“Neighborhood watch” model: embryonic epiblast cells assess positional information in relation to their neighbors

In many developing and regenerating systems, tissue pattern is established through gradients of informative morphogens, but we know little about how cells interpret these. Using experimental manipulation of early chick embryos including misexpression of an inducer (VG1 or ACTIVIN) and an inhibitor (BMP4), we test two alternative models for their ability to explain how the site of primitive streak formation is positioned relative to the rest of the embryo. In one model, cells read morphogen concentrations cell-autonomously. In the other, cells sense changes in morphogen status relative to their neighborhood. We find that only the latter model can account for the experimental results, including some counter-intuitive predictions. This mechanism (which we name “neighborhood watch” model) illuminates the classic “French Flag Problem” and how positional information is interpreted by a sheet of cells.TeaserHow do cells know their position in the embryo, to determine where gastrulation will start?

δ-Cells: The Neighborhood Watch in the Islet Community

Somatostatin-secreting δ-cells have aroused great attention due to their powerful roles in coordination of islet insulin and glucagon secretion and maintenance of glucose homeostasis. δ-cells exhibit neuron-like morphology with projections which enable pan-islet somatostatin paracrine regulation despite their scarcity in the islets. The expression of a range of hormone and neurotransmitter receptors allows δ-cells to integrate paracrine, endocrine, neural and nutritional inputs, and provide rapid and precise feedback modulations on glucagon and insulin secretion from α- and β-cells, respectively. Interestingly, the paracrine tone of δ-cells can be effectively modified in response to factors released by neighboring cells in this interactive communication, such as insulin, urocortin 3 and γ-aminobutyric acid from β-cells, glucagon, glutamate and glucagon-like peptide-1 from α-cells. In the setting of diabetes, defects in δ-cell function lead to suboptimal insulin and glucagon outputs and lift the glycemic set-point. The interaction of δ-cells and non-δ-cells also becomes defective in diabetes, with reduces paracrine feedback to β-cells to exacerbate hyperglycemia or enhanced inhibition of α-cells, disabling counter-regulation, to cause hypoglycemia. Thus, it is possible to restore/optimize islet function in diabetes targeting somatostatin signaling, which could open novel avenues for the development of effective diabetic treatments.

The Digilantes

Interviews with people who operate criminal record websites, crime watch networks, and social media feeds illustrate how today’s users of criminal records extend well beyond criminal justice officials, data brokers, statisticians, and employers. Instead, civilians use criminal justice data to create online communities that promise to do better report on, respond to, and prevent crime compared to existing structures. These “digilantes” use criminal records, arrest logs, and booking photos in their quest to create better forms of citizen journalism, victim support networks, and neighborhood watch networks. There is a tension centered around whether digilantes’ access to criminal records benefits broader society or whether publishing already public information harms subjects even more. What seems like a privacy violation to a website subject is simultaneously viewed as a social benefit by those who circulate criminal records.

“White Vigilantes?”

Positive loitering is a type of neighborhood watch practice that safety activists in Rogers Park and Uptown commonly used in order to try and suppress street crime and gang activity. In conducting positive loitering, the mostly white safety activists entered a context in which their racial category was marked, because the practice encouraged charges of racism and vigilantism. This chapter describes how two positive loitering groups positioned themselves in this contested territory. It shows how the groups embraced or avoided racially contested tactics, engaged or alienated black and Latino residents, and discussed racial challenges. Ironically, a positive loitering group in Uptown created an environment of interracial collaboration in their polarized neighborhood, while the group in Rogers Park incited racial conflict despite that neighborhood’s calmer political field.

Racial Displacement in Action?

With the help of Chicago Alternative Policing Strategy, Chicago’s community policing program, safety activists in Rogers Park and Uptown employed a set of powerful strategies for fighting crime—“problem building” and “problem business” interventions, increasing and directing police services by strategically calling 911, attending court hearings as “court advocates,” and reclaiming public space through “positive loitering,” a type of public neighborhood watch. All of these practices were ostensibly race-neutral, but critics could and sometimes did challenge them as tools of racial marginalization. In addition to describing grassroots public safety work, the chapter analyzes how antigentrification activists contested these practices. Furthermore, it shows how safety activists tried to inoculate their efforts against racial contestation by recruiting minority residents, deploying racially benign narratives, and carefully managing situations of conflict.