Dataset Information

Mutation in DHP receptor alpha 1 subunit (CACLN1A3) gene in a Dutch family with hypokalaemic periodic paralysis.

ABSTRACT: Hypokalaemic periodic paralysis (HypoPP) is characterised by transient attacks of muscle weakness of varying duration and severity accompanied by a drop in serum potassium concentration during the attacks. The largest known HypoPP family is of Dutch origin and consists of 277 members in the last five generations, 55 of whom have HypoPP inherited in an autosomal dominant pattern. Forty-eight persons including 28 patients with a proven diagnosis of HypoPP were used for linkage analysis. Microsatellite markers were used to exclude 45 to 50% of the genome and linkage to chromosome 1q31-32 was found. No recombinants were found between HypoPP and D1S412 and a microsatellite contained within the DHP receptor alpha 1 subunit (CACLN1A3) gene. A previously reported G to A mutation causing an arginine to histidine substitution at residue 528 in the transmembrane segment IIS4 of the CACLN1A3 gene was shown in patients by restriction analysis of genomic PCR products.

SUBMITTER: Boerman RH

PROVIDER: S-EPMC1050178 | biostudies-other | 1995 Jan

REPOSITORIES: biostudies-other

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Mutation in DHP receptor alpha 1 subunit (CACLN1A3) gene in a Dutch family with hypokalaemic periodic paralysis.

Boerman R H RH Ophoff R A RA Links T P TP van Eijk R R Sandkuijl L A LA Elbaz A A Vale-Santos J E JE Wintzen A R AR van Deutekom J C JC Isles D E DE

Journal of medical genetics 19950101 1

Hypokalaemic periodic paralysis (HypoPP) is characterised by transient attacks of muscle weakness of varying duration and severity accompanied by a drop in serum potassium concentration during the attacks. The largest known HypoPP family is of Dutch origin and consists of 277 members in the last five generations, 55 of whom have HypoPP inherited in an autosomal dominant pattern. Forty-eight persons including 28 patients with a proven diagnosis of HypoPP were used for linkage analysis. Microsatel ...[more]

PMID: 7897626

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Project description:We studied a two-generation family presenting with conditions that included progressive permanent weakness, myopathic myopathy, exercise-induced contracture before normokalaemic periodic paralysis or, if localized to the tibial anterior muscle group, transient compartment-like syndrome (painful acute oedema with neuronal compression and drop foot). 23Na and 1H magnetic resonance imaging displayed myoplasmic sodium overload, and oedema. We identified a novel familial Ca(v)1.1 calcium channel mutation, R1242G, localized to the third positive charge of the domain IV voltage sensor. Functional expression of R1242G in the muscular dysgenesis mouse cell line GLT revealed a 28% reduced central pore inward current and a -20 mV shift of the steady-state inactivation curve. Both changes may be at least partially explained by an outward omega (gating pore) current at positive potentials. Moreover, this outward omega current of 27.5 nS/nF may cause the reduction of the overshoot by 13 mV and slowing of the upstroke of action potentials by 36% that are associated with muscle hypoexcitability (permanent weakness and myopathic myopathy). In addition to the outward omega current, we identified an inward omega pore current of 95 nS/nF at negative membrane potentials after long depolarizing pulses that shifts the R1242G residue above the omega pore constriction. A simulation reveals that the inward current might depolarize the fibre sufficiently to trigger calcium release in the absence of an action potential and therefore cause an electrically silent depolarization-induced muscle contracture. Additionally, evidence of the inward current can be found in 23Na magnetic resonance imaging-detected sodium accumulation and 1H magnetic resonance imaging-detected oedema. We hypothesize that the episodes are normokalaemic because of depolarization-induced compensatory outward potassium flux through both delayed rectifiers and omega pore. We conclude that the position of the R1242G residue before elicitation of the omega current is decisive for its conductance: if the residue is located below the gating pore as in the resting state then outward currents are observed; if the residue is above the gating pore because of depolarization, as in the inactivated state, then inward currents are observed. This study shows for the first time that functional characterization of omega pore currents is possible using a cultured cell line expressing mutant Ca(v)1.1 channels. Likewise, it is the first calcium channel mutation for complicated normokalaemic periodic paralysis.

Dataset Information

Mutation in DHP receptor alpha 1 subunit (CACLN1A3) gene in a Dutch family with hypokalaemic periodic paralysis.

Publications

Mutation in DHP receptor alpha 1 subunit (CACLN1A3) gene in a Dutch family with hypokalaemic periodic paralysis.

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