Diversity of Plasmodium falciparum chloroquine resistance transporter (pfcrt) exon 2 haplotypes in the Pacific from 1959 to 1979.

Nearly one million deaths are attributed to malaria every year. Recent reports of multi-drug treatment failure of falciparum malaria underscore the need to understand the molecular basis of drug resistance. Multiple mutations in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) are involved in chloroquine resistance, but the evolution of complex haplotypes is not yet well understood. Using over 4,500 archival human serum specimens collected from 19 Pacific populations between 1959 and 1979, the period including and just prior to the appearance of chloroquine treatment failure in the Pacific, we PCR-amplified and sequenced a portion of the pfcrt exon 2 from 771 P. falciparum-infected individuals to explore the spatial and temporal variation in falciparum malaria prevalence and the evolution of chloroquine resistance. In the Pacific, the prevalence of P. falciparum varied considerably across ecological zones. On the island of New Guinea, the decreases in prevalence of P. falciparum in coastal, high-transmission areas over time were contrasted by the increase in prevalence during the same period in the highlands, where transmission was intermittent. We found 78 unique pfcrt haplotypes consisting of 34 amino acid substitutions and 28 synonymous mutations. More importantly, two pfcrt mutations (N75D and K76T) implicated in chloroquine resistance were present in parasites from New Hebrides (now Vanuatu) eight years before the first report of treatment failure. Our results also revealed unexpectedly high levels of genetic diversity in pfcrt exon 2 prior to the historical chloroquine resistance selective sweep, particularly in areas where disease burden was relatively low. In the Pacific, parasite genetic isolation, as well as host acquired immune status and genetic resistance to malaria, were important contributors to the evolution of chloroquine resistance in P. falciparum.

Inherited and somatic mitochondrial DNA mutations in Guam amyotrophic lateral sclerosis and parkinsonism-dementia.

There is increasing evidence for mitochondrial dysfunction in neurodegenerative disorders, although the exact role of mitochondrial DNA (mtDNA) mutations in this process is unresolved. We investigated inherited and somatic mtDNA substitutions and deletions in Guam amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD). Hypervariable segment 1 sequences of Chamorro mtDNA revealed that the odds ratio of a PD or ALS diagnosis was increased for individuals in the E1 haplogroup while individuals in the E2 haplogroup had decreased odds of an ALS or PD diagnosis. Once the disorders were examined separately, it became evident that PD was responsible for these results. When the entire mitochondrial genome was sequenced for a subset of individuals, the nonsynonymous mutation at nucleotide position 9080, shared by all E2 individuals, resulted in a significantly low odds ratio for a diagnosis of ALS or PD. Private polymorphisms found in transfer and ribosomal RNA regions were found only in ALS and PD patients in the E1 haplogroup. Somatic mtDNA deletions in the entire mtDNA genome were not associated with either ALS or PD. We conclude that mtDNA haplogroup effects may result in mitochondrial dysfunction in Guam PD and reflect Guam population history. Thus it is reasonable to consider Guam ALS and PD as complex disorders with both environmental prerequisites and small genetic effects.

The contribution of mitochondrial dysfunction to a gene-environment model of Guamanian ALS and PD.

Scientific investigations of amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD) of Guam have implicated genetic and environmental risk factors in their etiology. Using brain tissue, we investigated mitochondrial dysfunction and report a higher frequency of somatic mutations in the light strand promoter (LSP) of the mitochondrial control region in Guam ALS and PD patients than in Guam controls, along with the presence of inherited mutations that may contribute to a novel gene-environment interaction risk model. Along with other risk factors, they demonstrate both the importance and significance of genetic and environmental contributions to Guam ALS and PD etiology.