CCR5 and schizophrenia: Although in most cases the behavior of susceptibility or protective risk variants are shared through populations [18], some differential effects for the same alleles in different populations have been established, like the European-specific protective effects to HIV1 infection progression by the 32-bp deletion allele of the CCR5 gene [34-36] or the presence of two different haplotype blocks in the NRG1 gene that give susceptibility to schizophrenia in European and East Asian populations, respectively [37].