Alam Mohammad Tauqeer, Agarwal Richa, Sharma Yagya D
Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India.
Mol Biochem Parasitol. 2007 Jun;153(2):178-85. doi: 10.1016/j.molbiopara.2007.03.003. Epub 2007 Mar 12.
Only limited but contrasting reports are available on microsatellites based population structure of Plasmodium vivax. Further, there is complete lack of information on microsatellites in the flanking regions of the P. vivax drug resistance genes to trace the origin and spread of the drug resistant vivax malaria. Therefore, we scanned +/-300 kb flanking sequences of the P. vivax dihydrofolate reductase (pvdhfr) gene for di-nucleotide microsatellite repeats with minimum of 8 unit array length. Only 13 such repeats were detected in this region as compared to 738 di-nucleotide repeats present in +/-300 kb flanking region of P. falciparumdhfr gene. We have analyzed here the nucleotide sequence of 110 Indian P. vivax isolates for four of these di-nucleotide microsatellites (two in the nearest regions at -38.83 kb and +6.15 kb, and two in the farthest regions at -230.54 kb and +283.28 kb). All the four microsatellites were found to be highly polymorphic in the population where number of alleles varied from 4 to 10 with the median values of 9-11 at these loci. The expected heterozygosity (He) at these loci ranged from 0.50 to 0.82. We did not find any association between pvdhfr mutations and the flanking microsatellite alleles. There was a regional variation in the microsatellites polymorphism which was not associated with the reported prevalent rates of drug resistance or malaria transmission. In conclusion, the level of microsatellite polymorphism in P. vivax is as high as in P. falciparum. These results will be valuable in understanding the evolutionary history of the pvdhfr alleles as well as for designing the malaria control strategies.
关于间日疟原虫基于微卫星的群体结构，仅有有限且相互矛盾的报告。此外，对于间日疟原虫耐药基因侧翼区域的微卫星，完全缺乏相关信息以追踪耐药间日疟的起源和传播。因此，我们扫描了间日疟原虫二氢叶酸还原酶（pvdhfr）基因侧翼±300 kb的序列，寻找二核苷酸微卫星重复序列，其最小阵列长度为8个单位。在该区域仅检测到13个此类重复序列，而恶性疟原虫dhfr基因侧翼±300 kb区域存在738个二核苷酸重复序列。我们在此分析了110份印度间日疟原虫分离株的核苷酸序列，针对其中4个二核苷酸微卫星（两个在最近区域，分别位于-38.83 kb和+6.15 kb，另外两个在最远区域，分别位于-230.54 kb和+283.28 kb）。结果发现，所有这4个微卫星在群体中具有高度多态性，等位基因数量从4到10不等，这些位点的中位数为9 - 11。这些位点的预期杂合度（He）范围为0.50至0.82。我们未发现pvdhfr突变与侧翼微卫星等位基因之间存在任何关联。微卫星多态性存在区域差异，这与报告的耐药流行率或疟疾传播率无关。总之，间日疟原虫的微卫星多态性水平与恶性疟原虫一样高。这些结果对于理解pvdhfr等位基因的进化历史以及设计疟疾控制策略将具有重要价值。
