These findings provide compelling evidence that MR-1 might be a diagnostic marker and therapeutic target for solid tumours, myelogenous leukaemia and PNKD.
Sequencing the whole coding region of PNKD/MR-1 gene identified a heterozygous c.20 C>T (p.Ala7Val) mutation which was clearly segregated in the five affected patients.
Taking into account that previous haplotype analyses did not reveal evidence for common founders among several PNKD families, our present findings strengthen three implications: (1) autosomal dominant PNKD seems to be a homogenous disorder, for which the MR-1 gene is the major disease gene; (2) mainly two recurrent MR-1 missense mutations (57% V7, 43% V9) account for the genetic variance of familial PNKD; (3) it supports current evidence that some of the recurrent MR-1 mutations may have arisen independently by de novo mutation at functionally convergent key sites of the brain-specific MR-1L isoform.
The function of MR1 is unknown, but the 2 mutations identified in the 4 families with PNKD studied to date are predicted to disrupt the amino terminal alpha-helix suggesting that this region of the gene is critical for proper gene function under stressful conditions.
Genetic data localized the underlying mutation to the FPD1 locus (familial paroxysmal dyskinesia type 1) on chromosome 2q and support locus homogeneity for the Mount-Reback syndrome.
Very few SLC2A1-mutated patients with a spastic paraplegia phenotype have been reported so far, and they are associated with paroxysmal choreo-athetosis (i.e., DYT9).
Clinical features were evaluated, and all subjects were screened for MR-1, SLC2A1, and CLCN1 genes, which are the causative genes of paroxysmal nonkinesigenic dyskinesia (PNKD), paroxysmal exertion-induced dyskinesia, and myotonia congenita (MC), respectively.
A large German/Dutch pedigree has formerly been described as paroxysmal choreoathetosis/spasticity (DYT9) and linked close to but not including the SLC2A1 locus on chromosome 1p.
Recently, the first genes have been identified for paroxysmal nonkinesigenic dyskinesia (MR1) and paroxysmal exercise-induced dyskinesia (PED) (SLC2A1).
Emerging evidence suggests the functional BK channel alterations produced by different <i>KCNMA1</i> alleles may associate with semi-distinct patient symptoms, such as paroxysmal nonkinesigenic dyskinesia (PNKD) with GOF and ataxia with LOF.