Papers by Sulayman Dib-hajj
Exon/intron boundaries in the regions encoding the trans-membrane segments of voltage-gated Na ch... more Exon/intron boundaries in the regions encoding the trans-membrane segments of voltage-gated Na channel genes are conserved, supporting their proposed evolution from a single domain channel, while the exons encoding the cytoplasmic loops are less conserved with their evolutionary heritage being less defined. (SCN11A) encodes the tetrodotoxin-resistant (TTX-R) sodium channel Nav 1.9a/NaN, which is preferentially expressed in nociceptive primary sensory neurons of dorsal root ganglia (DRG) and trigeminal ganglia. SCN11a is localized to human chromosome 3 (3p21–24) close to the other TTX-R sodium channel genes SCN5a and SCN10a. An alternative transcript, Nav1.9b, has been detected in rat DRG and trigeminal ganglion. Nav1.9b is predicted to produce a truncated protein due to a frame-shift, which is introduced by the new sequence of exon 23c (E23c). In human and mouse SCN11A, divergent splicing signals prevent utilization of E23c. Unlike exons 5A/N in genes encoding TTX-sensitive sodium channels, which appear to have resulted from exon duplication, E23c might have evolved from the conversion of an intronic sequence. Although a functional role for Nav1.9b has yet to be established, intron-to-exon conversion may represent a mechanism for ion channels to acquire novel features.
Molecular and cellular biology, 1992
Group II introns can be folded into highly conserved secondary structures with six major substruc... more Group II introns can be folded into highly conserved secondary structures with six major substructures or domains. Domains 1 and 5 are known to play key roles in self-splicing, while the roles of domains 2, 3, 4, and 6 are less clear. A trans assay for domain 5 function has been developed which indicates that domain 5 has a binding site on the precursor RNA that is not predicted from any secondary structure element. In this study, the self-splicing group II intron 5 gamma of the coxI gene of yeast mitochondrial DNA was deleted for various intron domains, singly and in combinations. Those mutant introns were characterized for self-splicing reactions in vitro as a means of locating the domain 5 binding site. A single deletion of domain 2, 3, 4, or 6 does not block in vitro reactions at either splice junction, though the deletion of domain 6 reduces the fidelity of 3' splice site selection somewhat. Even the triple deletion lacking domains 2, 4, and 6 retains some self-splicing act...
Domain 5 (D5) is a highly conserved, largely helical substructure of group II introns that is ess... more Domain 5 (D5) is a highly conserved, largely helical substructure of group II introns that is essential for self-splicing. Only three of the 14 base pairs present in most D5 structures (A2 U33, G3 U32, and C4 G31) are nearly invariant. We have studied effects of point mutations of those six nucleotides on self-splicing and in vivo splicing of aI5g,
Nucleic Acids Research, 1993
The role of domain 5 (d5) from the self-splicing group II Intron Sy of the COXI gene of yeast mit... more The role of domain 5 (d5) from the self-splicing group II Intron Sy of the COXI gene of yeast mitochondrlal DNA In branching and 3' splice site utilization has been studied using a substrate transcript lacking d5 (Ad5 RNA). This RNA Is completely unreactive In vitro, but releases 5' exon by hydrolysis under various reaction conditions when d5 RNA is added In trans. Under an extreme reaction condition, some accurate branching and splicing occur. Much more efficient use of a 3' splice site is obtained when Ad5 RNA is complemented by a transcript containing the wild-type domains 5 and 6 plus the 3' exon. While most Ad5 RNA molecules In that protocol still react by hydrolysis at the 5' splice site, the branching that occurs uses only the d6 tethered to d5 that Is provided in trans. The use of this d6 and the 3' splice site also linked to d5, along with the observed Indifference to the other d6 and 3' splice site resident in the Ad5 RNA, Indicates that d5 plays a key role in positioning d6 for the first reaction step as well as In 3' splice site use. Two models for the manner by which d5 interacts with d6 are discussed.
Chromosoma, 1983
The pattern of DNA sequence organization in the genome of Cycas revoluta was analyzed by DNA/DNA ... more The pattern of DNA sequence organization in the genome of Cycas revoluta was analyzed by DNA/DNA reassociation. Reassociation of 400 base pair (bp) fragments to various Cot values indicates the presence of at least four kinetic classes: the foldback plus very highly repetitive sequences (15%), the fast repeats (24%), the slow repeats (44%), and the single copy (17%). The latter component reassociates with a rate constant of I x 10 -4 M-1 s-1 corresponding to a complexity of 1.6 x 10 6 kb per haploid genome. A haploid C. revoluta nucleus contains approximately 10.3 pg DNA. The single-copy sequences account for about 28% of the DNA, but only 17% reassociate with single-copy kinetics because of interspersion with repetitive sequences. -The interspersion of repetitive and single-copy sequences was examined by reassociation of DNA fragments of varying length to Cot values of 70 and 500. A major (65%) and homogeneous class of single-copy sequences averaging 1,100 bp in length is interspersed in a short period pattern with repeated sequences. A minor (35%) heterogeneous single-copy component is interspersed in a long-period pattern. The majority of repetitive sequences have a length distribution of 100-350 bp with subclasses averaging 150 and 300 bp in length. Repeat sequences with a wide range in sizes exceeding 2 kilobase pair (kb) are also present in this genome. -The size and distribution of inverted repeat (ir) sequences in the DNA of C. revoluta were studied by electron microscopy. It is estimated that there are approximately 4 x 10 6 ir pairs (one per 2.33 kb) that form almost equal numbers of looped and unlooped palindromes. This high value is 2.5 times that found in wheat DNA. These palindromes are in general randomly distributed in the genome with an average interpalindrome distance of 1.6 kb. The majority (about 85%) of ir sequences of both types of palindromes belong to a main-size class, with an average length of 210 bp in the unlooped and and 163 bp in the looped type. These values are comparable to those reported for some other plant and animal genomes. Distribution of length of single stranded loops showed a main-size class (75%) with an average length of 220 bp.
Molecular pain, 2016
Nav1.8 sodium channels, encoded by SCN10A, are preferentially expressed in nociceptive neurons an... more Nav1.8 sodium channels, encoded by SCN10A, are preferentially expressed in nociceptive neurons and play an important role in human pain. Although rare gain-of-function variants in SCN10A have been identified in individuals with painful peripheral neuropathies, whether more common variants in SCN10A can have an effect at the channel level and at the dorsal root ganglion, neuronal level leading to a pain disorder or an altered normal pain threshold has not been determined. Candidate single nucleotide polymorphism association approach together with experimental pain testing in human subjects was used to explore possible common SCN10A missense variants that might affect human pain sensitivity. We demonstrated an association between rs6795970 (G > A; p.Ala1073Val) and higher thresholds for mechanical pain in a discovery cohort (496 subjects) and confirmed it in a larger replication cohort (1005 female subjects). Functional assessments showed that although the minor allele shifts chann...
Progress in Inflammation Research, 2005
... Joel A. Black, Bryan C. Hains, Sulayman D. Dib-Hajj and Stephen G. Waxman ... Nat Neurosci 1:... more ... Joel A. Black, Bryan C. Hains, Sulayman D. Dib-Hajj and Stephen G. Waxman ... Nat Neurosci 1: 653–655 53 Okuse K, Chaplan SR, McMahon SB, Luo ZD, Calcutt NA, Scott BP, Akopian AN, Wood JN (1997) Regulation of expression of the sensory neurons-specific sodium chan ...
Neuroscience Letters, 2010
Journal of neurology, neurosurgery, and psychiatry, Jan 8, 2016
Gain-of-function mutations in Nav1.9 have been identified in three families with rare heritable p... more Gain-of-function mutations in Nav1.9 have been identified in three families with rare heritable pain disorders, and in patients with painful small-fibre neuropathy. Identification and functional assessment of new Nav1.9 mutations will help to elucidate the phenotypic spectrum of Nav1.9 channelopathies. Patients from a large family with early-onset pain symptoms were evaluated by clinical examination and genomic screening for mutations in SCN9A and SCN11A. Electrophysiological recordings and multistate modelling analysis were implemented for functional analyses. A novel Nav1.9 mutation, p.Arg222His, was identified in patients with early-onset pain in distal extremities including joints and gastrointestinal disturbances, but was absent from an asymptomatic blood relative. This mutation alters channel structure by substituting the highly conserved first arginine residue in transmembrane segment 4 (domain 1), the voltage sensor, with histidine. Voltage-clamp recordings demonstrate a hyp...
JAMA neurology, Jan 18, 2016
There is a need for more effective pharmacotherapy for chronic pain, including pain in inherited ... more There is a need for more effective pharmacotherapy for chronic pain, including pain in inherited erythromelalgia (IEM) in which gain-of-function mutations of sodium channel NaV1.7 make dorsal root ganglion (DRG) neurons hyperexcitable. To determine whether pain in IEM can be attenuated via pharmacotherapy guided by genomic analysis and functional profiling. Pain in 2 patients with IEM due to the NaV1.7 S241T mutation, predicted by structural modeling and functional analysis to be responsive to carbamazepine, was assessed in a double-blind, placebo-controlled study conducted from September 2014 to April 21, 2015. Functional magnetic resonance imaging assessed patterns of brain activity associated with pain during treatment with placebo or carbamazepine. Multielectrode array technology was used to assess the effect of carbamazepine on firing of DRG neurons carrying S241T mutant channels. Behavioral assessment of pain; functional magnetic resonance imaging; and assessment of firing in ...
PloS one, 2016
Human genetic studies show that the voltage gated sodium channel 1.7 (Nav1.7) is a key molecular ... more Human genetic studies show that the voltage gated sodium channel 1.7 (Nav1.7) is a key molecular determinant of pain sensation. However, defining the Nav1.7 contribution to nociceptive signalling has been hampered by a lack of selective inhibitors. Here we report two potent and selective arylsulfonamide Nav1.7 inhibitors; PF-05198007 and PF-05089771, which we have used to directly interrogate Nav1.7's role in nociceptor physiology. We report that Nav1.7 is the predominant functional TTX-sensitive Nav in mouse and human nociceptors and contributes to the initiation and the upstroke phase of the nociceptor action potential. Moreover, we confirm a role for Nav1.7 in influencing synaptic transmission in the dorsal horn of the spinal cord as well as peripheral neuropeptide release in the skin. These findings demonstrate multiple contributions of Nav1.7 to nociceptor signalling and shed new light on the relative functional contribution of this channel to peripheral and central noxious...
Brain, 2016
Inherited erythromelalgia, the first human pain syndrome linked to voltage-gated sodium channels,... more Inherited erythromelalgia, the first human pain syndrome linked to voltage-gated sodium channels, is widely regarded as a genetic model of human pain. Because inherited erythromelalgia was linked to gain-of-function changes of sodium channel Nav1.7 only a decade ago, the literature has mainly consisted of reports of genetic and/or clinical characterization of individual patients. This paper describes the pattern of pain, natural history, somatosensory profile, psychosocial status and olfactory testing of 13 subjects with primary inherited erythromelalgia with mutations ofSCN9A, the gene encoding Nav1.7. Subjects were clinically profiled using questionnaires, quantitative sensory testing and olfaction testing during the in-clinic phase of the study. In addition, a detailed pain phenotype for each subject was obtained over a 3-month period at home using diaries, enabling subjects to self-report pain attacks, potential triggers, duration and severity of pain. All subjects reported pain and heat in the extremities (usually feet and/or hands), with pain attacks triggered by heat or exercise and relieved mainly by non-pharmacological manoeuvres such as cooling. A large proportion of pain attacks (355/1099; 32%) did not involve a specific trigger. There was considerable variability in the number, duration and severity of pain attacks between subjects, even those carrying the same mutation within a family, and within individuals over the 12-13 week observation period. Most subjects (11/13) had pain between attacks. For these subjects, mean pain severity between pain attacks was usually lower than that during an attack. Olfaction testing using the Sniffin'T test did not demonstrate hyperosmia. One subject had evidence of orthostatic hypotension. Overall, there was a statistically significant correlation between total Hospital Anxiety and Depression Scale scores (P= 0.005) and pain between attacks and for Hospital Anxiety and Depression Scale Depression scores and pain between attacks (P= 0.001). Hospital Anxiety and Depression Scale scores for five subjects were below the threshold for mild anxiety or depression and none of the 13 subjects were severely anxious and/or depressed. Quantitative sensory testing revealed significantly increased detection thresholds for cold and warm stimuli at affected, compared to unaffected sites. By contrast, significantly decreased cold and heat pain thresholds were found at unaffected sites. Sensory profiles varied considerably between affected and unaffected sites, suggesting the existence of small fibre neuropathy in symptomatic sites. This in-depth clinical characterization of a well-defined inherited erythromelalgia population indicates the importance of characterizing the pain phenotype in individuals before undertaking clinical trials, given the inherent variability of pain both between and within inherited erythromelalgia subjects, even those within a family who carry the same mutation.
Neurobiology of Disease, 2016
Mutations of the neuronal sodium channel gene SCN8A are associated with lethal movement disorders... more Mutations of the neuronal sodium channel gene SCN8A are associated with lethal movement disorders in the mouse and with human epileptic encephalopathy. We describe a spontaneous mouse mutation, Scn8a(9J), that is associated with a chronic movement disorder with early onset tremor and adult onset dystonia. Scn8a(9J) homozygotes have a shortened lifespan, with only 50% of mutants surviving beyond 6months of age. The 3bp in-frame deletion removes 1 of the 3 adjacent isoleucine residues in transmembrane segment DIVS6 of Nav1.6 (p.Ile1750del). The altered helical orientation of the transmembrane segment displaces pore-lining amino acids with important roles in channel activation and inactivation. The predicted impact on channel activity was confirmed by analysis of cerebellar Purkinje neurons from mutant mice, which lack spontaneous and induced repetitive firing. In a heterologous expression system, the activity of the mutant channel was below the threshold for detection. Observations of decreased nerve conduction velocity and impaired behavior in an open field are also consistent with reduced activity of Nav1.6. The Nav1.6Δ1750 protein is only partially glycosylated. The abundance of mutant Nav1.6 is reduced at nodes of Ranvier and is not detectable at the axon initial segment. Despite a severe reduction in channel activity, the lifespan and motor function of Scn8a(9J/9J) mice are significantly better than null mutants lacking channel protein. The clinical phenotype of this severe hypomorphic mutant expands the spectrum of Scn8a disease to include a recessively inherited, chronic and progressive movement disorder.
Nature reviews. Neuroscience, 2015
The voltage-gated sodium channel NaV1.9 is preferentially expressed in nociceptors and has been s... more The voltage-gated sodium channel NaV1.9 is preferentially expressed in nociceptors and has been shown in rodent models to have a major role in inflammatory and neuropathic pain. These studies suggest that by selectively targeting NaV1.9, it might be possible to ameliorate pain without inducing adverse CNS side effects such as sedation, confusion and addictive potential. Three recent studies in humans - two genetic and functional studies in rare genetic disorders, and a third study showing a role for NaV1.9 in painful peripheral neuropathy - have demonstrated that NaV1.9 plays an important part both in regulating sensory neuron excitability and in pain signalling. With this human validation, attention is turning to this channel as a potential therapeutic target for pain.
Drug Discovery Today: Disease Mechanisms, 2006
... increased from 1.24 ± 0.58 Hz for neurons transfected with wild-type channels, to 5.34 ± 1.21... more ... increased from 1.24 ± 0.58 Hz for neurons transfected with wild-type channels, to 5.34 ± 1.21 Hz for neurons transfected with the F1449V mutant channels ... Both of these effects are hallmarks of the hyperexcitablity that is seen in nociceptive neurons in neuropathic pain models. ...
Neuromolecular medicine, Jan 20, 2015
Painful small fiber neuropathy is a challenging medical condition with no effective treatment. No... more Painful small fiber neuropathy is a challenging medical condition with no effective treatment. Non-genetic causes can be identified in one half of the subjects. Gain-of-function variants of sodium channels Nav1.7 and Nav1.8 have recently been associated with painful small fiber neuropathy. More recently, mutations of sodium channel Nav1.9 have been linked to human pain disorders, with two gain-of-function mutations found in patients with painful small fiber neuropathy. Here we report a novel Nav1.9 mutation, a glycine 699 substitution by arginine (G699R) in the domain II S4-S5 linker, identified in a patient with painful small fiber neuropathy. In this study, we assayed the mutant channels by voltage-clamp in superior cervical ganglion neurons, which do not produce endogenous Nav1.8 or Nav1.9 currents, and provide a novel platform where Nav1.9 is expressed at relatively high levels. Voltage-clamp analysis showed that the mutation hyperpolarizes (-10.1 mV) channel activation, depolar...
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Papers by Sulayman Dib-hajj