Polymorphism of alpha1-antitrypsin in Pamir populations. Reproductive compensation--possible mechanism for maintaining genetic diversity gor PI genes in human populations

The distribution of the phenotype and gene frequencies of alpha 1-antitrypsin among Pamir's aborigines localized at high altitudes was studied. The Kirghizes of Murgab studied include mainly the mongoloid component in their composition. Populations of the Khuf river valley in West Pamir anthropologically belong to South caucasoids. The following frequencies of PI genes have been registered in Kirghizes (N = 102): M1 = 0.6961, M2 = 0.2108, M3 = 0.0539, Z = 0.0245, I = 0.0049, S = 0.0049, N = 0.0049; in the Khuf population (N = 122): M1 = 0.7910, M2 = 0.0943, M3 = 0.0984, Z = 0.0082, I = 0.0041, S = 0.0041; in the Pastkhuff population (N = 38): M1 = 0.7237, M2 = 0.1579, M3 = 0.1053, Z = 0.0132. A parallele biodemographic investigation in the Murgab population showed that couples, with one of the partners carrying the rare variant of PI demonstrated statistically significant increase in successful outcomes of pregnancies. The same cohort has displayed lower infant mortality rates, the absence of miscarried fetus and stillborn babies. Our results point to the possible existence of a mechanism of reproductive compensation serving to uphold the genetic diversity of PI genes.