MMP-7 is a metalloproteinase and its functions include breaking down of extracellular matrix, degrading proteoglycans, fibronectin, elastin and casein.33 MMP-7 cleaves synaptosomal-associated protein of 25 kDa (SNAP-25), an intraneuronal protein that is important for neurotransmitter release.34 This gene (rs6039769 variant) was also reported to be associated with early onset bipolar disorder.35 Here, FN1 is linked to bipolar disorder.