Donata Luiselli

Analysis of nucleotide diversity of NAT2 coding region reveals homogeneity across Native American populations and high intra-population diversity

N-acetyltransferase 2 (NAT2), an important enzyme in clinical pharmacology, metabolizes antibiotics such as isoniazid and sulfamethoxazole, and catalyzes the transformation of aromatic and heterocyclic amines from the environment and diet into carcinogenic intermediates. Polymorphisms in NAT2 account for variability in the acetylator phenotype and the pharmacokinetics of metabolized drugs. Native Americans, settled in rural areas and large cities of Latin America, are under-represented in pharmacogenetics studies; therefore, we sequenced the coding region of NAT2 in 456 chromosomes from 13 populations from the Americas, and two from Siberia, detecting nine substitutions and 11 haplotypes. Variants *4 (37%), *5B (23%) and *7B (24%) showed high frequencies. Average frequencies of fast, intermediate and slow acetylators across Native Americans were 18, 56 and 25%, respectively. NAT2 intra-population genetic diversity for Native Americans is higher than East Asians and similar to the rest of the world, and NAT2 variants are homogeneously distributed across native populations of the continent.

Human CHIT1 gene distribution: new data from Mediterranean and European populations

AbstractA 24 bp duplication in the CHIT1 gene (H allele) is associated with a deficiency in the activity of chitotriosidase, an enzyme with the capability to hydrolyse chitin. A recent study in European and two sub-Saharan populations suggested a relationship between the presence of the mutation, improved environmental conditions, and the disappearance of parasitic diseases, including Plasmodium falciparum malaria. This result was not supported by the high frequency of the 24 bp duplication in a sample from Taiwan, an area with high malaria endemicity until 40 years ago. In this study, we analysed the frequency variability of the H allele in Mediterranean populations and its internal variability in Sardinia (Italy) with respect to malaria, which had been endemic on the island until its eradication during 1946–1950. The pattern of H frequency distributions is not consistent with the hypothesis of selective pressures acting on CHIT1 gene. The Morans index coefficient and correlogram seem to indicate, indeed, that allele distribution was determined by random factors. The pattern of frequency distribution suggests a possible Asiatic origin of the H allele, but it could be possible also that the mutant allele had diffused out of Africa, and was subsequently lost from African populations.

Human Microevolution and the Atlantic Slave Trade

Populations derived from the Atlantic slaving process provide unique opportunities for studying key evolutionary determinants of current patterns of human cultural and biological variation. Examination of the genetic patterning of the small plantation island of São Tomé (Gulf of Guinea) using a study design that avoids the use of preconceived ethno‐linguistic labels to define genetic sampling units reveals that, despite the fact that maximum distance between any two sampled sites is less than 50 km, the island has an unusual level of genetic structure that is mainly caused by the grouping of Angolar Creole‐speakers in a separate cluster carrying a distinctive imprint of genetic drift. This pattern may have been shaped by a kin‐structured founder effect associated with the flight of a patrilineal clan of rebel slaves who established a remarkably successful maroon community in the vicinity of the plantation complex. The observation that population‐discontinuous jumps may occur even under social conditions of massive coercive amalgamation provides an illustration of the way in which human clusters emerge and eventually shape the genetic background of human populations.