According to some papers and databases, PADI2 gene can expressed and actually over-expressed in different tissue such as breast, lung and brain (myelination) to name a few. It appears that PADI2 plays a role in the proliferation of normal mammary epithelium:
So, PADI2 is not a tissue or cell specific gene. It has also been shown that PADI2 can be expressed and found in neurons and plays a role in the onset and progression of neurodegenerative human disorders, including Alzheimer disease and multiple sclerosis, and it has also been implicated in glaucoma pathogenesis. This gene exists in a cluster with four other paralogous genes. [provided by RefSeq, Jul 2008]: