ASO silencing of a glycosyltransferase, Poglut1 , improves the liver phenotypes in mouse models of Alagille syndrome

BACKGROUND AND AIMS

Paucity of intrahepatic bile ducts (BDs) is caused by various etiologies and often leads to cholestatic liver disease. For example, in patients with Alagille syndrome (ALGS), which is a genetic disease primarily caused by mutations in jagged 1 ( JAG1) , BD paucity often results in severe cholestasis and liver damage. However, no mechanism-based therapy exists to restore the biliary system in ALGS or other diseases associated with BD paucity. Based on previous genetic observations, we investigated whether postnatal knockdown of the glycosyltransferase gene protein O -glucosyltransferase 1 ( Poglut1) can improve the ALGS liver phenotypes in several mouse models generated by removing one copy of Jag1 in the germline with or without reducing the gene dosage of sex-determining region Y-box 9 in the liver.

APPROACH AND RESULTS

Using an ASO established in this study, we show that reducing Poglut1 levels in postnatal livers of ALGS mouse models with moderate to profound biliary abnormalities can significantly improve BD development and biliary tree formation. Importantly, ASO injections prevent liver damage in these models without adverse effects. Furthermore, ASO-mediated Poglut1 knockdown improves biliary tree formation in a different mouse model with no Jag1 mutations. Cell-based signaling assays indicate that reducing POGLUT1 levels or mutating POGLUT1 modification sites on JAG1 increases JAG1 protein level and JAG1-mediated signaling, suggesting a likely mechanism for the observed in vivo rescue.

CONCLUSIONS

Our preclinical studies establish ASO-mediated POGLUT1 knockdown as a potential therapeutic strategy for ALGS liver disease and possibly other diseases associated with BD paucity.

Sox9 Is a Modifier of the Liver Disease Severity in a Mouse Model of Alagille Syndrome

BACKGROUND AND AIMS

Alagille syndrome (ALGS) is a multisystem developmental disorder characterized by bile duct (BD) paucity, caused primarily by haploinsufficiency of the Notch ligand jagged1. The course of the liver disease is highly variable in ALGS. However, the genetic basis for ALGS phenotypic variability is unknown. Previous studies have reported decreased expression of the transcription factor SOX9 (sex determining region Y-box 9) in late embryonic and neonatal livers of Jag1-deficient mice. Here, we investigated the effects of altering the Sox9 gene dosage on the severity of liver disease in an ALGS mouse model.

APPROACH AND RESULTS

Conditional removal of one copy of Sox9 in Jag1+/- livers impairs the biliary commitment of cholangiocytes and enhances the inflammatory reaction and liver fibrosis. Loss of both copies of Sox9 in Jag1+/- livers further worsens the phenotypes and results in partial lethality. Ink injection experiments reveal impaired biliary tree formation in the periphery of P30 Jag1+/- livers, which is improved by 5 months of age. Sox9 heterozygosity worsens the P30 biliary tree phenotype and impairs the partial recovery in 5-month-old animals. Notably, Sox9 overexpression improves BD paucity and liver phenotypes in Jag1+/- mice without ectopic hepatocyte-to-cholangiocyte transdifferentiation or long-term liver abnormalities. Notch2 expression in the liver is increased following Sox9 overexpression, and SOX9 binds the Notch2 regulatory region in the liver. Histological analysis shows a correlation between the level and pattern of SOX9 expression in the liver and outcome of the liver disease in patients with ALGS.

CONCLUSIONS

Our results establish Sox9 as a dosage-sensitive modifier of Jag1+/- liver phenotypes with a permissive role in biliary development. Our data further suggest that liver-specific increase in SOX9 levels is a potential therapeutic approach for BD paucity in ALGS.

miR-489 Suppresses Proliferation and Invasion of Human Bladder Cancer Cells

MicroRNAs (miRNAs) have been shown to be involved in bladder cancer progression. miR-489 (also known as miR-489-3p) was recently reported to be a tumor suppressor in several cancers. However, its exact role and mechanism in the progression of bladder cancer are largely unknown. In this study, we explore the role of miR-489 in the proliferation and invasion of human bladder cancer cells. The miR-489 expression levels were detected in bladder cancer and normal adjacent tissues, as well as in human normal bladder epithelial cells and bladder cancer cell lines. The results showed that miR-489 was sharply reduced in bladder cancer tissues and cell lines. Then the miR-489 mimic or oligo anta-miR-489 was transfected into T24 and UMUC3 bladder cancer cell lines. The results showed that the miR-489 mimic greatly increased the miR-489 level and significantly decreased the proliferation and invasion of T24 and UMUC3 cells. In contrast, the anta-miR-489 had a completely opposite effect on miR-489 expression, cell proliferation, and cell invasion. Moreover, bioinformatics and luciferase reporter gene assays confirmed that miR-489 targeted the mRNA 3'-untranslated region (3'-UTR) region of Jagged1 (JAG1), a Notch ligand. In conclusion, miR-489 suppressed proliferation and invasion of human bladder cancer cells.

SNP array mapping of chromosome 20p deletions: genotypes, phenotypes, and copy number variation

The use of array technology to define chromosome deletions and duplications is bringing us closer to establishing a genotype/phenotype map of genomic copy number alterations. We studied 21 patients and five relatives with deletions of the short arm of chromosome 20 using the Illumina HumanHap550 SNP array to: 1) more accurately determine the deletion sizes; 2) identify and compare breakpoints; 3) establish genotype/phenotype correlations; and 4) investigate the use of the HumanHap550 platform for analysis of chromosome deletions. Deletions ranged from 95 kb to 14.62 Mb, and all of the breakpoints were unique. Eleven patients had deletions between 95 kb and 4 Mb and these individuals had normal development, with no anomalies outside of those associated with Alagille syndrome (AGS). The proximal and distal boundaries of these 11 deletions constitute a 5.4-Mb region, and we propose that haploinsufficiency for only 1 of the 12 genes in this region causes phenotypic abnormalities. This defines the JAG1-associated critical region, in which deletions do not confer findings other than those associated with AGS. The other 10 patients had deletions between 3.28 Mb and 14.62 Mb, which extended outside the critical region, and, notably, all of these patients had developmental delay. This group had other findings such as autism, scoliosis, and bifid uvula. We identified 47 additional polymorphic genome-wide copy number variants (>20 SNPs), with 0 to 5 variants called per patient. Deletions of the short arm of chromosome 20 are associated with relatively mild and limited clinical anomalies. The use of SNP arrays provides accurate high-resolution definition of genomic abnormalities.