Expression of acid-sensing ion channels and selection of reference genes in mouse and naked mole rat.

Laura-Nadine Schuhmacher,Ewan St. John Smith

doi:10.1186/s13041-016-0279-2

Expression of acid-sensing ion channels and selection of reference genes in mouse and naked mole rat.

Laura-Nadine Schuhmacher, Ewan St. John Smith

Open Access

https://doi.org/10.1186/s13041-016-0279-2

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Abstract

Acid-sensing ion channels (ASICs) are a family of ion channels comprised of six subunits encoded by four genes and they are expressed throughout the peripheral and central nervous systems. ASICs have been implicated in a wide range of physiological and pathophysiological processes: pain, breathing, synaptic plasticity and excitotoxicity. Unlike mice and humans, naked mole-rats do not perceive acid as a noxious stimulus, even though their sensory neurons express functional ASICs, likely an adaptation to living in a hypercapnic subterranean environment. Previous studies of ASIC expression in the mammalian nervous system have often not examined all subunits, or have failed to adequately quantify expression between tissues; to date there has been no attempt to determine ASIC expression in the central nervous system of the naked mole-rat. Here we perform a geNorm study to identify reliable housekeeping genes in both mouse and naked mole-rat and then use quantitative real-time PCR to estimate the relative amounts of ASIC transcripts in different tissues of both species. We identify RPL13A (ribosomal protein L13A) and CANX (calnexin), and β-ACTIN and EIF4A (eukaryotic initiation factor 4a) as being the most stably expressed housekeeping genes in mouse and naked mole-rat, respectively. In both species, ASIC3 was most highly expressed in dorsal root ganglia (DRG), and ASIC1a, ASIC2b and ASIC3 were more highly expressed across all brain regions compared to the other subunits. We also show that ASIC4, a proton-insensitive subunit of relatively unknown function, was highly expressed in all mouse tissues apart from DRG and hippocampus, but was by contrast the lowliest expressed ASIC in all naked mole-rat tissues.

Highlights

Acid-sensing ion channels (ASICs) are a group of six ion channels encoded by four different genes, splice variants of the genes encoding ASIC1 and ASIC2 produce ASIC1a and ASIC1b, and ASIC2a and ASIC2b respectively [1]
Considering that NaV1.7 expression is largely restricted to the peripheral nervous system [23, 24], any central adaptations to hypercapnia may result from differential ASIC expression and it is necessary to determine if there are any differences in ASIC brain expression in the naked mole-rat compared to mouse
The geNorm algorithm ranked the twelve control genes according to their pairwise expression stability in five brain regions, spinal cord and dorsal root ganglia (DRG) neurons

Summary

Introduction

Acid-sensing ion channels (ASICs) are a group of six ion channels encoded by four different genes, splice variants of the genes encoding ASIC1 and ASIC2 produce ASIC1a and ASIC1b, and ASIC2a and ASIC2b respectively [1]. The predominant endogenous activator of ASICs is protons and combinations of different ASIC subunits produces homoand heterotrimers with different biophysical and pharmacological properties [2,3,4]. The NaV1.7 variation is conserved in a variety of hibernating species [21] and insensitivity to acid in these species is likely due to an adaptation to living in a hypercapnic environment [14, 22]. Considering that NaV1.7 expression is largely restricted to the peripheral nervous system [23, 24], any central adaptations to hypercapnia may result from differential ASIC expression and it is necessary to determine if there are any differences in ASIC brain expression in the naked mole-rat compared to mouse

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Conclusion