Total protein content and protein synthesis within pre-elongation stage bovine embryos

Abstract

Protein content was measured in zona‐free bovine oocytes and pre‐elongation stage embryos, following in vitro maturation, fertilisation, and then culture in Synthetic Oviduct Fluid medium supplemented with amino acids and 8 mg ml‐1 bovine serum albumin (BSA). Values (ng embryo‐1) of 122 ± 7.8, 137 ± 8.6, 111 ± 8.8, 115 ± 10.4, 139 ± 9.0 and 152 ± 10.1 were obtained for zona‐free mature oocytes, 2‐cell (day 2), 8‐cell (day 3), compact morula (day 6), blastocyst (day 7), and expanded blastocyst (day 8) stage embryos, respectively. The protein content of day 7 zona‐enclosed blastocysts was 337 ± 58.0 ng embryo‐1. These values suggest that prior to compaction and blastulation, the early cleavage stage bovine embryo has a higher rate of protein degradation than that of synthesis. Net growth is observed only after initiation of compaction. The protein content of day 7 blastocysts was measured in embryos following in vitro production and culture in the same media supplemented with either 0.5% w/v polyvinyl alcohol (PVA), 8 mg ml‐1 BSA, 8 mg ml‐1 BSA and further supplemented with 10% fetal calf serum (FCS) from the beginning of culture (FCS‐D1), 8 mg ml‐1 BSA and 10% FCS from the fourth day of culture (day 5 of development) or from in vivo‐derived day 7 blastocysts. Protein content was significantly (P< 0.05) lower in PVA‐cultured embryos than other treatments. To determine if this difference in PVA‐cultured embryos was due to a difference in the rate of protein synthesis, comparisons were made between day 7 embryos derived from BSA‐culture and either PVA‐culture, FCS‐D1 culture or in vivo‐derived embryos. Despite differences in diameter, no significant difference was observed in the incorporation of L‐[2,3,4,5,6‐3H]‐phenylalanine into the TCA‐precipitable fraction in any of the three comparisons made. However, incubation in the presence of FITC‐labelled BSA or β‐casein and examination under either fluorescence or confocal microscopy revealed that protein in the extra‐embryonic environment was actively taken up by the trophectoderm of day 7 blastocysts, most likely by endocytosis. These results suggest that exogenous protein is an important nutritive source, probably maintaining intracellular amino acid pools. Results obtained from the production of embryos in protein‐free medium should be viewed with the knowledge that such embryos differ metabolically from those embryos grown in the presence of protein, including in vivo‐derived embryos. Mol. Reprod. Dev. 50:139–145, 1998. © 1998 Wiley‐Liss, Inc.

Dynamic Changes in the Proteome of Early Bovine Embryos Developed In Vivo

“…Upregulated proteins (cluster 1) from the 4–6 cell to the blastocyst stages evidenced a significant enrichment in RNA metabolism and protein translation, presumably to provide enough materials to support further development. This is globally in accordance with previous data on protein synthesis in bovine embryo that indicated a higher rate of protein degradation than that of synthesis in early stages, the net protein growth per embryo starting only after morula compaction ( Thompson et al, 1998 ). In line with our data, upregulated proteins during in vivo development of mouse embryos tended to execute protein translation and RNA metabolism while downregulated proteins were mostly involved in protein transport, protein localization and cell cycle ( Gao et al, 2017 ).…”

The proteomic analysis of bovine embryos developed in vivo or in vitro reveals the contribution of the maternal environment to early embryo

“…The present results indicate that in vitro fertilization and culture conditions led to a higher abundance of proteins involved in RNA metabolism and translation at the time of EGA. Although spending more resources for protein synthesis, the blastocysts produced in vitro did not display a higher number of proteins compared to in vivo -developed blastocysts, in line with previous data reporting similar total protein contents in bovine blastocysts of both origins [ 38 ]. The higher abundance of translation-related proteins in in vitro -derived embryos may be due to an upregulation of genes coding for those proteins coupled or not with a lower turn-over of those proteins, as compared to in vivo .…”

“…The number of proteins identified were highest in both groups of blastocysts compared with earlier stages. This was expected as protein synthesis has been reported to overcome protein degradation after EGA, leading to an increased amount of proteins per embryo [ 38 ]. The PCA of all quantified proteins evidenced gaps between blastocysts and compact morulas in both groups of embryos and also between in vivo and in vitro blastocysts.…”

The quiet embryo hypothesis: Molecular characteristics favoring viability

“…This is not surprising as less viable embryos will have arrested prior to blastocyst formation, and a transition to significant transcription occurs at this cell stage in cattle (Kanka, 2003;Ko, 2004). The blastocyst data are consistent with those of Thompson et al (1998), who found there was no difference in the incorporation of 3 H-phenylalanine between in vivo and IVP day 7-bovine blastocysts.…”