced in mouse uterine stromal cells undergoing decidualization, only RRM2 is regulated by progesterone, a key regulator of decidualization. Further studies showed that the induction of progesterone on RRM2 expression in stromal cells is mediated by the AKT/c-MYC pathway. RRM2 can also be induced by replication stress and DNA damage during decidualization through the ATR/ATM-CHK1-E2F1 pathway. The weight of implantation sites and deciduoma was effectively reduced by specific inhibitors for RRM2. The expression of decidual/trophoblast prolactin-related protein (Dtprp), a reliable marker for decidualization in mice, was significantly reduced in deciduoma and steroid-induced decidual cells after HU treatment. Therefore, RRM2 may be an important effector of progesterone signaling to induce cell proliferation and decidualization in mouse uterus.

The polypyrimidine tract binding protein regulates desaturase alternative splicing and PUFA composition

The Δ6 desaturase, encoded by FADS2, plays a crucial role in omega-3 and omega-6 fatty acid synthesis. These fatty acids are essential components of the central nervous system, and they act as precursors for eicosanoid signaling molecules and as direct modulators of gene expression. The polypyrimidine tract binding protein (PTB or hnRNP I) is a splicing factor that regulates alternative pre-mRNA splicing. Here, PTB is shown to bind an exonic splicing silencer element and repress alternative splicing of FADS2 into FADS2 AT1. PTB and FADS2AT1 were inversely correlated in neonatal baboon tissues, implicating PTB as a major regulator of tissue-specific FADS2 splicing. In HepG2 cells, PTB knockdown modulated alternative splicing of FADS2, as well as FADS3, a putative desaturase of unknown function. Omega-3 fatty acids decreased by nearly one half relative to omega-6 fatty acids in PTB knockdown cells compared with controls, with a particularly strong decrease in eicosapentaenoic acid (EPA) concentration and its ratio to arachidonic acid (ARA). This is a rare demonstration of a mechanism specifically altering the cellular omega-3 to omega-6 fatty acid ratio without any change in diet/media. These findings reveal a novel role for PTB, regulating availability of membrane components and eicosanoid precursors for cell signaling.

The integrative analysis of microRNA and mRNA expression in mouse uterus under delayed implantation and activation

Background

Delayed implantation is a developmental arrest at the blastocyst stage and a good model for embryo implantation. MicroRNAs (miRNAs) have been shown to be involved in mouse embryo implantation through regulating uterine gene expression. This study was to have an integrative analysis on global miRNA and mRNA expression in mouse uterus under delayed implantation and activation through Illumina sequencing.

Methodology/Principal Findings

By deep sequencing and analysis, we found that there are 20 miRNAs up-regulated and 42 miRNAs down-regulated at least 1.2 folds, and 268 genes up-regulated and 295 genes down-regulated at least 2 folds under activation compared to delayed implantation, respectively. Many different forms of editing in mature miRNAs are detected. The percentage of editing at positions 4 and 5 of mature miRNAs is significantly higher under delayed implantation than under activation. Although the number of miR-21 reference sequence under activation is slightly lower than that under delayed implantation, the total level of miR-21 under activation is higher than that under delayed implantation. Six novel miRNAs are predicted and confirmed. The target genes of significantly up-regulated miRNAs under activation are significantly enriched.

Conclusions

miRNA and mRNA expression patterns are closely related. The target genes of up-regulated miRNAs are significantly enriched. A high level of editing at positions 4 and 5 of mature miRNAs is detected under delayed implantation than under activation. Our data should be valuable for future study on delayed implantation.

Estrogen regulates amiloride-binding protein 1 through CCAAT/enhancer-binding protein-beta in mouse uterus during embryo implantation and decidualization

Embryo implantation is an intricate interaction between receptive uterus and active blastocyst. The mechanism underlying embryo implantation is still unknown. Although histamine and putrescine are important for embryo implantation and decidualization, excess amount of histamine and putrescine is harmful. Amiloride binding protein 1 (Abp1) is a membrane-associated amine oxidase and mainly metabolizes histamine and putrescine. In this study, we first showed that Abp1 is strongly expressed in the decidua on d 5-8 of pregnancy. Abp1 expression is not detected during pseudopregnancy and under delayed implantation but is detected after estrogen activation. Because Abp1 is mainly localized in the decidua and also strongly expressed during in vitro decidualization, Abp1 might play a role during mouse decidualization. The regulation of estrogen on Abp1 is mediated by transcription factor CCAAT/enhancer-binding protein-β. Abp1 expression is also regulated by cAMP, bone morphogenetic protein 2, and ERK1/2. Abp1 may be essential for mouse embryo implantation and decidualization.

Role of secretory protease inhibitor SPINK3 in mouse uterus during early pregnancy

Successful embryo implantation depends on intricate epithelial-stromal cross-talk. However, molecular modulators involved in this cellular communication remain poorly elucidated. Using multiple approaches, we have investigated the spatiotemporal expression and regulation of serine protease inhibitor Kazal type 3 (SPINK3) in mouse uterus during the estrous cycle and early pregnancy. In cycling mice, both SPINK3 mRNA and protein are only expressed during proestrus. In the pregnant mouse, the expression levels of both SPINK3 mRNA and protein increase on days 5-8 and then decline. Spink3 mRNA is expressed exclusively in the uterine glandular epithelium, whereas SPINK3 protein is localized on the surface of both luminal and glandular epithelium and in the decidua. Moreover, SPINK3 in the decidua has been observed in the primary decidual zone on day 6 and the secondary decidual zone on days 7-8; this is tightly associated with the progression of decidualization. SPINK3 has also been found in decidual cells of the artificially decidualized uterine horn but not control horn, whereas Spink3 mRNA localizes in the glands of both horns. The expression of endometrial Spink3 is not regulated by the blastocyst according to its expression pattern during pseudopregnancy and delayed implantation but is induced by progesterone and further augmented by a combination of progesterone and estrogen in ovariectomized mice. Thus, uterine-gland-derived SPINK3, as a new paracrine modulator, might play an important role in embryo implantation through its influence on stromal decidualization in mice.

Fatty Acid Desaturase 3 (Fads3) is a singular member of the Fads cluster

Since its identification in 2000, no function has been attributed to the Fatty Acid Desaturase 3 (Fads3) gene. This gene is located within the Fads cluster, which also contains Fads1 and Fads2, coding respectively for the Δ5- and Δ6- desaturases. Based on the sequence homology between these three genes, Fads3 may be a new fatty acid desaturase. It is thus essential to understand its involvement in Polyunsaturated Fatty Acid (PUFA) biosynthesis in order to improve our knowledge on lipid metabolism. Gene expression studies provided evidences on the specificity of Fads3 compared to Fads1 and Fads2, concerning the tissue distribution, alternative splicing and regulation. These works also identified possible physiological functions in which Fads3 could be involved. Thus, the Fads3 gene was transcripted in many tissues, and displayed a weak expression in the liver compared to other organs such as the lung or spleen. Fads3 was also showed to be a target gene for NK-κB, MYCN or p63 transcription factors and could consequently be involved in cell survival mechanisms. Polymorphism analysis underlined the possible implication of Fads3 in lipid homeostasis, particularly by modulating cholesterol and triglyceride plasma levels. In terms of proteins, FADS3 has been recently described in rodents. One of the identified isoforms may display the classical structure of a fatty acid desaturase but no enzymatic activity has been observed yet. Therefore, it is essential to consider the desaturase diversity in terms of catalysis and substrates to elucidate the FADS3 function.

The fatty acid desaturase 3 gene encodes for different FADS3 protein isoforms in mammalian tissues

In 2000, Marquardt et al. (A. Marquardt, H. Stöhr, K. White, and B. H. F. Weber. 2000. cDNA cloning, genomic structure, and chromosomal localization of three members of the human fatty acid desaturase family. Genomics. 66: 176-183.) described the genomic structure of the fatty acid desaturase (FADS) cluster in humans. This cluster includes the FADS1 and FADS2 genes encoding, respectively, for the Delta 5- and Delta 6-desaturases involved in polyunsaturated fatty acid biosynthesis. A third gene, named FADS3, has recently been identified but no functional role has yet been attributed to the putative FADS3 protein. In this study, we investigated the FADS3 occurrence in rat tissues by using two specific polyclonal antibodies directed against the N-terminal and C-terminal ends of rat FADS3. Our results showed three potential protein isoforms of FADS3 (75 kDa, 51 kDa, and 37 kDa) present in a tissue-dependent manner. The occurrence of these FADS3 isoforms did not depend on the mRNA level determined by real-time PCR. In parallel, mouse tissues were also tested and showed the same three FADS3 isoforms but with a different tissue distribution. Finally, we reported the existence of FADS3 in human cells and tissues but different new isoforms were identified. To conclude, we showed in this study that FADS3 does exist under multiple protein isoforms depending on the mammalian tissues. These results will help further investigations to determine the physiological function of FADS3.

Novel fatty acid desaturase 3 (FADS3) transcripts generated by alternative splicing

Fatty acid desaturase 1 and 2 (FADS1 and FADS2) code for the key desaturase enzymes involved in the biosynthesis of long chain polyunsaturated fatty acids in mammals. FADS3 shares close sequence homology to FADS1 and FADS2 but the function of its gene product remains unknown. Alternative transcripts (AT) generated by alternative splicing (AS) are increasingly recognized as an important mechanism enabling a single gene to code for multiple gene products. We report the first AT of a FADS gene, FADS3, generated by AS. Aided by ORF Finder, we identified putative coding regions of eight AT for FADS3 with 1.34 kb (classical splicing), 1.14 (AT1), 0.77 (AT2), 1.25 (AT3), 0.51 (AT4), 0.74 (AT6), and 1.11 (AT7). In addition we identified a 0.51 kb length transcript (AT5) that has a termination codon within intron 8-9. The expression of each AT was analyzed in baboon neonate tissues and in differentiated and undifferentiated human SK-N-SH neuroblastoma cells. FADS3 AT are expressed in 12 neonate baboon tissues and showed reciprocal increases and decreases in expression changes in response to human neuronal cell differentiation. FADS3 AT, conserved in primates and under metabolic control in human cells, are a putative mediator of LCPUFA biosynthesis and/or regulation.

Identification of differentially expressed genes in the uterine endometrium on day 12 of the estrous cycle and pregnancy in pigs

Maternal recognition of pregnancy in pigs occurs approximately on Day (D) 12 of pregnancy and is critical for embryo implantation. The presence of the conceptus in the uterine lumen during this period changes uterine endometrial function to prepare for attachment of the conceptus to the endometrial epithelial cells and maintain luteal function in the ovary. Although much is known about endometrial gene expression, the genes expressed in the uterine endometria and the cellular and molecular mechanisms of those gene products during the period of implantation and maternal recognition of pregnancy in pigs are still not completely defined. To better understand the interactions between the maternal uterus and conceptus during the implantation process, we searched genes differentially expressed in the endometria on D12 of pregnancy compared to those on D12 of the estrous cycle. A new reverse transcription-polymerase chain reaction (RT-PCR)-based method that involves annealing control primers (ACPs) was employed. Using 120 ACPs, we sequenced 12 differentially expressed genes (DEGs) and identified those genes using the Basic Local Alignment Search Tool (BLAST). Northern blot hybridization analysis confirmed the differential expression of those DEGs in the uterine endometrium. In situ hybridization analysis determined the cell-type specific expression of the DEGs in the uterine endometrium. Further analysis of the DEGs found in this study will provide insights into the cellular and molecular basis of maternal and fetal interactions during the period of maternal recognition of pregnancy in the pig. Mol. Reprod. Dev. 76: 75-84, 2009. (c) 2008 Wiley-Liss, Inc.

Perspectives of DNA microarray and next-generation DNA sequencing technologies

DNA microarray and next-generation DNA sequencing technologies are important tools for high-throughput genome research, in revealing both the structural and functional characteristics of genomes. In the past decade the DNA microarray technologies have been widely applied in the studies of functional genomics, systems biology and pharmacogenomics. The next-generation DNA sequencing method was first introduced by the 454 Company in 2003, immediately followed by the establishment of the Solexa and Solid techniques by other biotech companies. Though it has not been long since the first emergence of this technology, with the fast and impressive improvement, the application of this technology has extended to almost all fields of genomics research, as a rival challenging the existing DNA microarray technology. This paper briefly reviews the working principles of these two technologies as well as their application and perspectives in genome research.

MicroRNA expression and regulation in mouse uterus during embryo implantation

MicroRNAs (miRNAs) are 21-24-nucleotide non-coding RNAs found in diverse organisms. Although hundreds of miRNAs have been cloned or predicted, only very few miRNAs have been functionally characterized. Embryo implantation is a crucial step in mammalian reproduction. Many genes have been shown to be significantly changed in mouse uterus during embryo implantation. However, miRNA expression profiles in the mouse uterus between implantation sites and inter-implantation sites are still unknown. In this study, miRNA microarray was used to examine differential expression of miRNAs in the mouse uterus between implantation sites and inter-implantation sites. Compared with inter-implantation sites, there were 8 up-regulated miR-NAs at implantation sites, which were confirmed by both Northern blot and in situ hybridization. miR-21 was highly expressed in the subluminal stromal cells at implantation sites on day 5 of pregnancy. Because miR-21 was not detected in mouse uterus during pseudopregnancy and under delayed implantation, miR-21 expression at implantation sites was regulated by active blastocysts. Furthermore, we showed that Reck was the target gene of miR-21. Our data suggest that miR-21 may play a key role during embryo implantation.

Myeloid ecotropic viral integration site 1 (MEIS) 1 involvement in embryonic implantation

BACKGROUND

The HOXA10 homeobox gene controls embryonic uterine development and adult endometrial receptivity. The three-amino-acid loop extension (TALE) family homeobox genes like myeloid ecotropic viral integration site 1 (MEIS) provide enhanced target gene activation and specificity in HOX-regulated cellular processes by acting as HOX cofactors.

METHODS AND RESULTS

Analysis of an Affymetrix data set in the public domain showed high expression of MEIS1 in human endometrium. MEIS1 expression was confirmed during the human menstrual cycle by RT-PCR and in situ hybridization and was increased during the secretory compared with proliferative phase of the cycle (P = 0.0001), the time of implantation. To assess the importance of maternal Meis1 expression in a mouse model, the uteri of Day 2 pregnant mice were injected with Meis1 over-expression or small interfering RNA (siRNA) constructs. Blocking Meis1 expression by siRNA before implantation significantly reduced average implantation rates (P = 0.00001). Increased or decreased Meis1 expression significantly increased or decreased the expression of integrin beta3, a transcriptional target of HOXA10 and an important factor in early embryo-endometrium interactions (P = 0.006). Manipulating Meis1 expression before implantation also dramatically affected the number of pinopodes, uterine endometrial epithelial projections that develop at the time of endometrial receptivity.

CONCLUSIONS

The results suggest that in mouse, meis1 contributes to regulating endometrial development during the menstrual cycle and establishing the conditions necessary for implantation.

Differential expression and regulation of integral membrane protein 2b in rat male reproductive tissues

AIM

To examine the expression and regulation of integral membrane protein 2b (Itm2b) in rat male reproductive tissues during sexual maturation and under different treatments by in situ hybridization.

METHODS

Testis, epididymis, and vas deferens were collected on days 1-70 to examine Itm2b expression during sexual maturation. To further examine the regulation of Itm2b, adult rats underwent surgical castration and cryptorchidism. Ethylene dimethane sulfonate and busulfan treatments were carried out to test the regulation of Itm2b after destruction of Leydig cells and germ cells.

RESULTS

In testis, Itm2b expression was moderately detected in the adluminal area of seminiferous cords on days 1-10, and detected at a low level in the spermatogonia on days 20 and 30. The Itm2b level was markedly increased in Leydig cells from day 20 to day 70. In epididymis and vas deferens, Itm2b was detected from neonate to adults, and the signal gradually increased in accordance with sexual maturation. Itm2b expression was significantly downregulated in epididymis and vas deferens of castrated rats, and strongly stimulated when castrated rats were treated with testosterone. Cryptorchidism led to a significant decline of Itm2b expression in testis and caput epididymis. Itm2b expression in epididymis and vas deferens was significantly decreased after the Leydig cells were destroyed by ethylene dimethane sulfonate. Busulfan treatment produced no obvious change in Itm2b expression in epididymis or vas deferens.

CONCLUSION

Our data suggested that Itm2b expression is upregulated by testosterone and might play a role in rat male reproduction.

Effects of androgen on embryo implantation in the mouse delayed-implantation model

OBJECTIVE

To examine the effects of androgen on implantation and decidualization in the mouse delayed-implantation model.

DESIGN

Experimental animal study.

SETTING

University research laboratory.

ANIMAL(S)

Sexually mature female mice (Kunming White strain).

INTERVENTION(S)

Delayed and activated implantation; pseudopregnancy; embryo transfer (ET); E(2) assay; inhibitor.

MAIN OUTCOME MEASURE(S)

Effects of androgen on embryo implantation were determined by treating the mice under delayed implantation with different doses of testosterone propionate (TP); the effects of androgen on the expression of implantation-related genes were examined by in situ hybridization.

RESULT(S)

Delayed implantation could be initiated by TP. Dihydrotestosterone was also able to initiate implantation in the delayed-implantation model. The implantation window could be maintained for at least 48 hours by 5 mg TP per mouse. Prostaglandin endoperoxide synthase 2 (Ptgs2) and microsomal prostaglandin E synthase (mPtges) were aberrantly expressed in mouse uterus at implantation sites after delayed implantation was activated by high doses of TP.

CONCLUSION(S)

A low dose of TP led to a delay in embryo implantation, but a high dose caused aberrant expression of both Ptgs2 and mPtges at the implantation site. It is possible that high doses of TP may disturb peri-implantation development or may be involved in early pregnancy loss by disturbing the uterine prostaglandin system.