Loss of imprinting of insulin-like growth factor-II (IGF2) gene in distinguishing specific biologic subtypes of Wilms tumor.

BACKGROUND: Loss of imprinting (LOI) of the insulin-like growth factor-II (IGF2) gene, an epigenetic alteration associated with expression of the normally silent maternal allele, was observed first in Wilms tumor. Although LOI has subsequently been detected in most adult tumors, the biologic role of LOI in cancer remains obscure. We analyzed the imprinting status of Wilms tumors with respect to pathologic subtype, stage, and patient's age at diagnosis and examined the expression of genes potentially affected by LOI. METHODS: Of 60 Wilms tumors examined, 25 were informative for an ApaI polymorphism in the IGF2 gene, allowing analysis of allele-specific gene expression, and could be classified by pathologic subtype. Gene expression was measured quantitatively by real-time polymerase chain reaction, and pathologic analysis was blinded for genetic status. All statistical tests were two-sided. RESULTS: We observed LOI of IGF2 in nine (90%) of 10 Wilms tumors classified as having a pathologic subtype associated with a later stage of renal development and in only one (6.7%) of 15 Wilms tumors with a pathologic subtype associated with an earlier stage of renal development (P< .001). LOI was associated with a 2.2-fold increase (95% confidence interval [CI] = 1.6-fold to 3.1-fold) in IGF2 expression (P< .001). Children whose Wilms tumors displayed LOI of IGF2 were statistically significantly older at diagnosis (median = 65 months; interquartile range [IQR] = 47-83 months) than children whose tumors displayed normal imprinting (median = 24 months; IQR = 13-35 months; P< .001). CONCLUSIONS: These data demonstrate a clear relationship between LOI and altered expression of IGF2 in Wilms tumors and provide a molecular basis for understanding the divergent pathogenesis of this cancer. Analysis of LOI could provide a valuable molecular tool for the classification of Wilms tumor.

Loss of imprinting of insulin-like growth factor-II in Wilms' tumor commonly involves altered methylation but not mutations of CTCF or its binding site.

Loss of imprinting (LOI) is the most common molecular abnormality in Wilms' tumor (WT), other embryonal cancers, and most other tumor types. LOI in WT involves activation of the normally silent maternal allele of the insulin-like growth factor-II (IGF2) gene, silencing of the normally active maternal allele of the H19 gene, and aberrant methylation of a differentially methylated region (DMR) upstream of the maternal copy of H19. Recently, the transcription factor CTCF, which binds to the H19 DMR, has been implicated in the maintenance of H19 and IGF2 imprinting. Here, we show that mutations in the CTCF gene or in the H19 DMR do not occur at significant frequency in WT, nor is there transcriptional silencing of CTCF. We also confirm that methylation of the H19 DMR in WT with LOI includes the CTCF core consensus site. However, some WTs with normal imprinting of IGF2 also show aberrant methylation of CTCF binding sites, indicating that methylation of these sites is necessary but not sufficient for LOI in WT.

Gene regulatory functions of Drosophila fish-hook, a high mobility group domain Sox protein.

In this study we investigate the gene regulatory functions of Drosophila Fish-hook (Fish), a high mobility group (HMG) Sox protein that is essential for embryonic segmentation. We show that the Fish HMG domain binds to the vertebrate Sox protein consensus DNA binding sites, AACAAT and AACAAAG, and that this binding induces an 85 degrees DNA bend. In addition, we use a heterologous yeast system to show that the NH2-terminal portion of Fish protein can function as a transcriptional activator. Fish directly regulates the expression of the pair rule gene, even-skipped (eve), by binding to multiple sites located in downstream regulatory regions that direct formation of eve stripes 1, 4, 5, and 6. Fish may function along with the Drosophila POU domain proteins Pdm-1 and Pdm-2 to regulate eve transcription, as genetic interactions were detected between fish and pdm mutants. Finally, we determined that Fish protein is expressed in a dynamic pattern throughout embryogenesis, and is present in nuclear and cytoplasmic compartments.

Quantitative trait loci modulate neutrophil infiltration in the liver during LPS-induced inflammation.

A crucial aspect of the inflammatory response is the recruitment of activated neutrophils (PMN) to the site of damage. Lytic enzymes and oxygen radicals released by PMN are important in clearing an infection or cellular debris, but can also produce host tissue damage. Failure to properly regulate the inflammatory response contributes to a variety of human diseases like sepsis and multiple organ dysfunction syndrome, the leading cause of morbidity and mortality in surgical intensive care units. Many aspects of human disease pathology, including hepatic PMN infiltration, can be recapitulated in mice using an endotoxic shock model. Six quantitative trait loci that predispose to high infiltration of PMN in hepatic sinusoids after high-dose endotoxin administration were provisionally identified. Two of these loci, Hpi1 and Hpi2 on mouse chromosomes 5 and 13, were mapped to the significant and highly significant level using a low-resolution genome scan on 122 intercross animals. These loci interact epistatically to produce a high degree of PMN infiltration. Intercross and recombinant inbred strain mice with a specific genotype at these loci always had a high infiltration response, indicating that genotype analysis at just these two loci can accurately predict a high PMN infiltration response. Genetic predisposition to the degree of PMN infiltration in the inflammatory response in mice suggests that analogous genetic mechanisms occur in human beings that could be used for diagnostic purposes.