Loss-of-function ENPP1 mutations cause both generalized arterial calcification of infancy and autosomal-recessive hypophosphatemic rickets

The analysis of rare genetic disorders affecting phosphate homeostasis led to the identification of several proteins that are essential for the renal regulation of phosphate homeostasis; for example, fibroblast growth factor 23 (FGF23), which inhibits renal phosphate reabsorption and 1,25-dihydroxyvitamin D synthesis. Here, we report presumable loss-of-function mutations in the ENPP1 gene (ectonucleotide pyrophosphatase/phosphodiesterase) in members of four families affected with hypophosphatemic rickets. We provide evidence for the conclusion that ENPP1 is the fourth gene-in addition to PHEX, FGF23, and DMP1-that, if mutated, causes hypophosphatemic rickets resulting from elevated FGF23 levels. Surprisingly, ENPP1 loss-of-function mutations have previously been described in generalized arterial calcification of infancy, suggesting an as yet elusive mechanism that balances arterial calcification with bone mineralization.

Whole genome sequencing of a single Bos taurus animal for single nucleotide polymorphism discovery

The next generation sequencing of a single cow genome with low-to-medium coverage has revealed 2.44 million new SNPs.

Background

The majority of the 2 million bovine single nucleotide polymorphisms (SNPs) currently available in dbSNP have been identified in a single breed, Hereford cattle, during the bovine genome project. In an attempt to evaluate the variance of a second breed, we have produced a whole genome sequence at low coverage of a single Fleckvieh bull.

Results

We generated 24 gigabases of sequence, mainly using 36-bp paired-end reads, resulting in an average 7.4-fold sequence depth. This coverage was sufficient to identify 2.44 million SNPs, 82% of which were previously unknown, and 115,000 small indels. A comparison with the genotypes of the same animal, generated on a 50 k oligonucleotide chip, revealed a detection rate of 74% and 30% for homozygous and heterozygous SNPs, respectively. The false positive rate, as determined by comparison with genotypes determined for 196 randomly selected SNPs, was approximately 1.1%. We further determined the allele frequencies of the 196 SNPs in 48 Fleckvieh and 48 Braunvieh bulls. 95% of the SNPs were polymorphic with an average minor allele frequency of 24.5% and with 83% of the SNPs having a minor allele frequency larger than 5%.

Conclusions

This work provides the first single cattle genome by next-generation sequencing. The chosen approach - low to medium coverage re-sequencing - added more than 2 million novel SNPs to the currently publicly available SNP resource, providing a valuable resource for the construction of high density oligonucleotide arrays in the context of genome-wide association studies.

Homozygosity mapping reveals PDE6C mutations in patients with early-onset cone photoreceptor disorders

Cone photoreceptor disorders form a clinical spectrum of diseases that include progressive cone dystrophy (CD) and complete and incomplete achromatopsia (ACHM). The underlying disease mechanisms of autosomal recessive (ar)CD are largely unknown. Our aim was to identify causative genes for these disorders by genome-wide homozygosity mapping. We investigated 75 ACHM, 97 arCD, and 20 early-onset arCD probands and excluded the involvement of known genes for ACHM and arCD. Subsequently, we performed high-resolution SNP analysis and identified large homozygous regions spanning the PDE6C gene in one sibling pair with early-onset arCD and one sibling pair with incomplete ACHM. The PDE6C gene encodes the cone alpha subunit of cyclic guanosine monophosphate (cGMP) phosphodiesterase, which converts cGMP to 5'-GMP, and thereby plays an essential role in cone phototransduction. Sequence analysis of the coding region of PDE6C revealed homozygous missense mutations (p.R29W, p.Y323N) in both sibling pairs. Sequence analysis of 104 probands with arCD and 10 probands with ACHM revealed compound heterozygous PDE6C mutations in three complete ACHM patients from two families. One patient had a frameshift mutation and a splice defect; the other two had a splice defect and a missense variant (p.M455V). Cross-sectional retinal imaging via optical coherence tomography revealed a more pronounced absence of cone photoreceptors in patients with ACHM compared to patients with early-onset arCD. Our findings identify PDE6C as a gene for cone photoreceptor disorders and show that arCD and ACHM constitute genetically and clinically overlapping phenotypes.

Loss of the metalloprotease ADAM9 leads to cone-rod dystrophy in humans and retinal degeneration in mice

Cone-rod dystrophy (CRD) is an inherited progressive retinal dystrophy affecting the function of cone and rod photoreceptors. By autozygosity mapping, we identified null mutations in the ADAM metallopeptidase domain 9 (ADAM9) gene in four consanguineous families with recessively inherited early-onset CRD. We also found reduced photoreceptor responses in Adam9 knockout mice, previously reported to be asymptomatic. In 12-month-old knockout mice, photoreceptors appear normal, but the apical processes of the retinal pigment epithelium (RPE) cells are disorganized and contact between photoreceptor outer segments (POSs) and the RPE apical surface is compromised. In 20-month-old mice, there is clear evidence of progressive retinal degeneration with disorganized POS and thinning of the outer nuclear layer (ONL) in addition to the anomaly at the POS-RPE junction. RPE basal deposits and macrophages were also apparent in older mice. These findings therefore not only identify ADAM9 as a CRD gene but also identify a form of pathology wherein retinal disease first manifests at the POS-RPE junction.

Clinical and molecular delineation of the 17q21.31 microdeletion syndrome

BACKGROUND

The chromosome 17q21.31 microdeletion syndrome is a novel genomic disorder that has originally been identified using high resolution genome analyses in patients with unexplained mental retardation.

AIM

We report the molecular and/or clinical characterisation of 22 individuals with the 17q21.31 microdeletion syndrome.

RESULTS

We estimate the prevalence of the syndrome to be 1 in 16,000 and show that it is highly underdiagnosed. Extensive clinical examination reveals that developmental delay, hypotonia, facial dysmorphisms including a long face, a tubular or pear-shaped nose and a bulbous nasal tip, and a friendly/amiable behaviour are the most characteristic features. Other clinically important features include epilepsy, heart defects and kidney/urologic anomalies. Using high resolution oligonucleotide arrays we narrow the 17q21.31 critical region to a 424 kb genomic segment (chr17: 41046729-41470954, hg17) encompassing at least six genes, among which is the gene encoding microtubule associated protein tau (MAPT). Mutation screening of MAPT in 122 individuals with a phenotype suggestive of 17q21.31 deletion carriers, but who do not carry the recurrent deletion, failed to identify any disease associated variants. In five deletion carriers we identify a <500 bp rearrangement hotspot at the proximal breakpoint contained within an L2 LINE motif and show that in every case examined the parent originating the deletion carries a common 900 kb 17q21.31 inversion polymorphism, indicating that this inversion is a necessary factor for deletion to occur (p<10(-5)).

CONCLUSION

Our data establish the 17q21.31 microdeletion syndrome as a clinically and molecularly well recognisable genomic disorder.

Identification of novel mutations in patients with Leber congenital amaurosis and juvenile RP by genome-wide homozygosity mapping with SNP microarrays

PURPOSE

Leber congenital amaurosis (LCA) and juvenile retinitis pigmentosa (RP) cause severe visual impairment early in life. Thus far, mutations in 13 genes have been associated with autosomal recessive LCA and juvenile RP. The purpose of this study was to use homozygosity mapping to identify mutations in known LCA and juvenile RP genes.

METHODS

The genomes of 93 consanguineous and nonconsanguineous patients with LCA and juvenile RP were analyzed for homozygous chromosomal regions by using SNP microarrays. This patient cohort was highly selected, as mutations in the known genes had been excluded with the LCA mutation chip, or a significant number of LCA genes had been excluded by comprehensive mutation analysis. Known LCA and juvenile RP genes residing in the identified homozygous regions were analyzed by sequencing. Detailed ophthalmic examinations were performed on the genotyped patients.

RESULTS

Ten homozygous mutations, including seven novel mutations, were identified in the CRB1, LRAT, RPE65, and TULP1 genes in 12 patients. Ten patients were from consanguineous marriages, but in two patients no consanguinity was reported. In 10 of the 12 patients, the causative mutation was present in the largest or second largest homozygous segment of the patient's genome.

CONCLUSIONS

Homozygosity mapping using SNP microarrays identified mutations in a significant proportion (30%) of consanguineous patients with LCA and juvenile RP and in a small number (3%) of nonconsanguineous patients. Significant homozygous regions which did not map to known LCA or juvenile RP genes and may be instrumental in identifying novel disease genes were detected in 33 patients.

Genomic deletion size at the epsilon-sarcoglycan locus determines the clinical phenotype

Myoclonus-dystonia (M-D, DYT11) is a dystonia plus syndrome characterized by brief myoclonic jerks predominantly of neck and upper limbs in combination with focal or segmental dystonia. It is caused by heterozygous mutations of the epsilon-sarcoglycan (SGCE) gene on chromosome 7q21.3. We present three patients with heterozygous large deletions in the 7q21.13-21.3 region. By quantitative analysis of single nucleotide polymorphism (SNP) oligonucleotide arrays, the deletion size was determined to range from 1.63 to 8.78 Mb. All deletions contained the maternally imprinted SGCE gene and up to 43 additional neighbouring genes. Two of the patients presented with typical M-D, whereas one paediatric patient with split-hand/split-foot malformation and sensorineural hearing loss (SHFM1D, OMIM 220600) had not developed M-D at the age of 9 years. This patient had the largest deletion of 8.78 Mb (7q21.13-21.3) containing also SHFM1, DLX6 and DLX5, which had been previously shown to be deleted in SHFM1D. In two patients, the deletions removed the paternal allele of the KRIT1 gene, which is a major cause of cavernous cerebral malformations type 1 (CCM1). Only the adult patient showed asymptomatic cavernous cerebral malformations on cranial MRI, underlining age-dependent penetrance and haploinsufficiency as pivotal features of patients with KRIT1 mutations. All three deletions contained the COL1A2 gene. In contrast to dominant negative point mutations, which cause osteogenesis imperfecta with bone fractures, haploinsufficiency of COL1A2 resulted only in subtle symptoms like recurrent joint subluxation or hypodontia. Assessing copy number variations by SNP arrays is an easy and reliable technique to delineate the size of human interstitial deletions. It will therefore become a standard technique to study patients, in whom heterozygous whole gene deletions are detected and information on neighbouring deleted genes is required for comprehensive genetic counselling and clinical management.

Copy-number variations measured by single-nucleotide-polymorphism oligonucleotide arrays in patients with mental retardation

Whole-genome analysis using high-density single-nucleotide-polymorphism oligonucleotide arrays allows identification of microdeletions, microduplications, and uniparental disomies. We studied 67 children with unexplained mental retardation with normal karyotypes, as assessed by G-banded chromosome analyses. Their DNAs were analyzed with Affymetrix 100K arrays. We detected 11 copy-number variations that most likely are causative of mental retardation, because they either arose de novo (9 cases) and/or overlapped with known microdeletions (2 cases). The eight deletions and three duplications varied in size from 200 kb to 7.5 Mb. Of the 11 copy-number variations, 5 were flanked by low-copy repeats. Two of those, on chromosomes 15q25.2 and Xp22.31, have not been described before and have a high probability of being causative of new deletion and duplication syndromes, respectively. In one patient, we found a deletion affecting only a single gene, MBD5, which codes for the methyl-CpG-binding domain protein 5. In addition to the 67 children, we investigated 4 mentally retarded children with apparent balanced translocations and detected four deletions at breakpoint regions ranging in size from 1.1 to 14 Mb.

Genomewide association analysis of coronary artery disease

BACKGROUND

Modern genotyping platforms permit a systematic search for inherited components of complex diseases. We performed a joint analysis of two genomewide association studies of coronary artery disease.

METHODS

We first identified chromosomal loci that were strongly associated with coronary artery disease in the Wellcome Trust Case Control Consortium (WTCCC) study (which involved 1926 case subjects with coronary artery disease and 2938 controls) and looked for replication in the German MI [Myocardial Infarction] Family Study (which involved 875 case subjects with myocardial infarction and 1644 controls). Data on other single-nucleotide polymorphisms (SNPs) that were significantly associated with coronary artery disease in either study (P<0.001) were then combined to identify additional loci with a high probability of true association. Genotyping in both studies was performed with the use of the GeneChip Human Mapping 500K Array Set (Affymetrix).

RESULTS

Of thousands of chromosomal loci studied, the same locus had the strongest association with coronary artery disease in both the WTCCC and the German studies: chromosome 9p21.3 (SNP, rs1333049) (P=1.80x10(-14) and P=3.40x10(-6), respectively). Overall, the WTCCC study revealed nine loci that were strongly associated with coronary artery disease (P<1.2x10(-5) and less than a 50% chance of being falsely positive). In addition to chromosome 9p21.3, two of these loci were successfully replicated (adjusted P<0.05) in the German study: chromosome 6q25.1 (rs6922269) and chromosome 2q36.3 (rs2943634). The combined analysis of the two studies identified four additional loci significantly associated with coronary artery disease (P<1.3x10(-6)) and a high probability (>80%) of a true association: chromosomes 1p13.3 (rs599839), 1q41 (rs17465637), 10q11.21 (rs501120), and 15q22.33 (rs17228212).

CONCLUSIONS

We identified several genetic loci that, individually and in aggregate, substantially affect the risk of development of coronary artery disease.

Novel compound heterozygous TULP1 mutations in a family with severe early-onset retinitis pigmentosa

OBJECTIVE

To describe the clinical characteristics and determine the genetic defect in a Surinamese family with autosomal recessive retinitis pigmentosa.

METHODS

Family members underwent blood sampling and ophthalmologic examinations. After exclusion of all known mutations in all genes involved in autosomal recessive retinitis pigmentosa, a genome-wide linkage scan was performed using 11,555 single-nucleotide polymorphisms spread throughout the genome. Mutation analysis of the TULP1 gene was performed by direct sequencing.

RESULTS

All affected family members had a severe retinal dystrophy with a history of nystagmus, low visual acuity, and nyctalopia since infancy. The scotopic and photopic responses were nonrecordable on electroretinography. A genome-wide scan suggested linkage to the chromosomal region containing the TULP1 gene. Mutation analysis of TULP1 identified novel compound heterozygous mutations (p.Arg482Trp and p.Leu504fsX140) in all affected family members.

CONCLUSIONS

The affected members of the Surinamese family have a severe early-onset form of autosomal recessive retinitis pigmentosa, which is caused by compound heterozygous mutations in the TULP1 gene. Clinical Relevance Clinical and molecular genetic characterization of autosomal recessive retinitis pigmentosa may help to provide a more accurate prognosis in individual patients. This study confirms that TULP1 mutations cause a severe early-onset form of autosomal recessive retinitis pigmentosa.

Involvement of DFNB59 mutations in autosomal recessive nonsyndromic hearing impairment

In a consanguineous Turkish family, a locus for autosomal recessive nonsyndromic hearing impairment (ARNSHI) was mapped to chromosome 2q31.1-2q33.1. Microsatellite marker analysis in the complete family determined the critical linkage interval that overlapped with DFNB27, for which the causative gene has not yet been identified, and DFNB59, a recently described auditory neuropathy caused by missense mutations in the DFNB59 gene. The 352-amino acid (aa) DFNB59 gene product pejvakin is present in hair cells, supporting cells, spiral ganglion cells, and the first three relays of the afferent auditory pathway. A novel homozygous nonsense mutation (c.499C>T; p.R167X) was detected in the DFNB59 gene, segregating with the deafness in the family. The mRNA derived from the mutant allele was found not to be degraded in lymphocytes, indicating that a truncated pejvakin protein of 166 aa may be present in the affected individuals. Screening of 67 index patients from additional consanguineous Turkish families with autosomal recessive hearing impairment revealed a homozygous missense mutation (c.547C>T; p.R183W) that segregates with the hearing impairment in one family. Furthermore, in a panel of 83 Dutch patients, two additional novel mutations (c.509_512delCACT; p.S170CfsX35 and c.731T>G; p.L244R), which were not present in ethnically matched controls, were found heterozygously. Together, our data indicate that also nonsense mutations in DFNB59 cause nonsyndromic hearing loss, but that mutations in DFNB59 are not a major cause of nonsyndromic hearing impairment in the Turkish and Dutch population.

Mutations in LCA5, encoding the ciliary protein lebercilin, cause Leber congenital amaurosis

Leber congenital amaurosis (LCA) causes blindness or severe visual impairment at or within a few months of birth. Here we show, using homozygosity mapping, that the LCA5 gene on chromosome 6q14, which encodes the previously unknown ciliary protein lebercilin, is associated with this disease. We detected homozygous nonsense and frameshift mutations in LCA5 in five families affected with LCA. In a sixth family, the LCA5 transcript was completely absent. LCA5 is expressed widely throughout development, although the phenotype in affected individuals is limited to the eye. Lebercilin localizes to the connecting cilia of photoreceptors and to the microtubules, centrioles and primary cilia of cultured mammalian cells. Using tandem affinity purification, we identified 24 proteins that link lebercilin to centrosomal and ciliary functions. Members of this interactome represent candidate genes for LCA and other ciliopathies. Our findings emphasize the emerging role of disrupted ciliary processes in the molecular pathogenesis of LCA.

Idiopathic generalized epilepsy phenotypes associated with different EFHC1 mutations

We sequenced 61 patients with various idiopathic generalized epilepsy (IGE) syndromes for mutations in the EFHC1 gene. We detected three novel heterozygous missense mutations (I174V, C259Y, A394S) and one possibly pathogenic variant in the 3' UTR (2014t>c). The mutation I174V was also detected in 1 of 372 screened patients with temporal lobe epilepsy. We conclude that mutations in the EFHC1 gene may underlie different types of epilepsy syndromes.

A novelLRRK2 mutation in an Austrian cohort of patients with Parkinson's disease

To investigate the frequency of mutations in the Leucine-Rich Repeat Kinase 2 gene (LRRK2) in a sample of Austrian Parkinson's disease (PD) patients, we sequenced the complete coding region in 16 patients with autosomal dominant PD. Furthermore, we sequenced exons 31, 35, and 41 additionally in 146 patients with idiopathic PD and 30 patients with dementia with Lewy bodies. Furthermore, all 192 patients were screened for 21 putative LRRK2 mutations. While the most common mutation G2019S and the risk variant G2385R were not found in our samples, we detected a novel missense mutation (S973N) in a patient with familial, late-onset and dopa-responsive PD.

DMP1 mutations in autosomal recessive hypophosphatemia implicate a bone matrix protein in the regulation of phosphate homeostasis

Hypophosphatemia is a genetically heterogeneous disease. Here, we mapped an autosomal recessive form (designated ARHP) to chromosome 4q21 and identified homozygous mutations in DMP1 (dentin matrix protein 1), which encodes a non-collagenous bone matrix protein expressed in osteoblasts and osteocytes. Intact plasma levels of the phosphaturic protein FGF23 were clearly elevated in two of four affected individuals, providing a possible explanation for the phosphaturia and inappropriately normal 1,25(OH)2D levels and suggesting that DMP1 may regulate FGF23 expression.

Mutations in the CEP290 (NPHP6) gene are a frequent cause of Leber congenital amaurosis

Leber congenital amaurosis (LCA) is one of the main causes of childhood blindness. To date, mutations in eight genes have been described, which together account for approximately 45% of LCA cases. We localized the genetic defect in a consanguineous LCA-affected family from Quebec and identified a splice defect in a gene encoding a centrosomal protein (CEP290). The defect is caused by an intronic mutation (c.2991+1655A-->G) that creates a strong splice-donor site and inserts a cryptic exon in the CEP290 messenger RNA. This mutation was detected in 16 (21%) of 76 unrelated patients with LCA, either homozygously or in combination with a second deleterious mutation on the other allele. CEP290 mutations therefore represent one of the most frequent causes of LCA identified so far.

Mutations in the CLCN2 gene are a rare cause of idiopathic generalized epilepsy syndromes

Mutations in the chloride channel gene CLCN2 have been reported in families with generalized and focal epilepsy syndromes. To evaluate the contribution of mutations in the CLCN2 gene to the etiology of epilepsies in our population, we screened 96 patients with different epilepsy syndromes and a putative genetic background. No definite mutations were found in our study population. We conclude that mutations in the CLCN2 gene are only a rare cause of idiopathic generalized epilepsy.

Mutations in the lipoma HMGIC fusion partner-like 5 (LHFPL5) gene cause autosomal recessive nonsyndromic hearing loss

In two large Turkish consanguineous families, a locus for autosomal recessive nonsyndromic hearing loss (ARNSHL) was mapped to chromosome 6p21.3 by genome-wide linkage analysis in an interval overlapping with the loci DFNB53 (COL11A2), DFNB66, and DFNB67. Fine mapping excluded DFNB53 and subsequently homozygous mutations were identified in the lipoma HMGIC fusion partner-like 5 (LHFPL5) gene, also named tetraspan membrane protein of hair cell stereocilia (TMHS) gene, which was recently shown to be mutated in the "hurry scurry" mouse and in two DFNB67-linked families from Pakistan. In one family, we found a homozygous one-base pair deletion, c.649delG (p.Glu216ArgfsX26) and in the other family we identified a homozygous transition c.494C>T (p.Thr165Met). Further screening of index patients from 96 Turkish ARNSHL families and 90 Dutch ARNSHL patients identified one additional Turkish family carrying the c.649delG mutation. Haplotype analysis revealed that the c.649delG mutation was located on a common haplotype in both families. Mutation screening of the LHFPL5 homologs LHFPL3 and LHFPL4 did not reveal any disease causing mutation. Our findings indicate that LHFPL5 is essential for normal function of the human cochlea.

Polypeptide GalNAc-transferase T3 and familial tumoral calcinosis. Secretion of fibroblast growth factor 23 requires O-glycosylation

Mutations in the gene encoding the glycosyltransferase polypeptide GalNAc-T3, which is involved in initiation of O-glycosylation, were recently identified as a cause of the rare autosomal recessive metabolic disorder familial tumoral calcinosis (OMIM 211900). Familial tumoral calcinosis is associated with hyperphosphatemia and massive ectopic calcifications. Here, we demonstrate that the secretion of the phosphaturic factor fibroblast growth factor 23 (FGF23) requires O-glycosylation, and that GalNAc-T3 selectively directs O-glycosylation in a subtilisin-like proprotein convertase recognition sequence motif, which blocks processing of FGF23. The study suggests a novel posttranslational regulatory model of FGF23 involving competing O-glycosylation and protease processing to produce intact FGF23.

Hereditary hypophosphatemic rickets with hypercalciuria is caused by mutations in the sodium-phosphate cotransporter gene SLC34A3

Hypophosphatemia due to isolated renal phosphate wasting results from a heterogeneous group of disorders. Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is an autosomal recessive form that is characterized by reduced renal phosphate reabsorption, hypophosphatemia, and rickets. It can be distinguished from other forms of hypophosphatemia by increased serum levels of 1,25-dihydroxyvitamin D resulting in hypercalciuria. Using SNP array genotyping, we mapped the disease locus in two consanguineous families to the end of the long arm of chromosome 9. The candidate region contained a sodium-phosphate cotransporter gene, SLC34A3, which has been shown to be expressed in proximal tubulus cells. Sequencing of this gene revealed disease-associated mutations in five families, including two frameshift and one splice-site mutation. Loss of function of the SLC34A3 protein presumably results in a primary renal tubular defect and is compatible with the HHRH phenotype. We also show that the phosphaturic factor FGF23 (fibroblast growth factor 23), which is increased in X-linked hypophosphatemic rickets and carries activating mutations in autosomal dominant hypophosphatemic rickets, is at normal or low-normal serum levels in the patients with HHRH, further supporting a primary renal defect. Identification of the gene mutated in a further form of hypophosphatemia adds to the understanding of phosphate homeostasis and may help to elucidate the interaction of the proteins involved in this pathway.

Mutation in the neuronal voltage-gated sodium channel SCN1A in familial hemiplegic migraine

BACKGROUND

Familial hemiplegic migraine is an autosomal dominant severe subtype of migraine with aura characterised by some degree of hemiparesis during the attacks. So far, mutations in two genes regulating ion translocation-CACNA1A and ATP1A2-have been identified in pedigrees with this disease.

METHODS

To identify additional genes for familial hemiplegic migraine, we did a genome-wide linkage analysis of two disease pedigrees without mutations in CACNA1A and ATP1A2. Ion channel genes in the candidate interval were analysed for mutations, and the functional consequences of the recorded sequence alteration were determined.

FINDINGS

We identified a novel locus for familial hemiplegic migraine on chromosome 2q24. Sequencing of candidate genes in this region revealed a heterozygous missense mutation (Gln1489Lys) in the neuronal voltage-gated sodium channel gene SCN1A, mutations of which have been associated with epilepsy. This same mutation was present in three families with familial hemiplegic migraine. It results in a charge-altering aminoacid exchange in the so-called hinged-lid domain of the protein, which is critical for fast inactivation of the channel. Whole-cell recordings in transiently transfected tsA201 cells expressing the highly homologous SCN5A sodium channel showed that the mutation induces a two-fold to four-fold accelerated recovery from fast inactivation without altering any of the other channel parameters investigated.

INTERPRETATION

Dysfunction of the neuronal sodium channel SCN1A can cause familial hemiplegic migraine. Our findings have implications for the understanding of migraine aura. Moreover, our study reinforces the molecular links between migraine and epilepsy, two common paroxysmal disorders.