RNA‐sequencing reveals genes linked with oocyte developmental potential in bovine cumulus cells

Abstract

Cumulus cells provide an interesting biological material to perform analyses to understand the molecular clues determining oocyte competence. The objective of this study was to analyze the transcriptional differences between cumulus cells from oocytes exhibiting different developmental potentials following individual in vitro embryo production by RNA‐seq. Cumulus cells were allocated into three groups according to the developmental potential of the oocyte following fertilization: (1) oocytes developing to blastocysts (Bl+), (2) oocytes cleaving but arresting development before the blastocyst stage (Bl−), and (3) oocytes not cleaving (Cl−). RNAseq was performed on 4 (Cl−) or 5 samples (Bl+ and Bl−) of cumulus cells pooled from 10 cumulus‐oocyte complexes per group. A total of 49, 50, and 18 differentially expressed genes (DEGs) were detected in the comparisons Bl+ versus Bl−, Bl+ versus Cl− and Bl‐ versus Cl−, respectively, showing a fold change greater than 1.5 at an adjusted p value <0.05. Focussing on DEGs in cumulus cells from Bl+ group, 10 DEGs were common to both comparisons (10/49 from Bl+ vs. Bl−, 10/50 from Bl+ vs. Cl−). These DEGs correspond to 6 upregulated genes (HBE1, ITGA1, PAPPA, AKAP12, ITGA5, and SLC1A4), and 4 downregulated genes (GSTA1, PSMB8, FMOD, and SFRP4) in Bl+ compared to the other groups, from which 7 were validated by quantitative PCR (HBE1, ITGA1, PAPPA, AKAP12, ITGA5, PSMB8 and SFRP4). These genes are involved in critical biological functions such as integrin‐mediated cell adhesion, oxygen availability, IGF and Wnt signaling or PKA pathway, highlighting specific biological processes altered in incompetent in vitro maturation oocytes.

mtDNA content in cumulus cells does not predict development to blastocyst or implantation

“…Molecular analyses on CCs aiming to predict pregnancy success have been majorly based on transcriptomics analyses, leading to the identification of diverse putative markers for oocyte quality and subsequent embryo development ( Iager et al , 2013 ; Wathlet et al , 2013 ; Borup et al , 2016 ; Parks et al , 2016 ; Artini et al , 2017 ; Martínez-Moro et al ., 2022 ). However, the different transcriptional markers identified vary greatly between studies, and others have failed to find a correlation between pregnancy success and gene expression in CCs, either for genes previously suggested as potential markers ( Burnik Papler et al , 2015 ) or in global transcriptomics analyses ( Burnik Papler et al , 2015 ; Green et al , 2018 ).…”

Metabolomics analysis of human cumulus cells obtained from cumulus–oocyte complexes with different developmental potential

“…CCs constitute a readily available material on which to perform analyses aimed at inferring the developmental ability of the oocyte they nourished ( Kordus and LaVoie, 2017 ). Mitochondrial DNA and transcriptomics analyses of CC have failed to provide reliable and clinically useful markers of the embryo potential to establish pregnancy ( Green et al , 2018 ; Kumar et al , 2021 ; Liu et al , 2021 ; Martinez-Moro et al , 2022a , b , 2023 ), but metabolomics has remained largely unexplored, probably owing to the technical difficulties of performing such analysis of the limited amount of cells present in a COC. Herein, using an improved MS/MS protocol, more sensitive than nuclear magnetic resonance approaches ( Emwas, 2015 ), we were able to quantify the relative abundance of 98 compounds.…”

“…HA is a linear glycosaminoglycan, consisting of alternating units of glucuronic acid and GlNAc that plays an essential role during CC expansion ( Chen et al , 1990 ; Salustri et al , 1992 ). The increased content in erythronate may therefore be indicative of a greater or earlier CC expansion, which has been positively associated with oocyte quality in animal models ( Qian et al , 2003 ; Martinez-Moro et al , 2022a , b ).…”

“…Metabolomics analyses in the medium where the embryo develops (spent medium) have yielded promising preclinical markers to infer prospective pregnancy success, but the markers identified by independent groups vary and final clinical performance has been poor (reviewed by Hernandez-Vargas et al , 2020 ). Focusing on the search for molecular markers that could predict pregnancy potential in CC, global transcriptomics analysis ( Green et al , 2018 ; Martinez-Moro et al , 2023 ) or the amount of mitochondrial DNA ( Kumar et al , 2021 ; Liu et al , 2021 ; Martinez-Moro et al , 2022a , b ) have been reported to provide a poor predictive value of pregnancy outcome. Compared to these analyses, metabolomics provides a downstream view of CC function, integrating possible differences between competent and non-competent COCs occurring at upstream levels, such as gene expression, post-transcriptional modification, or enzymatic activity.…”

Identification of novel genes in cattle (Bos taurus) and biological insights into their function in embryo development

“…Understanding the genetic mechanisms underlying oocyte and embryo development is crucial for unveiling the causes of imbalance that lead to developmental arrest. The assessment of transcriptome profiles using high throughput sequencing has been fundamental in shedding light on gene expression differences between oocyte and embryo stages in cattle (Wrenzycki 2018; Martínez-Moro et al 2022; Graf et al 2014). Data from high throughput sequencing have also been used to enhance functional annotation by discovering novel mRNA isoforms and other potential classes of RNA molecules in cattle oocytes and embryos at different developmental stages (Gilchrist et al 2016; Mondou et al 2012; Ranjitkar et al 2023; Wang et al 2020).…”