Functional knockdowns mediated by endoplasmatic reticulum-retained antibodies (ER intrabodies) are a promising tool for research because they allow functional interference on the protein level. We demonstrate for the first time that ER intrabodies can induce a knock-down phenotype in mice. Surface VCAM1 was suppressed in bone marrow of heterozygous and homozygous ER intrabody mice (iER-VCAM1 mice). iER-VCAM1 mice did not have a lethal phenotype, in contrast to the constitutive knockout of VCAM1, but adult mice exhibited physiological effects in the form of aberrant distribution of immature B-cells in blood and bone marrow. The capability to regulate knock-down strength may spark a new approach for the functional study of membrane and plasma proteins, which may especially be valuable for generating mouse models that more closely resemble disease states than classic knockouts do.
Keywords: CMV, cytomegalovirus; ER, endoplasmatic reticulum; ES, embryonic stem cell; FITC, fluorescein isothiocyanate; KDEL; PE, phycoerythrin; ROSA26, reverse orientation splice acceptor 26; SA, streptavidin; VCAM1; VCAM1, vascular cell adhesion molecule 1; endoplasmatic reticulum; in vivo knockdown; intrabody; knockdown; knockout; membrane protein; mouse model.