Hisama FM

University of California, Irvine Medical Center

ORCID Profile OpenAlex Profile
3
EM Publications
40
h-index
(9,041 citations, 200 total works)

Research Topics

Genomics and Rare Diseases (49) Genetics and Neurodevelopmental Disorders (25) Genomic variations and chromosomal abnormalities (19) DNA Repair Mechanisms (18) Cancer Genomics and Diagnostics (17)

Erythromelalgia Publications

A case of inherited erythromelalgia.

Novella SP, Hisama FM, Dib-Hajj SD, Waxman SG
Nature clinical practice. Neurology •

A 15-year-old boy presented with recurrent episodes of erythema and burning pain in the distal extremities, which he had experienced since early childhood. The episodes were triggered by heat or exertion. His medical history revealed an extensive six-generation family history of similar symptoms. Neurological examination, MRI brain scan, electromyography, skin biopsy, laboratory blood testing, and DNA analysis. Juvenile onset primary erythromelalgia. Genetic counseling, and symptomatic management of neuropathic pain.

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Na(V)1.7 mutant A863P in erythromelalgia: effects of altered activation and steady-state inactivation on excitability of nociceptive dorsal root ganglion neurons.

Harty TP, Dib-Hajj SD, Tyrrell L, Blackman R, Hisama FM , et al.
The Journal of neuroscience : the official journal of the Society for Neuroscience •

Inherited erythromelalgia/erythermalgia (IEM) is a neuropathy characterized by pain and redness of the extremities that is triggered by warmth. IEM has been associated with missense mutations of the voltage-gated sodium channel Na(V)1.7, which is preferentially expressed in most nociceptive dorsal root ganglia (DRGs) and sympathetic ganglion neurons. Several mutations occur in cytoplasmic linkers of Na(V)1.7, with only two mutations in segment 4 (S4) and S6 of domain I. We report here a simplex case with an alanine 863 substitution by proline (A863P) in S5 of domain II of Na(V)1.7. The functional effect of A863P was investigated by voltage-clamp analysis in human embryonic kidney 293 cells and by current-clamp analysis to determine the effects of A863P on firing properties of small DRG neurons. Activation of mutant channels was shifted by -8 mV, whereas steady-state fast inactivation was shifted by +10 mV, compared with wild-type (WT) channels. There was a marked decrease in the rate of deactivation of mutant channels, and currents elicited by slow ramp depolarizations were 12 times larger than for WT. These results suggested that A863P could render DRG neurons hyperexcitable. We tested this hypothesis by studying properties of rat DRG neurons transfected with either A863P or WT channels. A863P depolarized resting potential of DRG neurons by +6 mV compared with WT channels, reduced the threshold for triggering single action potentials to 63% of that for WT channels, and increased firing frequency of neurons when stimulated with suprathreshold stimuli. Thus, A863P mutant channels produce hyperexcitability in DRG neurons, which contributes to the pathophysiology of IEM.

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Gain-of-function mutation in Nav1.7 in familial erythromelalgia induces bursting of sensory neurons.

Dib-Hajj SD, Rush AM, Cummins TR, Hisama FM, Novella S , et al.
Brain : a journal of neurology •

Erythromelalgia is an autosomal dominant disorder characterized by burning pain in response to warm stimuli or moderate exercise. We describe a novel mutation in a family with erythromelalgia in SCN9A, the gene that encodes the Na(v)1.7 sodium channel. Na(v)1.7 produces threshold currents and is selectively expressed within sensory neurons including nociceptors. We demonstrate that this mutation, which produces a hyperpolarizing shift in activation and a depolarizing shift in steady-state inactivation, lowers thresholds for single action potentials and high frequency firing in dorsal root ganglion neurons. Erythromelalgia is the first inherited pain disorder in which it is possible to link a mutation with an abnormality in ion channel function and with altered firing of pain signalling neurons.

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