"Highlights" calls attention to exciting advances in developmental biology that have recently been reported in Developmental Dynamics. Development is a broad field encompassing many important areas. To reflect this fact, the section spotlights significant discoveries that occur across the entire spectrum of developmental events and problems: from new experimental approaches, to novel interpretations of results, to noteworthy findings utilizing different developmental organisms.Two halves make a whole (Axonal Regeneration Proceeds Through Specific Axonal Fusion in Transected C. elegans Neurons by Brent Neumann, Ken C.Q. Nguyen, David H. Hall, Adela Ben-Yakar, and Massimo A. Hilliard, Dev Dyn 240:1365-1372) Two people in a relationship are said to become as one. However, after separation, their behaviors are not unlike that of injured axons: some wither and others continue along a new path. Here, Neumann et al. establish a new mode of axonal regeneration in Cae-norhabditis elegans that may serve as a better model for the recently separated. Upon laser-based axonal transection, the proximal segment of an injured ALM or PLM neuron grows, circumnavigates the injury site, and reconnects with its distal fragment. By 24 hr, the repair is complete: plasma membranes have fused and anterograde and retrograde cytoplasmic diffusion is restored. If re-connection fails or is incomplete, the distal portion degenerates in a Wallerian manner. What's more, when two adjacent neurons are transected simultaneously (ALN and ALM or PLN and PLM), the proximal axon nearly always faithfully rejoins its distal end. The cues and signaling events that regulate re-connection and self-recognition remain unknown, but are poised for discovery within this genetically tractable animal model. Perhaps more of the recently separated should take note of the injured ALM and PLM, who after injury can regenerate a bond that is as strong as ever.
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