Figure 1
From: Uncommon opsin’s retinal isomer is involved in mammalian sperm thermotaxis
Effect of vitamin A-starvation on mouse sperm thermotaxis. (a) Sperm thermotaxis of starved mice. All mice were 4-weeks old at the beginning of the starvation. The columns stand for the accumulation of spermatozoa in the warmer compartment, using the two-compartment separation tube7,8 (mean ± SEM). All values were normalized according to the average number of spermatozoa in the cold chamber (12.8 × 106 cells). N is the number of mice tested. *P = 0.0005 according to Linear mixed effects model, with treatment and gradient as fixed factors, and mouse ID as a random factor. No significant difference was observed in the group of starved mice (P = 0.98). (b) Sperm thermotaxis of starved and replenished mice. All mice were 12-weeks old at the beginning of the experiment. The columns stand for the accumulation of spermatozoa in the warmer compartment (mean ± SEM). All values were normalized according to the average number of spermatozoa in the cold chamber (9.4 × 106 cells). N is the number of mice tested. *P < 0.002 for the difference between gradient and the no-gradient control according to Linear mixed effects model, with treatment and gradient as fixed factors, and mouse ID as a random factor. Post-hoc comparisons were done using Tukey’s test. The statistical analyses were carried out using the R packages ‘lme4’, ‘lmerTest’ and ‘lsmeans’. The difference between the sperm concentrations in panel a and b is probably due to the younger age of the mice in panel a than those in panel b, resulting in their higher motility. This higher motility in a is reflected in the higher sperm concentration in the columns of no-gradient control in panel a relative to b. The difference did not affect the result of the thermotaxis assay because each assay had its own no-gradient control from the very same sample. (c) Capacitation and motility of the sperm samples measured in panel b. Note that the Y axis has a different meaning for each group of columns, as written below the groups. The values shown are the mean ± SEM of 8, 7 and 8 starved, non-starved and replenished mice, respectively (capacitation) or of 10, 8 and 9 starved, non-starved and replenished mice (motility). [The motility parameters and capacitation level of the non-starved group are also presented as wild-type mice in Roy et al.10 (Fig. 6b and Table S3 there)]. An insignificant difference between the groups (P > 0.05) was established by one-way ANOVA with Tukey–Kramer post-test using InStat statistical software.
