Picture from Luo S et al. (2010) Cell "TGF- and insulin signaling regulate reproductive aging via oocyte and germline ...."

Figure 7.TGF-b Sma/Mab signaling regulates genes important for age-associated oocyte quality maintenance(A-F) RNAi treatments of TGF-b target genes accelerate oocyte quality decline, increasing the percentage of unhatched embryos (orange) and/or unfertilized oocytes (yellow) earlier in life (compare with Figure 6C). mlh-1, math-33, and F47G4.4 RNAis have greater effects (A-C), while F52D10.2, uev-2, and pme-5 have milder effects (D-F). Wild type treated with RNAis shown in Figure S7C-F, I-J).(G) uev-2 RNAi treatment significantly increases sma-2's production of unhatched embryos after gamma-irradiation, while pme-5 and mlh-1 do not. Animals were mated with young wt males after irradiation.(H) Model of reproductive aging regulation by the TGF-b Sma/Mab (pink) and insulin/IGF-1 signaling (red) pathways. Ligands (Insulin-Like Peptides, TGF-b DBL-1) are secreted neuronally and mediate signaling to the soma (hypodermis, intestine, and muscle), generating as yet unidentified secondary signals to regulate reproduction. These secondary signals block distal germline and oocyte integrity maintenance with age, resulting in germline morphology decline, slowed germ cell proliferation, and a decline in oocyte quality. Downstream effectors in oocytes include chromosome segregation, cell cycle, and DNA damage response/repair genes, etc. Declines in embryonic viability and infertility mark reproductive cessation. The germline and somatic gonad regulate somatic aging (Hsin and Kenyon, 1999), suggesting a bi-directional signaling flow in the coordination of somatic and germline aging. (Photo courtesy of Ian Chin-Sang.)

Picture from Cook, Steven J. et al. (2021) MicroPubl Biol

Figure 1. AVH and AVJ neurons and hlh-34 expression: A: AVH and AVJ display a nearly identical position and axon trajectory in the lateral ganglion of C. elegans. Images used with permission from Wormatlas. B: Whole-animal lateral and dorsoventral overviews of hlh-34prom::gfp (otIs768 transgene) expressing young larvae. Animals imaged in a NeuroPAL (otIs669) background with only GFP emission shown for simplicity. C: Expression pattern of otIs768 and sIs14542 transgenic reporters in a NeuroPAL (otIs669) background. GFP signal is only observed in the AVH neuron. D: Embryonic expression pattern of otIs768. At ~360 minutes the GFP signal is observed in the AVH neuron and its dying sibling cell. All animals were imaged in a NeuroPAL (otIs669) background with only GFP emission shown for simplicity. E: Lineages of AVH/J in red. CEPsoDL/R shown in orange. Dying siblings of AVH shown as 'x'. F: hlh-34 locus and promoter fragment used in the sIs14542 transgene. Coordinates are V:13709947..13712813 in WS140 and V:13707915..13707382 in WS280. The size of the promoter used in the leEx1692 strain, kindly provided by Ian Hope, could not be unambiguously determined. The strain used in the first publication on hlh-34 (Cunningham et al. 2012) used 2.5kb upstream of hlh-34. G: Heatmap of scRNA expression (Taylor et al. 2021), showing hlh-34 expression and other markers of AVH and AVJ identity.