During the differentiation of sperm most cellular proteins and organelles are degraded as they are no longer needed. Actin filaments in the cell help to collect and move cytoplasmic material in maturing sperm, and a cellular chopping machine called the proteasome degrades proteins into amino acids. Shown is a confocal microscopy image of a Drosophila spermatid stained for nuclei (blue), actin filaments (red), and proteasomes (green). A recent study uncovered a role for ADP-ribosylation by tankyrase in the assembly and activity of proteasomes. The image depicting this critical stage of sperm differentiation was selected by the NIGMS for inclusion in the May 2013 issue of Biomedical Beat, a monthly compendium of noteworthy NIGMS-supported research. See also Cho-Park PF and Steller, H 2013. Proteasome regulation by ADP-ribosylation. Cell 153:614-627.
Actin was detected using Alexa 546 phalloidin and proteasomes with transgeneic GFP-alpha6T, a proteosome subunit. Maturing sperm cells in the testis were fixed with formaldehyde, stained, and observed using confocal microscopy with a 40x 1.2 NA objective lens. The image is a projection of a z-stack with step size 1.2 micrometers.
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