Comparison of oocyte mRNA localization patterns in sterlet Acipenser ruthenus and African clawed frog Xenopus laevis

Abstract

In oocytes, RNA localization has critical implications, as assembly of proteins in particular subcellular domains is crucial to embryo development. The distribution of mRNA molecules can identify and characterize localized transcripts. The goal of this study was to clarify the origin of primordial germ cells in the oocyte body plan and to reveal the generation of cell lineages by localized RNAs. The distribution of 12 selected mRNAs in sterlet Acipenser ruthenus oocytes was investigated by qPCR tomography and compared with known patterns of mRNA localization in Xenopus laevis. We investigated the distribution of two gene clusters in the ooplasm along the animal-vegetal axis of the sturgeon oocyte, both of which showed clearly defined intracellular gradient pattern remarkably similar to their distribution in the frog oocyte. We elucidated the localization of sturgeon egg germplasm markers belonging to the vegetal group of mRNAs. The mRNAs coding otx1, wnt11, and veg1 found to be localized in the sturgeon animal hemisphere are, in contrast, distributed in the vegetal hemisphere in amphibian. Actinopterygii and Sarcopterygii, two major lineages of osteichthyan vertebrates, split about 476 Ma (Blair & Hedges, ), albeit basal lineages share conserved biological features. Acipenseriformes is one the most basal living lineages of Actinopterygii, having evolved about 200 Ma (Bemis, Birstein, & Waldman, ), contemporaneous with modern amphibians (Roelants et al., ).

Asymmetry in previtellogenic and early vitellogenic oocytes, ultrastructure of follicular cells and egg envelope in the pigmented sterlet, Acipenser ruthenus L. 1758 (Chondrostei, Acipenseriformes)

“…show an increasing gradient toward the vegetal region. Contrary to the situation described in X. laevis, in the animal region of A. ruthenus the otx1, wnt11, and veg1 mRNAs are localized (Pocherniaieva et al, 2018).…”

“…In the ovulated oocytes of A. ruthenus , the distribution of mRNAs that encode determinants of the germplasm ( dnd, vasa , and ddx25 mRNAs) show an increasing gradient toward the vegetal region. Contrary to the situation described in X. laevis , in the animal region of A. ruthenus the otx1 , wnt11 , and veg1 mRNAs are localized (Pocherniaieva et al, 2018).…”

Germline cysts and asymmetry in early previtellogenic ovarian follicles in cultured albino females of sterlet Acipenser ruthenus L. 1758 (Chondrostei, Acipenseriformes)

“…Recently it has been shown that in A. ruthenus ovulated oocytes, the distribution of mRNAs dnd , vasa , and ddx25 coding for germplasm determinants is uneven and shows increasing gradient towards the vegetal pole (Pocherniaieva et al 2018). In this pole, the primordial germ cells (PGCs) develop (Ostaszewska and Dabrowski 2009; Saito et al 2014).…”

Evolutionary conservation of maternal RNA localization in fishes and amphibians revealed by TOMO-Seq

“…Contrastingly the endoderm of the A. ruthenus develops in the meridian area while the meso-and ectoderm layers shift towards the animal part compared to X. laevis. The vegetal part of A. ruthenus contains the primordial germ cell factors and also the yolk, which is used as an extra-embryonic tissue with nutritional function (Dettlaff et al 1993;Saito et al 2014;Pocherniaieva et al 2018). The D. rerio fate map closely resembles that of the A. ruthenus (Fig.…”