Astrocytes infiltrate and engulf degenerating MB γ neurons at 6h APF.

<p>(A–C) Confocal Z-projections of brains expressing alrm-GAL4 driven mCD8::GFP focusing on the MB medial (A) or dorsal (B) lobes or the peduncle (C) at 6 h APF as depicted by the cartoons on the left (A₁–C₁). Fas II staining shows clear spherical holes devoid of FasII expression in the MB γ dorsal (A₂) and medial (B₂) lobes and a slight decrease in FasII staining in the peduncle (C₃). These holes are occupied by astrocyte extensions (A₃–C₃) infiltrating into the MB axon bundle (arrows in A₄–C₄). Magenta represents anti-FasII staining. Green is alrm-GAL4 driven mCD8::GFP. (D-E) Confocal single slices of the MB dorsal lobe tip (D) and the peduncle (E). While γ neurons were labeled by the Q-system (ET40-QF driving QUAS-mtdT-3xHA expression), astrocytes were labeled by alrm-GAL4 driven mCD8::GFP expression. At 6 h APF, γ axons are largely fragmented at the dorsal tip lobe (D₂) but only few fragments are detected at the peduncle (E₂). While astrocytes infiltrate both the dorsal lobe (D₄) and the peduncle (E₄), clear engulfment events can only be seen around the dorsal tip (D₄). Red is QF-ET40 driven QUAS-mtdt-3xHA. Green is alrm-GAL4 driven mCD8::GFP. The scale bars are 20 μm. Genotypes: (A–C) w;alrm-GAL4;alrm-GAL4,UAS-mCD8::GFP/+ (D–E) y,w;QF-ET40,QUAS-mtdT-3xHA/+;alrm-GAL4,UAS-mCD8::GFP/+.