An older 2003 review of linkage studies also listed seven genes as likely to increase risk for a later diagnosis of the disorder. Two reviews suggested that the evidence was strongest for two genes known as dysbindin ("DTNBP1") and neuregulin (NRG1), and that a number of other genes (such as "COMT", "RGS4", "PPP3CC", "ZDHHC8", "DISC1", and "AKT1") showed some early promising results. Knockout studies in "Drosophila" show that reduced expression of dysbindin reduced glutamatergic synaptic transmission, resulting in impaired memory. Variations near the gene "FXYD6" have also been associated with schizophrenia in the UK but not in Japan. In 2008, rs7341475 single nucleotide polymorphism (SNP) of the reelin gene was associated with an increased risk of schizophrenia in women, but not in men. This female-specific association was replicated in several populations. Studies have found evidence that the protein phosphatase 3 known as calcineurin might be involved in susceptibility to schizophrenia.