Lactase non-persistence (adult-type hypolactasia) results in digestive system malabsorption of lactose, the carbohydrate macronutrient present in milk. Human DNA sequence variants associated with intestinal lactase persistence and non-persistence have recently been identified. This research project focuses on characterization of the genetic determinants of intestinal lactase persistence in humans. We have previously characterized molecular mechanisms regulating intestine-specific expression of the rat lactase gene in cell culture and in living animals. We will now direct attention to characterization of the molecular mechanisms mediating human lactase gene persistence and non- persistence and the temporal decline of lactase in rodents. Preliminary studies have shown that DNA sequences in the region of lactase gene polymorphisms can bind nuclear proteins and enhance lactase promoter activity. We hypothesize that DNA polymorphisms associated with lactase persistence function to regulate lactase gene transcription in adult human enterocytes via differential interaction with specific nuclear protein transcription factors. Research objectives are therefore aimed at defining the mechanistic roles of genetic determinants of human lactase persistence.
In Aim 1, we will characterize a functional role for DNA polymorphisms associated with persistence of lactase gene transcription in humans. Functional characterization of lactase gene polymorphisms will be investigated in cell culture and in vivo in transgenic mice.
In Aim 2, we will define the molecular mechanisms regulating human lactase persistence gene transcription. The goals of this aim will be to identify and characterize nuclear proteins capable of interacting with DNA sequences in the region of lactase gene polymorphisms associated with lactase persistence and to characterize whether the nuclear proteins function to regulate lactase transcription.
In Aim 3, to complement our investigation of the mechanism of lactase persistence in humans, we will further elucidate mechanisms regulating the temporal decline of lactase in rodents. Knowledge of mechanisms regulating human lactase gene expression may provide future novel diagnostic, therapeutic or prognostic strategies for gastrointestinal disorders that result in loss or inappropriate gain of epithelial cell digestive function. Our combination of in vitro and in vivo experimental approaches will elucidate roles for the genetic determinants associated with lactase persistence and non-persistence.

Public Health Relevance

Adult-onset hypolactasia, lactase non-persistence, renders much of the world's adult human population intolerant of excessive consumption of milk and other dairy products. In some adults, however, high levels of lactase enzyme activity persist in adulthood presumably due to inheritance of a genetic mutation that prevents the normal maturational decline in lactase expression. Knowledge of mechanisms regulating expression of the digestive lactase gene may provide novel strategies for enhancing expression of digestive enzymes in intestinal diseases and will have broad implications for understanding regulation of other genes with aging.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
3R01DK060715-10S1
Application #
8720278
Study Section
Clinical and Integrative Gastrointestinal Pathobiology Study Section (CIGP)
Program Officer
Carrington, Jill L
Project Start
2001-12-01
Project End
2014-06-30
Budget Start
2013-09-15
Budget End
2014-06-30
Support Year
10
Fiscal Year
2013
Total Cost
$129,817
Indirect Cost
$49,197
Name
Stanford University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
Chen, Chin; Sibley, Eric (2012) Expression profiling identifies novel gene targets and functions for Pdx1 in the duodenum of mature mice. Am J Physiol Gastrointest Liver Physiol 302:G407-19
Fang, Lin; Ahn, Jong Kun; Wodziak, Dariusz et al. (2012) The human lactase persistence-associated SNP -13910*T enables in vivo functional persistence of lactase promoter-reporter transgene expression. Hum Genet 131:1153-9
Chen, Chin; Fang, Rixun; Chou, Lin-Chiang et al. (2012) PDX1 regulation of FABP1 and novel target genes in human intestinal epithelial Caco-2 cells. Biochem Biophys Res Commun 423:183-7
Chen, Chin; Leavitt, Tripp; Sibley, Eric (2012) Intestinal Pdx1 mediates nutrient metabolism gene networks and maternal expression is essential for perinatal growth in mice. Biochem Biophys Res Commun 424:549-53
Olds, Lynne C; Ahn, Jong Kun; Sibley, Eric (2011) 13915*G DNA polymorphism associated with lactase persistence in Africa interacts with Oct-1. Hum Genet 129:111-3
Sibley, Eric; Ahn, Jong Kun (2011) Theodore E. Woodward Award: lactase persistence SNPs in African populations regulate promoter activity in intestinal cell culture. Trans Am Clin Climatol Assoc 122:155-65
Fu, Ya-Yuan; Lu, Chih-Hsuan; Lin, Chi-Wen et al. (2010) Three-dimensional optical method for integrated visualization of mouse islet microstructure and vascular network with subcellular-level resolution. J Biomed Opt 15:046018
Chen, Chin; Fang, Rixun; Davis, Corrine et al. (2009) Pdx1 inactivation restricted to the intestinal epithelium in mice alters duodenal gene expression in enterocytes and enteroendocrine cells. Am J Physiol Gastrointest Liver Physiol 297:G1126-37
Fu, Ya-Yuan; Lin, Chi-Wen; Enikolopov, Grigori et al. (2009) Microtome-free 3-dimensional confocal imaging method for visualization of mouse intestine with subcellular-level resolution. Gastroenterology 137:453-65
Fu, Ya-Yuan; Sibley, Eric; Tang, Shiue-Cheng (2008) Transient cytochalasin-D treatment induces apically administered rAAV2 across tight junctions for transduction of enterocytes. J Gen Virol 89:3004-8

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