Multiple ERβ antisera label in ERβ knockout and null mouse tissues

In the process of characterizing a custom-made affinity-purified antiserum for estrogen receptor beta (ERβ), ck5912, we used a number of common tests for specificity of ck5912 along with that of 8 commercially available ERβ antisera: Affinity Bioreagents PA1-310B, Invitrogen D7N, Upstate 06-629, Santa Cruz H150, Y19, L20, 1531, and Abcam 9.88. We tested their recognition of recombinant ERβ (rERβ) versus rERα, ERβ versus ERα transfected into cell lines, as well as labeling in wildtype (WT) versus estrogen receptor beta knockout (βERKO) and null (ERβ ST L−/L−) mouse ovary, hypothalamus, and hippocampus. To our surprise, we found that while most of these antisera passed some tests, giving the initial impression of specificity, western blot analysis showed that all of them recognized apparently identical protein bands in WT, βERKO and ERβ ST L−/L− tissues. We share these results with the goal of helping other researchers avoid pitfalls in interpretation that could come from use of these ERβ antisera.