Figure 3. rRNA gene copy number decreases in germ cells during aging.
(A) rRNA gene copy number quantification by qPCR from 0 day and 40 day old testes. Mean ±SD (p-value *≤0.05 t-test). (B–D) FISH on testis mitotic chromosome spreads. DAPI (white), 18S rDNA (red), 240 bp IGS (green), (AATAAAC)n (blue). Bar: 2.5 μm. Y chromosome, identified by the presence of (AATAAAC)n, is indicated by cyan outline, and X chromosome is indicated by yellow outline. (E) Y:X signal intensity ratio for the 18S rDNA in mitotic germ cells in day 0, day 40 old wild type (yw) testes, and X/Df(YS)bb testes. Bracket indicates mean ±SD. p-values from Student’s t-test is shown. (F) Y:X signal intensity ratio for the IGS in mitotic germ cells in day 0, day 40 old wild type (yw) testes, and X/Df(YS)bb testes. Bracket indicates mean ±SD. p-values from Student’s t-test is shown. Note that different Y:X ratios for 18S vs. IGS probes indicates that Y rDNA locus might have higher number of IGS repeats per rDNA unit. (G) Examples of GSCs with atypical nucleolar morphology from X/Df(YS)bb flies at 0 days (red outline). Fibrillarin (red), DAPI (blue), Vasa (green), FasIII (white). The hub is denoted by (*). Bar: 5 μm. (H) Distribution of GSC nucleolar morphologies in X/Df(YS)bb flies compared to 0 and 40-day-old WT flies, as a percentage of total GSCs scored (n, number of GSCs scored). Chi-squared test, p-values listed.
Figure 3—figure supplement 1. The Df(YS)bb- from Kyoto Stock Center chromosome does not have any detectable 240-IGS sequence.
