Maternal Transcripts of Hox Genes Are Found in Oocytes of Platynereis dumerilii (Annelida, Nereididae)

Abstract

Hox genes are some of the best studied developmental control genes. In the overwhelming majority of bilateral animals, these genes are sequentially activated along the main body axis during the establishment of the ground plane, i.e., at the moment of gastrulation. Their activation is necessary for the correct differentiation of cell lines, but at the same time it reduces the level of stemness. That is why the chromatin of Hox loci in the pre-gastrulating embryo is in a bivalent state. It carries both repressive and permissive epigenetic markers at H3 histone residues, leading to transcriptional repression. There is a paradox that maternal RNAs, and in some cases the proteins of the Hox genes, are present in oocytes and preimplantation embryos in mammals. Their functions should be different from the zygotic ones and have not been studied to date. Our object is the errant annelid Platynereis dumerilii. This model is convenient for studying new functions and mechanisms of regulation of Hox genes, because it is incomparably simpler than laboratory vertebrates. Using a standard RT-PCR on cDNA template which was obtained by reverse transcription using random primers, we found that maternal transcripts of almost all Hox genes are present in unfertilized oocytes of worm. We assessed the localization of these transcripts using WMISH.

Identification of Hox genes and their expression profiles during embryonic development of the emerging model organism, Macrobrachium olfersii

“…Our study provides new information suggesting that maternal expression of Ubx and abdA began to evolve (most likely convergently) early in arthropod evolution. Furthermore, maternal transcripts of nine Hox genes were found in oocytes of errant annelid Platynereis dumerilii (Maslakov et al, 2021) and of six Hox genes of different paralogical group has been found in oocytes and preimplantation embryos in mammals (bovine and mice) (Paul et al, 2011), but the roles of these Hox genes in early development are still unknown. Paul et al (2011) suggest that these Hox genes may be related to the control of oocyte maturation in mammals, while Maslakov et al (2021) suggest that these Hox transcripts are not translated and may be necessary for some crucial evolutionary conservative function, such as the epigenetic adjustment of the zygotic genome.…”

Echiuran Hox genes provide new insights into the correspondence between Hox subcluster organization and collinearity pattern

“…teleta [40] and the mollusc P. yessoensis [42]. However, another annelid, Platynereis dumerilii , displayed maternal expression pattern [56]. It remains unclear whether the maternal expression is lost in these three species or whether this maternal expression is an exception.…”

Comparative Hox genes expression within the dimorphic annelidStreblospio benedictireveals patterning variation during development

“…We used Hox genes of other spiralian species from Genbank: Platynereis dumerilii (Kukalova et al, 2007;Maslakov et al, 2021), Capitella teleta (Frobius et al, 2008), Owenia fusiformis (Martin-Zamora et al, 2023), Crassostrea virginica (Modak et al, 2021) and Lottia goshimai (Huan et al, 2020) to construct a gene phylogeny (Table S2, Supplementary Data1). Amino acid sequences were aligned using MUSCLE which is included in the SEAVIEW software (Edgar, 2004;Gouy et al, 2010).…”