The Genomic Variants Impacting Milk Yield and Composition
Current data from the Centers for Disease Control indicate that the rate of exclusive breast feeding to 6 months has risen to 24.9% nationwide, coming close to the healthy people 2020 goal of 25%. However, almost half of states in the U.S. still have rates below this goal. In addition, aside from the fact that breastfed infants and their mothers experience better health outcomes, the shortages of infant formula occurring over the last 24 months strongly indicate that continued efforts to understand the biology of lactation and to support breastfeeding are more important than ever. Our team has used GWAS with whole genome and RNA sequencing data in an inbred mouse mapping panel to identify quantitative trait loci (QTL) and sets of lactation-dependent, mammary-expressed, genes that determine milk yield and composition in mice. Our current work is generating a dataset from a large-scale RNA-seq initiative for genome-wide identification mammary-specific expression QTL (eQTL) in the lactating mouse. We have used computational tools to model variant-gene, and gene-gene interactions as regulatory networks. These networks can identify candidate variants and genes that occupy important positions or modules within the system giving them greater potential to have a high impact without compromising organism fitness. We are expanding these results to the large collection of other maternal traits that we have measured. This research project will increase our understanding of how variation in maternal genome determines lactation success. Our working hypothesis is that species-conserved gene-variant modules within regulatory networks cooperate to optimize lactation outcomes.
Impact of the Maternal Microbiome on Milk Yield and Composition
The microbiota is known to be significant regulator of human physiology and disease. In the mammary gland, there is known to be both a breast tissue microbiome as well as a breast milk microbiome and both the origin and significance of these populations are subjects of vigorous debate and research. There is also evidence to support the idea that the intestinal microbiome can influence the dynamics of circulating hormones such as estrogen and oxytocin as well as some growth factors such as IGF-I. Work by our team has employed 16S sequencing of the maternal fecal microbiome from inbred mouse strains with extreme differences in ability to produce milk in support of their growing litters. Using antenatal antibiotic treatment and fecal microbiome transplantation we are testing the importance of changes in the maternal microbiota to milk production and composition.