Blastocyst implantation failure relates to impaired translational machinery gene expression

Gamma-aminobutyric acid (GABA) can affect physiological processes in preimplantation embryos via GABAA and GABAB receptors

Purpose

Several widely used substances (e.g., some therapeutics or food supplements) can act on gamma-aminobutyric acid (GABA) receptors, and we investigated whether the activation of these receptors could affect the preimplantation embryo.

Methods

Transcripts of all GABA receptor subunits and selected proteins were examined using quantitative RT-PCR and immunohistochemistry. To analyze the effects of receptor activation, in vitro culture of mouse preimplantation embryos with natural and synthetic GABA receptor ligands was used.

Results

We detected nine GABA receptor transcripts in mouse blastocysts and 14 GABA receptor transcripts in ovulated oocytes. The results of this study indicate that ionotropic GABA_A receptors can be formed from α5, β3, and γ3 (or δ, π) subunits, GABA_A-ρ receptors can be formed from ρ2 subunits and metabotropic GABA receptors can be formed from GABA_B1b and GABA_B2 subunits in mouse blastocysts. Supplementing the culture medium with GABA at concentrations of 2-10 mM or with specific GABA_A and GABA_B receptor agonists (at concentrations of 10-100 μM) significantly increased the proportion of dead cells in blastocysts. The GABA-induced effects were prevented by pretreatment of embryos with GABA_A and GABA_B receptor antagonists.

Conclusion

The results of this study indicate that GABA and synthetic GABA receptor ligands can negatively affect preimplantation embryos via GABA_A and GABA_B receptors.

Machine Learning-Based Co-Expression Network Analysis Unravels Potential Fertility-Related Genes in Beef Cows

Simple Summary

Female reproductive failure is still a challenge for the beef industry. Several biological processes that underlie fertility-related traits, such as the establishment of pregnancy and embryo survival, are still unclear. Increased availability of transcriptomic data has allowed a deep investigation of the potential mechanisms involved in fertility. This study investigated candidate gene biomarkers predictive of pregnancy status and underlying fertility-related networks. To this end, we integrated gene expression profiles through supervised machine learning and gene network modeling. We identified nine biologically relevant endometrial gene biomarkers that could discriminate against pregnancy status in cows. These biomarkers were co-expressed with genes critical for uterine receptivity, including endometrial tissue remodeling, focal adhesion, and embryo development. This study outlined key pathways involved with pregnancy success and provided predictive candidate biomarkers for pregnancy outcome in cows.

Abstract

Reproductive failure is still a challenge for beef producers and a significant cause of economic loss. The increased availability of transcriptomic data has shed light on the mechanisms modulating pregnancy success. Furthermore, new analytical tools, such as machine learning (ML), provide opportunities for data mining and uncovering new biological events that explain or predict reproductive outcomes. Herein, we identified potential biomarkers underlying pregnancy status and fertility-related networks by integrating gene expression profiles through ML and gene network modeling. We used public transcriptomic data from uterine luminal epithelial cells of cows retrospectively classified as pregnant (P, n = 25) and non-pregnant (NP, n = 18). First, we used a feature selection function from BioDiscML and identified SERPINE3, PDCD1, FNDC1, MRTFA, ARHGEF7, MEF2B, NAA16, ENSBTAG00000019474, and ENSBTAG00000054585 as candidate biomarker predictors of pregnancy status. Then, based on co-expression networks, we identified seven genes significantly rewired (gaining or losing connections) between the P and NP networks. These biomarkers were co-expressed with genes critical for uterine receptivity, including endometrial tissue remodeling, focal adhesion, and embryo development. We provided insights into the regulatory networks of fertility-related processes and demonstrated the potential of combining different analytical tools to prioritize candidate genes.

Construction of Copy Number Variation Map Identifies Small Regions of Overlap and Candidate Genes for Atypical Female Genitalia Development

Copy number variations (CNVs) have been implicated in various conditions of differences of sexual development (DSD). Generally, larger genomic aberrations are more often considered disease-causing or clinically relevant, but over time, smaller CNVs have been associated with various forms of DSD. The main objective of this study is to identify small CNVs and the smallest regions of overlap (SROs) in patients with atypical female genitalia (AFG) and build a CNV map of AFG. We queried the DECIPHER database for recurrent duplications and/or deletions detected across the genome of AFG individuals. From these data, we constructed a chromosome map consisting of SROs and investigated such regions for genes that may be associated with the development of atypical female genitalia. Our study identified 180 unique SROs (7.95 kb to 45.34 Mb) distributed among 22 chromosomes. The most SROs were found in chromosomes X, 17, 11, and 22. None were found in chromosome 3. From these SROs, we identified 22 genes as potential candidates. Although none of these genes are currently associated with AFG, a literature review indicated that almost half were potentially involved in the development and/or function of the reproductive system, and only one gene was associated with a disorder that reported an individual patient with ambiguous genitalia. Our data regarding novel SROs requires further functional investigation to determine the role of the identified candidate genes in the development of atypical female genitalia, and this paper should serve as a catalyst for downstream molecular studies that may eventually affect the genetic counseling, diagnosis, and management of these DSD patients.

An integrated genome-wide multi-omics analysis of gene expression dynamics in the preimplantation mouse embryo

Early mouse embryos have an atypical translational machinery that consists of cytoplasmic lattices and is poorly competent for translation. Hence, the impact of transcriptomic changes on the operational level of proteins is predicted to be relatively modest. To investigate this, we performed liquid chromatography–tandem mass spectrometry and mRNA sequencing at seven developmental stages, from the mature oocyte to the blastocyst, and independently validated our data by immunofluorescence and qPCR. We detected and quantified 6,550 proteins and 20,535 protein-coding transcripts. In contrast to the transcriptome – where changes occur early, mostly at the 2-cell stage – our data indicate that the most substantial changes in the proteome take place towards later stages, between the morula and blastocyst. We also found little to no concordance between the changes in protein and transcript levels, especially for early stages, but observed that the concordance increased towards the morula and blastocyst, as did the number of free ribosomes. These results are consistent with the cytoplasmic lattice-to-free ribosome transition being a key mediator of developmental regulation. Finally, we show how these data can be used to appraise the strengths and limitations of mRNA-based studies of pre-implantation development and expand on the list of known developmental markers.

Magnetic Resonance Imaging Reveals Distinct Roles for Tissue Transglutaminase and Factor XIII in Maternal Angiogenesis During Early Mouse Pregnancy

OBJECTIVE

The early embryo implantation is characterized by enhanced uterine vascular permeability at the site of blastocyst attachment, followed by extracellular-matrix remodeling and angiogenesis. Two TG (transglutaminase) isoenzymes, TG2 (tissue TG) and FXIII (factor XIII), catalyze covalent cross-linking of the extracellular-matrix. However, their specific role during embryo implantation is not fully understood. Approach and Results: For mapping the distribution as well as the enzymatic activities of TG2 and FXIII towards blood-borne and resident extracellular-matrix substrates, we synthetized selective and specific low molecular weight substrate analogs for each of the isoenzymes. The implantation sites were challenged by genetically modifying the trophoblast cells in the outer layer of blastocysts, to either overexpress or deplete TG2 or FXIII, and the angiogenic response was studied by dynamic contrast-enhanced-magnetic resonance imaging. Dynamic contrast-enhanced-magnetic resonance imaging revealed a decrease in the permeability of decidual vasculature surrounding embryos in which FXIII were overexpressed in trophoblast cell. Reduction in decidual blood volume fraction was demonstrated when either FXIII or TG2 were overexpressed in embryonic trophoblast cell and was elevated when trophoblast cell was depleted of FXIII. These results were corroborated by histological analysis.

CONCLUSIONS

In this study, we report on the isoenzyme-specific roles of TG2 and FXIII during the early days of mouse pregnancy and further reveal their involvement in decidual angiogenesis. Our results reveal an important magnetic resonance imaging-detectable function of embryo-derived TG2 and FXIII on regulating maternal angiogenesis during embryo implantation in mice.Visual Overview: An online visual overview is available for this article.

Molecular cloning and characterization of porcine ribosomal protein L21

Ribosomal protein L21 (RPL21) is a structural component of the 60S subunit of the eukaryotic ribosome. This protein has an important role in protein synthesis and the occurrence of hereditary diseases. Pig is a common laboratory model, however, to the best of our knowledge, its RPL21 gene has not been cloned to date. In this study, we cloned and identified the full-length sequence of the pig RPL21 gene for the first time. In addition, we examined its expression pattern and function by using overexpression or knockdown approaches. As a result, we obtained a 604 bp segment that contains a 483 bp open reading frame encoding 160 amino acids. The pig RPL21 gene is located in the “+” strand of chromosome 11, which spans 2167 bp from 4199792 to 4201958. Pig RPL21 protein has nine strands and two helices in its secondary structure. Pig RPL21 is predominantly expressed in ovary and lung, at lower levels in kidney, small intestine, and skin, and at the lowest levels in heart and liver. Furthermore, RPL21 expression is closely connected with cell proliferation and cell cycle arrest. The results are intended to provide useful information for the further study of pig RPL21.

Perspectives: MRI of angiogenesis

Angiogenesis, the expansion of the vascular bed, is an important component in remodeling of tissues and organs. Such remodeling is essential for coping with substantial and sustained increase in the demands for supply of oxygen and nutrients and the timely removal of waste products. The vasculature, and its effectiveness in systemic delivery to all parts of the body, regulates the distribution of immune cells and the delivery of therapeutics as well as the dissemination of disease. Therefore, the vascular bed is possibly one of the key organs involved in homeostasis, in health and disease. The critical role of the vasculature in health, and the accessibility to non invasive probing by MRI, renders MRI as a modality of choice for monitoring the vasculature and its adaption to challenges.