The maternal‐zygotic transition and zygotic activation of the Mnemiopsis leidyi genome occurs within the first three cleavage cycles. Issue 11 (10th November 2017)

• Record Type: Journal Article
• Authors: Davidson, Phillip L.; Koch, Bernard J.; Schnitzler, Christine E.; Henry, Jonathan Q.; Martindale, Mark Q.; Baxevanis, Andreas D.; Browne, William E.
• Is Part Of: Molecular reproduction and development. Volume 84:Issue 11(2017)
• Page Start: 1218
• Page End: 1229
• Publication Date: 2017-11-10
• Subjects: chromatin remodeling -- ctenophora -- gene expression -- maternal transcript degradation -- RNAseq; Reproduction -- Periodicals; Molecular biology -- Periodicals; Molecular genetics -- Periodicals; Embryology -- Periodicals; 571.8
• DOI: 10.1002/mrd.22926
• Languages: English
• ISSNs: 1040-452X

Abstract

Abstract : The maternal‐zygotic transition (MZT) describes the developmental reprogramming of gene expression marked by the degradation of maternally supplied gene products and activation of the zygotic genome. While the timing and duration of the MZT vary among taxa, little is known about early‐stage transcriptional dynamics in the non‐bilaterian phylum Ctenophora. We sought to better understand the extent of maternal mRNA loading and subsequent differential transcript abundance during the earliest stages of development by performing comprehensive RNA‐sequencing‐based analyses of mRNA abundance in single‐ and eight‐cell stage embryos in the lobate ctenophore Mnemiopsis leidyi . We found 1, 908 contigs with significant differential abundance between single‐ and eight‐cell stages, of which 1, 208 contigs were more abundant at the single‐cell stage and 700 contigs were more abundant at the eight‐cell stage. Of the differentially abundant contigs, 267 were exclusively present in the eight‐cell samples, providing strong evidence that both the MZT and zygotic genome activation (ZGA) have commenced by the eight‐cell stage. Many highly abundant transcripts encode genes involved in molecular mechanisms critical to the MZT, such as maternal transcript degradation, serine/threonine kinase activity, and chromatin remodeling. Our results suggest that chromosomal restructuring, which is critical to ZGA and the initiation of transcriptional regulation necessary for normal development, begins by the third cleavage within 1.5 hr post‐fertilization in M. leidyi .