NUTRITION AND EPIGENETIC PROGRAMMING OF OBESITY DURING DEVELOPMENT
Children's Nutrition Research Center
Project Number: 6250-51000-055-50
Specific Cooperative Agreement
Start Date: Apr 01, 2009
End Date: Mar 31, 2014
Obj 1: Identify genes that show epigenetic dysregulation in obesity using a candidate-gene approach. Subobj 1A. Characterize developmental establishment of DNA methylation at hypothalamic genes known to affect food intake regulation. Subobj 1B. Compare DNA methylation and expression of these genes between lean and obese mice. Obj 2: Determine if methylation and expression of specific genes in hypothalamus and/or adipose tissue differ between lean and obese mice. Subobj 2A. Identify genomic loci in hypothalamus and adipose tissue at which epigenetic dysregulation is associated with obesity. Subobj 2B. Determine if interindividual epigenetic variation at these loci is found before the onset of obesity. Obj 3: Determine if maternal obesity and/or nutrition before and during pregnancy persistently alters epigenetic regulation in offspring hypothalamus or adipose tissue. Subobj 3A. Identify genomic loci at which epigenetic dysregulation is induced by maternal obesity. Subobj 3B. Determine if this induced epigenetic dysregulation can be prevented by altering maternal diet. Obj 4: Identify placental epigenetic mechanisms that affect fetal nutrition, growth and development. Subobj 4A. Use methylation-specific amplification in conjunction with MSAM of genomic DNA extracted from trophoblast of normal term placentas and androgenetic complete hydatidiform moles to identify novel imprinted genes and other epigenetically regulated genes in trophoblast that play a role in regulation of fetal nutrition. Subobj 4B. Analyze how NLRP7, which is mutated in women with biparental hydatidiform moles, contributes to imprinting in early embryo and placenta. NLRP7 protein, known to have a role in innate immunity, may be a link between environmental changes (such as suboptimal maternal nutrition) and imprinting alterations during development. Obj 5: Determine how programming of glucose intolerance, obesity, and epigenetic dysregulation of skeletal muscle-growth in mice is affected by maternal diet during development. Preliminary data show that offspring of mice exposed to maternal low-protein (MLP) diet have reduction in skeletal muscle mass at <1 yr of age and possibly glucose intolerance. Subobj 5A. Extend phenotypic studies on muscle development, glucose tolerance, growth and obesity to include maternal methyl-donor depleted (MDD) diets and to follow offspring exposed to MLP or MDD diets for up to 18 months. Subobj 5B. To find the molecular basis for the altered muscle phenotype after MLP diet, we will perform array-based gene expression and methylation profiling, as well as gene expression analysis and DNA methylation analysis of candidate genes in hindleg muscle-tissues from 21-d-old and 1-yr-old mice exposed to MLP diet. Obj. 6 Utilize genome-wide DNA methylation profiling to determine if epigenetic programming/reprogramming contribute to lineage-specific patterns of gene expression. Obj. 7 Develop a targeted knock-in mouse model.
Children's Nutrition Research Center scientists will use the agouti viable yellow (Avy) mouse model to study the effects of maternal obesity on the risk of obesity in the offspring. DNA methylation in two tissues is known to play important roles in body weight regulation, hypothalamus and adipose tissue. Scientists will study this by using both a candidate gene approach and a genome-wide DNA methylation profiling technique (MSAM). In human studies, our research team will use MSAM and commercially available methylation screening tools such as the Illumina Infinium methylation array to identify genomic regions of differential methylation in complete hydatidiform moles compared with normal term placentas. Also, to characterize the role of NLRP7 in genomic imprinting, we will use chromatin immunoprecipitation to assess interactions of NLRP7 with chromatin, identify DNA binding sites of NLRP7 by electromobility shift assays, and screen for NLRP7 protein binding partners using yeast two-hybrid assays. Lastly, previous studies in a mouse model of the effects of maternal low protein diet on skeletal muscle development in the offspring will be extended to include longer-term studies and additional types of early exposures. This research will investigate fundamental mechanisms regulating DNA methylation during development, and characterize their involvement in nutritional programming during critical ontogenic periods.