How to translate text using browser tools
13 September 2021 Allele-specific expression analysis reveals conserved and unique features of preimplantation development in equine ICSI embryos
D.E. Goszczynski, P.S. Tinetti, Y.H. Choi, P.J. Ross, K. Hinrichs
Author Affiliations +

Embryonic genome activation and dosage compensation are major genetic events in early development. Combined analysis of single embryo RNA-seq data and parental genome sequencing was used to evaluate parental contributions to early development and investigate X-chromosome dynamics. In addition, we evaluated dimorphism in gene expression between male and female embryos. Evaluation of parent-specific gene expression revealed a minor increase in paternal expression at the 4-cell stage that increased at the 8-cell stage. We also detected eight genes with allelic expression bias that may have an important role in early development, notably NANOGNB. The main actor in X-chromosome inactivation, XIST, was significantly upregulated at the 8-cell, morula, and blastocyst stages in female embryos, with high expression at the latter. Sexual dimorphism in gene expression was identified at all stages, with strong representation of the X-chromosome in females from the 16-cell to the blastocyst stage. Female embryos showed biparental X-chromosome expression at all stages after the 4-cell stage, demonstrating the absence of imprinted X-inactivation at the embryo level. The analysis of gene dosage showed incomplete dosage compensation (0.5 < X:A < 1) in MII oocytes and embryos up to the 4-cell stage, an increase of the X:A ratio at the 16-cell and morula stages after genome activation, and a decrease of the X:A ratio at the blastocyst stage, which might be associated with the beginning of X-chromosome inactivation. This study represents the first critical analysis of parent- and sex-specific gene expression in early equine embryos produced in vitro.

Summary sentence

Early development of equine ICSI-derived embryos involves activation of the paternal genome at the 4-cell stage; genes with allele-specific expression bias; sexual dimorphism in gene expression with strong representation of the X-chromosome; expression of XIST in both sexes since genome activation with increasingly higher expression in late female embryos; absence of parent-specific X-inactivation at the embryo level; and scarce dosage compensation until the blastocyst stage.

© The Author(s) 2021. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail:
D.E. Goszczynski, P.S. Tinetti, Y.H. Choi, P.J. Ross, and K. Hinrichs "Allele-specific expression analysis reveals conserved and unique features of preimplantation development in equine ICSI embryos," Biology of Reproduction 105(6), 1416-1426, (13 September 2021).
Received: 30 March 2021; Accepted: 10 September 2021; Published: 13 September 2021
allelic bias
Dosage compensation
gene expression
genome activation
sexual dimorphism
Get copyright permission
Back to Top