Genotype-phenotype associations in SCN1A-related epilepsies

Zuberi, S., Brunklaus, A., Birch, R., Reavey, E., Duncan, J. and Forbes, G.H. (2011) Genotype-phenotype associations in SCN1A-related epilepsies. Neurology, 76(7), pp. 594-600. (doi: 10.1212/WNL.0b013e31820c309b)

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Publisher's URL: http://dx.doi.org/10.1212/WNL.0b013e31820c309b

Abstract

Objective: Most mutations in SCN1A-related epilepsies are novel and when an infant presents with febrile seizures (FS) it is uncertain if they will have simple FS, FS+, or develop a severe epilepsy such as Dravet syndrome. Our objective was to examine whether the nature of a SCN1A mutation affects the epilepsy phenotype.

Methods: We retrospectively evaluated clinical and genetic data from 273 individuals with SCN1A mutations identified in our laboratory and reviewed data from 546 published cases. We examined whether the mutation class or distribution or nature of amino acid substitution correlated with the epilepsy phenotype, using the Grantham Score (GS) as a measure of physicochemical difference between amino acids.

Results: Compared to missense mutations, truncating mutations were associated with earlier mean onset of prolonged seizures (7.4 vs 8.8 months; p = 0.040), myoclonic seizures (16.4 vs 19.4 months; p = 0.041), and atypical absence seizures (19.1 vs 30.6 months; p = 0.001). The median GS was higher in patients with Dravet syndrome compared to polymorphisms (94 vs 58; p = 0.029) and orthologs (94 vs 45; p < 0.001). A high GS was correlated with early onset of seizures (rs = −0.235; p = 0.008). Missense mutations occurred most frequently in the voltage and ion-pore regions where changes in amino acid polarity were greater in the Dravet group compared to the genetic epilepsy with febrile seizures plus group (3.6 vs 2.7; p = 0.031).

Conclusions: These findings help define the clinical significance of specific SCN1A mutations based on mutation class and amino acid property and location.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Zuberi, Dr Sameer
Authors: Zuberi, S., Brunklaus, A., Birch, R., Reavey, E., Duncan, J., and Forbes, G.H.
College/School:College of Medical Veterinary and Life Sciences
Journal Name:Neurology
Publisher:Lippincott Williams & Wilkins
ISSN:0028-3878
ISSN (Online):1526-632X
Published Online:19 January 2011

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