Fig. 2. Male sex increases mortality, cognitive deficits, and synaptic protein abnormalities in hAPP mice.

(A) Shown are Kaplan-Meier survival curves of male hAPP mice (n = 1572, blue) compared with female hAPP mice (n = 1589, red); all mice had intact gonads (log-rank test, P < 0.001). (B) All mice except those in (A) underwent gonadectomy (Gnx) at about 2.5 months of age; this was followed by behavioral testing conducted from 4 to 7 months of age and survival analysis conducted until 3 years of age. (C) Shown are Kaplan-Meier survival curves of male (n = 116) compared to female (n = 123) hAPP mice after gonadectomy (log-rank test, P < 0.05). (D) Shown are spatial learning curves of mice (age 4 to 7 months; n = 10 to 15 per group) tested in the Morris water maze during hidden platform training and when the platform was visible. Data points are daily average of total distance traveled to reach the platform over four trials. Mixed-model ANOVA for hidden training: female hAPP versus male hAPP mice, P < 0.05. (E) A probe trial was conducted after hidden platform learning and removal of the escape platform. Percentage of time mice spent in the target quadrant of the maze, indicating memory for platform location, versus the average time spent in the other three quadrants is shown; *P < 0.05; ***P < 0.001. The dashed line represents chance performance (25%). (F) Shown is passive avoidance, fear memory of mice (age 3 to 3.5 months; n = 7 to 10 per group) reflected by latency to enter the dark chamber during training and testing 1 day after an electric shock to the foot. Two-way ANOVA: hAPP effect, P < 0.01; hAPP by sex interaction, P < 0.05. (G) Forgetting of passive avoidance memory in a separate cohort of mice (age 5 to 6 months; n = 10 to 12 per group), reflected by latency to enter a dark chamber 1, 5, and 8 days after a foot shock, was measured. The dashed line represents latency to enter the dark chamber during training, which did not differ among groups. (H) Percentage loss of fear memory from days 1 to 5 is shown. The dashed line represents the average for nontransgenic (NTG) animals. (I) Shown is quantitation of calbindin immunoreactivity in mouse dentate gyrus (age 5 to 7 months; n = 11 to 14 mice per group). Two-way ANOVA: hAPP effect, P < 0.05; hAPP by sex interaction, P < 0.05. Means are relative to NTG male control mice, arbitrarily defined as 1. (J) Soluble Aβ1-42 amounts in the mouse hippocampus determined by enzyme-linked immunosorbent assay (ELISA) are shown (age 3 months; n = 8 to 11 mice per group). (K) Representative immunostaining of hippocampal Aβ deposits in coronal brain sections from a male (top, M) and female (bottom, F) hAPP mouse (age 14.5 to 15 months). Scale bar, 200 μm; magnification, ×4. (L) Quantitation of percentage area covered by Aβ deposits in hAPP mice (age 14.5 to 15 months; n = 11 per group). Behavioral studies in male and female NTG and hAPP mice were performed across seven independent cohorts including in fig. S4. #P = 0.06; *P < 0.05; **P < 0.01; ***P < 0.001 [Bonferroni-Holm for (F), (G), and (I)]. Data are presented as means ± SEM.