RESUMEN
The sum of squared score (SSU) and sequence kernel association test (SKAT) are the two good alternative tests for genetic association studies in case–control data. Both SSU and SKAT are derived through assuming a dose-response model between the risk of disease and genotypes. However, in practice, the real genetic mode of inheritance is impossible to know. Thus, these two tests might lose power substantially as shown in simulation results when the genetic model is misspecified. Here, to make both the tests suitable in broad situations, we propose two-phase SSU (tpSSU) and two-phase SKAT (tpSKAT), where the Hardy–Weinberg equilibrium test is adopted to choose the genetic model in the first phase and the SSU and SKAT are constructed corresponding to the selected genetic model in the second phase. We found that both tpSSU and tpSKAT outperformed the original SSU and SKAT in most of our simulation scenarios. By applying tpSSU and tpSKAT to the study of type 2 diabetes data, we successfully identified some genes that have direct effects on obesity. Besides, we also detected the significant chromosomal region 10q21.22 in GAW16 rheumatoid arthritis dataset, with P \10-6 . These findings suggest that tpSSU and tpSKAT can be effective in identifying genetic variants for complex diseases in case–control association studies
RESUMEN
<p><b>OBJECTIVE</b>To summarize the clinical features of those Duchenne and Becker muscular dystrophy (DMD and BMD) patients who are complicated with epilepsy, and try to analyze the genotype- phenotype correlation.</p><p><b>METHOD</b>By a retrospective analysis of 307 patients with DMD and BMD who attended Peking University First Hospital from February 2006 to September 2014,7 patients complicated with epilepsy were identified and their clinical data were collected. The possible mechanism of epilepsy in DMD and BMD patients was proposed after analyzing the genotype-phenotype correlation.</p><p><b>RESULT</b>(1) Among 307 DMD and BMD patients, 7 cases had epilepsy, the prevalence was 2. 28%. (2) The age of onset of epilepsy ranged from 8 months to 11 years. Focal seizure was the most common seizure type (6 cases) , while other seizure types were also involved, such as generalized tonic-clonic seizure. As to epilepsy syndromes, 1 boy was diagnosed as benign childhood epilepsy with centrotemporal spikes (BECT). Six patients were treated with 1 or 2 types of antiepileptic drugs and seizures were controlled well. On follow-up, 6 of the 7 children had normal mental development, while the remaining 1 patient was diagnosed as mild mental retardation. (3) DMD gene mutations of all 7 patients were analyzed. Exons deletions were found in 6 cases while point mutation was found in 1 case.</p><p><b>CONCLUSION</b>The prevalence of epilepsy in DMD and BMD patients was higher than the prevalence in normal population. The age of onset of epilepsy varies, and focal seizure may be the most common seizure type. Some patients may also present as some kind of epilepsy syndrome, such as BECT. In most patients, seizures can be controlled well by 1 or 2 types of antiepiletic drugs. No clear correlation was found between genotype and phenotype in DMD and BMD patients who were complicated with epilepsy, probably due to limited number of cases.</p>