Finally, we demonstrate that when these variants are present on the same haplotype there is an increase in cell proliferation in vitro. Whilst none of the results obtained provides unequivocal evidence for the role of ITGB4 in susceptibility to psychotic illness, considered together they are of interest and justify further investigation this gene and its variants in schizophrenia. The gene discussed is ITGB4; the disease is schizophrenia.