Infantile seizures and other epileptic phenotypes in a Chinese family with a missense mutation of KCNQ2.
BACKGROUND
Benign familial infantile seizures (BFIS) is a form of idiopathic epilepsy characterized by clusters of afebrile seizures occurring around the sixth month of life and a favorable outcome. Linkage analysis has revealed that three chromosomal segments, 19q12-q13.1, 16p12-q12, and 2q23-31, are linked to this disorder.


METHODS
We report here a large Chinese family in which all 17 affected members had had infantile seizures with onset at age 2-4 months, with two of these also manifesting seizures later in life accompanied with either choreoathetosis or myokymia. Linkage analysis in this family confirmed a previous report of genetic heterogeneity in BFIS - since linkage was excluded at the above-mentioned known BFIS loci - and suggested a possible linkage to the KCNQ2 gene, which is believed to be a voltage gated potassium channel gene responsible for benign familial neonatal seizures (BFNS).


CONCLUSIONS
Sequencing of the KCNQ2 gene revealed that all 17 affected family members carried a heterozygous Gly-to-Val (G271V) mutation in the conserved pore region that resulted from a guanine-to-thymine transition in exon 5 of KCNQ2. The same mutation with a comparable localization in the KCNQ3 (G310V) gene has been found in BFNS patients. The same conserved amino acid was also found to be mutated in the KCNQ1 gene in a family with Long QT Syndrome.
Zhou
Xihui
X
Department of Pediatrics, First Affiliated Hospital, Ion Channel Disease Laboratory, Medical College of Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China. zhouxih@mail.xjtu.edu.cn
Ma
Aiqun
A
Liu
Xiaohong
X
Huang
Chen
C
Zhang
Yanmin
Y
Shi
Ruiming
R
Mao
Shiwei
S
Geng
Tao
T
Li
Shengbin
S
D017668:Age of Onset; D016022:Case-Control Studies; D002681:China; D004827:Epilepsy / Q000208:ethnology / Q000235:genetics*; D005192:Family Health; D018740:Genetic Heterogeneity; D008040:Genetic Linkage; D006801:Humans; D007223:Infant; D051658:KCNQ2 Potassium Channel / Q000235:genetics*; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree
D051658:KCNQ2 Potassium Channel; C496914:KCNQ2 protein, human