Progress 10/01/02 to 09/30/07
Outputs
OUTPUTS: OBJECTIVE 1. Over the past year we have continued with studies on transgenic mice that are able to exogenously synthesize omega-3 (n-3) fatty acids (FA). We compared the effect of varying the n-3 FA levels present in both the gestational and lactational environment on the brain FA composition 10 day old suckling pups. We found that the ratio of n-6:n-3 FA in both the prenatal and neonatal diet directly affected the lipid composition of the pups' brains. We also compared the effects of these different n-3 FA environments on growth and adipose development, and found that the n-6:n-3 FA ratio present in the perinatal diet influenced growth and lipid metabolism throughout life. Abnormalities that have been observed in some of our transgenic mouse lines were more fully characterized during the course of the past year. The omega-3 desaturase transgenic mouse line was found to produce litters with an average size of 2.7 pups per litter, whereas wildtype females produced an average
of 7.2 pups per litter. It was determined that this reduced litter size was partially associated with the fact that a large number of implanted fetuses from pregnant transgenic females get resorbed during pregnancy. We also characterized the agalactic phenotype (absence or failure to secrete of milk) observed with transgenic mice expressing a delta-12 fatty acid desaturase gene under the control of the goat beta-casein promoter. Lactating females appear to have difficulty producing enough milk to nurse their pups, and the consistency of the milk itself is highly viscous. Mammary glands from transgenic and non-transgenic control mice were collected at various stages of development (pre-and post-puberty, pregnancy and lactation). Examination of mammary gland whole mounts revealed the formation of normal lobular alveoli structures in both transgenic and control virgins, however mammary development during pregnancy and continuing into lactation was severely stunted in transgenic mice. We
plan to further examine the probable causes for these aberrant phenotypes in the coming year. OBJECTIVE 3. The animal biotechnology website at UC Davis continues to be maintained and updated with information on animal biotechnology and genomics (http://animalscience.ucdavis.edu/animalbiotech). This includes links to the National Beef Cattle Evaluation Consortium (NBCEC) validation of commercial DNA tests for beef producers. A chapter entitled "Manipulation of Milk Fat Composition Through Transgenesis" was published in a book called "Bioactive Components in Milk." A paper on use of SNPs for paternity analysis and genetic evaluation on cattle ranches was published, and a NBCEC "Beef Sire Selection Workshop" was held in conjunction with the California Cattlemen's Association Annual Convention. Presentations on "Animal Biotechnology" were given at various venues including the ADSA-PSA-AMPA-ASAS Joint Annual Convention, the Transgenic Animal Conference, and the 2nd Symposium for
Agricultural Biotechnology Risk Analysis Research. Additionally, presentations on animal cloning were given at various producer meetings in anticipation of the release of the FDA's final risk assessment on animal clones.
PARTICIPANTS: Undergraduate Students: Kumitaa Theva Das, UC Davis Graduate Students: Kathleen Bongiovanni, Genetics MS student Kristin Deines, Animal Biology MS student William Pohlmeier, Animal Biology MS student Faculty: Dr. Ed DePeters, Animal Science Staff: Scott Taylor, SRA, Animal Science Kristine Lewis, SRA, Animal Science OBJECTIVE 3 Graduate Students: William Pohlmeier, Animal Biology MS student UC Faculty: Dr. Juan F. Medrano, Animal Science M. Cecilia T. Penedo, Veterinary Genetics Laboratory UC Cooperative Extension Advisors: Dan Drake, UCCE Livestock Advisor, Siskiyou County UC Staff: Kristine Lewis, SRA, Animal Science Collaborators: D. J. Garrick, Iowa State University R. L. Weaber, University of Missouri R. L. Quaas, Cornell University E. J. Pollak, Cornell University R. M. Thallman, USDA Meat Animal Research Center Partners: National Beef Cattle Evaluation Consortium California Beef Cattle Improvement Association California Cattlemen's Association Western United
Dairymen
TARGET AUDIENCES: OBJECTIVE 1 Human health researchers Publication of research in peer-reviewed research journals (eg Pediatric Research, Lipids) targets the audience of human health researchers who may be interested in the transgenic mice as models for their research. OBJECTIVE 3 Livestock producers. Educational materials on the applications of DNA-based biotechnologies including the website on marker-assisted selection, and research and extension on commercial genetic tests, and the use of SNPs for parentage identification in multisire pastures is made available on the animal biotechnology website, and knowledge is extended at producer meetings. Animal biotechnology researchers and extension educators. Presentations on the status and problems faced by the animal biotechnology industry at conferences, and publication of applied uses of animal biotechnologies in production journals (eg. Animal Science) targets this audience. General Public. Educational materials, including streaming
media information on biotechnology are made accessible and freely on the animal biotechnology website (http://animalscience.ucdavis.edu/animalbiotech/Outreach). Additionally no-cost ANR peer-reviewed educational fact sheets on animal biotechnology have been developed for download by the general audience (http://anrcatalog.ucdavis.edu).
PROJECT MODIFICATIONS: None
Impacts
The transgenic mouse research we have been conducting could have impacts on both human health research and ultimately the dairy industry. The endogenous mammary gland production of n-3 fatty acids in a transgenic mammal offers a unique opportunity to dissociate the effects of dietary fatty acids on fetal development from those of postnatal nutrition. Using this model we were able to answer questions related to the contribution of milk lipids to n-3 FA accretion in the neonatal brain. This research has practical relevance with regard to the implications of n-3 FA supplementation on infant brain development. We were also able to examine the effect of varying the n-6:n-3 FA ratio of milk on adipogenesis and the development of obesity. Fatty acids have been shown to play a central role in controlling the expression of genes involved in fatty acid metabolism and adipogenesis (formation of fat). High n-6 fatty acid intake early in life has been associated with hyperplasia
(increase in the number of the cells) and hypertrophy (increase in cell size) of white adipose tissue, whereas n-3 fatty acids have been shown to limit adipose stores by decreasing both fat cell number and the size of fat cells. The n-3 transgenic mouse model therefore has great utility to researchers interested in the interaction between fatty acid intake and human health. Understanding the mammary gland abnormalities observed in transgenic mice expressing the delta-12 fatty acid desaturase gene may be of great interest to researchers interested in mammary gland development and breast cancer. If the cause of impaired mammary development can be elucidated in this transgenic model, it may suggest an approach to prevent the growth of cancerous mammary tissue. Finally, increasing the n-3 content of dairy and beef products would be an effective way to increase the n-3 content of the American diet with resulting positive health benefits, and would offer a transgenic animal application with
obvious and immediate consumer benefits. Applications of animal biotechnologies and genomics are developing rapidly. There is a need to develop educational materials both for livestock producers on how and why they might want to apply DNA-based biotechnologies (parentage determination, genetic markers, genome-enabled selection etc.) on their ranches, and also the general public to inform the debate over some of the more controversial biotechnologies like genetic engineering and cloning. Relatively few scientists actively participate in the public discourse by developing educational materials detailing the science-based risks and benefits, in addition to the ethical issues, occasioned by these potentially-compelling technologies. The animal biotechnology website at UC Davis had 16,196 hits last year from all over the world, and provided information to both livestock producers and other interested parties on animal biotechnologies. Outreach presentations on topics ranging from cloning
to marker-assisted selection to audiences of producers and the general public provided a forum to disseminate science-based information on the uses and applications of a wide variety of different animal biotechnologies.
Publications
- A. L. Van Eenennaam, R. L. Weaber, D. J. Drake, M. C. T. Penedo, R. L. Quaas, D. J. Garrick, E. J. Pollak. 2007. DNA-based paternity analysis and genetic evaluation in a large commercial cattle ranch setting. Journal of Animal Science. 85:3159-3169.
- K. D. Bongiovanni, E. J. DePeters, and A. L. Van Eenennaam. 2007. Neonatal Growth and Development of Mice Raised on Milk Transgenically-Enriched with Omega-3 Fatty Acids. Pediatric Research. 62(4):412-6.
- A. L. Van Eenennaam. 2007. Animal biotechnology: where to from here? Abstract 805. 2007 ADSA-PSA-AMPA-ASAS Joint Annual Convention. July 7-12, 2007. San Antonio, TX. J. Anim. Sci. Vol. 85, Suppl. 1. Page 623 (Abstract).
- A. L. Van Eenennaam. 2007. Transgenic Animals: Where to from here? Transgenic Animal Research Conference VI. August 12-16, 2007. Tahoe City, CA. Transgenic Research 16: 839-840 (Abstract).
- K. C. Deines, K. A. Lewis and A. L. Van Eenennaam. 2007. Investigation of the Agalactic Phenotype in Fat-2 Transgenic Mice. Transgenic Animal Research Conference VI. August 12-16, 2007. Tahoe City, CA. Transgenic Research 16: 861-862 (Abstract).
- W. E. Pohlmeier, K. A. Lewis and A. L. Van Eenennaam. 2007. Reproductive Abnormalities in Fat-1 Transgenic Mice. Transgenic Animal Research Conference VI. August 12-16, 2007. Tahoe City, CA. Transgenic Research 16: 861 (Abstract).
- Deines, K. C. 2007. Analysis of the Impact of Differing n-3 PUFA Gestational and Lactational Environments on Adipose Development in Transgenic Fat-1 Mice and Investigation of the Agalactic Phenotype in Fat-2 Transgenic Mice. M.S. thesis in Animal Biology, UC Davis.
- A. L. Van Eenennaam, and J. F. Medrano. 2008. Manipulation of Milk Fat Composition Through Transgenesis, pages 343-354, Chapter in "Bioactive Components in Milk", Edited by Z. Bosze. Springer. 483 pp.
|
Progress 01/01/06 to 12/31/06
Outputs
OBJECTIVE 1. We have developed a transgenic mouse line that is able to endogenously synthesize omega-3 fatty acids in the mammary gland and produce milk with elevated levels of n-3 fatty acids. Experiments over the past year have examined the effects of neonatal n-3 FA supplementation with this omega-3 milk on cognitive development and obesity in mice. Our studies showed that consumption of the omega-3 milk resulted in the earlier maturation of visual abilities. They also revealed that neonatal provision of n-3 FA led to a decrease in the n-6:n-3 FA ratio in the brain, but that this difference diminished over time following prolonged exposure to a high n-6 FA diet after weaning. Early growth rate was correlated with dietary n-3 FA intake, with an increased rate of gain being observed in pups raised on control milk as compared to those raised on transgenic milk during the nursing period. Sixteen week body weight measurements of mice initially raised on either
transgenic or wildtype dams revealed no statistically significant difference between treatment groups, however the average mesenteric fat pad weight from mice in the control-fed group was heavier than that obtained from mice in the transgenic-fed treatment group. The adiposity index reflected a trend for the transgenically-fed mice to be leaner than their wildtype-fed counterparts, and similarly the body mass index (BMI) revealed a trend towards lower values for the transgenic-raised mice as compared to mice raised on control dams, although this data did not attain statistical significance. Interestingly, the mice raised on wildtype females had a significantly higher feed intake as adults as compared to the mice raised on transgenic females. To further investigate the effects of neonatal n-3 FA intake on obesity we plan to carry out further experiments with additional assays and monitoring which may reveal subtle trends with important ramifications to Western nations where changes
have in maternal diet (i.e. an increased n-6:n-3 FA ratio) and formula feeding have greatly increased the proportion of n-6 FA of neonatal diets. OBJECTIVE 3. Progress on objective three during the past year included the maintenance of the website (http://animalscience.ucdavis.edu/LivestockBiotechnology) for NC1010, and the animal biotechnology website (http://animalscience.ucdavis.edu/animalbiotech). Web pages detailing the results of the validation of commercial DNA tests for beef cattle producers were developed in conjunction with the NBCEC (National Beef Cattle Evaluation Consortium; http://www.nbcec.org/nbcec/). Details of this validation process were presented at the World Congress of Genetics Applied to Livestock Production and submitted to the Journal of Animal Science. The use of Marker Assisted Selection in Beef Cattle was also the topic of presentations given at the Beef Improvement Federation Convention and the NBCEC's Beef Genetics Roundup What's Happening in Beef Cattle
Genetics? teleconference. A chapter on DNA-Based Biotechnologies for beef producers was published in the NBCEC Beef Sire Selection Manual, and What is the future of Animal Biotechnology? appeared in California Agriculture.
Impacts
As a result of increased consumption of vegetable oils high in n-6 polyunsaturated fatty acids (PUFA), and the reduced consumption of fish and other foods rich in n-3 PUFA, typical Western diets contain n-6:n-3 PUFA ratios that are greater than 10. Health studies suggest that a dietary n-6:n-3 PUFA ratio closer to 5 would be more favorable. There is some evidence that high levels of n-6 PUFA during pregnancy and early infancy are associated with adipogenesis (differentiation of fat cells), and this may be a contributing factor in the development of obesity. Increasing the n-3 PUFA content of ruminant products offers a way to improve the nutritional content of an important component of the American diet, and provides a compelling example of how biotechnology could be employed to produce functional foods for the enhancement of human health. Independent, third-party validation of commercial DNA tests provides producers with some assurance that DNA-based tests perform in
accordance with the claims of the marketing companies, and may help to generate some of the data required to facilitate the integration of marker data into the national cattle evaluation. Publications detailing the applications of animal biotechnology in livestock production help to facilitate the adoption of genomic discoveries in commercial agriculture. Animal biotechnologies such as genetic engineering and cloning have come under increasing public scrutiny, and there is a need for general audience publications featuring science-based information on the uses and practice of these controversial technologies
Publications
- Bongiovanni, K. D., E. J. DePeters, and A. L. Van Eenennaam. 2006. Developmental and Behavioral Assessment of Neonatal Mice Raised on Milk Transgenically-Enriched with Omega-3 Fatty Acids. Abstract 827. Final program and abstract guide. XIV International Plant & Animal Genome Meeting, San Diego, CA, Jan.14-18, 2006. http://www.intl-pag.org/14/abstracts/PAG14_P827.html
- Bongiovanni, K. D. 2006. An analysis of the adiposity phenotype and cognitive benefits arising from the dietary supplementation omega-3 fats via a transgenic mouse model. M.S. thesis in Genetics, UC Davis.
- Kao, B. T., K. A. Lewis, E. J. DePeters, and A. L. Van Eenennaam. 2006. Endogenous Production and Elevated Levels of Long-Chain n-3 Fatty Acids in the Milk of Transgenic Mice. Journal of Dairy Science. 89:3195-3201.
- Kao, B. T., E. J. DePeters, and A.L. Van Eenennaam. 2006. Mice Raised on Milk Transgenically-Enriched with n-3 PUFA have Increased Brain Docosahexaenoic Acid. Lipids. 41(6):543-9. Sondeno, R. S., K. R. Nicholas, and A. L. Van Eenennaam. 2006. Identification of the echidna (Tachyglossus aculeatus) lysophosphatidic acid acyltransferase (LPAAT). Abstract 659. Final program and abstract guide. XIV International Plant & Animal Genome Meeting, San Diego, CA, Jan.14-18, 2006.
- Sondeno, R.S. 2006. Isolation of Tachyglossus aculeatus Lysophosphatidic Acid Acyltransferase (LPAAT) and characterization of Bos taurus and Arabidopsis thaliana LPAAT. M.S. thesis in Genetics, UC Davis.
- Van Eenennaam, A. L., J. Li, R. M. Thallman, R. L. Quaas, M. E. Dikeman, C. A. Gill, D. E. Franke, and M. G. Thomas. 2006. Validation of commercial DNA tests for quantitative beef quality traits. Journal of Animal Science. Accepted.
- Van Eenennaam, A. L., D. J. Drake, and M. C. T. Penedo. 2006. Paternity analysis in a large commercial ranch setting. Eighth World Congress of Genetics Applied to Livestock Production. August 13-18, 2006, Belo Horizonte, MG. Brazil.
|
Progress 01/01/05 to 12/31/05
Outputs
OBJECTIVE 1. The free-living nematode Caenorhabditis elegans is able to synthesize alpha-linolenic acid by virtue of the only known example of an omega 3 (n3) desaturase enzyme in the animal kingdom. It was hypothesized that the transgenic expression of this enzyme in the mammary gland would increase the n3 fatty acid content of milk and could provide an approach for the development of novel dairy-based dietary sources of n3 PUFA. To test this hypothesis, transgenic mice expressing the C. elegans n3 desaturase under the control of a lactation-induced mammary gland promoter were produced. Mid-lactation milk was collected and the PUFA composition of milk triacylglycerols and phospholipids were analyzed. Milk phospholipids had significantly decreased levels of n6 PUFAs and increased levels of n3 PUFAs. Levels of ALA and EPA were also significantly increased in the milk triacylglycerol fraction, although the change was of a lesser magnitude. The transgenic status of the
dams significantly impacted the brain fatty acid profile of their suckling pups. It appeared that there was a preferential uptake and bioconcentration of docosahexaenoic acid in the brains of pups nursed on transgenic dams. We are currently assessing the behavioral developmental of neonatal mice raised on this n3-enriched milk. Milk triacylglyceride (TG) structure has important human health implications. As a result of the echidna's unique milk TG structure, we were interested in identifying and examining the substrate specificity of the echidna lysophosphatidic acid acyltransferase (LPAAT). Gene-specific Genome Walker primers were designed based on highly conserved domains found in LPAAT sequences from a variety of species. Using bovine LPAAT as a probe on Southern blots of the PCR reactions, we identified an initial 99 base pair sequence with 100% similarity to a highly conserved exon of multiple mammalian LPAAT protein sequences. Additional gene-specific primers based on this
sequence and other conserved LPAAT domains were then used to walk along the echidna DNA until the entire genomic LPAAT coding sequence was identified. We are currently working to functionally characterize the substrate specificity of this enzyme. OBJECTIVE 3. Progress on objective three during the past year included the maintenance of website (http://animalscience.ucdavis.edu/LivestockBiotechnology) for NC1010. This website has links to the NC1010 website, goals, participant contact links, genome databases, cattle extension webpages, breed associations, and outreach. Producer-targeted publications on the use of DNA-based markers in dairy and beef cattle selection programs were made available on the outreach section of the website. I worked in conjunction with the NBCEC (National Beef Cattle Evaluation Consortium; http://www.nbcec.org/nbcec/) to develop web pages detailing the results of their validation of commercial DNA tests for beef cattle producers. I also gave presentations to
NBCEC's National Animal Breed Seminar Series Teleconference and Large Herd Manager's Symposium. I also developed some general audience peer-reviewed fact sheets on the use of genetic engineering in animal agriculture.
Impacts
The fatty acid species composition and triacylglyceride structure are of importance when considering the nutritional effects of dietary fat. Omega-3 (n-3) polyunsaturated fatty acids (PUFAs) are essential components of the diet, and are well documented for their beneficial effects on cardiovascular health. Adequate intake of docosahexaenoic acid (DHA, 22:6n3) is crucial for optimal nervous system function, particularly in infants. Since vertebrates lack the omega-3 fatty acid desaturase responsible for synthesizing n-3 PUFAs they can only be obtained through dietary sources. As a result of increased consumption of vegetable oils rich in n-6 fatty acids, and the reduced consumption of fish and other foods rich in n-3 fatty acids, typical Western diets contain n-6:n-3 PUFA ratios that are greater than 10. Health studies suggest that a dietary n-6:n-3 PUFA ratio closer to 5 would be more favorable. Triacylglyceride (TG) structure also has important human health
implications. Bovine milk TG contains a high proportion of saturated fatty acids in the readily absorbed sn-2 position, which is undesirable from a human health perspective. Increasing the n-3 PUFA and/or altering the triacylglyceride structure of beef and dairy products offers a way to improve the nutritional content of an important component of the American diet, and provides a compelling example of how biotechnology could be employed to produce functional foods for the enhancement of human health. Outreach activities facilitate the adoption of genomic discoveries in commercial agriculture.
Publications
- R. S. Sondeno and A. L. Van Eenennaam. 2005. Cloning and characterization of lysophosphatidic acid acyltransferase (LPAAT) from the echidna (Tachyglossus aculeatus). Transgenic Animal Research Conference V. August 14-18, 2005, Tahoe City, California.
- K. C. Morimoto, A. L. Van Eenennaam, E. J. DePeters, and J. F. Medrano. 2005. Hot Topic: Endogenous Production of Omega-3 and Omega-6 Fatty Acids in Mammalian Cells. Journal of Dairy Science. 88(3) 1142-1146.
- Van Eenennaam, A.L. 2005. Genetic Engineering Fact Sheet 6: Genetic Engineering and Animal Feed. University of California, Division of Agriculture and Natural Resources, Agricultural Biotechnology in California Series, Publication # 8183. http://anrcatalog.ucdavis.edu/pdf/8183.pdf
- Van Eenennaam, A.L. 2005. Genetic Engineering Fact Sheet 7: Genetic Engineering and Animal Agriculture. University of California, Division of Agriculture and Natural Resources, Agricultural Biotechnology in California Series, Publication # 8184. http://anrcatalog.ucdavis.edu/pdf/8184.pdf
- Van Eenennaam, A. L. 2005. "DNA-Based Biotechnologies" Chapter in the National Beef Cattle Evaluation Consortium Beef Sire Selection Manual. In press.
- Van Eenennaam, A. L. 2005. What is the future of animal biotechnology ? California Agriculture. In press.
- B. T. Kao, E. J. DePeters, and A. L. Van Eenennaam. 2005. Brain fatty acid composition and postnatal growth of neonates raised on transgenic milk high in omega-3 fatty acids. Transgenic Animal Research Conference V. August 14-18, 2005, Tahoe City, California.
|
Progress 01/01/04 to 12/31/04
Outputs
Objective 1. Two projects directed towards improving the quality of triacylglycerides for human nutrition are in progress. The goal of the first project is to produce triacylglycerides with a higher overall proportion of polyunsaturated fatty acids (PUFAs). Vertebrates lack the desaturase enzymes required to make linoleic and alpha-linolenic PUFA, and are dependent on dietary sources of these essential PUFA. Adenovirus-mediated transgenic coexpression of Caenorhabditis elegans delta-12 and n-3 fatty acid desaturases in mammary epithelial cell culture enabled the endogenous production of essential PUFA and decreased ratios of monounsaturated fatty acids:PUFA (1.12:0.77) and n-6:n-3 fatty acids (1.91:0.69) in phosopholipids. Following these successful results from in vitro cell culture experiments, the C. elegans fatty acid desaturase genes were expressed in vivo under the control of a lactation-induced mammary gland promoter in transgenic mice. The phospholipid
fraction of milk produced by transgenic omega-3 desaturase mice contained significantly decreased levels of n-6 PUFAs (linoleic acid 18:2n6, arachidonic acid 20:4n6), a concomitant increase in n-3 PUFAs (alpha-linolenic acid 18:3n3, eicosapentaenoic acid 20:5n3), and an overall decrease in the n-6: n-3 PUFA ratio. These results suggest a potential route for the development of sustainable dietary sources of land-based beef and dairy products rich in endogenously-produced n-3 PUFA. The goal of the second project is to examine the function of genes that have the potential to modify the triacylglyceride structure of milk fat. The milk of the echidna (Tachyglossus aculeatus), a primitive monotreme mammal of New Guinea and Australia, is unusual in that it has a fatty acid distribution similar to that found in vegetable oils. As a result of the echidna's unique milk TG structure, we were interested in identifying and examining the substrate specificity of the echidna lysophosphatidic acid
acyltransferase (LPAAT) enzyme, also known as 1-acyl sn-glycerol-3-phosphate acyltransferase (1-AGPAT). Gene-specific 'Genome Walker' primers were designed based on highly conserved motifs of known LPAATs from various plants, bacteria, yeast and mammals. These primers amplified many different-sized PCR bands from echidna DNA, and Southern analysis using a bovine LPAAT cDNA probe was used to identify the faint band containing a homologous partial genomic sequence. We are now in the process of identifying the full length echidna LPAAT sequence and functionally characterizing its substrate specificity. Objective 3: Progress on objective three during the past year includes maintenance of the NC1010 website (http://animalscience.ucdavis.edu/LivestockBiotechnology). This website has links to the North Central Regional Association of Agricultural Experiment Station Directors website, NC1010 goals, participant contact links, bovine and other speices genomic databases, cattle extension
webpages, breed associations, and outreach.
Impacts
The species composition and triacylglyceride structure are of importance when considering the nutritional effects of dietary fat. Omega-3 (n-3) polyunsaturated fatty acids (PUFAs) are essential components of the diet, and are well documented for their beneficial effects on cardiovascular health. Since vertebrates lack the omega-3 fatty acid desaturase responsible for synthesizing n-3 PUFAs they can only be obtained through dietary sources. As a result of increased consumption of vegetable oils rich in n-6 fatty acids, and the reduced consumption of fish and other foods rich in n-3 fatty acids, typical Western diets contain n-6:n-3 PUFA ratios that are greater than 10. Health studies suggest that a dietary n-6:n-3 PUFA ratio closer to 5 would be more favorable for cardiovascular well being. Triacylglyceride (TG) structure also has important human health implications. The absorption of dietary fatty acids in the sn-2 position of the glycerol backbone is favored over the
absorption of those located in the sn-1 and sn-3 positions. The sn-2 position of bovine milk TG contains a high proportion of saturated fatty acids, which is undesirable from a human dietary perspective. Increasing the n-3 PUFA and/or altering the triacylglyceride structure of beef and dairy products offers a way to improve the nutritional content of an important component of the American diet within the realm of existing food preferences, and provides a compelling example of how biotechnology could be employed to produce functional foods for the enhancement of human health.
Publications
- B. T. Kao, E. J. DePeters, and A. L. Van Eenennaam. 2005. Endogenous Production of Omega-3 Fatty Acids in the Mammary Gland of Transgenic Mice. Final program and abstract guide. XIII International Plant & Animal Genome Meeting, San Diego, CA, Jan.15-19, 2005.
- Van Eenennaam, A. L. 2004. DNA-based Marker-Assisted Selection in Beef Cattle. Chapter in 'Cow-Calf Management Guide & Cattle Producer's Library'. University of Idaho Moscow, ID. Accepted.
|
Progress 01/01/03 to 12/31/03
Outputs
The objective of the first project is to produce triacylglycerides with a higher overall proportion of polyunsaturated fatty acids (PUFAs). This will be attempted by expressing the C. elegans delta12 and delta15 fatty acid desaturase genes under the control of a lactation-induced mammary gland promoter in transgenic mice. The coding sequences of the C. elegans delta12 and delta15 fatty acid desaturases (DNA kindly supplied by Dr. John Browse, Washington State University, Pullman, WA) were subcloned into the milk expression vector pBC1 (Invitrogen; Carlsbad, CA) using standard DNA cloning techniques. Transgenic mice (C57/BL6 x DBA) were generated by pronuclear microinjection. DNA from potentially-mosaic founder mice was extracted from toe and tail clips of pups and screened for the presence of the transgene. In anticipation of position effects on transgene-expression, multiple transgenic founder animals were generated for each construct. A total of nine founder animals
were identified. Four founders carried the delta12 desaturase (3 female, 1 male), and five founders carried the delta15 desaturase (4 female, 1 male). These transgenic founders were crossed with the C57/BL6 inbred mouse strain, and the resultant pups will be screened to determine which of the mosaic founders are germline transgenic and to establish transgenic lines. Preliminary data indicate that four founder lines of each desaturase (delta12 and delta15) are transmitting the transgene. The objective of the second project is to examine the function of genes that have the potential to modify the triacylglyceride structure of milk fat. Over the past year a research collaboration was established with Dr. Kevin Nicholas from The University of Melbourne in Australia. We plan to identify the echidna mammary lysophosphatidic acid acyltransferase gene and examine the effects of heterologous expression of this gene on the lipid biosynthetic pathway and triacylglyceride structure. Progress on
objective three during the past year included the development of website (http://animalscience.ucdavis.edu/LivestockBiotechnology) for NC1010. This website has links to the North Central Regional Association of Agricultural Experiment Station Directors website, NC1010 goals, participant contact links, bovine genomic databases, other species genome databases, cattle extension webpages, breed associations, and outreach. The outreach section currently contains a prototype producer-targeted handout entitled Marker-Assisted Selection in Beef Cattle, a PowerPoint slide show that accompanies the handout, and links to relevant conferences and workshops.
Impacts
The species composition and triacylglyceride structure are of importance when considering the nutritional effects of dietary fat. During the past year I initiated research designed to modify milk lipid biosynthesis to improve the nutritional quality of milk fat for human consumption.
Publications
- Van Eenennaam, A. 2003. NC1010 website (http://animalscience.ucdavis.edu/LivestockBiotechnology)
|
|