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United States Department of Agriculture

Agricultural Research Service

Research Project: FUNCTIONAL GENOMICS OF LACTATION: EFFECTS OF GENETICS, HORMONES AND SUBSTRATES Project Number: 3092-51000-054-20
Project Type: Specific Cooperative Agreement

Start Date: Apr 01, 2009
End Date: Mar 31, 2014

Objective:
Objective 1: Determine gene expression in human lactating mammary epithelium. Subobjective 1A: Determine the pattern of mammary epithelial gene expression using milk fat globule mRNA from delivery through the first 4 weeks of lactation. Compare these results with those in mothers of premature infants and teenage mothers over a similar period of time. Subobjective 1B: Characterize the mRNA response to exogenous lactogenic hormones. Objective 2: Characterize inbred mouse strains for lactation performance, gene expression and weight gain among offspring in lean and obese animals, making use of a cross-fostering design where appropriate. Subobjective 2A. Identify genes in which strain-dependent differences in mammary gland gene expression, and SNP haplotype, are correlated with strain-dependent differences in milk production, lactation persistence, mammary gland development, or milk composition. Subobjective 2B. Determine the extent to which genes identified from the whole genome scan and microarray work described in 2A are responsible for the lactation defect in mice with maternal obesity. Objective 3: Study the effect of nutrients on mammary gland development and function in mouse models. Define the critical window for effects on mammary gland development and function. Subobjective 3A1. Determine effect of exposure to low protein diet by analyzing mammary gland development, milk production, and milk composition, as well as gene expression and gene promoter methylation in mammary gland tissue of dams exposed to diets with low protein content during gestation. Subobjective 3A2. Use a mouse model for tissue-specific alteration of Dnmt1 levels to confirm role of DNA methylation in effects of low protein diet on mammary gland development. Subobjective 3B. Define critical window for effect of low protein diet on mammary gland function by limiting nutritional intervention to specific developmental windows. Subobjective 3C. Determine impact of low protein diet on genetic variants for mammary gland development and lactation capacity as identified in objective 2.

Approach:
Children's Nutrition Research Center researchers will determine gene expression in human lactating mammary epithelium by isolating mRNA from human colostrum or milk over the first 4 weeks post partum and the expression arrays measured to determine the relative gene express over this period of time. Data from groups of mothers will be assessed to prove or disprove our hypotheses. A variety of potential lactogenic hormones will be administered short term (over 3 days) to normal women with established lactation between 6 and 12 weeks post partum. The hormones initially to be tested are prolactin, cortisol, and IGF-1. Breast milk will be collected every 3 hr and RNA isolated for measurement of expression of mRNA expression using microchip technology. The data will be compared to that already obtained from similar studies in women prior to and following the administration of recombinant human growth hormone. Additionally, a panel of lactation traits will be measured in 32 inbred strains of mice. The data from these measurements will be used as phenotype data in combination with whole genome SNP data to conduct a statistical association analysis across the entire mouse genome. The Viable yellow agouti (Avy) mouse will be used as a model of maternal obesity. Gene expression will be determined by microarray analysis of mammary tissue samples collected from obese and lean Avy females during early lactation. Genes that are differentially expressed between lean and obese females will then be compared to the list of genes identified to test for overlap. The lactation traits, as well as gene expression and epigenetic profiles will be measured in transgenic animals containing the conditional allele for Dnmt1 (dnmt1-lox2) and a mammary gland specific Cre recombinase to determine the effects of deletion in the mammary gland of Dnmt1. The data will be compared to those of low protein diets.

Last Modified: 12/18/2014
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