A novel KCNQ2 K526N missense mutation was identified in four family members with BFNC, which altered the voltage-dependence of activation of potassium channels in vitro.
Case Report (n=4)
The novel KCNQ2 K526N mutation alters M-channel function and may explain the phenotypic variability of neurologic symptoms in BFNC.
BACKGROUND: Benign familial neonatal convulsion (BFNC) is a rare autosomal dominant disorder caused by mutations in two genes, KCNQ2 and KCNQ3, encoding for potassium channel subunits underlying the M-current. This current limits neuronal hyperexcitability by causing spike-frequency adaptation. METHODS: The authors describe a BFNC family with four affected members: two of them exhibit BFNC only while the other two, in addition to BFNC, present either with a severe epileptic encephalopathy or with focal seizures and mental retardation. RESULTS: All affected members of this family carry a novel missense mutation in the KCNQ2 gene (K526N), disrupting the tri-dimensional conformation of a C-terminal region of the channel subunit involved in accessory protein binding. When heterologously expressed in CHO cells, potassium channels containing mutant subunits in homomeric or heteromeric configuration with wild-type KCNQ2 and KCNQ3 subunits exhibit an altered voltage-dependence of activation, without changes in intracellular trafficking and plasma membrane expression. CONCLUSION: The KCNQ2 K526N mutation may affect M-channel function by disrupting the complex biochemical signaling involving KCNQ2 C-terminus. Genetic rather than acquired factors may be involved in the pathophysiology of the phenotypic variability of the neurologic symptoms associated with BFNC in the described family.
Borgatti et al. (2004) conducted a case report in Benign familial neonatal convulsion (BFNC) (n=4). KCNQ2 K526N mutation was evaluated on Potassium channel function and clinical phenotype. A novel KCNQ2 K526N missense mutation was identified in four family members with BFNC, which altered the voltage-dependence of activation of potassium channels in vitro.