Figure 4. Aβ42-independent synaptic loss in C. elegans model of FAD.

(A) Design of C. elegans transgenic model and visualization of synaptic puncta in the parental juIs1 line. Transgenic lines were obtained by microinjection of human APP C99 and/or human PSEN1 (driven by pan-neuronal rgef-1 promoter) into the parental line juIs1. rol-6 (dominant roller) was used as the coinjection marker to select for transformants. Right: a representative confocal image showing a series of synaptic puncta marked by GFP-tagged synaptobrevin along the dorsal nerve cord of juIs1.

(B) Lifespan of double-transgenic lines C99 + PSEN1 and C99 I45F + PSEN1 and monogenic line C99 I45F. Kaplan-Meier curves of n animals show the fraction of animals alive at different days.

(C) Quantification of the dorsal and ventral synaptic puncta in the transgenic lines. Average number of synaptic puncta per 100 μm in n transgenic worms for each day is shown in the vertical boxplots. Horizontal lines at the top and bottom of each box represent the maximum and minimum values, respectively. Upper and lower ends of a box mark quartile Q1 and Q3 values, respectively. The horizontal line inside the box shows the median value and marks Q2. Two-way ANOVA for all possible pairs using Tukey’s post hoc test; *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p < 0.0001. Statistical differences are shown only for the earliest day on which significance was seen compared with day 1 in a given line.

(D) Sections (100 μm) of representative confocal microscopic images of dorsal (left) and ventral (right) nerve cords of transgenic animals. “s” denotes average number of synaptic puncta per 100 μm from n animals.

(E) Lifespan of double-transgenic line C99 V44F/I45F + PSEN1 and monogenic line C99 V44F/I45F compared with C99 + PSEN1 and C99 I45F + PSEN1 lines.

(F) Quantification of dorsal and ventral synaptic puncta in these transgenic lines. Two-way ANOVA for all possible pairs using Tukey’s post hoc test; *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p < 0.0001. Statistical differences are shown only for the earliest day on which significance was seen compared with day 1 in a given line.

(G) Sections (100 μm) of representative confocal microscopic images of dorsal and ventral synaptic puncta in these transgenic lines. All experiments shown were repeated with independent transgenic lines, giving similar results.