TMEM16C is involved in thermoregulation and protects rodent pups from febrile seizures

Tongfei A Wang,Chao Chen,Fen Huang,Shengjie Feng,Jason Tien,João M Braz,Allan I Basbaum,Yuh Nung Jan,Lily Yeh Jan

doi:10.1073/pnas.2023342118

Tongfei A Wang, Chao Chen + Show 7 more

Open Access

https://doi.org/10.1073/pnas.2023342118

Copy DOI

Abstract

Febrile seizures (FSs) are the most common convulsion in infancy and childhood. Considering the limitations of current treatments, it is important to examine the mechanistic cause of FSs. Prompted by a genome-wide association study identifying TMEM16C (also known as ANO3) as a risk factor of FSs, we showed previously that loss of TMEM16C function causes hippocampal neuronal hyperexcitability [Feenstra et al., Nat. Genet. 46, 1274-1282 (2014)]. Our previous study further revealed a reduction in the number of warm-sensitive neurons that increase their action potential firing rate with rising temperature of the brain region harboring these hypothalamic neurons. Whereas central neuronal hyperexcitability has been implicated in FSs, it is unclear whether the maximal temperature reached during fever or the rate of body temperature rise affects FSs. Here we report that mutant rodent pups with TMEM16C eliminated from all or a subset of their central neurons serve as FS models with deficient thermoregulation. Tmem16c knockout (KO) rat pups at postnatal day 10 (P10) are more susceptible to hyperthermia-induced seizures. Moreover, they display a more rapid rise of body temperature upon heat exposure. In addition, conditional knockout (cKO) mouse pups (P11) with TMEM16C deletion from the brain display greater susceptibility of hyperthermia-induced seizures as well as deficiency in thermoregulation. We also found similar phenotypes in P11 cKO mouse pups with TMEM16C deletion from Ptgds-expressing cells, including temperature-sensitive neurons in the preoptic area (POA) of the anterior hypothalamus, the brain region that controls body temperature. These findings suggest that homeostatic thermoregulation plays an important role in FSs.

Highlights

Body temperature is a critical index of health in mammals, while fever is an evolutionarily conserved response to infection [1]
We developed rodent models of Febrile seizures (FSs) associated with deficient thermoregulation, including conditional knockout mice with TMEM16C eliminated from a hypothalamic neuronal population important for maintaining body temperature but not from most of the cortical and hippocampal neurons and sensory neurons
Using the mouse line of PGDS-Cre [31], we examined conditional knockout (cKO) mouse pups with TMEM16C eliminated from temperature-sensitive preoptic area of the anterior hypothalamus (POA) neurons

Summary

Results

Rat Pups Without TMEM16C Are More Susceptible to Hyperthermia-Induced Seizures. To test Tmem16c knockout (KO) rat pups (postnatal day 10 [P10]) for susceptibility to hyperthermia-induced seizures with an established protocol [23, 24], we exposed P10 rat pups to heated air (45 to 50 °C) from a hair dryer, one at a time (Fig. 1). As evident from the slope of Tc change in response to ambient temperature alteration, Tmem16c cKO mouse pups experienced a more rapid increase of Tc than their WT littermate controls when the ambient temperature was raised from 30 °C to 37 °C (SI Appendix, Fig. S4 B and G–J, P < 0.01, one-way ANOVA followed by Tukey’s multiple comparisons test) These findings provide evidence that the neuronal TMEM16C is important for thermoregulation and the propensity for hyperthermia-induced seizure. We used PGDS-Cre to knock out TMEM16C from Ptgds-expressing cells, including temperature-sensitive POA neurons, without affecting the integrity of the majority of hippocampal, cortical, and DRG neurons These P11 cKO mouse pups displayed greater susceptibility to hyperthermia-induced seizures (Fig. 3 A–D; n = 12 in each genotype; phases III and IV, P < 0.01, one-way ANOVA followed by Tukey’s multiple comparisons test). The poor thermoregulation of cKO mouse pups with TMEM16C elimination from Ptgds-expressing cells but not from the majority of hippocampal and cortical neurons or sensory neurons, taken together with their normal susceptibility to chemoconvulsant-induced seizures, suggest that their greater susceptibility to hyperthermia-induced seizures likely derives from their deficiency in homeostatic thermoregulation

Discussion

C Phase II

Materials and Methods