| %248310 | |||||||||||||||
| PLASMODIUM FALCIPARUM BLOOD INFECTION LEVEL | |||||||||||||||
| Alternative titles; symbols | |||||||||||||||
| PFBI PLASMODIUM FALCIPARUM PARASITEMIA | |||||||||||||||
| Cytogenetic location: 5q31-q33 Genomic coordinates (GRCh37): 5:130,600,000 - 159,900,000 (from NCBI) | |||||||||||||||
| Gene Phenotype Relationships | |||||||||||||||
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| Clinical Synopsis | |||||||||||||||
| TEXT | |||||||||||||||
| For general information on malaria and the influence of genetic factors on malaria susceptibility, progression, severity, and resistance, see 611162. | |||||||||||||||
| Population Genetics | |||||||||||||||
| Abel et al. (1992), using methods similar to those they used for studying the genetic basis of resistance to leprosy (246300) and schistosomiasis (181460), applied complex segregation analysis to falciparum malaria. The phenotype studied was parasite density (PD), which was based on the parasite/leukocyte ratio by counting 500 leukocytes on a Giemsa-stained thick smear. A logarithmic transformation, based on log(PD + 1), was applied to PD values to allow for zero counts. In studies of 42 Cameroonian families, Abel et al. (1992) concluded that there is a recessive major gene controlling the degree of infection in malaria. They estimated that the deleterious allele has a frequency of 0.44-0.48, indicating that about 21% of the population is predisposed to high levels of infection. | |||||||||||||||
| Mapping | |||||||||||||||
| Rihet et al. (1998) provided evidence for linkage of the level of blood infection with Plasmodium falciparum and the chromosome region 5q31-q33, which contains numerous candidate genes encoding immunologic molecules. They performed a sib-pair linkage analysis on 153 sibs from 34 families. The results, obtained by means of a 2-point Haseman-Elston method and a nonparametric approach, showed linkage of parasitemia to D5S393 (P = 0.002) and D5S658 (P = 0.0004). Multipoint analyses confirmed linkage, with a peak close to D5S658. The heritability of the locus was 0.48, according to the 2-point results, and 0.43, according to the multipoint results; this indicated that its variation accounted for approximately 45% of the variance of blood infection levels and that the locus plays a central role in the control of parasitemia. Garcia et al. (1998) and Flori et al. (2003) also found association between P. falciparum blood infection levels and 5q31-q33. Hernandez-Valladares et al. (2004) used an F(11) advance intercross line in a population of mice infected with Plasmodium chabaudi to identify mouse quantitative trait loci (QTLs) for control of parasitemia on mouse chromosomes 11 and 18, which carry regions homologous to human 5q31-q33. They identified a novel QTL for parasitemia control on mouse chromosome 11, linked to marker D11Mit242, and involved in the clearance stages of the parasites from the bloodstream. | |||||||||||||||
| REFERENCES | |||||||||||||||
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