Kv1.1 deficiency alters repetitive and social behaviors in mice and rescues autistic-like behaviors due to Scn2a haploinsufficiency

Abstract

Background: Autism spectrum disorder (ASD) and epilepsy are highly comorbid, suggesting potential overlap in genetic etiology, pathophysiology, and neurodevelopmental abnormalities; however, the nature of this relationship remains unclear. This work investigated how two ion channel mutations, one associated with autism (Scn2a-null) and one with epilepsy (Kcna1-null), interact to modify genotype-phenotype relationships in the context of autism. Previous studies have shown that Scn2a^+/- ameliorates epilepsy in Kcna1^-/- mice, improving survival, seizure characteristics, and brain-heart dynamics. Here, we tested the converse, whether Kcna1 deletion modifies ASD-like repetitive and social behaviors in Scn2a^+/- mice.

Methods: Mice were bred with various combinations of Kcna1 and Scn2a knockout alleles. Animals were assessed for repetitive behaviors using marble burying, grooming, and nestlet shredding tests and for social behaviors using sociability and social novelty preference tests.

Results: Behavioral testing revealed drastic reductions in all repetitive behaviors in epileptic Kcna1^-/- mice, but relatively normal social interactions. In contrast, mice with partial Kcna1 deletion (Kcna1^+/- ) exhibited increased self-grooming and decreased sociability suggestive of ASD-like features similar to those observed in Scn2a^+/- mice. In double-mutant Scn2a^+/- ; Kcna1^+/- mice, the two mutations interacted to partially normalize ASD-like behaviors associated with each mutation independently.

Conclusions: Taken together, these findings suggest that Kv1.1 subunits are important in pathways and neural networks underlying ASD and that Kcna1 may be a therapeutic target for treatment of Scn2a-associated ASD.

Keywords: autism spectrum disorder; channelopathies; comorbidity; epilepsy; ion channels.

FIGURE 1

Kcna1 ^–/– mice exhibit drastic reductions in repetitive behaviors. Repetitive behaviors of Kcna1 ^–/– mice (n = 12:5 males, 7 females) and wild‐type (WT) control animals (n = 13:6 males, 7 females) were evaluated in tests of marble burying (a), nestlet shredding (b), and self‐grooming (c). **, p < .01; ***, p ≤ .001 (unpaired two‐tailed Student's t test)

FIGURE 2

Kcna1 ^–/– mice exhibit normal social interactions. Social interactions were evaluated for WT (n = 7:3 male, 4 females) and Kcna1 ^–/– mice (n = 7:3 males, 4 females) using three‐chamber tests of sociability (a) and social novelty preference (b). In the sociability test, both genotypes exhibited a preference for the stranger mouse (S1) over the empty cup (E) as evidenced by the significantly greater amount of time spent in the S1 chamber (versus the E chamber) and in sniffing the S1 mouse (versus the empty cup). In the subsequent social novelty test, the preference for the original S1 mouse disappeared with the introduction of a second novel stranger mouse (S2) as both genotypes spent similar amounts of time exploring the side chambers and sniffing both stranger mice. Both genotypes exhibited a similar number of transitions from the middle chamber into the two side chambers suggesting no innate side preference. *, p < .05; ***, p < .01 (unpaired two‐tailed Student's t test)

FIGURE 3

Partial deletion of the Kcna1 gene rescues abnormal self‐grooming in Scn2a ^+/– mice. Repetitive behaviors were evaluated in tests of marble burying (a), nestlet shredding (b), and self‐grooming (c). Both Scn2a ^+/– and Kcna1 ^+/– mice exhibited significantly increased self‐grooming consistent with ASD‐like behavior. However, abnormal self‐grooming behavior was suppressed in double heterozygotes carrying both mutations (i.e., Scn2a ^+/–; Kcna1 ^+/–) indicative of reciprocal masking interactions between the two genes. Sample sizes per genotype were the following: for WT, n = 12 (9 males, 3 females); for Scn2a ^+/–, n = 12 (7 males, 5 females); for Kcna1 ^–/–, n = 9 (3 males, 6 females); for Scn2a ^+/–; Kcna1 ^–/–; n = 12 (10 males, 2 females), for Kcna1 ^+/–, n = 7 (2 males, 5 females); and for Scn2a ^+/–; Kcna1 ^+/–, n = 12 (6 males, 6 females). *, p < .05; **, p < .01; ***, p < .001; ****, p < .0001 (one‐way ANOVA with post hoc Tukey test)

FIGURE 4

Partial deletion of the Kcna1 gene rescues deficits in social novelty preference in Scn2a ^+/– mice. Social interactions were evaluated using three‐chamber tests of sociability (a) and social novelty preference (b). Scn2a ^+/– mice (n = 10) exhibited relatively normal sociability but an abnormal decrease in social novelty preference, as evidenced by spending a significantly greater amount of time exploring the chamber with a familiar stranger mouse (S1) compared to the chamber with a novel stranger mouse (S2). Kcna1 ^+/– mice (n = 6) displayed abnormal sociability by exhibiting no significant preference for the stranger mouse (S1) over the empty cup (E) in terms of time spent in each chamber and sniffing time. However, in double heterozygotes carrying both mutations (i.e., Scn2a ^+/–; Kcna1 ^+/–; n = 6) sociability and social novelty preference were normalized, further suggesting reciprocal masking interactions between the two genes. All genotypes exhibited a similar number of transitions from the middle chamber into the two side chambers suggesting no innate side preference. Sample sizes per genotype were the following: for WT, n = 9 (7 males, 2 females); for Scn2a ^+/–, n = 10 (5 males, 5 females); for Kcna1 ^–/–, n = 9 (5 males, 4 females); for Scn2a ^+/–; Kcna1 ^–/–; n = 11 (9 males, 2 females), for Kcna1 ^+/–, n = 6 (4 males, 2 females); and for Scn2a ^+/–; Kcna1 ^+/–, n = 6 (5 males, 1 female). Sample sizes were 6–11 mice per genotype. *, p < .05; **, p < .01; ***, p < .001 (unpaired two‐tailed Student's t test)