Figure 4. Translation of a small group of genes is boosted during oocyte arrest.

(A) Normalized total translation levels from ribosome profiling in 0–2 hr embryos compared to oocytes stored for two days. (B) Plot showing that most genes are translated at higher levels in the 0–2 hr embryo than the 2 day stored oocyte. Examples of the 243 more highly translated ‘pilot light genes’ are labeled in orange. (C) The hatch rate of stored oocytes from wild type (blue), Df(sHSP)/+ (green), or Df(sHSP)/Df(sHSP) (purple) females after indicated storage period (‘oocyte age’). Deletion of Hsp26 and Hsp27 accelerated the rate of decline during storage (N = 3 at each point). (D–G) GO analysis (PANTHER) of genes with significantly (p<0.01, Student’s t-test) increased (D,F) or decreased (E,G) translation in 2- day-old mature oocytes compared to 0–2-hr embryos (D,E) or growing follicles (F,G). Error bars in (A) and (C) denote SD. FDR = false discovery rate.

Figure 4—figure supplement 1. Deletion of the small heat shock protein gene locus.

(A) Normalized ribosome footprinting (upper tracks) and mRNA-seq (lower tracks) read depths in the 67B small heat shock protein gene cluster, are compared for replicate experiments from oocytes stored for 2 days (orange) and from 0–2-hr embryos (blue). Above the tracks is a map of the gene cluster, as well as the position of an FRT recombination-induced deletion of all but the left-most two genes that were generated. Two genes, Hsp26 and Hsp27, are transcribed and translated in both stored oocytes and 0–2-hr embryos. (B) Wild type (WT) and Df(sHSP)/Df(sHSP) ovarioles were stained with antibodies specific for Hsp26 and Hsp27. Both genes are expressed during oogenesis and are abundant in later stages (stage 10 shown). However, expression was absent above background in stage 10 follicles from the Df(sHSP)/Df(sHSP) ovarioles. (C) Plot showing similar stage distributions of 4–8-hr embryos derived from non-aged or aged Df(sHSP)/+ or Df(sHSP)/Df(sHSP) oocytes, suggesting that the premature loss of viability of oocytes lacking small heat shock proteins is not due to an acceleration of meiotic spindle defects observed in aged wild type oocytes.

Figure 4—figure supplement 2. Genes preferentially translated during oocyte arrest are not protected from widespread age-associated reduced translation efficiency.

(A) Cumulative distribution plot showing that genes that are translationally upregulated in arrested oocytes (orange) as compared to 0–2-hr embryos show a slightly greater reduction in translation efficiency during aging as a group as compared to the distribution of all genes translated in oocytes. (B) Volcano plot showing that genes preferentially translated in oocytes (orange) as compared to early embryos are globally reduced in translation during oocyte aging.