Opinion in 2011

Satellite cells are a heterogeneous population of stem and progenitor cells with crucial roles in muscle repair and regeneration. Although paired-box 7 (PAX7) is necessary to maintain the undifferentiated stem cell state, a requirement for PAX7 in adult satellite cells was recently challenged and remains controversial.

Although the multivesicular body (MVB) is classically defined as an intermediate that delivers material for lysosomal degradation, its role in the sequestration of glycogen synthase kinase 3 during WNT signalling has revealed a positive influence of this organelle in signalling control. This Opinion article proposes that this function of MVBs as a signalling organelle is physiologically relevant during development and may be common to diverse signalling pathways.

Caspase 8 initiates apoptosis but also has non-apoptotic roles during embryonic development and for immune cell proliferation. Recent findings indicate that the non-apoptotic functions of caspase 8 are defined by the suppression of receptor-interacting protein kinase 3 (RIPK3), a kinase that triggers programmed necrosis.

The phosphodiesterase autotaxin (ATX) produces the lipid mediator lysophosphatidic acid (LPA) to regulate diverse processes, including cell migration and proliferation. Studies of the structure of ATX may shed new light on how ATX recognizes its substrates and associates with the cell surface to promote specificity in LPA signalling.

Differentiated cells can become pluripotent through reprogramming by nuclear transfer, cell fusion and induced pluripotent stem cell technology. The characteristics of reprogramming by nuclear transfer and cell fusion suggest that they occur in a deterministic, rather than a stochastic, manner.

The production of mature and export-competent messenger ribonucleoproteins (mRNPs) is a multistep process that is regulated in a spatial and temporal manner. Recent studies suggest that post-translational modifications play a part in coordinating the co-transcriptional assembly, remodelling and export of mRNP complexes through nuclear pores.

Alan Turing showed that spatial patterns can be generated when two morphogens diffuse and react. Although he realized the importance of mechanics, it has only recently become clear that mechanical processes (forces and flows generated by motors) can also contribute to patterning when coupled to chemical reactions.

The improper distribution of chromosomes during mitosis can contribute to malignant transformation. Higher eukaryotes have developed strategies for eliminating mitosis-incompetent cells, one of which is mitotic catastrophe. From a functional perspective, mitotic catastrophe can be defined as an oncosuppressive mechanism that precedes (and is distinct from) apoptosis, necrosis or senescence.

The p53 family of transcription factors have diverse roles during development and in cancer. However, there is increasing evidence that their ancestral function may have been to regulate unique aspects of maternal fertility.

Computational morphodynamics has provided great insights into the highly dynamic process of plant development. This is because it combines live imaging to observe development as it happens, image processing to extract data, and computational modelling to test hypotheses against quantitative information.

Unlike somatic cells, stem cells persist throughout life, which may increase their risk of accumulating DNA damage. recent studies indicate that stem cells use different mechanisms (such as the error-prone non-homologous end joining pathway) from somatic cells to maintain genomic integrity, which could have deleterious consequences for their long-term function.

Mesenchymal stem cells (MSCs) are multipotent progenitors derived from tissue stroma that differentiate into adipocytes, chondrocytes and osteoblasts when expandedin vitro. Although the properties of the in vitro-expanded progeny are well defined, the in vivobiology of MSCs is only just beginning to be elucidated.

Single-cell measurements and lineage-tracing experiments are revealing that cell-to-cell variability is often the result of deterministic processes, despite the existence of intrinsic noise in molecular networks. As this determinism usually represents uncharacterized molecular regulatory mechanisms, cell-to-cell variability should be studied as a discipline of molecular cell biology.