P–154 The role of the X Chromosome in early human embryo metabolism

Study question What role does the X chromosome play in early embryo metabolism? Does X chromosome copy number contribute to sex differences in early embryonic metabolism? Summary answer Chromosome X contains several metabolism-related genes that are expressed prior to X-inactivation, suggesting that their dosage plays a role in sex-biased regulation of embryo metabolism. What is known already Published reports indicate that sex differences in preimplantation embryo metabolism exist across mammalian species, including humans. Two observations supporting this are that male embryos reach blastocyst stage earlier than their female counterparts, and that glucose uptake and processing is thought to be higher in female compared to male embryos. It has been hypothesized that these differences reflect the location of the metabolism gene G6PD, the rate limiting enzyme in the Pentose Phosphate Pathway, on Chromosome X. Study design, size, duration This study is a reanalysis of publicly available RNA-seq data, including 1176 single cells from 59 blastocysts (24 E5, 18 E6, 17 E7) published in one study (Petropoulos et al 2016). Participants/materials, setting, methods Cells were subjected to a digital karyotype inference algorithm and aneuploid samples were removed from the dataset. Sex differential gene expression analyses (DE) were then performed in euploid trophectoderm cells (TE; 233 XY from 16 embryos and 180 XX cells from 12 embryos). Cell numbers from ICM were too sparse to compare. Main results and the role of chance Analysis of XX and XY TE revealed 618 significantly differentially expressed genes (DEGs; 507 upregulated in XX cells, and 111 upregulated in XY cells). These genes are spread across autosomes and sex chromosomes. Interestingly, G6PD is not significantly more highly expressed in XX cells. Gene Ontology (GO) analysis of the XX-biased DEGs revealed a transcriptional sex bias in metabolism-related GO categories, including “mitochondrial ATP synthesis coupled electron transport”, and “respiratory chain complex I”. Gene-level assessment revealed that the drivers of these enrichments are spread across the genome, but 28/64 reside on Chromosome X (hypergeometric p-value = 5.984473e–27), including NDUFA1, NDUFB11, and COX7B (components of the electron transport chain), and SLC25A5 (an ATP/ADP transporter involved in maintaining mitochondrial membrane potential). This indicates a direct role for multiple X-linked genes in sex-biased regulation of embryo metabolism. Metabolic genes that are not sex-biased are distributed across the genome, with no significant enrichment on Chromosome X (76/266, hypergeometric p-value=0.607). Together, these data indicate that GO metabolic term X enrichment is a feature of sex-biased expression and not due to an accumulation of metabolism-related genes on the X. Limitations, reasons for caution This analysis draws on publicly available data, and thus we are unable to perform orthogonal validation of karyotype calls. Additionally, while the initial dataset is large, the quality-filtered dataset (euploid XX and XY TE) is small, and single cell data is infamously variable. Further data collection is required. Wider implications of the findings: Our analysis of sex-biased gene expression in early human embryos suggests a more important role for the X chromosome in modulating sex biases in early embryo metabolism than previously recognized. This study provides insight into the mechanisms underlying the development of metabolic sex differences throughout the lifespan. Trial registration number NA

Different Co-Culture Systems Have a Useful Impact on Preimplantation Embryo Development

The production of in vitro produced embryos of good morphological quality and viability is a prerequisite for successful assisted reproduction biotechnologies in animal breeding and human. The co-culturing system has been applied to improve preimplantation development that could subsequently resulted in successful pregnancy. There are different types of reproductive and non-reproductive cells that have been used during preimplantation development. The most well-known reproductive cells are those recovered from ovaries (cumulus and granulosa cells), oviduct and endometrium cells. While, in last decade stem cells such as mesenchymal stem cells and murine embryonic fibroblasts that originated from different tissues have been used to support early embryonic development. The positive effect co-culturing system was suggested to be due to direct mechanical cell-to-cell contact that occurred between the dividing embryos embryo and helper cells in addition to secretions of various bioactive biological components like growth factors and scavenging the deleterious byproducts that resulted from embryo metabolism. In current review, we will highlight the effects of different couture systems on embryo development and their suggested mechanisms to exert the beneficial impacts.

Variation in quality of newly hatched chicks from Japanese breeder quail fed guava extract

The aim of this study was to evaluate the effects of guava extract as a dietary supplement for Japanese quail hens on incubation parameters, intestinal development, and the quality of newly hatched chicks. Six hundred and forty-eight eggs were collected from Japanese quail hens fed diets with 0.0, 3.0, 6.0, and 9.0 g/kg of guava extract. The study consisted of four treatments, six replicates, and 27 eggs per replicate. The guava extract contained 2% ellagic acid. The eggs were incubated at 37.5 °C and 65% relative air humidity. The hatch window, hatchability, embryo development in unhatched eggs, quality of newly hatched quails, and intestinal histomorphometry of a duodenum segment were evaluated. Differences among the treatments in hatchability and the hatch window were not significant. The guava extract did not affect mortality rate, live pecking, dead pecking, and contaminated and inverted eggs. The number of infertile eggs was lower in the groups that received 3.0 and 9.0 g/kg of extract in their diets. Use of up to 3.0 g/kg of guava extract in the diet increased the weight of both eggs and newly hatched chicks. The quality score of newly hatched quail was similar across treatments. The inclusion of 3.0 g/kg of guava extract in the diet of Japanese quail breeder hens increased the hatchling weight of the chicks and improved the villus to crypt ratio of their duodenum. Keywords: embryology, embryo metabolism, hatchery, incubation, breeder nutrition

Mitochondria as a biomarker for IVF outcome

Mitochondria play an essential role in generating energy for embryo development and maintaining embryo metabolism through key cellular functions including ion homeostasis, amino acid metabolism, glycolysis, fatty acid metabolism, signal transduction and apoptotic regulation. Recent literature suggests that mitochondrial content and function may be related to implantation success and embryo viability. Some studies have linked increased levels of mitochondrial DNA to aneuploidy, advanced maternal age and euploid blastocyst with implantation failure, while others have failed to demonstrate similar findings. This review aims to provide an overview of the current literature surrounding the possibilities of using mitochondria as an additional biomarker for infertility treatment outcome and summarize the reasons as to why there are inconsistencies in these studies.