TNFAIP3 and arthritic joint disease: A recent study wherein mice carrying three distinct targeted mutations of the zinc finger 7 (ZF7) domain of A20, which binds to M1-linked Ub chains, all developed digit arthritis with symptoms that are common to psoriatic arthritis, whereas mice that expressed point mutations in the OTU or ZF4 motifs did not exhibit this phenotype [91].