P-121 Identification of differentially expressed genes common to the developmental potential, maternal age, and morphology in human blastocysts
Authors: Kai Y , Mei H , Kawano H , Nakajima N , Takai A , Kumon M , Inoue A , Yamashita N 
Published: June 2023

Abstract

Study question
Is it possible to apply RNA-sequencing to assisted reproductive technology (ART) to predict blastocyst quality?

Summary answer
We identified 14 commonly identified differentially expressed genes by grouping blastocysts according to three distinct parameters such as developmental potential, maternal age, and Gardner score

What is known already
In ART, while the selection of a suitable embryo for transfer is critical for a successful pregnancy, neither preimplantation genetic testing nor morphological and chronological evaluation of the embryo can fully guarantee a successful pregnancy. Recently, transcriptional events in early human embryonic development have been analyzed using RNA-sequencing (RNA-seq) and researchers are attempting to apply this information to ART. We have reported that 96 differentially expressed genes (DEGs) were identified using RNA-seq of each inner cell mass (ICM) and trophectoderm (TE) in blastocysts classified according to the developmental potential which correlates with pregnancy rate at the ESHRE 37th annual meeting.

Study design, size, duration
After retrospectively analyzing 1,890 cases undergoing freeze-thaw blastocyst transfer from March 2018 to December 2020 to examine the correlation between blastocyst developmental potential and pregnancy rate, a total 13 blastocysts cryopreserved between February 2011 and September 2018, then scheduled for disposal and with consented, were subjected to RNA-seq to identify genes associated with pregnancy expectation. RNA-seq data were then examined whether common DEGs could be found when classified by maternal age and Gardner score, respectively.

Participants/materials, setting, methods
Blastocysts were donated by infertile couples undergoing c-IVF or ICSI cycles at the Yamashita Shonan Yume Clinic with informed consent under ethical approval. TE cells and ICM cells were collected from blastocysts classified by developmental potential and subjected to RNA-seq to identify DEGs. In addition, RNA-seq data were regrouped by maternal age and Gardner score to find common DEGs. DEGs (q-value &lt; 0.01) were identified using the R package “DESeq2” (version 1.32.0).

Main results and the role of chance
When the RNA-seq data obtained from blastocysts classified according to pregnancy expectation were re-grouped by maternal age and re-analyzed, we identified 7 and 17 genes that were down- and up-regulated in the elder group, respectively, in ICM. In TE, 2 and 12 genes were down- and up-regulated in the elder group, respectively. On the other hand, when re-grouped by Gardner score (&lt;BB versus &lt;BB), we identified 26 and 29 genes that were down- and up-regulated in the poor group, respectively, in ICM. In TE, 64 and 20 genes were down- and up-regulated in the poor group, respectively. A comparison of these genes and DEGs identified by the pregnancy expectation found 14 common genes. By comparison with the elder group, we identified one gene (UCHL1) that was commonly up-regulated in TE. By comparison with the poor Gardner score group, one gene (CMTM7) was commonly down-regulated and three genes (LINC00458, DYNLRB1, and UBL4A) were commonly up-regulated in ICM, and 5 genes (LRIG3, SLC28A3, CXADR, LOC727896, and ATP1B1) were commonly down-regulated and 5 genes (UCHL1, BZW2, NABP1, HEXIM1, and PLEKHA6) were commonly up-regulated in TE.

Limitations, reasons for caution
Although we established an expected pregnancy rate concerning the degree of blastocyst development from retrospective clinical outcomes and used it as a surrogate marker for assigning biopsied blastocysts to different analysis groups, it remains unknown whether the gene expression profiles accurately reflect the pregnancy outcomes.

Wider implications of the findings
UCHL1 expression was commonly increased with lower blastocyst developmental potential, higher maternal age, and lower Gardner score. Since UCHL1 has been reported to be essential for blastocyst development in mice, our results suggest that UCHL1 may also be a marker of blastocyst quality in humans.

Trial registration number
not applicable