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Mutations in SCN9A, encoding a sodium channel alpha subunit, in patients with primary erythermalgia.

ABSTRACT: Primary erythermalgia is a rare autosomal dominant disease characterised by intermittent burning pain with redness and heat in the extremities. A previous study established the linkage of primary erythermalgia to a 7.94 cM interval on chromosome 2q, but the causative gene was not identified. We performed linkage analysis in a Chinese family with primary erythermalgia, and screened the mutations in the two candidate genes, SCN9A and GCA, in the family and a sporadic patient. Linkage analysis yielded a maximum lod score of 2.11 for both markers D2S2370 and D2S2330. Based on critical recombination events in two patients in the family, we further limited the genetic region to 5.98 cM between D2S2370 and D2S2345. We then identified two missense mutations in SCN9A in the family (T2573A) and the sporadic patient (T2543C). Our data suggest that mutations in SCN9A cause primary erythermalgia. SCN9A, encoding a voltage-gated sodium channel alpha subunit predominantly expressed in sensory and sympathetic neurones, may play an important role in nociception and vasomotor regulation.

SUBMITTER: Yang Y

PROVIDER: S-EPMC1735695 | biostudies-other | 2004 Mar

REPOSITORIES: biostudies-other

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Mutations in SCN9A, encoding a sodium channel alpha subunit, in patients with primary erythermalgia.

Yang Y Y Wang Y Y Li S S Xu Z Z Li H H Ma L L Fan J J Bu D D Liu B B Fan Z Z Wu G G Jin J J Ding B B Zhu X X Shen Y Y

Journal of medical genetics 20040301 3

Primary erythermalgia is a rare autosomal dominant disease characterised by intermittent burning pain with redness and heat in the extremities. A previous study established the linkage of primary erythermalgia to a 7.94 cM interval on chromosome 2q, but the causative gene was not identified. We performed linkage analysis in a Chinese family with primary erythermalgia, and screened the mutations in the two candidate genes, SCN9A and GCA, in the family and a sporadic patient. Linkage analysis yiel ...[more]

PMID: 14985375

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Project description:BackgroundThe amiloride-sensitive Epithelial Sodium Channel (ENaC) is critical in maintaining Na+ balance, extracellular fluid volume and long term blood pressure control. ENaC is composed of three main subunits alpha, beta, & gamma. While alpha ENaC is critical for channel functionality, beta & gamma ENaC maximize channel function. To date, there are four alternatively spliced forms of the alpha subunit of ENaC (alpha ENaC-a, -b, -c, & -d) that have been published in rats, in addition to the major alpha ENaC transcript. While alpha ENaC-a, -c & -d transcripts are low abundance transcripts compared to full-length alpha ENaC, alpha ENaC-b is a higher abundance and salt-sensitive transcript compared to full-length alpha ENaC.Presentation of the hypothesisalpha ENaC-b protein, which is preferentially produced in Dahl R rats, to a greater extent on high salt diet, exerts a dominant negative effect on full-length alpha ENaC subunit by physically binding to and trapping full-length alpha ENaC subunit in the endoplasmic reticulum, and finally accelerating full-length alpha ENaC proteolytic degradation in a dose-dependent manner.Testing the hypothesis1) To examine the mRNA and protein abundance of alpha ENaC-b relative to alpha ENaC full-length in kidney, lung, and taste tissues of Dahl rats. 2) To compare the expression (mRNA and protein) of alpha ENaC-b in kidneys of Dahl S and R rats on regular and high salt diet. 3) To examine the putative binding of alpha ENaC-b proteins to full-length alpha ENaC in vitro and to determine the impact of such binding on full-length alpha ENaC expression in vitro.Implications of the hypothesisOur studies will be the first to demonstrate the over-expression of salt-sensitive alpha ENaC-b spliced form in kidney tissues of Dahl R rats at the expense of full-length alpha ENaC. The current proposal will provide highly novel insights into the putative mechanisms leading to ENaC hypoactivity in high-salt-fed Dahl R rats. Finally, findings from the present proposal will uncover a new mechanism by which alternative splicing may control the regulation of ENaC expression/function.

Project description:Insect voltage-gated sodium (Nav) channels are formed by a well-known pore-forming ?-subunit encoded by para-like gene and ancillary subunits related to TipE from the mutation "temperature-induced-paralysis locus E." The role of these ancillary subunits in the modulation of biophysical and pharmacological properties of Na(+) currents are not enough documented. The unique neuronal ancillary subunit TipE-homologous protein 1 of Drosophila melanogaster (DmTEH1) strongly enhances the expression of insect Nav channels when heterologously expressed in Xenopus oocytes. Here we report the cloning and functional expression of two neuronal DmTEH1-homologs of the cockroach, Periplaneta americana, PaTEH1A and PaTEH1B, encoded by a single bicistronic gene. In PaTEH1B, the second exon encoding the last 11-amino-acid residues of PaTEH1A is shifted to 3'UTR by the retention of a 96-bp intron-containing coding-message, thus generating a new C-terminal end. We investigated the gating and pharmacological properties of the Drosophila Nav channel variant (DmNav1-1) co-expressed with DmTEH1, PaTEH1A, PaTEH1B or a truncated mutant PaTEH1?(270-280) in Xenopus oocytes. PaTEH1B caused a 2.2-fold current density decrease, concomitant with an equivalent ?-subunit incorporation decrease in the plasma membrane, compared to PaTEH1A and PaTEH1?(270-280). PaTEH1B positively shifted the voltage-dependences of activation and slow inactivation of DmNav1-1 channels to more positive potentials compared to PaTEH1A, suggesting that the C-terminal end of both proteins may influence the function of the voltage-sensor and the pore of Nav channel. Interestingly, our findings showed that the sensitivity of DmNav1-1 channels to lidocaine and to the pyrazoline-type insecticide metabolite DCJW depends on associated TEH1-like subunits. In conclusion, our work demonstrates for the first time that density, gating and pharmacological properties of Nav channels expressed in Xenopus oocytes can be modulated by an intron retention process in the transcription of the neuronal TEH1-like ancillary subunits of P. americana.

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Mutations in SCN9A, encoding a sodium channel alpha subunit, in patients with primary erythermalgia.

Publications

Mutations in SCN9A, encoding a sodium channel alpha subunit, in patients with primary erythermalgia.

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