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

• Published in: Biochemical and biophysical research communications Vol. 610; pp. 77 - 84
• Main Authors: Shibata, Yasuhiro, Kumamoto, Natsuko, Sakuma, Eisuke, Ishida, Yusuke, Ueda, Takashi, Shimada, Shoichi, Ugawa, Shinya
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25.06.2022
• Subjects: Acid Sensing Ion Channels - genetics; Acid Sensing Ion Channels - metabolism; Animals; ASIC2a; Ataxia; Brain atrophy; Cerebellum - pathology; Gain of Function Mutation; Mutation; Neurodegeneration; Rats; Rotarod test; Transgenic rat; ASIC2a; H&E; Brain atrophy; Rotarod test; C. elegans; Transgenic rat; mRNA; PFA; SDS-PAGE; Neurodegeneration; RT-PCR; Ataxia; cDNA
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2022.04.030

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 (ASIC2aG430F), 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 ASIC2aG430F 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 ASIC2aG430F channel induced lethal degeneration in Tg brain neurons expressing both ASIC2aG430F and ASIC2a channels. ·Transgenic (Tg) rats carrying an ASIC2a gain-of-function mutation were produced.·The brain volume, especially cerebellar volume, of Tg rats significantly decreased.·Cerebellar Purkinje and granule cells markedly degenerated in Tg rats.·Rotarod tests revealed that Tg rats developed an early-onset ataxic gait.·This is the first description of an ASIC gain-of-function mutant mammal.