Loss of the distal-proximal GLP-1/Notch activation gradient in the aging C. elegans germline

In <i>C. elegans</i> hermaphrodites, the distal tip cells (DTCs) capping the gonad arms provide a Notch ligand, the niche signal that maintains germline stem cell pools. Using fixed germlines, it was recently shown that the transcription of a Notch target gene decreased relatively early-on during adulthood. Here, we used the genetically encoded Notch Sensor Able to detect Lateral Signaling Activity (SALSA) to examine the pattern of GLP-1/Notch activity across the aging distal gonad <i>in vivo</i> . Interestingly, we find that the robust and progressively decreasing distal-proximal Notch activation gradient that is observed in young adults gets largely lost during aging.