We have generated transgenic rabbits that express the entire human apoA-I/C-III/A-IV gene cluster. As in humans, h-apoA-I and h-apoC-III were expressed in liver and intestine, whereas h-apoA-IV mRNA was detected in intestine only. Transgenic rabbits had significantly higher plasma total cholesterol, HDL-cholesterol and total phospholipid concentrations than non-transgenic littermates. In contrast to similar transgenic mice previously generated, which have gross hypertriglyceridemia, triglyceride concentrations were only moderately raised in transgenic rabbits. Plasma and HDL from transgenic rabbits were more effective than those from controls in promoting cholesterol efflux from cultured hepatoma cells. They had lower LCAT, lower CETP and higher PLTP activities than non-transgenic littermates. Cholesterol-feeding produced major increases in plasma lipids. The qualitative response to the diet was not modified by cluster expression. Human apoA-I concentration was halved by cholesterol-feeding, whereas h-apoC-III and h-apoA-IV concentrations were not significantly altered. Cholesterol efflux from hepatoma cells to plasma and HDL was not altered by the diet. Since lipoprotein metabolism of rabbits closely resembles that of humans, human apoA-I/C-III/A-IV transgenic rabbits may provide a reliable model for studies of the transcriptional regulation of the cluster, and for evaluating the effects of different agents on the expression of the three genes.

Objective-Expression of human apolipoprotein (h-apo) A-IV in apoE-deficient (apoE(0)) mice (h-apoA-IV/E-0) reduces susceptibility to atherosclerosis. Chronic infection mimicked by exposure to lipopolysaccharide (LPS) increases the size of atherosclerosis lesions in apoE(0) mice. Thus, we used h-apoA-IV/E-0 mice to determine whether h-apoA-IV plays a protective role after LPS administration.Methods and Results-We injected apoE(0), h-apoA-IV/E-0, and C57Bl/6 (wild-type) mice intraperitoneally with either LPS or phosphate-buffered saline (PBS) every week for 10 weeks. Atherosclerotic lesions were significantly smaller in h-apoA-IV/E-0 mice treated with LPS than in their apoE(0) counterparts. The titers of IgG2a and IgG2b autoantibodies to oxidized low-density lipoprotein (LDL) were higher in the LPS-group of h-apoA-IV/E-0 mice than in apoE(0) mice, suggesting that the Th1 response is stronger in the presence of h-apoA-IV. Lymphocytes from the blood, liver, spleen, and thymus of h-apoA-IV/E-0 mice treated with LPS produced less IL-4, INF-gamma, and TNF-alpha proinflammatory cytokines than their apoE(0) counterparts. Furthermore, we demonstrated that recombinant h-apoA-IV blocks the LPS-induced stimulation of monocytes.Conclusions-The expression of h-apoA-IV in apoE(0) mice reduces the susceptibility to atherogenesis and decreases the secretion of proinflammatory cytokines after LPS administration.

Transferrin (Tf), the iron-transport protein of vertebrate serum, is mainly synthesized in hepatocytes but is also found in other cell-types including oligodendrocytes. Our laboratory has characterized in a human oligodendrial cell line the presence of a new Tf transcript containing an alternative exon 1b replacing the classical exon 1 and conducting to the elimination of the signal peptide sequence. In this manuscript, we show by RT-PCR and 5′-RACE experiments that alternative transcripts also exist in mouse and rat and are found in brain mRNA preparations. Mouse alternative first exon is homologous to human exon 1b while rat Tf gene was found to use a new first exon named 1c. In all species, the alternative transcript does not contain the signal peptide sequence and possibly encode for a Tf protein devoid of signal peptide showing that this phenomenon is not restricted to human gene. We also present genomic sequence data from the previously unknown 5′ genomic rat region, which allowed the alignment of the alternative exons 1 in the three species.

The Interleukin Enhancer Binding Factor 3 (ILF3) gene has been mapped to chromosome 19 in humans and to chromosome 9 in mice. Several reported double-stranded RNA binding proteins including NF90, ILF3, MPP4 and DRBP76 have been suggested to be isoforms of the ILF3 gene but this has not been clearly established. We isolated several ilf3 transcripts from a melanoma cDNA library and two corresponding genomic fragments, and report alternative splicing and polyadenylation site selection in the human ILF3 gene. We show the existence of an alternative splice site responsible for the sequence divergence in the 3′ part of the transcripts. Another alternative splicing event at a site between the two double-stranded RNA binding motifs leads to the additional presence in some cases of a four amino acids NVKQ peptide. We also describe the utilization of three distinct polyadenylation signals and the generation of an ilf3 transcript with a long extended 3′ UTR. The expression of the different transcripts was evaluated. We used a GenBank sequence for the part of chromosome 19 corresponding to the ILF3 gene to determine the exon-intron organization of the entire gene which spans 38 kb and is divided into 21 exons.