Female sex mitigates motor and behavioural phenotypes in TDP-43Q331K knock-in mice

Abstract

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are overlapping neurodegenerative disorders. ALS is more commonly seen in men than women and the same may be the case for FTD. Preclinical models demonstrating sex-specific vulnerability may help to understand female resistance to ALS-FTD and thereby identify routes to therapy. We previously characterised a TDP-43^Q331K knock-in mouse, which demonstrated behavioural phenotypes reminiscent of ALS-FTD in males. Here we present our behavioural observations of female TDP-43^Q331K mutants. Female TDP-43^Q331K knock-in mice displayed increased weight relative to wild-type and increased food intake at 20 months of age, much later than previously observed in male mutants. Spontaneous digging behaviour was initially normal and only declined in mutants in the second year of life. Gait analysis using Catwalk ( https://www.noldus.com/catwalk-xt ) found significant deficits in the second year of life, while nocturnal running behaviour was attenuated from ~ 250 days of life. These results indicate that while female TDP-43^Q331K knock-in mice do display progressive behavioural phenotypes, these are less severe than we previously noted in male mutants. Further studies of male and female TDP-43^Q331K knock-in mice may help to unravel the mechanisms underlying sex-specific vulnerability in ALS-FTD.

Figure 1

Female TDP-43^Q331K/Q331K mice show marked weight gain over time, and age-dependent trends towards increased food intake and reduced marble burying. (a) Body weight from 8 to 21 months of age (n = 6–10 wild-type, 8–10 mutants) is significantly increased in mutants (overall P = 0.0005; mixed-effect analysis). (b) Food intake at 9, 13 and 20 months of age (n = 10 per genotype (9 months); 9 wild-type, 8 mutants (13 months); 8 wild-type, 9 mutants (20 months)) (overall P = 0.3260; two-way ANOVA). (c) Marble burying from 8 to 20 months of age (n = 10 per genotype (8, 9, 10 and 12 months); 9 per genotype (14 months); 8 per genotype (20 months)) shows no significant difference between groups (P = 0.6689; unpaired t-test). Error bars represent mean ± s.e.m, except in (c) where they are median ± interquartile range. ***P < 0.001.

Figure 2

Catwalk gait analysis of female wild-type and TDP-43^Q331K/Q331K mice shows gait deficits in aged mutants. (a) Hindlimb base of support (BOS) (P < 0.05; two-way ANOVA). (b) Hindlimb swing time (P < 0.0001; two-way ANOVA). (c) Hindlimb swing speed (P < 0.05; two-way ANOVA). (d) Percentage of diagonal walking (P < 0.05; two-way ANOVA). (e) Percentage of 3-paw walking (P < 0.01; two-way ANOVA). (f) Percentage of 4-paw walking (P < 0.05 at 20 months on multiple comparisons; two-way ANOVA). All data is from 8 to 20 months of age (n = 10 per genotype (8 months); 10 wild-type, 9 mutants (10 and 12 months); 9 per genotype (14 months); 9 wild-type, 7 mutants (20 months)). Error bars represent mean ± s.e.m. *P < 0.05, **P < 0.01, ****P < 0.0001.

Figure 3

Running wheel analysis of female wild-type and TDP-43^Q331K/Q331K mice shows reduced running in mutants. (a) Time run per 24 h (P < 0.0001; two-way ANOVA). (b) Distance run per 24 h (P < 0.0001; two-way ANOVA). c Mean speed run per 24 h (P < 0.0001; two-way ANOVA). All data are from 230 to 618 days of age (n = 8–10 wild-type, 7–10 mutants). Error bars represent mean ± s.e.m. ****P < 0.0001.

Figure 4

Compound muscle action potentials in 12-month-old mutant mice are no different to wild-type. n = 3 per genotype. P = 0.6689, unpaired t-test. Error bars represent mean ± s.e.m.