Genomic organization and sequence of the Gus-s alpha allele of the murine beta-glucuronidase gene

Blockade of IP-10/CXCR3 Promotes Progressive Renal Fibrosis

BACKGROUND/AIM

Fibrosis is a hallmark of progressive organ disease. The 10-kDa interferon-inducible protein IP-10/CXCL10 is a potent chemoattractant for activated T lymphocytes, natural killer cells, and monocytes. However, the involvement of IP-10 in the pathogenesis of renal diseases via its receptor, CXCR3, remains unclear. To contribute to the clarification of this issue was the aim of this study.

METHODS

The impacts of IP-10 on renal fibrosis were investigated in a unilateral ureteral obstruction model in CXCR3-deficient mice and mice treated with anti-IP-10-neutralizing monoclonal antibody. Anti-IP-10 monoclonal antibody (5 mg/kg/day) was injected intravenously once a day until sacrifice on days 1, 4, or 7 after treatment. The effects of IP-10 were confirmed in cultured tubular epithelial cells.

RESULTS

IP-10 and CXCR3 were upregulated in progressive renal fibrosis. Blockade of IP-10/CXCR3 promotes renal fibrosis, as evidenced by increases in interstitial fibrosis and hydroxyproline contents, concomitant decrease in hepatocyte growth factor expression, and converse increase in transforming growth factor-beta1 in diseased kidneys. IP-10 blockade affected neither macrophage nor T cell infiltration in diseased kidneys.

CONCLUSION

These results suggest that blockade of IP-10 via CXCR3 contributes to renal fibrosis, possibly by upregulation of transforming growth factor-beta1, concomitant with downregulation of hepatocyte growth factor.

Widespread correction of lysosomal storage following intrahepatic injection of a recombinant adeno-associated virus in the adult MPS VII mouse

Mucopolysaccharidosis type VII is a lysosomal storage disease caused by deficiency of the acid hydrolase beta-glucuronidase. MPS VII mice develop progressive lysosomal accumulation of glycosaminoglycans within multiple organs, including the brain. Using this animal model, we investigated whether gene transfer mediated by a recombinant adeno-associated virus (rAAV) type 2 vector is capable of reversing the progression of storage in adult mice. We engineered an rAAV2 vector to carry the murine beta-glucuronidase cDNA under the transcriptional direction of the human elongation factor-1alpha promoter. Intrahepatic administration of this vector in adult MPS VII mice resulted in stable hepatic beta-glucuronidase expression (473 +/- 254% of that found in wild-type mouse liver) for at least 1 year postinjection. There was widespread distribution of vector genomes and beta-glucuronidase within extrahepatic organs. The level of enzyme activity was sufficient to reduce lysosomal storage within the liver, spleen, kidney, heart, lung, and brain. Within selected regions of the brain, neuronal, glial, and perivascular cells had histopathologic evidence of reduced storage. Also, brain alpha-galactosidase and beta-hexosaminidase enzyme levels, secondarily elevated by the storage abnormality, were normalized. These data demonstrate that peripheral administration of an rAAV2 vector in adult MPS VII mice can lead to transgene expression levels sufficient for improvements in both the peripheral and the central manifestations of this disease.

Recombinant adeno-associated virus-mediated correction of lysosomal storage within the central nervous system of the adult mucopolysaccharidosis type VII mouse

The central nervous system (CNS) is a predominant site of involvement in several lysosomal storage diseases (LSDs); and for many patients, these diseases are diagnosed only after the onset of symptoms related to the progressive accumulation of macromolecules within lysosomes. The mucopolysaccharidosis type VII (MPS VII) mice are deficient for the lysosomal enzyme beta-glucuronidase and, by early adulthood, develop a significant degree of glycosaminoglycan storage within neuronal, glial, and leptomeningeal cells. Using this animal model, we investigated whether gene transfer mediated by a recombinant adeno-associated virus (rAAV) vector is capable of reversing the progression of storage lesions within the CNS. Adult MPS VII mice received intracerebral injections of 4 X 10(7) infectious units of a rAAV vector carrying the murine beta-glucuronidase (gus-s(a)) cDNA under the transcriptional direction of the cytomegalovirus immediate-early promoter and enhancer. By 1 month after vector administration, transgene-derived beta-glucuronidase was present surrounding the injection site. Enzyme levels were between 50 and 240% of that found in wild-type mice. This level of beta-glucuronidase activity was sufficient to reduce the degree of lysosomal storage. Moreover, the reduction in storage was maintained for at least 3 months post-rAAV administration. These data demonstrate that rAAV vectors can transduce the diseased CNS of MPS VII mice and mediate levels of transgene expression necessary for a therapeutic response. Thus, rAAV vectors are potential tools in the treatment of the mucopolysaccharidoses and other lysosomal storage diseases.

Analysis of the 5' flanking region of the human beta-glucuronidase gene

We have sequenced 4.2 kb of the 5' flanking region of the human beta-glucuronidase gene, compared this sequence to the 5' upstream sequence reported for the murine gene, determined the transcription start sites of the human gene, and studied expression of human minigene deletion constructs in COS cells. The 200 bp immediately 5' to the translation initiation codon have a high G + C content (72%) and contain no TATA box, two properties commonly associated with "housekeeping genes." The sequence 5' to -200 bp contains seven Alu repetitive elements which account for more than 50% of this flanking sequence. From deletion analysis of minigene constructs, 200 bp of 5' sequence appeared sufficient for maximal expression in transfected COS cells. S1 nuclease protection analysis showed that transcription initiates from a cluster of sites around -30 bp in all tissues examined. In some cases, a low but detectable level of transcription also initiates 126 bp upstream of the ATG. Inspection of the sequence surrounding both start sites revealed some similarity to the recently described "initiator" transcriptional control element (S.T. Smale and D. Baltimore (1989), Cell 57: 103-113). Comparison of the 5'flanking sequence with that available from the murine beta-glucuronidase gene reveals only one 28-bp highly conserved region, which surrounds the -126 start site.

Genomic organization and DNA sequence of the mouse kidney androgen-regulated protein (KAP) gene

The gene for kidney androgen-regulated protein (KAP) is expressed under androgenic control in the epithelial cells of the renal cortical proximal tubules. However, there is an androgen-independent component of the expression of this gene that occurs specifically in the outermedullary S3 segments of the proximal tubules. In these cells, the KAP gene is estrogen responsive and its expression is dependent on pituitary function. As a first step in correlating its interesting cell-specific and hormonal regulation with the structure of the gene, the genomic organization of the KAP gene was described and sequence of the gene and the proximal 1 kb of 5'-flanking DNA was determined. Sequence motifs were identified in the 5'-flanking DNA that may function in the regulation KAP gene expression by androgen, estrogen, and pituitary glycoprotein hormones. The gene is present in a single copy in the mouse genome and is 3,807 nucleotides in length. It contains 4 exons of 120, 177, 63, and 251 nucleotides and three intervening sequences of 1,450, 126, and 1,620 nucleotides. The gene exhibits a high degree of a genetic polymorphism as revealed by comparison of restriction digests of DNA from two highly inbred strains, BALB/c and C57BL/6.

Cloning and characterization of the human beta-glucuronidase gene

We have isolated a cosmid clone that contains GUSB, the human gene encoding beta-glucuronidase. The 21-kb gene contains 12 exons ranging from 85 to 376 bp in length. Exon 6 corresponds to the 153-bp deletion in the shorter of two types of cDNAs reported earlier, supporting the hypothesis that this cDNA arose by alternate splicing leading to exon skipping. The insert contains 4.2 kb of sequence upstream from the first exon and 6 kb 3' of the last exon. The clone expresses human beta-glucuronidase in stably transformed rat XCtk- cells. Comparison of the human gene organization with that recently reported for the murine beta-glucuronidase gene revealed that the intron/exon boundaries are identical. In the splice junctions, the most highly conserved regions are those identified as consensus sequences, and these are at least as highly conserved as bases encoding the translated portion of the gene.

Use of antisense RNA to help identify a genomic clone for the 5' region of mouse beta-glucuronidase

It was possible to gauge the inhibition of mouse beta-glucuronidase expression by injecting RNA, made from both strands of subclones of a cosmid containing the complete gene, into mouse blastomeres at the four-cell stage. Although our initial screen did not identify the 5' region, we were able to isolate a subclone containing homology to 20 bp coding for N-terminal amino acids of rat and human beta-glucuronidase structural genes. Antisense RNA prepared from one strand of the 350 bp Pst I subclone inhibited beta-glucuronidase expression by 89% while RNA prepared from the other strand had little effect. The subclone appears to correspond to the 350 bp fragment identified by others as one including the ATG start site of mouse beta-glucuronidase.