Haemoglobin C protects against clinical Plasmodium falciparum malaria

Haemoglobin C (HbC; beta6Glu --> Lys) is common in malarious areas of West Africa, especially in Burkina Faso. Conclusive evidence exists on the protective role against severe malaria of haemoglobin S (HbS; beta6Glu --> Val) heterozygosity, whereas conflicting results for the HbC trait have been reported and no epidemiological data exist on the possible role of the HbCC genotype. In vitro studies suggested that HbCC erythrocytes fail to support the growth of P. falciparum but HbC homozygotes with high P. falciparum parasitaemias have been observed. Here we show, in a large case-control study performed in Burkina Faso on 4,348 Mossi subjects, that HbC is associated with a 29% reduction in risk of clinical malaria in HbAC heterozygotes (P = 0.0008) and of 93% in HbCC homozygotes (P = 0.0011). These findings, together with the limited pathology of HbAC and HbCC compared to the severely disadvantaged HbSS and HbSC genotypes and the low betaS gene frequency in the geographic epicentre of betaC, support the hypothesis that, in the long term and in the absence of malaria control, HbC would replace HbS in central West Africa.

mtDNA analysis reveals a major late Paleolithic population expansion from southwestern to northeastern Europe

mtDNA sequence variation was studied in 419 individuals from nine Eurasian populations, by high-resolution RFLP analysis, and it was followed by sequencing of the control region of a subset of these mtDNAs and a detailed survey of previously published data from numerous other European populations. This analysis revealed that a major Paleolithic population expansion from the "Atlantic zone" (southwestern Europe) occurred 10,000-15,000 years ago, after the Last Glacial Maximum. As an mtDNA marker for this expansion we identified haplogroup V, an autochthonous European haplogroup, which most likely originated in the northern Iberian peninsula or southwestern France at about the time of the Younger Dryas. Its sister haplogroup, H, which is distributed throughout the entire range of Caucasoid populations and which originated in the Near East approximately 25,000-30,000 years ago, also took part in this expansion, thus rendering it by far the most frequent (40%-60%) haplogroup in western Europe. Subsequent migrations after the Younger Dryas eventually carried those "Atlantic" mtDNAs into central and northern Europe. This scenario, already implied by archaeological records, is given overwhelming support from both the distribution of the autochthonous European Y chromosome type 15, as detected by the probes 49a/f, and the synthetic maps of nuclear data.

Familial progressive sensorineural deafness is mainly due to the mtDNA A1555G mutation and is enhanced by treatment of aminoglycosides

Hearing loss involves both genetic and environmental factors. A mutation (A1555G) in the mtDNA has been associated with aminoglycoside-induced and nonsyndromic sensorineural deafness. The pathological significance of this mutation in Caucasoid families has not been established, and its relationship with antibiotic treatment is not well understood. We studied 70 Spanish families with sensorineural deafness (36 congenital and 34 late onset) for the mtDNA A1555G mutation. The A1555G mutation was found in 19 families with maternally transmitted deafness but not in the other 51 families or in 200 control subjects. In 12 families all the patients with the A1555G mutation who received aminoglycosides became deaf, representing 30.3% of the deaf patients in these families. None of the deaf patients from seven other families received aminoglycosides. Overall, only 17.7% of the patients with deafness and the A1555G mutation had been treated with aminoglycosides. The age at onset of deafness was lower (median age 5 years, range 1-52 years) in those treated with aminoglycosides than in those who did not receive antibiotics (median age 20 years, range 1-65 years) (P < .001). The mtDNA of these families belongs to haplotypes common in Europeans. These data indicate that the A1555G mutation accounts for a large proportion of the Spanish families with late-onset sensorineural deafness, that the A1555G mutation has an age-dependent penetrance for deafness (enhanced by treatment with aminoglycosides), and that mtDNA backgrounds probably do not play a major role in disease expression.

Haplotype and phylogenetic analyses suggest that one European-specific mtDNA background plays a role in the expression of Leber hereditary optic neuropathy by increasing the penetrance of the primary mutations 11778 and 14484

mtDNAs from 37 Italian subjects affected by Leber hereditary optic neuropathy (LHON) (28 were 11778 positive, 7 were 3460 positive, and 2 were 14484 positive) and from 99 Italian controls were screened for most of the mutations that currently are associated with LHON. High-resolution restriction-endonuclease analysis also was performed on all subjects, in order to define the phylogenetic relationships between the mtDNA haplotypes and the LHON mutations observed in patients and in controls. This analysis shows that the putative secondary/intermediate LHON mutations 4216, 4917, 13708, 15257, and 15812 are ancient polymorphisms, are associated in specific combinations, and define two common Caucasoid-specific haplotype groupings (haplogroups J and T). On the contrary, the same analysis shows that the primary mutations 11778, 3460, and 14484 are recent and are due to multiple mutational events. However, phylogenetic analysis also reveals a different evolutionary pattern for the three primary mutations. The 3460 mutations are distributed randomly along the phylogenetic trees, without any preferential association with the nine haplogroups (H, I, J, K, T, U, V, W, and X) that characterize European populations, whereas the 11778 and 14484 mutations show a strong preferential association with haplogroup J. This finding suggests that one ancient combination of haplogroup J-specific mutations increases both the penetrance of the two primary mutations 11778 and 14484 and the risk of disease expression.