In vivo-derived horse blastocysts show transcriptional upregulation of developmentally important genes compared with in vitro-produced horse blastocysts.

This study investigated the genetic differences between horse embryos produced naturally (in vivo) and those produced in a lab (in vitro) due to observed differences in their development. Key genes active in natural embryos were identified and the findings could help improve laboratory methods of horse embryo production.

Study Purpose and Methods

The goal of this research was to investigate the differences between equine blastocysts (early-stage embryos) produced in vitro and those derived in vivo. There was a noted discrepancy between the two in terms of developmental rate and morphology. A specialized method called Suppression Subtractive Hybridisation (SSH) was applied to make a cDNA library that is concentrated with transcripts predominantly displayed in natural equine blastocysts as opposed to those created in the lab.

• The SSH is a technique designed to find differences in gene expression. This approach works by subtracting common sequences between two samples to leave behind only the unique ones.
• A cDNA library is the DNA equivalent of the RNA molecules present in a cell. By analyzing these, researchers can understand what genes are switched on in that cell type.

Main Findings

From the pool of unique genes, six known to be related to embryonic development were chosen for further examination through a method called reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR).

• RT-qPCR is a laboratory technique often used in research to measure the amount of a specific RNA. This technology can indicate if a gene is more active in one sample compared to another.

Upon validation, five out of the six genes (FABP3, HSP90AA1, ODC, MOBKL3, and BEX2) were found to have significantly higher activity in natural equine blastocysts. One gene, MCM7, however, did not show any significant difference in expression levels between the two types of embryos.

Conclusion and Implications

The study findings highlight the genetic differences occurring in horse embryos depending on the method of their production – natural vs laboratory. The identified genes that are more active in natural embryos may play a key role in their development. This understanding could pave the way toward refining in vitro horse embryo production systems. Using the expression of these genes as markers, scientists could potentially evaluate and improve their in vitro methods to match more closely the natural in vivo conditions.