Reporter genes in transgenic mice

Abstract

Although in vivo models utilizing endogenous reporter genes have been exploited for many years, the use of reporter transgenes to dissect biological issues in transgenic animals has been a relatively recent development. These transgenes are often, but not always, of prokaryotic origin and encode products not normally associated with eukaryotic cells and tissues. Some encode enzymes whose activities are detected in cell and tissue homogenates, whereas others encode products that can be detected in situ at the single cell level. Reporter genes have been used to identify regulatory elements that are important for tissue-specific gene expression or for development; they have been used to produce in vivo models of cancer; they have been employed for the study of in vivo mutagenesis; and they have been used as a tool in lineage analysis and for marking cells in transplantation experiments. The most commonly used in situ reporter gene is lacZ, which encodes a bacterial beta-galactosidase, a sensitive histochemical marker. Although it has been used with striking success in cultured cells and in transgenic mouse embryos, its postnatal in vivo expression has been unreliable and disappointing. Nevertheless, the ability to express reporter genes in transgenic mice has been an invaluable resource, providing insights into in vivo biological mechanisms. The development of new in vivo models, such as those in which expression of transgenes can be activated or repressed, should produce transgenic animal systems that extend our capacity to address heretofore unresolved biological questions.

Proapoptotic BH3-Only Bcl-2 Family Member Bik/Blk/Nbk Is Expressed in Hemopoietic and Endothelial Cells but Is Redundant for Their Programmed Death

“…An equivalent discrepancy has been noted with a lacZ knock-in at the bim locus, which also presents very low or undetectable ␤-galactosidase activity in lymphoid areas of the lymph node, thymus, and spleen, even though RNA and protein analyses clearly indicate Bim expression in these cells (P. Bouillet, unpublished observation) (32), in which loss of Bim profoundly impairs apoptosis (4,5). Silencing of lacZ transgenes in hematopoietic cells has been documented previously (12,31), and hence silencing of the reporter gene might contribute to the lack of ␤-galactosidase activity in the lymphocytes in which it is located in the bik or bim locus. Another possibility is that a regulatory element needed for lymphoid expression of the locus resides within the region deleted in the replacement, such as in the deleted intron.…”

Considerations for Use of Recombinant Adenoviral Vectors: Dose Effect on Hepatic Cytochromes P450

“…A replication defective recombinant adenoviral vector expressing the E. coli ␤-galactosidase transgene, the most commonly used in situ reporter in preclinical development of gene transfer protocols (Cui et al, 1994) and routinely used in our laboratory, was administered in these studies. One day after administration of either 5.7 ϫ 10 11 or 5.7 ϫ 10 12 vp/kg of this vector, CYP3A1/2 protein expression was significantly suppressed by 59 and 60%, respectively, compared with the vehicle treatment group (P Յ 0.01, Fig.…”

Transgenic models of lymphoid neoplasia and development of a pan-hematopoietic vector

“…This conclusion may seem surprising, because lacZ has been widely used, particularly in studies on embryogenesis. However, a review on lacZ as a transgenic reporter (Cui et al, 1994) concluded that`its postnatal in vivo expression has been unreliable and disappointing'. Its erratic performance in long-term experiments would be explicable if the bacterial sequences stochastically inactivated certain linked promoters, so that the proportion of non-expressing cells increased over time.…”