The common neurotrophin receptor (p75NTR) regulates various functions in the developing and adult nervous system. Cell survival, cell death, axonal and growth cone retraction, and regulation of the cell cycle can be regulated by p75NTR‐mediated signals following activation by either mature or pro‐neurotrophins and in combination with various co‐receptors, including Trk receptors and sortilin. Here, we review the known functions of p75NTR by cell type, receptor‐ligand combination, and whether regulated intra‐membrane proteolysis of p75NTR is required for signalling. We highlight that (...) the generation of the intracellular domain fragment of p75NTR is associated with many of the receptor functions, regardless of its ligand and co‐receptor interactions. (shrink)

Evolutionary developmental biology (evo-devo) offers both an account of developmental processes and also new integrative frameworks for analyzing interactions between development and evolution. Biologists and philosophers are keen on evo-devo in part because it appears to offer a comfort zone between, on the one hand, what some take to be the relative inability of mainstream evolutionary biology to integrate a developmental perspective; and, on the other hand, what some take to be more intractable syntheses of development and evolution. In this (...) article, I outline core concerns of evo-devo, distinguish theoretical and practical variants, and counter Sterelny's recent argument that evo-devo's attention to development, while important, offers no significant challenge to evolutionary theory as we know it. (shrink)

A recent report by Blumenthal et al.1 provides convincing evidence that at least 15% of Caenorhabditis elegans genes are co‐transcribed within over a thousand operons. Polycistronic transcription of gene clusters is very rare in eukaryotes. The widespread occurrence of operons in C. elegans thus raises some interesting questions about the origin and function of these multigenic transcriptional units. BioEssays 24:983–987, 2002. © 2002 Wiley‐Periodicals, Inc.

The article discusses evolutionary aspects of mimicry from a semiotic viewpoint. The concept of semiotic scaffolding is used for this approach, and its relations with the concepts of exaptation and semiotic co-option are explained. Different dimensions of scaffolding are brought out as ontogenetic, evolutionary, physiological and cognitive. These dimensions allow for interpreting mimicry as a system that scaffolds itself. With the help of a number of mimicry cases, e.g. butterfly eyespots, brood parasitism, and plant mimesis, the evolutionary dynamics of mimicry (...) in the open bio-semiosphere is investigated. The main argument is that biological mimicry largely develops through sign relations and communicative relations between organisms. It is proposed that mimicry systems should be described as two-layered structures composed of the ecological composition of the species involved and the semiotic structure of their communication. (shrink)

Proper wiring of the nervous system requires tight control of the number of nerve terminals that innervate a target tissue. Recent work by Deppmann et al.,1 now suggests that this is achieved by feedback‐mediated neuronal competition for target‐derived survival cues. The authors' model is inspired by the theory for pattern formation based on self‐activation and lateral inhibition, proposed by Meinhardt and Gierer more than 30 years ago.2 BioEssays 30:929–933, 2008. © 2008 Wiley Periodicals, Inc.