Paraspeckles are nuclear bodies built on the long noncoding RNA Neat1. Using structural illumination microscopy, West et al. analyze the organization of paraspeckles at the submicron scale and show that paraspeckle proteins are arranged around bundles of Neat1, forming core-shell spheroidal structures dependent on the RNA binding protein Fus.

long noncoding RNA (lncRNA) is the molecular scaffold of paraspeckle nuclear bodies. Here, we report an improved RNA extraction method: extensive needle shearing or heating of cell lysate in RNA extraction reagent improved extraction by 20-fold (a property we term "semi-extractability"), whereas using a conventional method was trapped in the protein phase. The improved extraction method enabled us to estimate that approximately 50 molecules are present in a single paraspeckle. Another architectural lncRNA,, also exhibited similar semi-extractability. A comparison of RNA-seq data from needle-sheared and control samples revealed the existence of multiple semi-extractable RNAs, many of which were localized in subnuclear granule-like structures. The semi-extractability of correlated with its association with paraspeckle proteins and required the prion-like domain of the RNA-binding protein FUS This observation suggests that tenacious RNA-protein and protein-protein interactions, which drive nuclear body formation, are responsible for semi-extractability. Our findings provide a foundation for the discovery of the architectural RNAs that constitute nuclear bodies.

The POU-domain transcription factor Pou5f1 (Oct4) is restricted to pluripotent embryonic cells and the germ line of the mouse and is required for the maintenance of pluripotency of cells within the inner cell mass of the mouse blastocyst. Despite highly conserved genomic organization and regulatory regions between the mouse Oct4 gene and its bovine orthologue, bovine Oct4 protein is not restricted to the inner cell mass of blastocyst-stage embryos, suggesting that Oct4 may not be a key regulator of pluripotency in the bovine. We analyze the temporal and spatial distribution of Oct4 transcript in bovine oocytes and preimplantation-stage embryos, and in contrast to protein distribution, we find strong conservation between bovine and mouse. Oct4 transcript is present at low levels in the bovine oocyte. Similar to mouse, bovine Oct4 transcription begins one to two cell cycles after zygotic genome activation, followed by a sharp increase in transcription subsequent to compaction. Oct4 transcript is ubiquitously present in all cells of embryos at the morula stage; however, in Day 7 bovine blastocysts, Oct4 signal is not visible in the trophectoderm by in situ hybridization, indicating that transcriptional downregulation of Oct4 on differentiation is similar to that observed in mouse and other mammals. These results indicate that in contrast to protein distribution, regulation of Oct4 transcription is conserved between mammalian species.

Cell migration is an evolutionarily conserved mechanism that underlies the development and functioning of uni-and multicellular organisms and takes place in normal and pathogenic processes, including various events of embryogenesis, wound healing, immune response, cancer metastases, and angiogenesis. Despite the differences in the cell types that take part in different migratory events, it is believed that all of these migrations occur by similar molecular mechanisms, whose major components have been functionally conserved in evolution and whose perturbation leads to severe developmental defects. These mechanisms involve intricate cytoskeleton-based molecular machines that can sense the environment, respond to signals, and modulate the entire cell behavior. A big question that has concerned the researchers for decades relates to the coordination of cell migration in situ and its relation to the intracellular aspects of the cell migratory mechanisms. Traditionally, this question has been addressed by researchers that considered the intra-and extracellular mechanisms driving migration in separate sets of studies. As more data accumulate researchers are now able to integrate all of the available information and consider the intracellular mechanisms of cell migration in the context of the developing organisms that contain additional levels of complexity provided by extracellular regulation. This review provides a broad summary of the existing and emerging data in the cell and developmental biology fields regarding cell migration during development.

β‐ and γ‐cytoplasmic actin are nearly indistinguishable in their amino acid sequence, but are encoded by different genes that play non‐redundant biological roles. The key determinants that drive their functional distinction are unknown. Here, we tested the hypothesis that β- and γ-actin functions are defined by their nucleotide, rather than their amino acid sequence, using targeted editing of the mouse genome. Although previous studies have shown that disruption of β-actin gene critically impacts cell migration and mouse embryogenesis, we demonstrate here that generation of a mouse lacking β-actin protein by editing β-actin gene to encode γ-actin protein, and vice versa, does not affect cell migration and/or organism survival. Our data suggest that the essential in vivo function of β-actin is provided by the gene sequence independent of the encoded protein isoform. We propose that this regulation constitutes a global ‘silent code’ mechanism that controls the functional diversity of protein isoforms.