Defining the expression pattern of the LGI1 gene in BAC transgenic mice

The LGI1 gene has been implicated in the development of epilepsy and the invasion phenotype of glial cells. Controversy over the specific tissue expression pattern of this gene has stemmed from conflicting reports generated using immunohistochemistry and the polymerase chain reaction. LGI1 is one of a four-member family of secreted proteins with high homology and here we demonstrate, using GFP-tagged constructs from the four LGI1family members, that commonly used antibodies against LGI1 cross-react with different family members. With the uncertainty surrounding the use of commercially available antibodies to truly establish the expression pattern of LGI1, we generated transgenic mice carrying the LGI1-containing BAC, RP23-127G7, which had been modified to express the GFP reporter gene under the control of the endogenous regulatory elements required for LGI1 expression. Three founder mice were generated, and immunohistochemistry was used to determine the tissue-specific pattern of expression. In the brain, distinct regions of glial and neuronal cell expression were identified, as well as the choriod plexus, which is largely pia-derived. In addition, strong expression levels were identified in glandular regions of the prostate, individual tubules in the kidney, sympathetic ganglia in the kidney, sebaceous glands in the skin, the islets of Langerhans, the endometrium, and the ovary and testes. All other major organs analyzed were negative. The pattern of reporter gene expression was identical in three individual founder mice, arguing against a position effect altering expression profile due to the integration site of the BAC.     

Neurofilament gene expression in transgenic mice

1. DNA fragments that include the human neurofilament NF-L gene was found to be correctly expressed in the majority of neurons in transgenic mice. 2. The NF-L transgene product, which is detectable in situ with a species-specific monoclonal antibody, provides a powerful genotype marking system applicable to developmental and regeneration studies of the mammalian nervous system. 3. The proximal 5'-flanking region of the NF-L gene is sufficient to direct expression of a heterologous gene in the mouse nervous system.     

Tissue-specific expression of theHLA-DRA gene in transgenic mice

Transgenic mice were produced containing a 33 kilobase (kb) DNA fragment encompassing the five exons and all the known regulatory regions of the class IIHLA-DRA gene. The transgene displayed regulated expression [constitutive and interferon- (IFN)- induced] of the human products in most mouse tissues. The tissue distribution of theDRA transgene products more closely resembled that of their mouse homologues, the endogenous H-2 Ea products, than the wider distribution ofDRA products in humans. This was evident in several tissues (endothelia of small vessels, especially those of glomerular capillaries, Kupffer cells, and epithelial cells lining the gastrointestinal tract), known to differentially express class II molecules in the two species. Thus, the wider human specific pattern of expression requires an exact cis/trans complementation which is incompletely reconstituted in transgenic mice, suggesting that human specific cis-acting elements may have arisen during evolution to direct the expression of class II genes to those anatomical regions which usually lack them in the mouse. The only example of aberrant expression of theDRA gene in the present series of transgenic mice was in the dendritic and/or epithelial cells of the thymic cortex, which displayed greately reducedDRA levels in spite of a normal expression of the endogenous Ea molecules.     

Regulation of Thy-1 gene expression in transgenic mice

Genomic DNA fragments encompassing the human Thy-1 or mouse Thy-1.1 gene have been microinjected into pronuclei of mouse embryos homozygous for the Thy-1.2 allele. In the resulting transgenic mice, the human gene is expressed in a pattern characteristic of normal human tissues, and is not influenced by the pattern of endogenous mouse Thy-1 expression. The mouse Thy-1.1 gene fragment is expressed in a pattern typical of mouse Thy-1, although it is more limited in its distribution. The results indicate the presence of multiple cis-acting regulators of Thy-1 gene expression that have changed in both their character and arrangement over the course of Thy-1 gene evolution.     

Tissue-specific expression of the human renin gene in transgenic mice

Transgenic mice carrying human renin gene were produced by microinjection of 15 kilobases (kb) DNA molecules with up to 3 kb of 5'-flanking sequence and 1.2 kb of 3'-flanking sequence. The transgenes have been shown to be stably transmitted to progeny. It was revealed by RNase protection assay that the human renin gene in a transgenic mouse is expressed preferentially in the kidney. The human renin RNA was also detected at a small level in a variety of tissues such as brain, heart, lung, pancreas, spleen, stomach, testis, and thymus. The direct radioimmunoassay using a monoclonal antibody specific for the active site of human renin demonstrated the synthesis of human active renin in the transgenic mouse kidney. These results suggest that the human renin gene in the transgenic mouse is regulated in a tissue-specific manner.     

Developmental regulation for collagen II gene expression in transgenic mice

In order to evaluate the involvement of the type II collagen regulatory sequences in development, we have injected a construct containing a toxin gene under the control of the rat type II collagen promoter and enhancer. The construct, pDAS10-DTA, contained the diphtheria toxin A chain gene under the control of type II collagen sequences which had been used previously to target cartilagenous tissues in transgenics. Inspection of developing fetuses at various stages of gestation revealed a high number of aborted implants as well as abnormally developing fetuses. These abnormal fetuses were of small size, had shortened and underdeveloped limbs, cleft palates, and generally resembled a phenotype similar to chondrodystrophic mice. Histological comparisons of normal and abnormal fetuses indicated a reduced amount of extracellular matrix surrounding chondrocytes, and a disorganized appearance of the tissue. These results suggest that the expression of the toxin has occurred in chondrocytes and altered the survival and development of the transgenic mice. These results also indicate that the promoter and enhancer sequences contained in the transgene controlled the developmental expression of the type II collagen gene expression.     

Spatiotemporal expression pattern of DsRedT3/CCK gene construct during postnatal development of myenteric plexus in transgenic mice

Cholecystokinin (CCK) is an early marker of both neuronal and endocrine cell lineages in the developing gastrointestinal tract. To determine the quantitative properties and the spatial distribution of the CCK-expressing myenteric neurones in early postnatal life, a transgenic mouse strain with a CCK promoter-driven red fluorescent protein (DsRedT3/CCK) was established. The cell-specific expression of DsRedT3/CCK was validated by in situ hybridization with a CCK antisense riboprobe and by in situ hybridization coupled with immunohistochemistry involving a monoclonal antibody to CCK. A gradual increase in the DsRedT3/CCK-expressing enteric neurones with clear regional differences was documented from birth until the suckling to weaning transition, in parallel with the period of rapid intestinal growth and functional maturation. To evaluate the proportion of myenteric neurones in which DsRedT3/CCK transgene expression was colocalized with the enteric neuronal marker peripherin, immunofluorescence techniques were applied. All DsRedT3/CCK neurones were peripherin-immunoreactive and the proportion of DsRedT3/CCK-expressing myenteric neurones in the duodenum was the highest after the third week of life, when the number of peripherin-immunoreactive myenteric neurones in this region had decreased. Nearly all of the DsRedT3/CCK-expressing neurones also expressed 5-hydroxytryptophan (5-HT). Thus, by utilizing a new transgenic mouse strain, we have demonstrated a small number of CCK-expressing myenteric neurones with a developmentally regulated spatiotemporal distribution. The coexistence of CCK and 5-HT in the majority of these neurones suggests their possible regulatory role in feeding at the suckling to weaning transition.     

Tissue-specific expression of a vimentin--desmin hybrid gene in transgenic mice.

We have introduced a hybrid gene, pVVim2, composed of the 5' region of the hamster vimentin gene encoding the head and rod domain of vimentin and the 3' region of the hamster desmin gene encoding the tail domain of desmin, into the germ line of mice by pronuclear injection. RNA and protein analysis of mice transgenic for this construct showed that the pVVim2 gene was expressed at high levels in a developmental and tissue-specific manner. This indicates that the vimentin-derived segment of the fusion gene contains all the regulatory elements required for vimentin-specific expression. Immunohistochemical staining of fibroblast cultures derived from the transgenic mice with antibodies specific for vimentin and desmin demonstrated that the pVVim2 protein is assembled into filaments that co-localize with the endogenous vimentin filaments. The expression of pVVim2 protein in mesenchymal cells does not interfere with the function of vimentin in these cells.     

Tissue-specific and developmental expression of human transthyretin gene in transgenic mice

To analyze the regulation of transthyretin gene expression we have produced transgenic mice by microinjecting cloned human transthyretin genes into fertilized eggs of C57BL/6 mice. The 7.6-kilobase (kb) human transthyretin gene containing about 500 base pairs (bp) in the upstream region was used for microinjection. Seven out of nine transgenic mice had detectable amounts of human transthyretin in serum when analyzed by enzyme-linked immunosorbent assay. Transthyretin mRNA was detected in liver and yolk sac but not in other tissues including brain. The amount of mRNA was variable among transgenic mice and was about one-tenth of mouse endogenous transthyretin mRNA. Human and mouse transthyretin mRNAs were detected in liver of fetus and yolk sac at 13 days of gestation and unlike yolk sac the level of mRNA in liver increased gradually during development and reached the maximum at around 17 days of gestation. Human transthyretin was associated with mouse transthyretin to form tetramers as judged from the dilution curve of enzyme-linked immunosorbent assay and the spur formation in Ouchterlony assay.     

Regulation of the human apolipoprotein AIV gene expression in transgenic mice

The apolipoprotein (Apo) AI-CIII-AIV gene cluster has a complex pattern of gene expression that is modulated by both gene- and cluster-specific cis-acting elements. In particular the regulation of Apo AIV expression has been previously studied in vivo and in vitro including several transgenic mouse lines but a complete, consistent picture of the tissue-specific controls is still missing. We have analysed the role of the Apo AIV 3' flanking sequences in the regulation of gene expression using both in vitro and in vivo systems including three lines of transgenic mice. The transgene consisted of a human fragment containing 7 kb of the 5' flanking region, the Apo AIV gene itself and 6 kb of the 3' flanking region (-7+6 Apo AIV). Accurate analysis of the Apo AIV mRNA levels using quantitative PCR and Northern blots showed that the 7+6 kb Apo AIV fragment confers liver-specific regulation in that the human Apo AIV transgene is expressed at approximately the same level as the endogenous mouse Apo AIV gene. In contrast, the intestinal regulation of the transgene did not follow, the pattern observed with the endogenous gene although it produced a much higher intestinal expression following the accepted human pattern. Therefore, this animal model provides an excellent substrate to design therapeutic protocols for those metabolic derangements that may benefit from variations in Apo AIV levels and its anti-atherogenic effect.     

Transgenic Cre expression mice for generation of erythroid-specific gene alterations

Transgenic mice that express Cre recombinase in erythroid cell lineages were developed so that genes affecting erythropoiesis/hematopoiesis may be altered without necessarily affecting fetus viability. A micro-LCR cassette-beta-globin promoter-Cre recombinase gene (microLCR-betapr-Cre) construct was synthesized and used to generate transgenic mice. Concurrently, we produced mice containing a microLCR-loxP-flanked beta sickle gene (microLCR-loxP-beta(S)-loxP) construct. microLCR-betapr-Cre mice with intact transgenes in variable copy number were identified. Cre expression was assessed by RNAse protection and RT-PCR. Cre function was ascertained by breeding to microLCR-loxP-beta(S)-loxP mice. We demonstrate that beta(S) expression was not detected in the blood of bigenics, but the gene was present in nonerythroid cells. Thus, excision of the loxP-flanked beta(S) gene was restricted to erythroid cell lineages.     

Mosaic expression pattern of the nptII gene in transgenic tobacco plants Nu 21

Mosaic expression pattern of the nptII gene in transgenic tobacco Nu 21 leaf somatic cells was demonstrated. Inheritance of this phenotype (in T1-T4 and F1 backcrosses) was revealed. Three plant groups were distinguished, with low frequency of variegation manifestation (0-21.8%), with the high frequency of mosaic progeny (63.1 to 100%), and the intermediate type, where the frequency of the appearance of mosaic plants varied in a wide range, from 0 to 100%. The data obtained suggested the existence of two metastable states of a transgene in the leaf disk somatic cells (active and silenced), which could be associated with DNA modification, i.e., methylation of cytosine within the nptII gene sequence.     

Apolipoprotein E gene expression is reduced in apolipoprotein A-I transgenic mice

The levels of plasma apolipoprotein (apo) E, an anti-atherogenic protein involved in mammalian cholesterol transport, were found to be 2-3 fold lower in mice over-expressing human apoA-I gene. ApoE is mainly associated with VLDL and HDL-size particles, but in mice the majority of the apoE is associated with the HDL particles. Over-expression of the human apoA-I in mice increases the levels of human apoA-I-rich HDL particles by displacing mouse apoA-I from HDL. This results in lowering of plasma levels of mouse apoA-I. Since plasma levels of apoE also decreased in the apoA-I transgenic mice, the mechanism of apoE lowering was investigated. Although plasma levels of apoE decreased by 2-3 fold, apoB levels remained unchanged. As expected, the plasma levels of human apoA-I were almost 5-fold higher in the apoAI-Tg mice compared to mouse apoA-I in WT mice. If the over-expression of human apoA-I caused displacement of apoE from the HDL, the levels of hepatic apoE mRNA should remain the same in WT and the apoAI-Tg mice. However, the measurements of apoE mRNA in the liver showed 3-fold decreases of apoE mRNA in apoAI-Tg mice as compared to WT mice, suggesting that the decreased apoE mRNA expression, but not the displacement of the apoE from HDL, resulted in the lowering of plasma apoE in apoAI-Tg mice. As expected, the levels of hepatic apoA-I mRNA (transgene) were 5-fold higher in the apoAI-Tg mice. ApoE synthesis measured in hepatocytes also showed lower synthesis of apoE in the apoAI-Tg mice. These studies suggest that the integration of human apoA-I transgene in mouse genome occurred at a site that affected apoE gene expression. Identification of this locus may provide further understanding of the apoE gene expression.