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Biomedical subjects

J Pines

Publications and source records attributed to J Pines.

At least 55 records · Page 3Linked to original sources
PubMed1997

Following cell fate in the living mouse embryo.

It has been difficult to follow many of the dramatic changes in cell fate and cell migration during mouse development. This is because there has been no enduring marker that would allow cells to be recognised in the living embryo. We believe that we have overcome this problem by developing a novel form of green fluorescent protein, named MmGFP, that proves to be easily visible and non toxic to mouse cells and does not perturb embryogenesis. We show that synthetic mRNA encoding MmGFP can be injected into blastomeres to follow the fate of their progeny during preimplantation development. We have made a stable embryonic stem cell line that expresses MmGFP and introduced these fluorescent cells into mouse embryos. For the first time, we have been able to follow the fate of embryonic stem cells in living embryos and to observe directly the contribution of these cells to distinct lineages of the postimplantation embryo. This approach should lead to a more complete description of the dynamics of cell fate in the mouse.

Animals↗
PubMed1996

Cell cycle: reaching for a role for the Cks proteins.

The Cks proteins are essential components of the cyclin-dependent protein kinases that regulate mitosis in all eukaryotes, but their precise function remains obscure. The crystal structures of several Cks proteins offer insights into their roles during the cell cycle.

Adaptor Proteins, Signal Transducing↗
PubMed1996

An indelible lineage marker for Xenopus using a mutated green fluorescent protein.

We describe the use of a DNA construct (named GFP.RN3) encoding green fluorescent protein as a lineage marker for Xenopus embryos. This offers the following advantages over other lineage markers so far used in Xenopus. When injected as synthetic mRNA, its protein emits intense fluorescence in living embryos. It is non-toxic, and the fluorescence does not bleach when viewed under 480 nm light. It is surprisingly stable, being strongly visible up to the feeding tadpole stage (5 days), and in some tissues for several weeks after mRNA injection. We also describe a construct that encodes a blue fluorescent protein. We exemplify the use of this GFP.RN3 construct for marking the lineage of individual blastomeres at the 32- to 64-cell stage, and as a marker for single transplanted blastula cells. Both procedures have revealed that the descendants of one embryonic cell can contribute single muscle cells to nearly all segmental myotomes rather than predominantly to any one myotome. An independent aim of our work has been to follow the fate of cells in which an early regulatory gene has been temporarily overexpressed. For this purpose, we co-injected GFP.RN3 mRNA and mRNA for the early Xenopus gene Eomes, and found that a high concentration of Eomes results in ectopic muscle gene activation in only the injected cells. This marker may therefore be of general value in providing long term identification of those cells in which an early gene with ephemeral expression has been overexpressed.

Animals↗
PubMed1995

Human cyclins B1 and B2 are localized to strikingly different structures: B1 to microtubules, B2 primarily to the Golgi apparatus.

We have raised and characterized antibodies specific for human cyclin B2 and have compared the properties of cyclins B1 and B2 in human tissue culture cells. Cyclin B1 and B2 levels are very low in G1 phase, increase in S and G2 phases and peak at mitosis. Both B-type cyclins associate with p34cdc2; their associated kinase activities appear when cells enter mitosis and disappear as the cyclins are destroyed in anaphase. However, human cyclins B1 and B2 differ dramatically in their subcellular localization. Cyclin B1 co-localizes with microtubules, whereas cyclin B2 is primarily associated with the Golgi region. In contrast to cyclin B1, cyclin B2 does not relocate to the nucleus at prophase, but becomes uniformly distributed throughout the cell. The different subcellular locations of human cyclins B1 and B2 implicate them in the reorganization of different aspects of the cellular architecture at mitosis and indicate that different mitotic cyclin-cyclin-dependent kinase complexes may have distinct roles in the cell cycle.

Amino Acid Sequence↗
PubMed1995

Cyclins, CDKs and cancer.

The connections between cancer and the basic machinery of the cell cycle have taken a surprisingly long time to become apparent. However, the past 2 years has seen a dramatic increase in the number of cell cycles regulators that have been implicated as either protooncogenes or as tumour suppressor genes. In this review I will attempt to show how perturbations in the known cell cycle regulators may play a part in the process of oncogenesis.

Animals↗
PubMed1994

The differential localization of human cyclins A and B is due to a cytoplasmic retention signal in cyclin B.

We have shown previously that human cyclins A and B1 are localized differentially in the cell during interphase; cyclin A is nuclear and cyclin B1 is a cytoplasmic protein. To understand the basis of this difference we created deletion mutants and various chimeras between the two types of cyclin and expressed them in tissue culture cells by transient transfection. We find that the N-terminus of cyclin B1 contains a 42 amino acid region that is sufficient to retain the normally nuclear cyclin A in the cytoplasm. Conversely, deleting the cytoplasmic retention signal region from cyclin B1 causes the protein to become nuclear. Although the cytoplasmic retention signal region is outside the cyclin box, its sequence is well conserved in human cyclin B2, and is both necessary and sufficient to keep cyclin B2 in the cytoplasm. Thus we propose that the subcellular distribution of the B-type cyclins is determined primarily by a small region of the N-terminus which targets the cyclin--CDK complexes to particular structures in the cytoplasm.

Amino Acid Sequence↗
PubMed1994

Protein kinases and cell cycle control.

Protein kinases play a central role in the regulation of the eukaryotic cell cycle. Recent research has concentrated on a particular family of protein kinases, the cyclin-dependent kinases (CDKs), and their involvement in regulating particular cell cycle transitions, such as the initiation of DNA synthesis (S phase) or of cell division (mitosis). One can think of these enzymes as the basic machinery of the cell cycle; their activity is then modulated by proteins which transduce signals from the external environment, and by proteins that monitor the progress of events such as DNA replication or the formation of the mitotic spindle. This review will be structured so as to introduce the cyclin-CDK motif, outline which cyclin-CDKs are involved at different cell cycle stages, their direct regulation by other protein kinases and phosphatases, and lastly the importance of other protein kinases in the cell cycle.

Animals↗