Search

Ion transporters, and the resulting voltage gradients and electric fields, have been implicated in embryonic development and regeneration. These biophysical signals are key physiological aspects of the microenvironment that epigenetically regulate stem and tumor cell behavior. Here, we identify a previously unrecognized function for KCNQ1, a potassium channel known to be involved in human Romano--Ward and Jervell--Lange--Nielsen syndromes when mutated. Misexpression of its modulatory wild-type [beta]-subunit XKCNE1 in the Xenopus embryo resulted in a striking alteration of the behavior of one type of embryonic stem cell: the pigment cell lineage of the neural crest. Depolarization of embryonic cells by misexpression of KCNE1 non-cell-autonomously induced melanocytes to overproliferate, spread out, and become highly invasive of blood vessels, liver, gut, and neural tube, leading to a deeply hyperpigmented phenotype. This effect is mediated by the up-regulation of Sox10 and Slug genes, thus linking alterations in ion channel function to the control of migration, shape, and mitosis rates during embryonic morphogenesis. Taken together, these data identify a role for the KCNQ1 channel in regulating key cell behaviors and reveal the molecular identity of a biophysical switch, by means of which neoplastic-like properties can be conferred upon a specific embryonic stem cell subpopulation. cancer | ion channel | melanocyte | neural crest | KCNQ

Caterpillar crawling is distinct from that of worms and molluscs; it consists of a series of steps in different body segments that can be compared to walking and running in animals with stiff skeletons. Using a three-dimensional kinematic analysis of horizontal crawling in Manduca sexta, the tobacco hornworm, we found that the phase of vertical displacement in the posterior segments substantially led changes in horizontal velocity and the segments appeared to pivot around the attached claspers. Both of the motions occur during vertebrate walking. In contrast, vertical displacement and horizontal velocity in the anterior proleg-bearing segments were in phase, as expected for running gaits coupled by elastic storage. We propose that this kinematic similarity to running results from the muscular compression and release of elastic tissues. As evidence in support of this proposal, the compression and extension of each segment were similar to harmonic oscillations in a spring, although changes in velocity were 70° out of phase with displacement, suggesting that the spring was damped. Measurements of segment length within, and across, intersegmental boundaries show that some of these movements were caused by folding of the body wall between segments. These findings demonstrate that caterpillar crawling is not simply the forward progression of a peristaltic wave but has kinetic components that vary between segments. Although these movements can be compared to legged locomotion in animals with stiff skeletons, the underlying mechanisms of caterpillar propulsion, and in particular the contribution of elastic tissues, remain to be discovered., Introduction The movements of animals with stiff articulated skeletons, such as arthropods and vertebrates, have been studied extensively; they tend to be fast and precise, using joints with a few [...]

In light-producing cells (photocytes) of the firefly light organ, mitochondria are clustered in the cell periphery, positioned between the tracheolar air supply and the oxygen-requiring bioluminescent reactants which are sequestered in more centrally-localized peroxisomes. This relative positioning suggests that mitochondria could control oxygen availability for the light reaction. We hypothesized that active cellular respiration would make the interior regions of the photocytes relatively hypoxic, and that the 'on' signal for production of bioluminescence might depend on inhibition of mitochondrial oxygen consumption, which would allow delivered oxygen to pass through the peripheral mitochondrial zone to reach peroxisomes deep in the cell interior. We published recently that exogenous NO induces bioluminescence in the intact firefly; that NO mediates octopamine-induced bioluminescence in the dissected lantern, and that nitric oxide synthase is abundant in cells of the tracheolar system of the light organ. Additional experiments showed that nitric oxide gas (NO) inhibits respiration in isolated lantern mitochondria. Inhibition is reversed by bright light, and this inhibition is relieved when the light is turned off. Altogether, the results support the idea that NO triggers light production by reversible inhibition of mitochondrial respiration in lantern cells, and probably in tracheolar cells as well. The data also suggest that the light of bioluminescence itself relieves NO inhibition thus contributing to rapid on/off switching. While other mechanisms may be in play, NO production that is directly related to neural input appears to have a key role in the oxygen gating that controls flash communication signals.

Recent electrophysiological, pharmacological and molecular studies suggest that muscarinic ACh receptors (mAChRs) in insects are related to, but distinct from, their mammalian counterparts. Insect mAChRs perform two primary roles that are distinguished by their locations. Presynaptic mAChRs, present on sensory terminals, inhibit transmitter release, thereby reducing the effectiveness of specific afferent inputs. In contrast, postsynaptic mAChRs depolarize and increase the excitability of motoneurons and interneurons, thereby acting as dynamic-gain controls. This postsynaptic modulation is achieved in different ways in specific neurons but generally results from the activation of persistent inward and outward currents. At the level of neural processing, these distinct roles enable insect mAChRs to regulate the transfer of sensory information, and modulate the contributions of central neurons to central pattern generators and reflexes. Because these phenomena can be studied in identified neurons, a combination of physiological and molecular studies of mAChRs in insects should help to elucidate some of their behavioral roles. Furthermore, such studies could lead to the identification of general mechanisms of functional plasticity in neuronal networks.

Bioluminescent flashing is essential for firefly reproduction, yet the specific molecular mechanisms that control light production are not well understood. We report that light production by fireflies can be stimulated by nitric oxide (NO) gas in the presence of oxygen and that NO scavengers block bioluminescence induced by the neurotransmitter octopamine. NO synthase is robustly expressed in the firefly lantern in cells interposed between nerve endings and the light-producing photocytes. These results suggest that NO synthesis is a key determinant of flash control in fireflies., Firefly courtship depends on a remarkable flash communication system involving precisely timed, rapid bursts of bioluminescence. The duration of a single flash is typically a few hundred milliseconds, and flash [...]