A gain-of-function mutation in the acid-sensing ion channel 2a induces marked cerebellar maldevelopment in rats

Yasuhiro Shibata; Natsuko Kumamoto; Eisuke Sakuma; Yusuke Ishida; Takashi Ueda; Shoichi Shimada; Shinya Ugawa

doi:10.1016/j.bbrc.2022.04.030

A gain-of-function mutation in the acid-sensing ion channel 2a induces marked cerebellar maldevelopment in rats

Biochem Biophys Res Commun. 2022 Jun 25:610:77-84. doi: 10.1016/j.bbrc.2022.04.030. Epub 2022 Apr 11.

Authors

Yasuhiro Shibata¹, Natsuko Kumamoto¹, Eisuke Sakuma², Yusuke Ishida³, Takashi Ueda¹, Shoichi Shimada⁴, Shinya Ugawa⁵

Affiliations

¹ Department of Anatomy and Neuroscience, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi, 467-8601, Japan.
² Department of Integrative Anatomy, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi, 467-8601, Japan.
³ Division of Histology and Anatomy, Department of Medicine, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi, 981-8558, Japan.
⁴ Department of Neuroscience and Cell Biology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan; Addiction Research Unit, Osaka Psychiatric Research Center, Osaka Psychiatric Medical Center, Osaka, 541-8567, Japan.
⁵ Department of Anatomy and Neuroscience, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi, 467-8601, Japan. Electronic address: ugawa@med.nagoya-cu.ac.jp.

PMID: 35447498
DOI: 10.1016/j.bbrc.2022.04.030

Abstract

Specific amino acid substitutions in degenerin mechano-gated channels (DEGs) of C. elegans convert these channels into constitutively active mutants that induce the degeneration of neurons where DEGs are expressed. Acid-sensing ion channel-2a (ASIC2a), a proton-gated cation channel predominantly expressed in central neurons, is a mammalian ortholog of DEGs, and it can remain unclosed to be cytotoxic once the same mutations as the DEG mutants are introduced into its gene. Here we show that heterozygous transgenic (Tg) rats expressing ASIC2a-G430F (ASIC2a^G430F), the most active form of the gain-of-function mutants, under the control of the intrinsic ASIC2a promoter exhibited marked cerebellar maldevelopment with mild whole-brain atrophy. The Tg rats were small and developed an early-onset ataxic gait, as evidenced by rotarod and footprint tests. The overall gross-anatomy of the Tg brain was normal just after birth, but a reduction in brain volume, especially cerebellar volume, gradually emerged with age. Histological examination of the adult Tg brain revealed that the cell-densities of cerebellar Purkinje and granule cells were markedly reduced, while the cytoarchitecture of other brain regions was not significantly altered. RT-PCR and immunoblot analyses demonstrated that ASIC2a^G430F transcripts and proteins were already present in various regions of the neonatal Tg brain before the deforming cerebellum became apparent. These results suggest that, according to the spatiotemporal pattern of the wild-type (WT) ASIC2a gene expression, the ASIC2a^G430F channel induced lethal degeneration in Tg brain neurons expressing both ASIC2a^G430F and ASIC2a channels.

Keywords: ASIC2a; Ataxia; Brain atrophy; Neurodegeneration; Rotarod test; Transgenic rat.

MeSH terms

Acid Sensing Ion Channels* / genetics
Acid Sensing Ion Channels* / metabolism
Animals
Cerebellum* / pathology
Gain of Function Mutation*
Mutation
Rats

Substances

Acid Sensing Ion Channels
Asic2 protein, rat