A phosphoregulated RhoGEF feedback loop tunes cortical flow driven amoeboid migration in vivo

Cortical flow driven amoeboid migration utilizes friction from retrograde cortical actin flow to generate motion. Many cell types, including cancer cells, can assemble a cortical flow engine to migrate under confinement and low adhesion in vitro, but it remains unclear whether this engine is endogenously utilized in vivo. Moreover, in the context of a changing environment, it is not known how upstream regulation can set in motion and sustain a mutual feedback between flow and polarity. Here, we establish that Drosophila primordial germ cells (PGCs) utilize cortical flow driven amoeboid migration and that flows are oriented by external cues during developmental homing in vivo. The molecular basis of flow modulation is a phosphoregulated feedback loop involving RhoGEF2, a microtubule plus-end tracking RhoA specific RhoGEF, enriched at the rear of PGCs. RhoGEF2 depletion slows and disorganizes cortical flow, reducing migration speed, while RhoGEF2 activation accelerates cortical flow, thereby augmenting myosin II polarity and migration speed. Both perturbations impair PGC pathfinding, suggesting cortical flows must be tuned for accurate guidance. We surprisingly find that RhoGEF2 polarity and activation are independent of upstream canonical Gα12/13 signaling. Instead, its PDZ domain and conserved RhoA binding residues in its PH domain are required to establish a positive feedback loop that augments its basal activity. Upstream regulation of this feedback loop occurs via AMPK dependent multisite phosphorylation near a conserved EB1 binding SxIP motif, which releases RhoGEF2 from EB1 dependent inhibition. Thus, we reveal cortical flows as versatile, tunable engines for directed amoeboid migration in vivo.

First description of migratory behavior of humpback whales from an Antarctic feeding ground to a tropical calving ground

Background Despite exhibiting one of the longest migrations in the world, half of the humpback whale migratory cycle has remained unexamined. Until now, no study has provided a continuous description of humpback whale migratory behavior from a feeding ground to a calving ground. We present new information on satellite-derived offshore migratory movements of 16 Breeding Stock G humpback whales from Antarctic feeding grounds to South American calving grounds. Satellite locations were used to demonstrate migratory corridors, while the impact of departure date on migration speed was assessed using a linear regression. A Bayesian hierarchical state–space animal movement model (HSSM) was utilized to investigate the presence of Area Restricted Search (ARS) en route. Results 35,642 Argos locations from 16 tagged whales from 2012 to 2017 were collected. The 16 whales were tracked for a mean of 38.5 days of migration (range 10–151 days). The length of individually derived tracks ranged from 645 to 6381 km. Humpbacks were widely dispersed geographically during the initial and middle stages of their migration, but convened in two convergence regions near the southernmost point of Chile as well as Peru’s Illescas Peninsula. The state–space model showed almost no instances of ARS along the migratory route. The linear regression assessing whether departure date affected migration speed showed suggestive but inconclusive support for a positive trend between the two variables. Results suggestive of stratification by sex and reproductive status were found for departure date and route choice. Conclusions This multi-year study sets a baseline against which the effects of climate change on humpback whales can be studied across years and conditions and provides an excellent starting point for the investigation into humpback whale migration.

A mechanism for migrating bacterial populations to non-genetically adapt to new environments

Populations of chemotactic bacteria can rapidly expand into new territory by consuming and chasing an attractant cue in the environment, increasing the population's overall growth in nutrient-rich environments. Although the migrating fronts driving this expansion contain cells of multiple swimming phenotypes, the consequences of non-genetic diversity for population expansion are unknown. Here, through theory and simulations, we predict that expanding populations non-genetically adapt their phenotype composition to migrate effectively through multiple physical environments. Swimming phenotypes in the migrating front are spatially sorted by chemotactic performance, but the mapping from phenotype to performance depends on the environment. Therefore, phenotypes that perform poorly localize to the back of the group, causing them to selectively fall behind. Over cell divisions, the group composition dynamically enriches for high-performers, enhancing migration speed and overall growth. Furthermore, non-genetic inheritance controls a trade-off between large composition shifts and slow responsiveness to new environments, enabling a diverse population to out-perform a non-diverse one in varying environments. These results demonstrate that phenotypic diversity and collective behavior can synergize to produce emergent functionalities. Non-genetic inheritance may generically enable bacterial populations to transiently adapt to new situations without mutations, emphasizing that genotype-to-phenotype mappings are dynamic and context-dependent.

Unexpected localization of AQP3 and AQP4 induced by migration of primary cultured IMCD cells

Aquaporin-2–4 (AQP) are expressed in the principal cells of the renal collecting duct (CD). Beside their role in water transport across membranes, several studies showed that AQPs can influence the migration of cells. It is unknown whether this also applies for renal CD cells. Another fact is that the expression of these AQPs is highly modulated by the external osmolality. Here we analyzed the localization of AQP2–4 in primary cultured renal inner medullary CD (IMCD) cells and how osmolality influences the migration behavior of these cells. The primary IMCD cells showed a collective migration behavior and there were no differences in the migration speed between cells cultivated either at 300 or 600 mosmol/kg. Acute increase from 300 to 600 mosmol/kg led to a marked reduction and vice versa an acute decrease from 600 to 300 mosmol/kg to a marked increase in migration speed. Interestingly, none of the analyzed AQPs were localized at the leading edge. While AQP3 disappeared within the first 2–3 rows of cells, AQP4 was enriched at the rear end. Further analysis indicated that migration induced lysosomal degradation of AQP3. This could be prevented by activation of the protein kinase A, inducing localization of AQP3 and AQP2 at the leading edge and increasing the migration speed.

First Description of Migratory Behavior of Humpback Whales From an Antarctic Feeding Ground to a Tropical Breeding Ground

Background: Despite exhibiting one of the longest migrations in the world, half of the humpback whale migratory cycle has remained unexamined; until this point, no study has provided a continuous description of humpback whale migratory behavior from a feeding ground to a breeding ground. We present new information on the satellite derived offshore migratory movements of 16 humpback whales from Antarctic feeding grounds to South American breeding grounds. Satellite locations were used to demonstrate migratory corridors, while the impact of departure date on migration speed was assessed using a linear regression, and a Bayesian hierarchical state-space animal movement model was utilized to investigate the presence of feeding behavior en route. Results: 35,642 Argos locations from 16 tagged whales from 2012-2017 were collected. The 16 whales were tracked for an average of 38.5 days of migration (range 10-151 days). The length of individually derived tracks ranged from 645–6,381 km. Humpbacks were widely dispersed geographically during the initial and middle stages of their migration but convened in two bottleneck regions near the southernmost point of Chile as well as Peru’s Illescas Peninsula. The state space model found almost no instances of ARS, a proxy for feeding behavior, along the migratory route. The linear regression assessing whether departure date affected migration speed found suggestive but inconclusive support for a positive trend between the two variables. No clear stratification by sex or reproductive status, either in migration speed, departure date, or route choice, was found.Conclusions: Southern hemisphere humpback whale populations are recovering quickly from intense commercial whaling and, around the Antarctic Peninsula, are doing so in the face of a rapidly changing environment. The current lack of scientific knowledge on marine mammal migration is a major barrier to cetacean conservation. This multi-year study sets a baseline against which the effects of climate change on humpback whales can be studied across years and conditions and provides an excellent starting point for the investigation into humpback whale migration.

Determine the impact on fisheries by predicting the migration of fish near Scotland

As global warming getting more severe in recent decades, the seawater temperature has also increased dramatically, which leads Atlantic fish heading north, so are two important economic fish spcies in Scotland, Scottish herring and mackerel. This paper discusses the impact of temperature change on the two species, and offer improvement methods for the small Scotland-based fishing companies. According the history temperature data in Scotland and the surrounding waters, we use a time series algorithm to predict the temperature range over next 50 years. Then establish a cost equation with parameters based on the relative distance and temperature. We obtain minimum cost from the predicted temperature and the relative distance from shoals. The result shows that in the next 50 years, a portion of the Scottish herring will move first northeast and then north, and the mackerel will move near the coast of Norway. The speed range of fish is obtained from previous model. Furthermore, maximum range of fishing time is obtained under different fish migration speed and fishing vessel speed. The best, worst and most likely case for fishing companies are defined and found. Which are they can fish before 2033 at lowest fish migration speed, they can not fish at the highest speed after 2051, and can not sell fresh fish anymore at 2040 respectively.

Revealing migratory path, important stopovers and non-breeding areas of a boreal songbird in steep decline

The Olive-sided Flycatcher (Contopus cooperi) is a steeply declining aerial insectivore with one of the longest migrations of any North American passerine. We deployed light-level geolocators and archival GPS tags on breeders in boreal Alaska to determine migratory routes, important stopovers and non-breeding locations. Data from 16 individuals revealed a median 23,555 km annual journey (range: 19,387, 27,292 km) over 95 days (range: 83, 139 days) with wintering occurring in three regions of South America (NW Colombia/Ecuador, central Peru and W Brazil/S Peru). We developed a new method to identify “Important Stopovers” by quantifying intensity of use (a function of bird numbers and stop durations) along migratory routes. We identified 13 Important Stopovers that accounted for ~66% of the annual migratory period, suggestive of refueling activities. Some sites coincided with key areas previously identified for other Neotropical-Nearctic migrants. Percent land “protected” at Important Stopovers, as defined by IUCN, ranged from 3.8% to 49.3% (mean [95% CI]: 17.3% [9.6, 25.0]). Total migration speed did not differ by season (median: 255 km day-1, range: 182, 295km day-1), despite greater spring travel distances. Birds with longer non-breeding periods, however, migrated north faster. Climate-driven mismatches in migratory timing may be less of a concern for western than for eastern flycatcher populations, given recent con-generic analyses (C. sordidulus, C. virens). However, accelerated high-latitude changes, may nonetheless impact boreal breeders.

A phenotypic switch in the dispersal strategy of breast cancer cells selected for metastatic colonization

An important question in cancer evolution concerns which traits make a cell likely to successfully metastasize. Cell motility phenotypes, mediated by cell shape change, are strong candidates. We experimentally evolved breast cancer cells in vitro for metastatic capability, using selective regimes designed to simulate stages of metastasis, then quantified their motility behaviours using computer vision. All evolved lines showed changes to motility phenotypes, and we have identified a previously unknown density-dependent motility phenotype only seen in cells selected for colonization of decellularized lung tissue. These cells increase their rate of morphological change with an increase in migration speed when local cell density is high. However, when the local cell density is low, we find the opposite relationship: the rate of morphological change decreases with an increase in migration speed. Neither the ancestral population, nor cells selected for their ability to escape or invade extracellular matrix-like environments, displays this dynamic behavioural switch. Our results suggest that cells capable of distant-site colonization may be characterized by dynamic morphological phenotypes and the capacity to respond to the local social environment.