Reviews & Analysis

Cell migration research is taking some intriguing new turns. Emerging studies are revealing marked differences in the way that cells migrate in two versus three dimensions, plasticity in their migration mechanisms and diversity in the contribution of different Rho family GTPases that drive various modes of migration.

The physical link between integrin adhesion receptors and the actin cytoskeleton mediates bidirectional transmission of force and biochemical signals across the plasma membrane. This link is essential for the development and function of multicellular animals. Recent work reveals that the integrin-associated actin-binding protein talin provides the initial connections between integrins and the cytoskeleton, establishing a pivotal role for this connection in bi-directional integrin signalling.

Neurons exhibit distinct compositions in the axonal and dendrite plasma membrane, but it remains ambiguous whether or not a diffusion barrier is needed to keep the different components separated. Now, Nakada et al. utilize state of the art microscopy to follow the dynamics of single lipids or proteins inserted in different areas along the axonal and dendritic surface of neurons at different developmental stages. The results obtained shed new light on the mechanism underlying polarized segregation of membrane components in neurons.

E2F transcription factors coordinate the timely expression of genes during early cell-cycle progression. In addition, the E2F-1 subunit can induce apoptosis in response to DNA damage. New results reveal an unexpected function for E2F-1 in suppressing apoptosis, which may be important in explaining the contribution of E2F-1 to tumorigenesis.

Proteins that control the cell cycle would seem to have little to do with cell migration. However, a recent report indicates that Cdc2, a key cyclin-dependent kinase, can also enhance cell migration. Levels of Cdc2 are upregulated in cells that express high levels of the α_vβ₃ integrin, a protein that has long been implicated in enhanced migration and invasion of tumour cells.

Chordate claudins are core components of tight junctions. By contrast, VAB-9, a nematode four-pass transmembrane protein related to claudins, localizes to adherens junctions and contributes to cell adhesion and actin–plasma membrane association.

Mitochondrial membrane fusion contributes to the shape and distribution of mitochondria in the eukaryotic cytoplasm. Recent work shows that a key component of the fusion reaction, Mgm1p, is activated by a novel mitochondrial protease related to the Drosophila melanogaster signalling protein Rhomboid.

Changing the number of glutamate receptors (GluRs) in neuronal post-synaptic membranes is a critical way to alter the strength of synaptic transmission and is important for information storage in the brain. The molecular mechanisms regulating the delivery of GluRs to the synapse are emerging and a new link between NMDA-type GluRs, PSD-95-family scaffold proteins and the exocyst complex, reveals a novel pathway for synaptic trafficking.

Telomere shortening resulting from genome replication can trigger cellular senescence. In this issue Clark et al. show that rates of telomere attrition and the consequent replicative potential of cells are conserved during replicative cloning. This implies that these traits are genetically determined and raises interesting questions about their relationship to organismal phenotypes such as cancer, organ failure and ageing.

Signalling by growth factors, such as fibroblast growth factor (FGF), is critical for many of the morphogenetic events that shape the early embryo — including limb development. Recent findings regarding the regulation of FGF during limb development bridge the divide between results gained from in vitro biochemistry and the realities of in vivo development.

Covalent modification of DNA by methylation is crucial for maintaining the stability and structure of chromatin. Reports of the effects that altered methylation has for cancer development stress the importance of balanced genomic methylation.