COVER Butterfly wing patterns are mosaics of colored scales, as shown in this high-magnification image of a painted lady (Vanessa cardui) wing. A shared set of deeply conserved gene regulatory sequences are shown to control color pattern formation across species, suggesting that an ancient genetic architecture underlies wing pattern development. See pages 249 and 304.

Photo: Anyi Mazo-Vargas

ONLINE COVER Emission ratios in Arabidopsis root tips visualized with a genetically encoded fluorescent biosensor. The uptake and distribution of nitrate—a major nitrogen source and one of the most limiting factors in agricultural production—is critical to plant life. Visualizing this distribution at the cellular level provides an understanding of the fundamental aspects of nitrate uptake by plant roots. To do this, Chen et al. developed NitraMeter3.0, a genetically encoded fluorescent biosensor. The tool tracks both nitrate concentrations in real time and spatiotemporal changes during the plant life cycle.

ONLINE COVER Mangled Myelin. This month’s cover depicts a normal myelin sheath wrapped around the axon of a neuron next to a damaged myelin sheath impairing nerve function. Autoreactive T cells specific for epitopes in myelin proteins trigger demyelination in human multiple sclerosis and mice with experimental autoimmune encephalomyelitis (EAE). Yi and Miller et al. report that chimeric antigen receptor (CAR) T cells displaying a complex of MHC class II and a peptide from myelin oligodendrocyte protein (MOG) selectively target pathogenic T cells for elimination in mouse EAE initiated by MOG immunization, thereby preventing and treating autoimmune symptoms. Using CAR T cells with different functional efficacy, the authors found that higher affinity autoreactive T cells are required for initiation of disease onset but lower affinity cells are sufficient to maintain ongoing disease.

ONLINE COVER Physical Connections. Morphological computing leverages the dynamics of mechanical bodies for computation with the aim to decentralize the computing load. Inspired by artificial neural networks, Lee et al. have realized a mechanical neural network that uses interconnected beams with tunable stiffness to learn mechanical behaviors. Genetic and partial pattern search algorithms were applied to the mechanical neural network. This month's cover is a photograph of the mechanical neural network in operation.

ONLINE COVER This week, Udayasuryan et al. show that infection of normal and malignant pancreatic cells with the oral commensal microbe Fusobacterium nucleatum induces cytokine release that promotes migration and invasion by the cancer cells. In the pseudocolored scanning electron microscopy image, F. nucleatum (orange) are seen binding to and invading pancreatic cancer cells (purple).

ONLINE COVER Tracking TAMs. This two-photon microscopy image shows uptake of perfluorocarbon-containing nanoparticles (PFC-NPs; red) by tumor-associated microglia and macrophages (TAMs) in a central nervous system (CNS) tumor. Vasculature is shown in yellow and tumor cells are shown in green. Increased TAM abundance in CNS tumors has been correlated to more aggressive disease; however, monitoring these cells in patients has only been achievable using invasive biopsies. Here, Croci et al. showed that CNS TAMs could be monitored by magnetic resonance imaging (MRI) for PFC-NPs enriched for the stable isotope, fluorine-19 (¹⁹F). The authors found that TAMs could be tracked longitudinally and in response to radiotherapy, highlighting the potential of ¹⁹F MRI as a monitoring strategy for patients with CNS tumors.