An in vitro assay for neural crest cell migration through the somites

Neural crest cells in the trunk of the avian embryo come into contact with the somites and neural tube during the course of their migration. However, the relationship between the somites and the early migratory routes followed by these cells is not yet completely understood. Here, we use a tissue culture assay to examine if avian neural crest cells migrate through the somites. Cultures of quail somites were prepared from four adjacent regions along the neural axis in the trunk. Each region had four pairs of consecutive somites with region I being most anterior and region IV containing the last four segments. Within each region, the somites were separated from other tissues by enzymatic digestion and plated onto collagen-coated dishes. Immuno-cytochemical techniques were used to confirm that no neural crest cells, recognized by the HNK-1 antibody, were present on the surface of the somites at the time of explantation. After several days in culture, the explanted somites were screened to identify pigment cells. Because neural crest cells give rise to all of the melanocytes in the trunk, the presence of pigment cells indicated that neural crest precursors were contained within the initial explant. After 5–11 days in vitro, the percentage of somite cultures containing pigment cells in regions I through IV, respectively, was 36%, 51%, 31% and 1%. These results suggest that neural crest cells migrate through the somitic mesenchyme and first enter the somites between 5 to 9 segments rostral to the most recently formed somite

Absence of Neural Crest Cells from the Region Surrounding Implanted Notochords in Situ

Avian neural crest cells migrating along the trunk ventral pathway are distributed throughout the rostral half of the sclerotome with the exception of a neural crest cell-free space of approximately 85 μm width surrounding the notochord. To determine if this neural crest cell-free space results from the notochord inhibiting neural crest cell migration, a length of quail notochord was implanted lateral to the neural tube along the neural crest ventral migratory pathway of 2-day chicken embryos. The subsequent distribution of neural crest cells was analyzed in embryos fixed 2 days after grafting. When the donor notochord was isolated using collagenase, neural crest cells avoided the ectopic notochord and were absent from the area immediately surrounding the implant (mean distance of 43 μm). The neural crest cell-free space was significantly less when notochords were isolated using trypsin or chondroitinase digestion and was completely eliminated when notochords were fixed with paraformaldehyde or methanol prior to implantation. The implanted notochords did not appear to affect the overall number of neural crest cells, and therefore were unlikely to exert this effect by altering their viability. These results suggest that the notochord produces a substance that can inhibit neural crest cell migration and that this substance is trypsin and chondroitinase labile

The general fault in our fault lines

Pervading global narratives suggest that political polarization is increasing, yet the accuracy of such group meta-perceptions has been drawn into question. A recent US study suggests that these beliefs are inaccurate and drive polarized beliefs about out-groups. However, it also found that informing people of inaccuracies reduces those negative beliefs. In this work, we explore whether these results generalize to other countries. To achieve this, we replicate two of the original experiments with 10,207 participants across 26 countries. We focus on local group divisions, which we refer to as fault lines. We find broad generalizability for both inaccurate meta-perceptions and reduced negative motive attribution through a simple disclosure intervention. We conclude that inaccurate and negative group meta-perceptions are exhibited in myriad contexts and that informing individuals of their misperceptions can yield positive benefits for intergroup relations. Such generalizability highlights a robust phenomenon with implications for political discourse worldwide

The general fault in our fault lines

A pervading global narrative suggests that political polarisation is increasing in the US and around the world. Beliefs in increased polarisation impact individual and group behaviours regardless of whether they are accurate or not. One driver of polarisation are beliefs about how members of the out-group perceive us, known as group meta-perceptions. A 2020 study by Lees and Cikara in US samples suggests that not only are out-group meta-perceptions highly inaccurate, but informing people of this inaccuracy reduces negative beliefs about the out-group. Given the importance of these findings for understanding and mitigating polarisation, it is essential to test to what extent they generalise to other countries. We assess that generalisability by replicating two of the original experiments in 10,207 participants from 26 countries in the first experiment and 10 in the second. We do this by studying local group divisions, which we refer to as fault lines. In line with our hypotheses, results show that the pattern found in the US broadly generalises, with greater heterogeneity explained by specific policies rather than between-country differences. The replication of a simple disclosure intervention in the second experiment yielded a modest reduction in negative motive attributions to the out-group, similar to the original study. These findings indicate first that inaccurate and negative group meta-perceptions are exhibited in a large number of countries, not only the US, and that informing individuals of their misperceptions can yield positive benefits for intergroup relations. The generalisability of these findings highlights a robust phenomenon with major implications for political discourse worldwide

The general fault in our fault lines

Ruggeri et al. tested perceptions of opposing political party members in 10,207 participants from 26 countries. Results show that beliefs about others are overly negative but could be more realistic with transparency about actual group beliefs. Pervading global narratives suggest that political polarization is increasing, yet the accuracy of such group meta-perceptions has been drawn into question. A recent US study suggests that these beliefs are inaccurate and drive polarized beliefs about out-groups. However, it also found that informing people of inaccuracies reduces those negative beliefs. In this work, we explore whether these results generalize to other countries. To achieve this, we replicate two of the original experiments with 10,207 participants across 26 countries. We focus on local group divisions, which we refer to as fault lines. We find broad generalizability for both inaccurate meta-perceptions and reduced negative motive attribution through a simple disclosure intervention. We conclude that inaccurate and negative group meta-perceptions are exhibited in myriad contexts and that informing individuals of their misperceptions can yield positive benefits for intergroup relations. Such generalizability highlights a robust phenomenon with implications for political discourse worldwide