James J Cox

King's College London, Londinium, England, United Kingdom

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Publications (17)277.65 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Human studies have firmly implicated voltage-gated sodium channels in human pain disorders, and targeted and massively parallel genomic sequencing is beginning to be used in clinical practice to determine which sodium channel variants are involved. Missense substitutions of SCN9A, the gene encoding sodium channel NaV1.7, SCN10A, the gene encoding sodium channel NaV1.8, and SCN11A, the gene encoding sodium channel NaV1.9, produce gain-of-function changes that contribute to pain in many human painful disorders. Genomic sequencing might help to establish a diagnosis, and in the future might support individualisation of therapeutic approaches. However, in many cases, and especially in sodium channelopathies, the results from genomic sequencing can only be appropriately interpreted in the context of an extensive functional assessment, or family segregation analysis of phenotype and genotype.
    11/2014; 13(11):1152–1160.
  • Neurology 09/2014; · 8.25 Impact Factor
  • James J Cox, John N Wood
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    ABSTRACT: A new study shows that a specific mutation in SCN11A, which encodes the Nav1.9 voltage-gated sodium channel, underlies a human disorder characterized by insensitivity to pain. This finding provides fresh insights into human pain perception and suggests a new avenue for the development of analgesic drugs.
    Nature Genetics 11/2013; 45(11):1271-2. · 35.21 Impact Factor
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    ABSTRACT: We identified and clinically investigated two patients with primary erythromelalgia mutations (PEM), which are the first reported to map to the fourth domain of Nav1.7 (DIV). The identified mutations (A1746G and W1538R) were cloned and transfected to cell cultures followed by electrophysiological analysis in whole-cell configuration. The investigated patients presented with PEM, while age of onset was very different (3 vs. 61 years of age). Electrophysiological characterization revealed that the early onset A1746G mutation leads to a marked hyperpolarizing shift in voltage dependence of steady-state activation, larger window currents, faster activation kinetics (time-to-peak current) and recovery from steady-state inactivation compared to wild-type Nav1.7, indicating a pronounced gain-of-function. Furthermore, we found a hyperpolarizing shift in voltage dependence of slow inactivation, which is another feature commonly found in Nav1.7 mutations associated with PEM. In silico neuron simulation revealed reduced firing thresholds and increased repetitive firing, both indicating hyperexcitability. The late-onset W1538R mutation also revealed gain-of-function properties, although to a lesser extent. Our findings demonstrate that mutations encoding for DIV of Nav1.7 can not only be linked to congenital insensitivity to pain or paroxysmal extreme pain disorder but can also be causative of PEM, if voltage dependency of channel activation is affected. This supports the view that the degree of biophysical property changes caused by a mutation may have an impact on age of clinical manifestation of PEM. In summary, these findings extent the genotype-phenotype correlation profile for SCN9A and highlight a new region of Nav1.7 that is implicated in PEM.
    Neuromolecular medicine 01/2013; · 5.00 Impact Factor
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    ABSTRACT: Transient receptor potential (TRP) channels TRPC3 and TRPC6 are expressed in both sensory neurons and cochlear hair cells. Deletion of TRPC3 or TRPC6 in mice caused no behavioural phenotype, although loss of TRPC3 caused a shift of rapidly adapting (RA) mechanosensitive currents to intermediate-adapting currents in dorsal root ganglion sensory neurons. Deletion of both TRPC3 and TRPC6 caused deficits in light touch and silenced half of small-diameter sensory neurons expressing mechanically activated RA currents. Double TRPC3/TRPC6 knock-out mice also showed hearing impairment, vestibular deficits and defective auditory brain stem responses to high-frequency sounds. Basal, but not apical, cochlear outer hair cells lost more than 75 per cent of their responses to mechanical stimulation. FM1-43-sensitive mechanically gated currents were induced when TRPC3 and TRPC6 were co-expressed in sensory neuron cell lines. TRPC3 and TRPC6 are thus required for the normal function of cells involved in touch and hearing, and are potential components of mechanotransducing complexes.
    Open Biology 05/2012; 2(5):120068. · 3.27 Impact Factor
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    ABSTRACT: Genes encoding the α subunits of neuronal sodium channels have evolutionarily conserved sites of alternative splicing but no functional differences have been attributed to the splice variants. Here, using Na(V)1.7 as an exemplar, we show that the sodium channel isoforms are functionally distinct when co-expressed with β subunits. The gene, SCN9A, encodes the α subunit of the Na(V)1.7 channel, and contains both sites of alternative splicing that are highly conserved. In conditions where the intrinsic properties of the Na(V)1.7 splice variants were similar when expressed alone, co-expression of β1 subunits had different effects on channel availability that were determined by splicing at either site in the α subunit. While the identity of exon 5 determined the degree to which β1 subunits altered voltage-dependence of activation (P = 0.027), the length of exon 11 regulated how far β1 subunits depolarised voltage-dependence of inactivation (P = 0.00012). The results could have a significant impact on channel availability, for example with the long version of exon 11, the co-expression of β1 subunits could lead to nearly twice as large an increase in channel availability compared to channels containing the short version. Our data suggest that splicing can change the way that Na(V) channels interact with β subunits. Because splicing is conserved, its unexpected role in regulating the functional impact of β subunits may apply to multiple voltage-gated sodium channels, and the full repertoire of β subunit function may depend on splicing in α subunits.
    PLoS ONE 01/2012; 7(7):e41750. · 3.53 Impact Factor
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    ABSTRACT: We investigated three families whose offspring had extreme microcephaly at birth and profound mental retardation. Brain scans and postmortem data showed that affected individuals had brains less than 10% of expected size (≤10 standard deviation) and that in addition to a massive reduction in neuron production they displayed partially deficient cortical lamination (microlissencephaly). Other body systems were apparently unaffected and overall growth was normal. We found two distinct homozygous mutations of NDE1, c.83+1G>T (p.Ala29GlnfsX114) in a Turkish family and c.684_685del (p.Pro229TrpfsX85) in two families of Pakistani origin. Using patient cells, we found that c.83+1G>T led to the use of a novel splice site and to a frameshift after NDE1 exon 2. Transfection of tagged NDE1 constructs showed that the c.684_685del mutation resulted in a NDE1 that was unable to localize to the centrosome. By staining a patient-derived cell line that carried the c.83+1G>T mutation, we found that this endogeneously expressed mutated protein equally failed to localize to the centrosome. By examining human and mouse embryonic brains, we determined that NDE1 is highly expressed in neuroepithelial cells of the developing cerebral cortex, particularly at the centrosome. We show that NDE1 accumulates on the mitotic spindle of apical neural precursors in early neurogenesis. Thus, NDE1 deficiency causes both a severe failure of neurogenesis and a deficiency in cortical lamination. Our data further highlight the importance of the centrosome in multiple aspects of neurodevelopment.
    The American Journal of Human Genetics 05/2011; 88(5):523-35. · 11.20 Impact Factor
  • New England Journal of Medicine 01/2011; 364(1):91-3. · 54.42 Impact Factor
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    ABSTRACT: Autosomal recessive primary microcephaly (MCPH) is a disorder of neurodevelopment resulting in a small brain. We identified WDR62 as the second most common cause of MCPH after finding homozygous missense and frame-shifting mutations in seven MCPH families. In human cell lines, we found that WDR62 is a spindle pole protein, as are ASPM and STIL, the MCPH7 and MCHP7 proteins. Mutant WDR62 proteins failed to localize to the mitotic spindle pole. In human and mouse embryonic brain, we found that WDR62 expression was restricted to neural precursors undergoing mitosis. These data lend support to the hypothesis that the exquisite control of the cleavage furrow orientation in mammalian neural precursor cell mitosis, controlled in great part by the centrosomes and spindle poles, is critical both in causing MCPH when perturbed and, when modulated, generating the evolutionarily enlarged human brain.
    Nature Genetics 10/2010; 42(11):1010-4. · 35.21 Impact Factor
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    ABSTRACT: Nerve growth factor β (NGFβ) and tyrosine kinase receptor type A (TRKA) are a well studied neurotrophin/receptor duo involved in neuronal survival and differentiation. The only previously reported hereditary sensory neuropathy caused by an NGF mutation, c.661C>T (HSAN5), and the pathology caused by biallelic mutations in the TRKA gene (NTRK1) (HSAN4), share only some clinical features. A consanguineous Arab family, where five of the six children were completely unable to perceive pain, were mentally retarded, did not sweat, could not discriminate temperature, and had a chronic immunodeficiency, is reported here. The condition is linked to a new homozygous mutation in the NGF gene, c.[680C>A]+[681_682delGG]. Genetic linkage and standard sequencing techniques were used to identify the causative gene. Using wild-type or mutant over-expression constructs transfected into PC12 and COS-7 cells, the cellular and molecular consequences of the mutations were investigated. The mutant gene produced a precursor protein V232fs that was unable to differentiate PC12 cells. V232fs was not secreted from cells as mature NGFβ. Both the clinical and cellular data suggest that the c.[680C>A]+[681_682delGG] NGF mutation is a functional null. The HSAN5 phenotype is extended to encompass HSAN4-like characteristics. It is concluded that the HSAN4 and HSAN5 phenotypes are parts of a phenotypic spectrum caused by changes in the NGF/TRKA signalling pathway.
    Journal of Medical Genetics 10/2010; 48(2):131-5. · 5.70 Impact Factor
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    ABSTRACT: SCN9Aencodes the voltage-gated sodium channel Na(v)1.7, a protein highly expressed in pain-sensing neurons. Mutations in SCN9A cause three human pain disorders: bi-allelic loss of function mutations result in Channelopathy-associated Insensitivity to Pain (CIP), whereas activating mutations cause severe episodic pain in Paroxysmal Extreme Pain Disorder (PEPD) and Primary Erythermalgia (PE). To date, all mutations in SCN9A that cause a complete inability to experience pain are protein truncating and presumably lead to no protein being produced. Here, we describe the identification and functional characterization of two novel non-truncating mutations in families with CIP: a homozygously-inherited missense mutation found in a consanguineous Israeli Bedouin family (Na(v)1.7-R896Q) and a five amino acid in-frame deletion found in a sporadic compound heterozygote (Na(v)1.7-DeltaR1370-L1374). Both of these mutations map to the pore region of the Na(v)1.7 sodium channel. Using transient transfection of PC12 cells we found a significant reduction in membrane localization of the mutant protein compared to the wild type. Furthermore, voltage clamp experiments of mutant-transfected HEK293 cells show a complete loss of function of the sodium channel, consistent with the absence of pain phenotype. In summary, this study has identified critical amino acids needed for the normal subcellular localization and function of Na(v)1.7.
    Human Mutation 09/2010; 31(9):E1670-86. · 5.21 Impact Factor
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    ABSTRACT: Human monogenic pain syndromes have provided important insights into the molecular mechanisms that underlie normal and pathological pain states. We describe an autosomal-dominant familial episodic pain syndrome characterized by episodes of debilitating upper body pain, triggered by fasting and physical stress. Linkage and haplotype analysis mapped this phenotype to a 25 cM region on chromosome 8q12-8q13. Candidate gene sequencing identified a point mutation (N855S) in the S4 transmembrane segment of TRPA1, a key sensor for environmental irritants. The mutant channel showed a normal pharmacological profile but altered biophysical properties, with a 5-fold increase in inward current on activation at normal resting potentials. Quantitative sensory testing demonstrated normal baseline sensory thresholds but an enhanced secondary hyperalgesia to punctate stimuli on treatment with mustard oil. TRPA1 antagonists inhibit the mutant channel, promising a useful therapy for this disorder. Our findings provide evidence that variation in the TRPA1 gene can alter pain perception in humans.
    Neuron 06/2010; 66(5):671-80. · 15.77 Impact Factor
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    ABSTRACT: Dominant gain-of-function mutations that hyperpolarize activation of the Na(v)1.7 sodium channel have been linked to inherited erythromelalgia (IEM), a disorder characterized by severe pain and redness in the feet and hands in response to mild warmth. Pharmacotherapy remains largely ineffective for IEM patients with cooling and avoidance of triggers being the most reliable methods to relieve pain. We now report a 5 year old patient with pain precipitated by warmth, together with redness in her hands and feet. Her pain episodes were first reported at 12 months, and by the age of 15-16 months were triggered by sitting as well as heat. Pain has been severe, inducing self-mutilation, with limited relief from drug treatment. Our analysis of the patient's genomic DNA identified a novel Na(v)1.7 mutation which replaces isoleucine 234 by threonine (I234T) within domain I/S4-S5 linker. Whole-cell voltage-clamp analysis shows a I234T-induced shift of -18 mV in the voltage-dependence of activation, accelerated time-to-peak, slowed deactivation and enhanced responses to slow ramp depolarizations, together with a -21 mV shift in the voltage-dependence of slow-inactivation. Our data show that I234T induces the largest activation shift for Na(v)1.7 mutations reported thus far. Although enhanced slow-inactivation may attenuate the gain-of-function of the I234T mutation, the shift in activation appears to be dominant, and is consistent with the severe pain symptoms reported in this patient.
    European journal of pain (London, England) 04/2010; 14(9):944-50. · 3.37 Impact Factor
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    ABSTRACT: The gene SCN9A is responsible for three human pain disorders. Nonsense mutations cause a complete absence of pain, whereas activating mutations cause severe episodic pain in paroxysmal extreme pain disorder and primary erythermalgia. This led us to investigate whether single nucleotide polymorphisms (SNPs) in SCN9A were associated with differing pain perception in the general population. We first genotyped 27 SCN9A SNPs in 578 individuals with a radiographic diagnosis of osteoarthritis and a pain score assessment. A significant association was found between pain score and SNP rs6746030; the rarer A allele was associated with increased pain scores compared to the commoner G allele (P = 0.016). This SNP was then further genotyped in 195 pain-assessed people with sciatica, 100 amputees with phantom pain, 179 individuals after lumbar discectomy, and 205 individuals with pancreatitis. The combined P value for increased A allele pain was 0.0001 in the five cohorts tested (1277 people in total). The two alleles of the SNP rs6746030 alter the coding sequence of the sodium channel Nav1.7. Each was separately transfected into HEK293 cells and electrophysiologically assessed by patch-clamping. The two alleles showed a difference in the voltage-dependent slow inactivation (P = 0.042) where the A allele would be predicted to increase Nav1.7 activity. Finally, we genotyped 186 healthy females characterized by their responses to a diverse set of noxious stimuli. The A allele of rs6746030 was associated with an altered pain threshold and the effect mediated through C-fiber activation. We conclude that individuals experience differing amounts of pain, per nociceptive stimulus, on the basis of their SCN9A rs6746030 genotype.
    Proceedings of the National Academy of Sciences 03/2010; 107(11):5148-53. · 9.81 Impact Factor
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    ABSTRACT: The primary cilium is an antenna-like structure that protrudes from the cell surface of quiescent/differentiated cells and participates in extracellular signal processing. Here, we report that mice deficient for the lipid 5-phosphatase Inpp5e develop a multiorgan disorder associated with structural defects of the primary cilium. In ciliated mouse embryonic fibroblasts, Inpp5e is concentrated in the axoneme of the primary cilium. Inpp5e inactivation did not impair ciliary assembly but altered the stability of pre-established cilia after serum addition. Blocking phosphoinositide 3-kinase (PI3K) activity or ciliary platelet-derived growth factor receptor alpha (PDGFRalpha) restored ciliary stability. In human INPP5E, we identified a mutation affecting INPP5E ciliary localization and cilium stability in a family with MORM syndrome, a condition related to Bardet-Biedl syndrome. Together, our results show that INPP5E plays an essential role in the primary cilium by controlling ciliary growth factor and PI3K signaling and stability, and highlight the consequences of INPP5E dysfunction.
    Nature Genetics 09/2009; 41(9):1027-31. · 35.21 Impact Factor
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    ABSTRACT: The neurotrophin brain-derived neurotrophic factor (BDNF) inhibits food intake, and rodent models of BDNF disruption all exhibit increased food intake and obesity, as well as hyperactivity. We report an 8-year-old girl with hyperphagia and severe obesity, impaired cognitive function, and hyperactivity who harbored a de novo chromosomal inversion, 46,XX,inv(11)(p13p15.3), a region encompassing the BDNF gene. We have identified the proximal inversion breakpoint that lies 850 kb telomeric of the 5' end of the BDNF gene. The patient's genomic DNA was heterozygous for a common coding polymorphism in BDNF, but monoallelic expression was seen in peripheral lymphocytes. Serum concentration of BDNF protein was reduced compared with age- and BMI-matched subjects. Haploinsufficiency for BDNF was associated with increased ad libitum food intake, severe early-onset obesity, hyperactivity, and cognitive impairment. These findings provide direct evidence for the role of the neurotrophin BDNF in human energy homeostasis, as well as in cognitive function, memory, and behavior.
    Diabetes 01/2007; 55(12):3366-71. · 7.90 Impact Factor
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    ABSTRACT: The complete inability to sense pain in an otherwise healthy individual is a very rare phenotype. In three consanguineous families from northern Pakistan, we mapped the condition as an autosomal-recessive trait to chromosome 2q24.3. This region contains the gene SCN9A, encoding the alpha-subunit of the voltage-gated sodium channel, Na(v)1.7, which is strongly expressed in nociceptive neurons. Sequence analysis of SCN9A in affected individuals revealed three distinct homozygous nonsense mutations (S459X, I767X and W897X). We show that these mutations cause loss of function of Na(v)1.7 by co-expression of wild-type or mutant human Na(v)1.7 with sodium channel beta(1) and beta(2) subunits in HEK293 cells. In cells expressing mutant Na(v)1.7, the currents were no greater than background. Our data suggest that SCN9A is an essential and non-redundant requirement for nociception in humans. These findings should stimulate the search for novel analgesics that selectively target this sodium channel subunit.
    Nature 01/2007; 444(7121):894-8. · 38.60 Impact Factor

Publication Stats

979 Citations
277.65 Total Impact Points

Institutions

  • 2014
    • King's College London
      Londinium, England, United Kingdom
  • 2011
    • Yale-New Haven Hospital
      New Haven, Connecticut, United States
  • 2010
    • University of Cambridge
      • Department of Medical Genetics
      Cambridge, ENG, United Kingdom
  • 2007–2010
    • Cambridge Institute for Medical Research
      Cambridge, England, United Kingdom