Restricted tissue-specific but correct developmental expression mediated by a short human alpha 1AT promoter fragment in transgenic mice

Only low levels of exogenous N-acetyltransferase can be achieved in transgenic mice

Therapeutic and environmental aromatic amines and hydrazines are substrates for the arylamine N-acetyltransferases (NAT). In all, 10 transgenic lines containing either the human NAT1 or NAT2 transgene were developed using multiple promoters. The presence of the transgene was confirmed by determining copy number, mRNA and enzyme activity. Despite some lines having high copy numbers of the transgene, only modest or no increases in enzymatic activity could be found in a variety of tissues. The NAT1 transgene could not be bred to homozygosity. The cytomegalovirus (CMV)-promoted NAT1 transgene increased endogenous Nat1 mRNA levels in liver and had little effect on endogenous Nat2 mRNA levels. The presence of the CMV-promoted NAT2 transgene appeared to suppress endogenous hepatic Nat2 mRNA, but did not alter Nat1 mRNA levels. The failure to achieve high expression of any of the transgenes suggests that overexpression of NAT genes may have harmful effects during development.

Chromosomal elements regulate gene activity and chromatin structure of the human serpin gene cluster at 14q32.1

The human serine protease inhibitor (serpin) gene cluster at 14q32.1 contains a number of genes that are specifically expressed in hepatic cells. Cell-specific enhancers have been identified in several of these genes, but elements involved in locus-wide gene and chromatin control have yet to be defined. To identify regulatory elements in this region, we prepared a series of mutant chromosomal alleles by homologous recombination and transferred the specifically modified human chromosomes to hepatic cells for functional tests. We report that deletion of an 8-kb DNA segment upstream of the human alpha1-antitrypsin gene yields a mutant serpin allele that fails to be activated in hepatic cells. Within this region, a 2.3-kb DNA segment between kb -8.1 and -5.8 contains a previously unrecognized control region that is required not only for serpin gene activation but also for chromatin remodeling of the entire locus.

Differential influence of the E4 adenoviral genes on viral and cellular promoters

BACKGROUND

Strong and stable transgene expression is fundamental to the success of recombinant adenovirus vectors in human gene therapy. However, control of transgene expression is a complex process, involving both viral and cellular factors. In this study, the influence of the E4 adenoviral region on the activity of various promoters was investigated in vitro and in vivo.

METHODS

Pairs of isogenic E1o and E1oE4o vectors were generated and compared. Levels of transgene expression were determined by Northern blot, ELISA and FACS analysis. Initiation of transcription was studied by nuclear run-on assays.

RESULTS

Similar to the viral CMV and RSV promoters, the activity of the ubiquitous cellular PGK promoter required the presence of the E4 genes in vitro and in vivo. In contrast, transgene expression from selected liver- and tumor-specific promoters did not require E4 functions.

CONCLUSION

Together with the reported low liver toxicity of E1oE4o vectors, the independence of E4 of liver-specific promoters renders such vectors interesting alternatives to the use of gutless vectors.

Multiple copies of beta-lactoglobulin promoter do not function as LCR

Increasing the number of transcription factor binding sites within a construct can enhance expression. In an attempt to create a synthetic locus control region for mammary expression, we have generated beta-lactoglobulin-reporter constructs with multiple copies of the cluster of transcription sites normally located within the proximal promoter. These constructs were functionally tested by stable transfection of mammary epithelial cells in vitro and in transgenic mice in vivo. Rather than enhancing expression, multimerisation of the promoter region acted neither in vivo nor in vitro to enhance expression. Indeed, its presence reduced expression. This failure to enhance expression was reflected in the inability of this region to form a DNaseI hypersensitive site autonomously in mammary chromatin in vivo. It is implicit from our study that not all combinations of transcription factor binding sites will enhance transcription.

Transgenic animal models for the functional analysis of vasoactive peptides

The interplay of vasoactive peptide systems is an essential determinant of blood pressure regulation in mammals. While the endothelin and the renin-angiotensin systems raise blood pressure by inducing vasoconstriction and sodium retention, the kallikrein-kinin and the natriuretic-peptide systems reduce arterial pressure by eliciting vasodilatation and natriuresis. Transgenic technology has proven to be very useful for the functional analysis of vasoactive peptide systems. As an outstanding example, transgenic rats overexpressing the mouse Ren-2 renin gene in several tissues become extremely hypertensive. Several other transgenic rat and mouse strains with genetic modifications of components of the renin-angiotensin system have been developed in the past decade. Moreover, in recent years gene-targeting technology was employed to produce mouse strains lacking these proteins. The established animal models as well as the main insights gained by their analysis are summarized in this review.

Tracking H-2 alleles in transgenic mice by RFLP and heteroduplex analysis

Transgenic mice provide valuable tools for biological research including many areas of immunology. In studies involving the major histocompatibility complex (MHC), it is often necessary to place the desired transgene in a specific H-2 (the murine MHC) environment. In this regard, the strains commonly used for the production of transgenic mice also carry well characterized H-2 alleles and provide an appropriate genetic background for MHC related experiments. In this study, a highly polymorphic microsatellite of tetranucleotide repeats from the second intron of the class II Eb gene within the H-2 complex was used in order to identify the corresponding alleles. The relevant H-2 allele(s) along with the transgene were then tracked throughout the production of a chicken ovalbumin-specific transgenic strain. The technique involved PCR-amplification of a DNA sequence encompassing the H-2 specific microsatellite followed by RFLP and heteroduplex analyses. This approach is likely to find wide application in the background checking of transgenic mice, especially in immunological research requiring a defined H-2 background.