Protein phosphorylation and cell diversification in the mouse early embryo.

This dissertation reports the results of studies into the control of compaction of the mouse preimplantation embryo. Compaction is a post-translationally controlled rearrangement of cell contacts and the cytoskeleton that occurs at the 8-cell stage of development. This re-arrangement seems to be necessary for the differentiation of the two cell types present in the blastocyst. Protein phosphorylation is a post-translational modification believed to be important in the modulation of cell shape and cytoskeletal assembly. It is therefore feasible to propose a role for protein phosphorylation in compaction. Two types of approach have been used to investigate the possible role of protein phosphorylation in compaction. Firstly, embryos have been treated with two drugs, 6-dimethylaminopurine (DMAP) and a phorbol ester (phorbol myristate acetate, PMA), each of which seems to affect both protein phosphorylation and compaction. DMAP is an adenine analogue and putative inhibitor of protein phosphorylation that was found to perturb the cell cycle of mouse embryos. In addition, DMAP caused rapid cellular flattening of 4-cell and 8-cell embryos. However, this flattening was not accompanied by cell polarisation and did not seem to be mediated by the cell adhesion molecule uvomorulin. It is therefore unlikely to be related directly to the flattening that occurs at compaction. Phorbol esters, such as PMA, are potent stimulators of the membrane-associated, Ca2+- and phospholipid-dependent protein kinase, protein kinase C (PKC). Incubation in medium containing PMA had some effects on the cytoskeleton of oocytes and early embryos but caused severe, widespread disassembly of the cytoskeleton and reversal of flattening in 8-cell embryos. These effects of PMA, seen specifically at the 8-cell stage, may be related to the spatially restricted disassembly of the cytoskeleton that occurs naturally during compaction at the 8-cell stage. This interpretation provides indirect evidence for a possible role for PKC activity, and hence protein phosphorylation, in the process of compaction. The relationship between protein phosphorylation and the events occurring at the 8-cell stage has been examined more directly by labelling 4-cell and 8-cell embryos with [32P]orthophosphate and examining the phosphoproteins obtained by one and two-dimensional gel electrophoresis. By synchronising groups of embryos precisely to successive cleavage divisions prior to labelling, changes in phosphoprotein profile associated with passage through the 4-cell and 8-cell stages have been described. While many of the 32P-labelled phosphoproteins detectable after electrophoresis in one or two dimensions are similar at each stage examined, there are some changes associated specifically with passage through the 8-cell stage which may be related to the cell flattening and polarisation occurring at this time. In addition, the profile of 8-cell embryos differed according to the duration of pulse-labelling with [32Pjorthophosphate or the inclusion of "chase" periods. Finally, several treatments that affect features of compaction, including exposure to DMAP and PMA, have been used to assess the link between the observed changes in phosphoprotein profile and the events of compaction. Embryos were also incubated in protein synthesis inhibitors, which cause premature cell flattening in 4-cell embryos and in Ca2+-free medium, which prevents intercellular flattening and delays polarisation of 8-cell blastomeres. In each case, the relative labelling intensity of some of the phosphoproteins characteristic of untreated 8-cell embryos was altered. The behaviour of these phosphoproteins suggests that they may be important in the mechanism by which cells flatten and polarise or in the maintenance of flattened, polarised, cells; they now provide a focus for future study

Minor, substantial or wholesale amendments: it’s time to rethink changes to published articles and avoid unnecessary stigma

The present system of labelling changes made to published articles is confusing, inconsistently applied, and out of step with digital publishing. It carries negative connotations for authors, editors, and publishers. Is there a way to efficiently and neutrally flag a change to a published article in a way that says what happened that is separated from why it happened? Virginia Barbour, Theodora Bloom, Jennifer Lin and Elizabeth Moylan propose a new system for dealing with post-publication changes that focuses on moving away from the current, confusing, stigmatising terms, differentiating the scale of changes, and differentiating versions of articles. While some hold the view that post-publication corrections must be tied to punishment of “offenders”, the role of journals is to be neutral, to maintain the integrity of the literature and not to punish researchers

Please Welcome Our First Academic Editor-in-Chief

The PLoS Biology Editors explain the background to Jonathan Eisen's appointment as the journal's first Academic Editor-in-Chief

PRAD1 (Cyclin D1): A Parathyroid Neoplasia Gene on 11q13

Hyperparathyroidism is a central component of multiple endocrine neoplasia type 1 (MEN 1), and both sporadic and familial forms of parathyroid disease may share certain pathogenetic features. We recently identified a gene that is clonally rearranged with the PTH locus in a subset of sporadic parathyroid adenomas. This candidate oncogene, PRAD1 (previously D11S287), appears to contribute to parathyroid tumorigenesis in a fashion analogous to activation of C-MYC or BCL-2 by rearrangement with tissue-specific enhancers of the immunoglobulin genes in B-lymphoid neoplasia. The PRAD1 gene maps to 11q13 and has been linked to the BCL-1 breakpoint locus, although not to the most tightly linked MEN 1 markers, by pulsed field gel electrophoresis. PRAD1 may, in fact, be the long-sought BCL-1 lymphoma oncogene. PRAD1 encodes a novel type of cyclin protein and thus may normally function in controlling the cell cycle, perhaps through direct interaction with cdc2 or a related kinase. PRAD1\u27s possible primary, or more likely secondary, involvement in the pathogenesis of MEN 1-related tumors is unknown and under investigation

Mutational escape from the polyclonal antibody response to SARS-CoV-2 infection is largely shaped by a single class of antibodies

Monoclonal antibodies targeting a variety of epitopes have been isolated from individuals previously infected with SARS-CoV-2, but the relative contributions of these different antibody classes to the polyclonal response remains unclear. Here we use a yeast-display system to map all mutations to the viral spike receptor-binding domain (RBD) that escape binding by representatives of three potently neutralizing classes of anti-RBD antibodies with high-resolution structures. We compare the antibody-escape maps to similar maps for convalescent polyclonal plasma, including plasma from individuals from whom some of the antibodies were isolated. The plasma-escape maps most closely resemble those of a single class of antibodies that target an epitope on the RBD that includes site E484. Therefore, although the human immune system can produce antibodies that target diverse RBD epitopes, in practice the polyclonal response to infection is dominated by a single class of antibodies targeting an epitope that is already undergoing rapid evolution