Fig. 1

 Proteome Identification

(A) The biotinylation reaction was performed on freshly isolated brains. The yellow line depicts the location of the cross-section shown in (B).

(B) Cross-section through the telencephalon of a zebrafish. Biotinylated surfaces are depicted as magenta dots. The upper surface of the pallium borders the ventricle, located below the tela choroidea (white arrow) and is composed of the cell somata of the radial glia (depicted in green in the inset). The midline between both hemispheres is also filled by a thin part of the ventricle. After the biotinylation reaction, telencephalons were separated into the dorsal part (pallium) and ventral part (subpallium).

(C) Drawing of the fractions isolated by FACS and by biotinylation, depicting in green the radial glia, in dark blue the remaining cells of the telencephalon, in magenta the biotinylated fraction containing the cell surfaces of the radial glia, and in light blue the lysate fraction containing the remainder of these cells as well as the rest of the telencephalon.

(D–I) Histochemistry on cross-sections with streptavidin coupled to AlexaFluor 555 after biotinylation of the brain, revealing the expected binding of biotin on the cell surfaces in young (D–F) and old (G–I) brains.

(J) Cells of the GFP-positive and -negative fraction plated directly after the sorting; nuclei are stained by DAPI.

(K) Known proteins isolated on FACS-sorted radial glia.

(L) The overlaps between the surface fraction, lysate fraction, and GFP-positive fraction are represented. The majority (79.3%) of proteins identified in the FACS-GFP-positive fraction were also found in the biotinylated fraction.

(M) Identified proteins were categorized according to the presence of signal peptides and transmembrane domains, revealing an enrichment of plasma membrane proteins in the biotinylated fraction compared with the lysate and to the FACS-retrieved proteins.