Numerous types of DNA variation exist, ranging from SNPs to larger structural alterations such as copy number variants (CNVs) and inversions. Alignment of DNA sequence from different sources has been used to identify SNPs1,2 and intermediate-sized variants (ISVs)3. However, only a small proportion of total heterogeneity is characterized, and little is known of the characteristics of most smaller-sized (<50 kb) variants. Here we show that genome assembly comparison is a robust approach for identification of all classes of genetic variation. Through comparison of two human assemblies (Celera's R27c compilation and the Build 35 reference sequence), we identified © 2006 Nature Publishing Group Correspondence should be addressed to S.W.S. (steve@genet.sickkids.on.ca).. AUTHOR CONTRIBUTIONS The study was designed by R.K., S.W.S. and L.F. The GCA algorithm was created by R.K. Sequence alignment and computational analysis was performed by R.K., J.Z., J.R.M, J.W., C.Q., L.A. and R.J.M. FISH analysis was performed by Y.H., A.M.J.G., M.S. and C.L. PCR analysis was performed by M.A.R., L.P., L.A. and L.F. J.Z., J.R.M, J.W., C.Q., H.A., K.J., R.R., M.H., L.A., X.E., C.L., S.W.S. and L.F contributed to the analysis of overlap with genomic features, creation of data sets for such analysis and interpretation of the data. S.W.S. and L.F conceptualized, designed and coordinated the experiments. The paper was written by S.W.S and L.F. COMPETING INTERESTS STATEMENT:The authors declare that they have no competing financial interests. Some differences were simple insertions and deletions, but in regions containing CNVs, segmental duplication and repetitive DNA, they were more complex. Our results uncover substantial undescribed variation in humans, highlighting the need for comprehensive annotation strategies to fully interpret genome scanning and personalized sequencing projects.The most sensitive method for identifying all variation existing between two DNA donors is through direct comparison of accurately completed sequence assemblies of the genomes under study. For the human genome, there are two assembly products, one from the International Human Genome Sequencing Consortium (IHGSC)4 and another from Celera Genomics5, which used primarily clone-based sequencing and whole-genome shotgun sequencing, respectively. Although these assemblies have been evaluated for content and quality6-10, little effort has been made to make use of their differences to annotate new sequence variants. Although R27c contains some Build 35 sequences8, for this study we selected it over other Celera-only whole-genome shotgun assemblies (Build 35 also contains some Celera sequence). We rationalized that larger scaffolds would increase the likelihood of finding variants that might be missed using methods more sensitive to size restrictions, such as comparative genomic hybridization using arrays spotted with BAC clones (which has a lower limit of detection of ~50 kb)11 or fosmid-end sequencing (which, in current form, does not identify variants <8 k...

A systematic study on the structure and function of Glucose-6-phosphate dehydrogenase (G6PD) variations was carried out in China. A total of 155,879 participants were screened for G6PD deficiency by the G6PD/6PGD ratio method and 6,683 cases have been found. The prevalence of G6PD deficiency ranged from 0 to 17.4%. With informed consent, 1,004 cases from 11 ethnic-based groups were subjected to molecular analysis. Our results showed the followings: (1) The G6PD variants are consistent across traditional ethnic boundaries, but vary in frequencies across ethnic-based groups in Chinese population, (2) The G6PD variants in Chinese population are different from those in African, European, and Indian populations, (3) A novel G6PD-deficiency mutation, 274C-->T, has been found, and (4) Denaturing high performance liquid chromatography is of great advantage to detecting G6PD-deficient mutations for diagnosis and genetic counseling. Moreover, functional analysis of the human G6PD variants showed the following: (1) The charge property, polarity, pK-radical and side-chain radical of the substituting amino acid have an effect on G6PD activity, (2) The G6PDArg459 and Arg463 play important roles in anchoring NADP+ to the catalytic domain to maintain the enzymatic activity, and (3) The sequence from codon 459 to the carboxyl terminal is essential for the enzymatic function.

eThe recent reports of resistance in Plasmodium falciparum to artemisinin derivatives and their partner drugs demand intensive studies toward understanding the molecular mechanisms of resistance. In this study, we examined the in vitro susceptibility of 63 P. falciparum field isolates collected from the China-Myanmar border area to chloroquine (CQ) and piperaquine (PPQ). Parasite isolates remained highly resistant to CQ, with the geometric mean 50% inhibitory concentration (IC 50 ) of 252.7 nM and a range of 51.9 to 1,052.0 nM. In comparison, these parasites had a geometric mean IC 50 of 28.4 nM for PPQ, with a fairly wide range of 5.3 to 132.0 nM, suggesting that certain parasite isolates displayed relatively high levels of resistance to PPQ. Interestingly, within the 4 years of study, the parasites exhibited a continuous decline in susceptibilities to both CQ and PPQ, and there was a significant correlation between responses to CQ and PPQ (Pearson correlation coefficient ‫؍‬ 0.79, P < 0.0001). Consistent with the CQ-resistant phenotype, all parasites carried the pfcrt K76T mutation, and most parasites had the CVIET type that is prevalent in Southeast Asia. In contrast, pfmdr1 mutations were relatively rare, and no gene amplification was detected. Only the pfmdr1 N1042D mutation was associated with resistance to CQ. For the pfmrp1 gene, four substitutions reached relatively high prevalence of >22%, and the I876V mutation was associated with reduced sensitivity to CQ. However, we could not establish a link between PPQ responses and the polymorphisms in the three genes associated with quinoline drug resistance.