To determine the protein profile of the cyst found in JNK1/2LPC-KO mice, we performed a mass spectrometry analysis, which also revealed a high content of proteins typical for serum samples like albumin, serotransferrin, complement 3, and various isoforms of α-1-antitrypsin (SI Appendix, Table S1 and Dataset S1). The gene discussed is MAPK8; the disease is cyst.