1. ¹Department of Experimental Biology, University of Cagliari, SS 554, km 4,500, 09042 Monserrato (CA), Italy
2. ²Department of Human Genetics, University of Corsica, Corte, France
3. ³Department of Experimental Evolutionistic Biology, University of Bologna, Bologna, Italy
4. ⁴Department of Animal Biology, University of Barcelona, Barcelona, Spain

Correspondence: Ignazio Piras, Department of Experimental Biology, University of Cagliari, SS 554, km 4,500, 09042 Monserrato (CA), Italy. E-mail: ispiras@unica.it

Received 21 July 2006; Accepted 24 October 2006; Published online 15 November 2006.

Abstract

A 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 Moran's 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.