The H19 locus belongs to a cluster of imprinted genes that is linked to the human Beckwith-Wiedemann syndrome. The expression of H19 and its closely associated IGF2 gene is frequently deregulated in some human tumors, such as Wilms' tumors. In these cases, biallelic IGF2 expression and lack of expression of H19 are associated with hypermethylation of the imprinting center of this locus. These observations and others have suggested a potential tumor suppressor effect of the H19 locus. Some studies have also suggested that H19 is an oncogene, based on tissue culture systems. We show, using in vivo murine models of tumorigenesis, that the H19 locus controls the size of experimental teratocarcinomas, the number of polyps in the Apc murine model of colorectal cancer and the timing of appearance of SV40-induced hepatocarcinomas. The H19 locus thus clearly displays a tumor suppressor effect in mice.genomic imprinting ͉ Igf2 ͉ murine models T he H19-Igf2 locus is subject to genomic imprinting and has often been used as a paradigm for the study of this particular epigenetic regulation. The H19 locus produces a 2.5-kb noncoding, spliced, and polyadenylated RNA of yet-unknown function (1, 2). The Igf2 gene encodes a fetal growth factor, insulin-like growth factor 2. These two genes are located 90 kb apart and are oppositely imprinted: H19 is maternally expressed and Igf2 paternally expressed (1, 3). They belong to a large imprinted domain localized on chromosome 7 in mice and chromosome 11p15.5 in humans. The imprinting of Igf2 and H19 is controlled by a region located 4 kb upstream from the H19 transcription unit, defined as the H19 differentially methylated region (DMR) or imprinting control region (ICR) (4).The 11p15.5-imprinted domain is linked to the BeckwithWiedemann syndrome (BWS), which is characterized by overgrowth phenotypes of affected children as well as a predisposition to develop embryonal tumors such as Wilms' tumor or rhabdomyosarcomas (5). Among the molecular alterations involved in BWS, certain cases (20%) show paternal uniparental disomy (UPD); other cases (5-10%) have hypermethylation of the H19 DMR; and both lead to lack of expression of H19 as well as activation of IGF2. These patients have higher risk of developing tumors than patients with other molecular defects (6). Genetic and epigenetic alterations at 11p15.5 similar to those found in the BWS have also been demonstrated in nonsyndromic Wilms' tumors. A great number of these cases have either loss of the maternal allele (LOH) or LOI (7,8). It has thus been suggested that the H19 gene could have a possible tumor suppressor function (9). The first direct evidence for this tumor suppressor function was provided by in vitro experiments in which transfection of H19 cDNA into G401-transformed kidney cells resulted in loss of tumorigenicity of these cells (10). Subsequent experiments performed with in vitro culture systems suggested that H19 played a role as an oncogene rather than a tumor suppressor gene (11,12). This controversy has not yet been reso...

Spinal muscular atrophy (SMA) is a recessive autosomal disorder characterized by degeneration of lower motor neurons caused by mutations of the survival motor neuron gene (SMN1). No curative treatment is known so far. Mutant mice carrying homozygous deletion of Smn exon 7 directed to neurons display skeletal muscle denervation, moderate loss of motor neuron cell bodies and severe axonal degeneration. These features, similar to those found in human SMA, strongly suggest the involvement of a dying back process of motor neurons and led us to test whether neurotrophic factors might have a protective role in SMA. We report here the therapeutic benefits of systemic delivery of cardiotrophin-1 (CT-1), a neurotrophic factor belonging to the IL-6 cytokine family. Intra-muscular injection of adenoviral vector expressing CT-1, even at very low dose, improves median survival, delays motor defect of mutant mice and exerts protective effect against loss of proximal motor axons and aberrant cytoskeletal organization of motor synaptic terminals. In spite of the severity of SMA phenotype in mutant mice, CT-1 is able to slow down disease progression. Neuroprotection could be regarded as valuable therapeutic approach in SMA.

Spinal muscular atrophy (SMA) is a motor neuron disease caused by mutations of the survival motor neuron 1 gene (SMN1). No curative treatment is available. Mutant mice carrying homozygous deletion of Smn exon 7 directed to neurons display a degenerative process of motor neurons similar to that found in human SMA. To test whether riluzole, which exhibits neurotrophic properties, might have a protective role in SMA, mutant mice were treated with it after the onset of the degenerative process. Riluzole improved median survival and exerted a protective effect against aberrant cytoskeletal organization of motor synaptic terminals but not against loss of proximal axons. These results demonstrate that the disease course of SMA can be attenuated after the onset of neuromuscular defects and may warrant further investigation in a therapeutic trial in SMA.

A and Beaugrand M designed research; Nahon P selected patients; Pariès J analyzed data; Vaysse J tested IGF2 serum level; Couvert P, Kerjean A, Miroglio A and Chelly J performed molecular analyses; Couvert P and Ganne-Carrié N wrote the paper. Abstract AIM: To assess the predictive value of the insulinlike growth factor 2 (Igf2 ) methylation profile for the occurrence of Hepatocellular Carcinoma (HCC) in hepatitis C (HCV) cirrhosis. M E T H O D S : Pat ie nt s w i t h:(1) biops y-prove n compensated HCV cirrhosis; (2) available baseline frozen liver sample; (3) absence of detectable HCC; (4) regular screening for HCC; (5) informed consent for genetic analysis were studied. After DNA extraction from liver samples and bisulfite treatment, unbiased PCR and DHPLC analysis were performed for methylation analysis at the Igf2 locus. The predictive value of the Igf2 methylation profile for HCC was assessed by Kaplan-Meier and Cox methods. RESULTS: Among 94 included patients, 20 developed an HCC during follow-up (6.9 ± 3.2 years). The methylation profile was hypomethylated, intermediate and hypermethylated in 13, 64 and 17 cases, respectively. In univariate analysis, two baseline parameters were associated with the occurrence of HCC: age (P = 0.01) and prothrombin (P = 0.04). The test of linear tendency between the three ordered levels of Igf2 methylation and probability of HCC occurrence was significant (Log Rank, P = 0.043; Breslow, P = 0.037; Tarone-Ware, P = 0.039). CONCLUSION:

Methylation alterations at the IGF2 locus are more extensive than previously reported and DMR2 hypomethylation in lymphocyte DNA might be a specific epigenetic biomarker for familial adenomatous polyposis patients.