Agent-based modeling of DFNB1A prevalence with regard to intensity of selection pressure in isolated human population: will cochlear implantation increase the cases of hereditary deafness?

It was evidenced, that the increase in the prevalence of autosomal recessive deafness 1A (DFNB1A) in populations of European descent was promoted by assortative marriages among deaf people. Assortative marriages become possible with a widespread introduction of sign language resulting in increased the genetic fitness of deaf individuals, thus relaxing selection against deafness. Currently, cochlear implantation is becoming a common method of rehabilitation for deaf patients, restoring their hearing ability and promoting the acquirement of spoken language. Whether the mass cochlear implantation could affect the spread of hereditary deafness is unknown. We have developed an agent-based computer model for analysis of the spread of DFNB1A. Using the model, we tested impact of different intensity of selection pressure on an isolated human population for 400 years. The modeling of the "purifying" selection pressure on deafness resulted in decrease of the proportion of deaf individuals and the pathogenic allele frequency. The modeling of relaxed selection resulted in increase of the proportion of deaf individuals and the decrease of the pathogenic allele frequency. The results of neutral selection pressure modeling showed no significant changes in both the proportion of deaf individuals and the pathogenic allele frequency after 400 years. Thus, initially low genetic fitness of deaf people can be significantly increased in the presence of assortative mating by deafness, resulting in a higher prevalence of DFNB1A. Contrary, frequency of pathogenic allele and the incidence of hereditary hearing loss will not increase in a population where all deaf individuals undergo cochlear implantation.