Human pericentromeric tandemly repeated DNA is transcribed at the end of oocyte maturation and is associated with membraneless mitochondria-associated structures.

Most of the human genome is non-coding. However, some of the non-coding part is transcriptionally active. In humans, the tandemly repeated (TR) pericentromeric non-coding DNA-human satellites 2 and 3 (HS2, HS3)-are transcribed in somatic cells. These transcripts are also found in pre- and post-implantation embryos. The aim of this study was to analyze HS2/HS3 transcription and cellular localization of transcripts in human maturating oocytes. The maternal HS2/HS3 TR transcripts transcribed from both strands were accumulated in the ooplasm in GV-MI oocytes as shown by DNA-RNA FISH (fluorescence in-situ hybridization). The transcripts' content was higher in GV oocytes than in somatic cumulus cells according to real-time PCR. Using bioinformatics analysis, we demonstrated the presence of polyadenylated HS2 and HS3 RNAs in datasets of GV and MII oocyte transcriptomes. The transcripts shared a high degree of homology with HS2, HS3 transcripts previously observed in cancer cells. The HS2/HS3 transcripts were revealed by a combination of FISH and immunocytochemical staining within membraneless RNP structures that contained DEAD-box helicases DDX5 and DDX4. The RNP structures were closely associated with mitochondria, and are therefore similar to membraneless bodies described previously only in oogonia. These membraneless structures may be a site for spatial sequestration of RNAs and proteins in both maturating oocytes and cancer cells.

[Reason to split the genus Aurelia. Mesoglein from two populations differ].

The medusa, Aurelia aurita (Scyphozoa, Cnidaria), is considered to be a cosmopolitan species with a worldwide distribution in most seas from the poles to the tropics. Cnidarian is thought to possess two tissue layers: endoderm (gastroderm) and ectoderm, which are separated by huge mesoglea in medusa. The basic morphology of medusa is similar in different populations. Previously we have determined a new protein "mesoglein" as one of the main components of mesoglea. Deduced amino acid sequence of mesoglein contains Zona Pellucida (ZP) domain. In this paper, we have comparied of mesoglein and its gene in medusa from three habitats (White Sea (WsA), Black Sea (BsA), Japonic Sea (JsA)). The set of the mesoglea protein bands after SDS-PAGE is similar in all samples. Nevertheless, JsA mesogleins' M(r) is 53-55 kDa, while WsA and BsA mesogleins have M(r) of 47 kDa. Antibodies raised against WsA mesoglein recognize only mesogleins with M(r) of 47 kDa, but not 53-55 kDa, both on immunoblot and immunocytochemistry. Mesogleal cells and elastic fibrils are stained intensively in the mesoglea both from WsA and BsA but not from JsA. The possibility of gene divergency was checked by PCR with primers specific for WsA mesoglein gene. PCR products of expected length obtained on polyA-cDNA template from mesogleal cells of WsA and BsA medusa but not on cDNA of JsA medusa. Our results evidence that there are two different species in genus Aurelia: Aurelia aurita inhabits White and Black Seas while Aurelia sp. inhabits Japonic Sea. This is consistent with findings of other recept molecular biological studies.