Targeted deletion of the antisilencer/enhancer (ASE) element from intron 1 of the myelin proteolipid protein gene (Plp1) in mouse reveals that the element is dispensable for Plp1 expression in brain during development and remyelination.

Myelin proteolipid protein gene (Plp1) expression is temporally regulated in brain, which peaks during the active myelination period of CNS development. Previous studies with Plp1-lacZ transgenic mice demonstrated that (mouse) Plp1 intron 1 DNA is required for high levels of expression in oligodendrocytes. Deletion-transfection analysis revealed the intron contains a single positive regulatory element operative in the N20.1 oligodendroglial cell line, which was named ASE (antisilencer/enhancer) based on its functional properties in these cells. To investigate the role of the ASE in vivo, the element was deleted from the native gene in mouse using a Cre/lox strategy. Although removal of the ASE from Plp1-lacZ constructs profoundly decreased expression in transfected oligodendroglial cell lines (N20.1 and Oli-neu), the element was dispensable to achieve normal levels of Plp1 gene expression in mouse during development (except perhaps at postnatal day 15) and throughout the remyelination period following cuprizone-induced (acute) demyelination. Thus, it is possible that the ASE is non-functional in vivo, or that loss of the ASE from the native gene in mouse can be compensated for by the presence of other regulatory elements within the Plp1 gene.

Expression of myelin genes: comparative analysis of Oli-neu and N20.1 oligodendroglial cell lines.

The use of immortalized cells has been instrumental as a tool with which to study gene regulation. However, it is crucial to understand the status of a given cell line, especially when investigating the regulation of genes whose expression is developmentally regulated. Several immortalized cell lines have been derived from primary cultures of mouse oligodendrocytes. Two such cell lines, N20.1 and Oli-neu, were characterized here in terms of their relative expression of myelin genes at both the mRNA level and the protein level. Analysis of the splice isoforms expressed by the myelin proteolipid protein (Plp1), myelin basic protein (Mbp), and 2',3'-cyclic nucleotide 3'-phosphodiesterase (Cnp) genes, along with the relative amount of protein expressed by these genes, suggests that the cell lines are representative of immature oligodendrocytes, although Oli-neu cells appear to be farther along the differentiation pathway compared with N20.1 cells. Previous studies have shown that the developmental increase in Plp1 gene expression that occurs during the active myelination period is governed by transcription regulatory elements present within the first intron. The responsiveness of one of these elements, the so-called antisilencer/enhancer (ASE), was investigated in both cell lines. Results presented here suggest that the ASE has a much more potent effect in Oli-neu cells. Thus, the two cell lines appear to be at different stages and will be useful as a means to study transcription regulatory elements whose influence changes during development.

Biomarkers of Renal Injury in Cirrhosis: Association with Acute Kidney Injury and Recovery after Liver Transplantation.

BACKGROUND: To define urine or serum biomarkers in predicting renal function recovery after liver transplantation (LT). METHODS: Adults listed for LT (February 2011-July 2014) and with modified diet for renal disease-6 (MDRD-6) <60 mL/min provided urine/blood samples at baseline and serially until LT for biomarkers in serum (pg/mL) and urine (pg/mg creatinine). RESULTS: Of 271 LT listed patients (mean age 57 years, 63% males, median listing MELD 17.5), 1 year acute kidney injury (AKI) probability was 49%, with odds of 1.3-, 3.0-, 4.6-, and 8.5-fold times for listing MELD 16-20, 21-25, 26-30, and >30, compared to MELD <16. Thirty-seven people died over 1 year from the time of listing, with twofold increased odds with AKI. Among 67 patients with MDRD <60, only urinary epidermal growth factor was different comparing AKI (increase in serum creatinine ≥0.3 mg/dL from baseline within past 3 months) vs. no AKI (2,254 vs. 4,253, p = 0.003). Differences between acute tubular necrosis (ATN) and hepatorenal syndrome could not be ascertained for a small sample of 3 patients with ATN. Analyzing 15 of 43 receiving LT and MDRD-6 <30 prior to LT, biomarkers were not different comparing 5 patients recovering renal function (MDRD-6 >50 mL/min) at 6 months vs. 10 without recovery. CONCLUSIONS: AKI is common among LT listed patients, with a negative impact on transplant-free survival. Serum and urine biomarkers are not associated with the recovery of renal function after LT. Multicenter studies are suggested to (a) develop strategies to reduce the development of AKI and (b) derive novel biomarkers for use in accurately predicting renal recovery after LT.

Leydig cells express the myelin proteolipid protein gene and incorporate a new alternatively spliced exon.

Although the myelin proteolipid protein gene (Plp1) is highly expressed in the central nervous system encoding the most abundant myelin protein in oligodendrocytes, it is also expressed in other tissues, including testis. Transgenic studies with mice that harbor Plp1-lacZ fusion genes suggest that Leydig cells are the source of Plp1 gene expression in testis. However, virtually nothing is known about Plp1 gene regulation in Leydig cells, which is the focus of this study. The first intron contains both positive and negative regulatory elements that are important in regulating Plp1 gene expression in oligodendrocytes. To test whether these elements are functional in Leydig cells, a battery of Plp1-lacZ fusion genes with partial deletion of Plp1 intron 1 sequence was transfected into the mouse Leydig cell line, TM3. Results presented here suggest that an enhancer, which is very potent in oligodendrocytes, is only nominally active in TM3 cells. The intron also contains several negative regulatory elements that are operative in TM3 cells. Moreover a new exon (exon 1.2) was identified within the first 'intron' resulting in novel splice variants in TM3 cells. Western blot analysis suggests that these splice variants, along with those containing another alternatively spliced exon (exon 1.1) derived from intron 1 sequence, give rise to multiple Plp1 gene products in the mouse testis.