Alterations in expression of imprinted genes from the H19/IGF2 loci in a multigenerational model of intrauterine growth restriction (IUGR)

Abstract

Background The H19/IGF2 imprinted loci have attracted recent attention due to their role in cellular differentiation and proliferation, heritable gene regulation, and in utero or early postnatal growth and development. Expression from the imprinted H19/IGF2 locus involves a complex interplay of three means of epigenetic regulation: proper establishment of DNA methylation, promoter occupancy of CTCF and expression of microRNA-675 (miR675). We have previously demonstrated in a multigenerational rat model of intrauterine growth restriction the epigenetic heritability of adult metabolic syndrome in a F2 generation. We have further demonstrated abrogation of the F2 adult metabolic syndrome phenotype with essential nutrient supplementation of intermediates along the one-carbon pathway, and shown that alterations in the metabolome precede the adult onset of metabolic syndrome. However, the upstream molecular and epigenomic mediators underlying these observations have yet to be fully elucidated. Objective In the current study, we sought to characterize the impact of the intrauterine growth restricted lineage and essential nutrient supplementation on both levels and molecular mediators of H19 and IGF2 gene expression in the F2 generation. Study Design F2 intrauterine growth restricted and sham lineages were obtained by exposing P1 (grandmaternal) pregnant dams to bilateral uterine artery ligation or sham surgery at gestational day 19.5. F1 pups were allocated to the essential nutrient supplemented or control diet at postnatal day 21, and bred at 6–7 weeks of age. Hepatic tissues from the resultant F2 offspring at birth and at weaning (day 21) were obtained. Bisulfite modification and sequencing was employed for methylation analysis. H19 and IGF2 expression was measured by QPCR. Promoter occupancy was quantified using chromatin immunoprecipitation, or ChIP, against CTCF insulator proteins. Results Growth-restricted F2 on control diet demonstrated significant down-regulation in H19 expression as compared to sham lineage (0.7831 vs 1.287; p< 0.05); however, essential nutrient supplementation diet abrogates this difference (4.995 vs 5.100; p>0.05). Conversely, Igf2 was up regulated by essential nutrient supplemented diet on the sham lineage (2.0 fold, p=0.01), an effect that was not observed in the growth restricted offspring. A significant differential methylation was observed in the promoter region of region H19 among the intrauterine growth restricted lineage (18% vs 25%; p<0.05) on a control diet, while the essential nutrient supplemented diet was alternately associated with hypermethylation in both lineages (sham: 50%; IUGR: 84%, p<0.05). Consistent with essential nutrient supplementation impacting the epigenome, a decrease of CTCF promoter occupancy was observed in CTCF4 of the growth restricted lineage (2.45% vs 0.56%; p<0.05) on the control diet, an effect that was repressed with essential nutrient supplementaion. Conclusions Heritable growth restriction is associated with changes in H19 gene expression; the...

Effect of diet in females (F1) from prenatally undernourished mothers on metabolism and liver function in the F2 progeny is sex-specific

“…associated with reduced H19 expression, the imprinted gene integral to fetal growth and development via epigenetic modifications [41]. Strikingly, we found that growth-restricted F2 generation was not prone to develop obesity and associated metabolic disorders, contrary to previous studies [19,40].…”

Long-term cardiovascular consequences of fetal growth restriction: biology, clinical implications, and opportunities for prevention of adult disease

“…142 These epigenetic marks may also be transmitted to future generations. 134,143 This effect has also been demonstrated in animal models, showing that fetal adaptations such as endothelial dysfunction, hypertension, and insulin resistance are passed to the second and third generation of undernourished pregnant rats. 144 The relevance of epigenetics in the adaptation to chronic cardiac failure has been highlighted in human adults, with distinct reported signatures of DNA methylation in cardiac tissue.…”

Prenatal unhealthy diet, insulin‐like growth factor 2 gene (IGF2) methylation, and attention deficit hyperactivity disorder symptoms in youth with early‐onset conduct problems

“…Fifth, the IGF2 locus is a complex genomic region that produces multiple transcripts from alternative promoters, serves different biological functions, and is differentially expressed in different tissues and at different developmental periods. This gene may also shift from monoallelic to biallelic IGF2 promoter methylation during development (Issa, Vertino, Boehm, Newsham, & Baylin, ); can show sex differences in monoallelic tissue‐specific expression via parent of origin genetic effects (Pidsley et al., ); can show loss of imprinting due to diet (Waterland, Lin, Smith, & Jirtle, ); and has important functional genomic relationships (Gonzalez‐Rodriguez et al., ). Therefore, it will be important to establish the extent to which the present results can be replicated and extended with the addition of these molecular and epigenetic mediators and moderators.…”