ABSTRACT
Age-related hearing impairment (ARHI) is the most common sensory impairment among the elderly. It is a complex disorder influenced by genetic as well as environmental factors. SNPs in a candidate susceptibility gene, KCNQ4, were examined in two independent Caucasian populations. Two quantitative trait locus (QTL) values were investigated: Zhigh and Zlow, a measure of high and respectively low frequency hearing loss. In the first population, the statistical analysis of 23 genotyped SNPs spread across KCNQ4 resulted in significant p-values for two SNPs for Zhigh-SNP9 (NT_004511:g.11244177A > T) and SNP15 (NT_004511:g.11257005C > T; NP_004691:p.Ala259Ala), and one SNP for Zlow-SNP12 (NT_004511:g.11249550A > T). The linkage disequilibrium (LD) structure of KCNQ4 was subsequently determined in a 34-kb region surrounding the significant SNPs, resulting in three LD-blocks. LD-block 1 contains SNP9 and covers an area of 5 kb, LD-block 2 measures 5 kb and surrounds SNP13 (NT_004511:g.11253513A > G) to SNP18 (NT_004511:g.11257509G > A; NP_004691:p.Thr293Thr), and LD-block 3 spans 7 kb. Five tag-SNPs of block 1 and 2, and 2 extra SNPs were subsequently genotyped in the second population. Again, several SNPs were positively associated with ARHI: one SNP (SNP18) for the high frequencies and three SNPs (SNP9, SNP12, and SNP18) for the low frequencies, although only a single SNP (SNP12) resulted in significant p-values in both populations. Nevertheless, the associated SNPs of both populations were all located in the same 13-kb region in the middle of the KCNQ4 gene.
Subject(s)
Hearing Loss/genetics , KCNQ Potassium Channels/genetics , Adult , Age Factors , Aged, 80 and over , Analysis of Variance , DNA Mutational Analysis/methods , Female , Gene Frequency/genetics , Genetic Predisposition to Disease/genetics , Genotype , Haplotypes/genetics , Hearing Loss/pathology , Humans , Linkage Disequilibrium/genetics , Male , Middle Aged , Models, Genetic , Polymorphism, Single Nucleotide/genetics , Quantitative Trait Loci/geneticsABSTRACT
BACKGROUND: The pathophysiological role of the extensive interictal cerebral hypometabolism in complex partial seizures (CPS) in refractory mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS) is poorly understood. Our aim was to study ictal-interictal SPECT perfusion versus interictal fluorodeoxyglucose (FDG)-PET metabolic patterns. METHODS: Eleven adults with refractory unilateral mTLE-HS, who were rendered seizure free after epilepsy surgery, were included. All had an interictal FDG-PET and an interictal and ictal perfusion SPECT scan. FDG-PET data were reconstructed using an anatomy-based reconstruction algorithm, which corrected for partial volume effects, and analyzed semi-quantitatively after normalization to white matter activity. Using Statistical Parametric Mapping (SPM), we compared interictal metabolism of the patient group with a control group. We correlated metabolic with ictal perfusion changes in the patient group. RESULTS: Global cerebral grey matter glucose metabolism in patients was decreased 10-25% compared with control subjects. Interictal PET hypometabolism and ictal SPECT hypoperfusion were maximal in the ipsilateral frontal lobe. Ictal frontal lobe hypoperfusion was associated with crossed cerebellar diaschisis. The ipsilateral temporal lobe showed maximal ictal hyperperfusion and interictal hypometabolism, which was relatively mild compared with the degree of hypometabolism affecting the frontal lobes. CONCLUSION: Interictal hypometabolism in mTLE-HS was greatest in the ipsilateral frontal lobe and represented a seizure-related dynamic process in view of further ictal decreases. Crossed cerebellar diaschisis suggested that there is a strong ipsilateral frontal lobe inhibition during CPS. We speculate that surround inhibition in the frontal lobe is a dynamic defense mechanism against seizure propagation, and may be responsible for functional deficits observed in mTLE.