COVER A target cell expressing a fluorescently tagged protein (green) is illuminated by a blue laser and selected from a swirling pool of cells. New cell sorting technology combines the throughput and quantitative power of flow cytometry with the spatial resolution of multicolor fluorescence microscopy to enable isolation of cells with complex phenotypes at speeds up to 15,000 cells per second. See page 315.

Illustration: Tobias Wüstefeld/Illustratoren.de

ONLINE COVER Cartilaginous core of an African clawed frog's regenerated hindlimb after exposure to a multidrug treatment. Murugan et al. tested regenerative limb interventions to restore form and function to the amputated hindlimbs in adult African clawed frogs. A wearable bioreactor allowed for 24-hour exposure to the multidrug therapy and resulted in long-term regrowth, tissue repatterning, and functional restoration of the amputated hindlimb over 18 months. With similarly limited regenerative capacities to humans, adult African clawed frogs are an important model for potential limb regeneration which could benefit trauma victims and diabetics.

ONLINE COVER Trail Markers for Tissue Macrophages. This month's cover illustration depicts a trail marker post in a desert landscape that provides a guide to deciphering the diversity among mouse and human tissue-resident macrophages. The trio of phenotypes (TLF⁺, CCR2⁺ and MHC-II⁺) listed on the post represent three conserved macrophage subsets defined by Dick et al. These subsets share common core gene signatures and life cycles across 17 different mouse tissues.

ONLINE COVER Yutu-2 Makes Tracks. The lunar farside is an underexplored region of the Moon. On 3 January 2019, the Chang'E-4 lander, housing the Yutu-2 rover, touched down on the lunar farside in the Von Kármán crater inside the South Pole-Aitken basin—the deepest, largest, and oldest basin on the Moon. Ding et al. report the deployment of Yutu-2 rover on the lunar farside over a period of 2 years (25 lunar days); during this time the rover examined the lunar surface’s regolith, craters, and rocks. This month’s cover is a photograph of the lunar surface taken with Yutu-2’s navigation camera.

ONLINE COVER This week, Miyamoto et al. show that the phosphorylation of cytohesin-2, mediated by the kinase Fyn and adaptor protein SH2B1 and reduced by the phosphatase PTP4A1, determines the thickness of the myelin sheath generated by Schwann cells. The transmission electron microscopy–generated image shows myelination in a sciatic nerve cross section from mice.

ONLINE COVER Broad Coronavirus Neutralization. The cover depicts a silver armor of neutralizing antibodies capable of blocking SARS-CoV, SARS-CoV-2, and related bat coronaviruses. As SARS-CoV-2 variants of concern diminish the utility of existing monoclonal antibody therapeutics, antibodies are being developed that neutralize SARS-CoV-2, including variants of concern, and can also neutralize closely related coronaviruses. Martinez et al. have identified a monoclonal antibody, DH1047, which binds to a region of the receptor binding domain of spike protein that is highly conserved among SARS-CoV-2, SARS-CoV, and related bat coronaviruses. DH1047 neutralized SARS-CoV-2, SARS-CoV, and related coronaviruses in vitro, and mice treated with DH1047 were protected against infection after challenge with these viruses. These findings highlight the importance of developing broadly neutralizing antibodies to combat SARS-CoV-2 and closely related coronaviruses.