Gene expression changes in blastocyst hatching affect embryo implantation success in mice

Area of Science:

• Reproductive biology and developmental genetics.
• Mammalian embryonic development and implantation.
• Molecular mechanisms of blastocyst hatching.

Background:

• Blastocyst hatching from the zona pellucida (ZP) is critical for mammalian implantation.
• Previous work indicated blastocyst hatching site preferences correlate with pregnancy outcomes.
• Understanding these site-specific differences is key to improving fertility and developmental success.

Purpose of the Study:

• To characterize transcriptomic differences in mouse blastocysts based on hatching site and hatching status.
• To identify key genes and regulatory pathways involved in successful blastocyst hatching and implantation.
• To develop a predictive model for implantation success based on gene expression.

Main Methods:

• Transcriptome analysis (RNA sequencing) of mouse blastocysts at various hatching stages (expanding, hatching, hatched, non-hatching).
• Principal component analysis (PCA) and hierarchical cluster analysis to group blastocysts by gene expression profiles.
• Differential gene expression analysis to identify genes associated with hatching site and fertility outcomes.
• Immunofluorescence staining to detect specific proteins on blastocyst surfaces.
• Development of a LASSO regression model for predicting implantation success.

Main Results:

• Gene expression profiles clustered blastocysts into good fertility (A, B sites) and poor fertility (C, N sites) groups.
• 178 differentially expressed genes (DEGs), primarily immune-related, correlated with birth rate, regulated by TCF24 and DLX3.
• Key immune genes like Ptgs1, Lyz2, Il-1α, Cfb were upregulated, while Cd36 was downregulated during hatching.
• 307 DEGs were identified between expanding and hatched states, regulated by ATOH8 and SPIC.
• A predictive model using Lyz2, Cd36, Cfb, and Cyp17a1 showed potential for predicting implantation success.

Conclusions:

• Blastocyst hatching site influences developmental fate and implantation success.
• Embryonic immune properties play a significant role in hatching outcomes.
• Transcriptional changes during preimplantation development are crucial for successful implantation and maternal-fetal interactions.
• Specific DEGs and transcription factors regulate immune pathways essential for hatching and implantation.