Oral Presentation ESA-SRB-NZSE-CaSR 2026 in conjunction with ENSA

Temporal single-cell transcriptomics of the marsupial uteroplacental environment reveals coordinated endometrial responses to the implanting embryo (143712)

Alicia G Petrany 1 , Neil A Youngson 1 , Ben M Lawrence 1 , Deidre M Mattiske 1 , Rachel O'Neil 2 , Andrew J Pask 1
  1. School Of Biosciences, University Of Melbourne, Parkville, VIC, Australia
  2. Molecular and Cell Biology, University Of Connecticut, Storrs, CT, United States

Background

In marsupials, maternal pregnancy recognition and embryo implantation operate under different mechanisms to eutherians due to their delayed implantation and transient, superficial placentation. Marsupial gestation is typically completed within one oestrus cycle, therefore it was historically unclear whether a maternal recognition response is elicited for successful implantation (1), (2). Recent bulk transcriptomic studies have detected endometrial perturbations resembling maternal pregnancy recognition in marsupials (1), (3), but the timing and cellular localisation of these responses remains unresolved. To further clarify these mechanisms, temporal single-cell transcriptomics from the uteroplacental interface of the fat-tailed dunnart (Sminthopsis crassicaudata) were used to identify gene modules associated with maternal pregnancy recognition at a cellular resolution.

Methods

Tissue punches through either uterus only or uterus and yolk sac placenta were collected from pregnant fat-tailed dunnarts at five developmental stages (n=1 per stage) spanning pre-implantation (st. 23), embryo apposition (st. 25), early implantation (st. 28), and late gestation (st. 31 + 33)(4). Samples were profiled by single-nucleus RNA-seq on the PIPseeker T20 platform. Temporal differential expression was modelled using a custom negative binomial generalised additive model to identify time-dependent gene modules.

Results

A total of 133037 high-quality nuclei across 19 maternal and fetal cell types were recovered across the five samples. Temporal differential expression analysis identified a transcriptional switch in the endometrial luminal epithelium activated at apposition. At this switch, genes associated with conventional diestrous endometrial proliferation are abruptly silenced, while genes governing inflammation, extracellular matrix remodelling, mechanotransduction, adhesion, and growth factor signalling are activated and their expression is sustained for the remainder of gestation.

Conclusion

These findings provide the highest resolution profile of the late-gestation marsupial uteroplacental environment to date. The gene modules identified in this study provide insights into endometrial receptivity in marsupials and can be applied to ongoing assistive reproductive technology developments.  

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