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Amalfitano N, Macedo Mota LF, Rosa GJM, Cecchinato A, Bittante G. Role of CSN2, CSN3, and BLG genes and the polygenic background in the cattle milk protein profile. J Dairy Sci 2022; 105:6001-6020. [PMID: 35525618 DOI: 10.3168/jds.2021-21421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 02/28/2022] [Indexed: 11/19/2022]
Abstract
To devise better selection strategies in dairy cattle breeding programs, a deeper knowledge of the role of the major genes encoding for milk protein fractions is required. The aim of the present study was to assess the effect of the CSN2, CSN3, and BLG genotypes on individual protein fractions (αS1-CN, αS2-CN, β-CN, κ-CN, β-LG, α-LA) expressed qualitatively as percentages of total nitrogen content (% N), quantitatively as contents in milk (g/L), and as daily production levels (g/d). Individual milk samples were collected from 1,264 Brown Swiss cows reared in 85 commercial herds in Trento Province (northeast Italy). A total of 989 cows were successfully genotyped using the Illumina Bovine SNP50 v.2 BeadChip (Illumina Inc.), and a genomic relationship matrix was constructed using the 37,519 SNP markers obtained. Milk protein fractions were quantified and the β-CN, κ-CN, and β-LG genetic variants were identified by reversed-phase HPLC (RP-HPLC). All protein fractions were analyzed through a Bayesian multitrait animal model implemented via Gibbs sampling. The effects of days in milk, parity order, and the CSN2, CSN3, and BLG genotypes were assigned flat priors in this model, whereas the effects of herd and animal additive genetic were assigned Gaussian prior distributions, and inverse Wishart distributions were assumed for the respective co-variance matrices. Marginal posterior distributions of the parameters of interest were compared before and after the inclusion of the effects of the 3 major genes in the model. The results showed that a high portion of the genetic variance was controlled by the major genes. This was particularly apparent in the qualitative protein profile, which was found to have a higher heritability than the protein fraction contents in milk and their daily yields. When the genes were included individually in the model, CSN2 was the major gene controlling all the casein fractions except for κ-CN, which was controlled directly by the CSN3 gene. The BLG gene had the most influence on the 2 whey proteins. The genetic correlations showed the major genes had only a small effect on the relationships between the protein fractions, but through comparison of the correlation coefficients of the proteins expressed in different ways they revealed potential mechanisms of regulation and competitive synthesis in the mammary gland. The estimates for the effects of the CSN2 and CSN3 genes on protein profiles showed overexpression of protein synthesis in the presence of the B allele in the genotype. Conversely, the β-LG B variant was associated with a lower concentration of β-LG compared with the β-LG A variant, independently of how the protein fractions were expressed, and it was followed by downregulation (or upregulation in the case of the β-LG B) of all other protein fractions. These results should be borne in mind when seeking to design more efficient selection programs aimed at improving milk quality for the efficiency of dairy industry and the effect of dairy products on human health.
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Affiliation(s)
- Nicolò Amalfitano
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova (Padua), 35020 Legnaro (PD), Italy.
| | - Lucio Flavio Macedo Mota
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova (Padua), 35020 Legnaro (PD), Italy
| | - Guilherme J M Rosa
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison 53706
| | - Alessio Cecchinato
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova (Padua), 35020 Legnaro (PD), Italy
| | - Giovanni Bittante
- Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova (Padua), 35020 Legnaro (PD), Italy
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Wang M, Sun Z, Yu T, Ding F, Li L, Wang X, Fu M, Wang H, Huang J, Li N, Dai Y. Large-scale production of recombinant human lactoferrin from high-expression, marker-free transgenic cloned cows. Sci Rep 2017; 7:10733. [PMID: 28878310 PMCID: PMC5587717 DOI: 10.1038/s41598-017-11462-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 08/25/2017] [Indexed: 11/23/2022] Open
Abstract
Human lactoferrin (hLF) is a valuable protein for pharmaceutical products and functional foods, and worldwide demand for this protein has steadily increased. However, large-scale recombinant human lactoferrin (rhLF) production using current animal bioreactor techniques is limited by the low expression of foreign proteins, the use of antibiotic resistance genes and the down-regulation of endogenous milk proteins. Here, we generated a herd of marker-free, hLF bacterial artificial chromosome (BAC) transgenic cloned cows, as confirmed by Polymerase chain reaction, Southern blot and Western blot analyses. These transgenic cloned cows produced rhLF in milk at concentrations of 4.5–13.6 g/L. Moreover, the total protein content of the milk was increased. Over two hundred transgenic cloned cows were propagated by multiple ovulation and embryo transfer (MOET). A total of 400–450 g of rhLF protein, which shows similar enzymatic activity to natural hLF in iron binding and release, can be purified on a large scale from >100 L of milk per day. Our results suggested that transgenic bovine mammary bioreactors have the potential for large-scale protein production.
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Affiliation(s)
- Ming Wang
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Zhaolin Sun
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Tian Yu
- Kejienuo Biotechnology Company, Wuxi, China
| | - Fangrong Ding
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Ling Li
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Xi Wang
- Kejienuo Biotechnology Company, Wuxi, China
| | - Mingbo Fu
- Kejienuo Biotechnology Company, Wuxi, China
| | - Haiping Wang
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Jinming Huang
- Dairy cattle Research Center, Academy of Agricultural Sciences, Shandong, China
| | - Ning Li
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China.
| | - Yunping Dai
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China.
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Laible G, Smolenski G, Wheeler T, Brophy B. Increased gene dosage for β- and κ-casein in transgenic cattle improves milk composition through complex effects. Sci Rep 2016; 6:37607. [PMID: 27876865 PMCID: PMC5120311 DOI: 10.1038/srep37607] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 10/31/2016] [Indexed: 12/13/2022] Open
Abstract
We have previously generated transgenic cattle with additional copies of bovine β- and κ casein genes. An initial characterisation of milk produced with a hormonally induced lactation from these transgenic cows showed an altered milk composition with elevated β-casein levels and twofold increased κ-casein content. Here we report the first in-depth characterisation of the composition of the enriched casein milk that was produced through a natural lactation. We have analyzed milk from the high expressing transgenic line TG3 for milk composition at early, peak, mid and late lactation. The introduction of additional β- and κ-casein genes resulted in the expected expression of the transgene derived proteins and an associated reduction in the size of the casein micelles. Expression of the transgenes was associated with complex changes in the expression levels of other milk proteins. Two other major milk components were affected, namely fat and micronutrients. In addition, the sialic acid content of the milk was increased. In contrast, the level of lactose remained unchanged. This novel milk with its substantially altered composition will provide insights into the regulatory processes synchronizing the synthesis and assembly of milk components, as well as production of potentially healthier milk with improved dairy processing characteristics.
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Affiliation(s)
- Götz Laible
- AgResearch, Ruakura Research Centre, Hamilton, New Zealand
| | | | - Thomas Wheeler
- AgResearch, Ruakura Research Centre, Hamilton, New Zealand
| | - Brigid Brophy
- AgResearch, Ruakura Research Centre, Hamilton, New Zealand
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Abstract
It has been thirty years since the first genetically engineered animal with altered milk composition was reported. During the intervening years, the world population has increased from 5bn to 7bn people. An increasing demand for protein in the human diet has followed this population expansion, putting huge stress on the food supply chain. Many solutions to the grand challenge of food security for all have been proposed and are currently under investigation and study. Amongst these, genetics still has an important role to play, aiming to continually enable the selection of livestock with enhanced traits. Part of the geneticist's tool box is the technology of genetic engineering. In this Invited Review, we indicate that this technology has come a long way, we focus on the genetic engineering of dairy animals and we argue that the new strategies for precision breeding demand proper evaluation as to how they could contribute to the essential increases in agricultural productivity our society must achieve.
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Targeted microRNA expression in dairy cattle directs production of β-lactoglobulin-free, high-casein milk. Proc Natl Acad Sci U S A 2012; 109:16811-6. [PMID: 23027958 DOI: 10.1073/pnas.1210057109] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Milk from dairy cows contains the protein β-lactoglobulin (BLG), which is not present in human milk. As it is a major milk allergen, we wished to decrease BLG levels in milk by RNAi. In vitro screening of 10 microRNAs (miRNAs), either individually or in tandem combinations, identified several that achieved as much as a 98% knockdown of BLG. One tandem construct was expressed in the mammary gland of an ovine BLG-expressing mouse model, resulting in 96% knockdown of ovine BLG in milk. Following this in vivo validation, we produced a transgenic calf, engineered to express these tandem miRNAs. Analysis of hormonally induced milk from this calf demonstrated absence of BLG and a concurrent increase of all casein milk proteins. The findings demonstrate miRNA-mediated depletion of an allergenic milk protein in cattle and validate targeted miRNA expression as an effective strategy to alter milk composition and other livestock traits.
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The dominant expression of functional human lactoferrin in transgenic cloned goats using a hybrid lactoferrin expression construct. J Biotechnol 2012; 161:198-205. [PMID: 22789477 DOI: 10.1016/j.jbiotec.2012.06.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 06/08/2012] [Accepted: 06/11/2012] [Indexed: 01/10/2023]
Abstract
Human Lactoferrin (hLF) is an iron-binding protein with multiple physiological functions. As the availability of natural hLF is limited, alternative means of producing this biopharmaceutical protein have been extensively studied. Here we report on the dominant expression of recombinant human lactoferrin (rhLF) in transgenic cloned goats using a novel optimised construct made by fusing a 3.3 kb hLF minigene to the regulatory elements of the β-casein gene. The transgenic goat produced more than 30 mg/ml rhLF in its milk, and rhLF expression was stable during the entire lactation cycle. The rhLF purification efficiency from whole goat milk is approximately 70%, and its purity is above 98%. Compared with natural hLF, the rhLF from transgenic goats has similar biological characteristics including molecular mass, N-terminal sequence, isoelectric point, immunoreactivity and digestive stability. More importantly, the purified rhLF showed specific anti-tumour activity in the mouse model of melanoma experimental metastasis. Therefore, our study shows that the large-scale production of functional rhLF in transgenic goat milk could be an economical and promising source of human therapeutic use in the future.
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Bionaz M, Loor JJ. Gene networks driving bovine mammary protein synthesis during the lactation cycle. Bioinform Biol Insights 2011; 5:83-98. [PMID: 21698073 PMCID: PMC3118679 DOI: 10.4137/bbi.s7003] [Citation(s) in RCA: 217] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A crucial role for both insulin and mTOR in the regulation of milk protein synthesis is emerging. Bovine mammary biopsies harvested during late-pregnancy through end of subsequent lactation were used to evaluate via quantitative PCR the expression of 44 genes involved in pathways of insulin, mTOR, AMPK, and Jak2-Stat5 signalling and also glucose and amino acid (AA) transporters. We observed an increased expression during lactation of ELF5, AA and glucose transporters, insulin signaling pathway components, MAPK14, FRAP1, EIF4EBP2, GSK3A and TSC1 among mTOR signaling-related genes. Among ribosomal components RPL22 was down-regulated. The overall data support a central role of AA and glucose transporters and insulin signaling through mTOR for the regulation of protein synthesis in bovine mammary gland. Furthermore, the existence of translational competition favoring the translation of milk protein transcripts was inferred from the combined dataset.
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Affiliation(s)
- Massimo Bionaz
- Mammalian NutriPhysio Genomics, Department of Animal Sciences, University of Illinois, Urbana, IL 61801, USA
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Bonfatti V, Di Martino G, Cecchinato A, Vicario D, Carnier P. Effects of β-κ-casein (CSN2-CSN3) haplotypes and β-lactoglobulin (BLG) genotypes on milk production traits and detailed protein composition of individual milk of Simmental cows. J Dairy Sci 2010; 93:3797-808. [DOI: 10.3168/jds.2009-2778] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Accepted: 04/08/2010] [Indexed: 11/19/2022]
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Baddini ALQ, da Cunha LER, de Oliveira AMC, Cassella RJ. Determination of total protein in hyperimmune serum samples by near-infrared spectrometry and multivariate calibration. Anal Biochem 2010; 397:175-80. [DOI: 10.1016/j.ab.2009.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 10/06/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
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Baldassarre H, Schirm M, Deslauriers J, Turcotte C, Bordignon V. Protein profile and alpha-lactalbumin concentration in the milk of standard and transgenic goats expressing recombinant human butyrylcholinesterase. Transgenic Res 2009; 18:621-32. [PMID: 19296233 DOI: 10.1007/s11248-009-9254-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Accepted: 03/06/2009] [Indexed: 11/24/2022]
Abstract
The expression of recombinant proteins of pharmaceutical interest in the milk of transgenic farm animals can result in phenotypes exhibiting compromised lactation performance, as a result of the extraordinary demand placed on the mammary gland. In this study, we investigated differences in the protein composition of milk from control and transgenic goats expressing recombinant human butyrylcholinesterase. In Experiment 1, the milk was characterized by gel electrophoresis and liquid chromatography/mass spectrometry in order to identify protein bands that were uniquely visible in the transgenic milk and/or at differing band densities compared with controls. Differences in protein content were additionally evaluated by computer assisted band densitometry. Proteins identified in the transgenic milk only included serum proteins (i.e. complement component 3b, ceruloplasmin), a cytoskeleton protein (i.e. actin) and a stress-induced protein (94 kDA glucose-regulated protein). Proteins exhibiting evident differences in band density between the transgenic and control groups included immunoglobulins, serum albumin, beta-lactoglobulin and alpha-lactalbumin. These results were found to be indicative of compromised epithelial tight junctions, premature mammary cell death, and protein synthesis stress resulting from transgene expression. In Experiment 2, the concentration of alpha-lactalbumin was determined using the IDRing assay and was found to be significantly reduced on day 1 of lactation in transgenic goats (4.33 +/- 0.97 vs. 2.24 +/- 0.25 mg/ml, P < 0.01), but was not different from non-transgenic controls by day 30 (0.99 +/- 0.46 vs. 0.90 +/- 0.11 mg/ml, P > 0.05). We concluded that a decreased/delayed expression of the alpha-lactalbumin gene may be the cause for the delayed start of milk production observed in this herd of transgenic goats.
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Affiliation(s)
- H Baldassarre
- Pharmathene Canada Inc., P.O. Box 320, St. Telesphore, QC, H0P 1Y0, Canada.
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Milk composition studies in transgenic goats expressing recombinant human butyrylcholinesterase in the mammary gland. Transgenic Res 2008; 17:863-72. [PMID: 18483775 DOI: 10.1007/s11248-008-9184-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Accepted: 04/24/2008] [Indexed: 10/22/2022]
Abstract
The use of the mammary gland of transgenic goats as a bioreactor is a well established platform for the efficient production of recombinant proteins, especially for molecules that cannot be adequately produced in traditional systems using genetically engineered microorganisms and cells. However, the extraordinary demand placed on the secretory epithelium by the expression of large amounts of the recombinant protein, may result in a compromised mammary physiology. In this study, milk composition was compared between control and transgenic goats expressing high levels (1-5 g/l) of recombinant human butyrylcholinesterase in the milk. Casein concentration, as evaluated by acid precipitation, was significantly reduced in the transgenic compared with the control goats throughout lactation (P < 0.01). Milk fatty acid composition for transgenic goats, as determined by gas chromatography, was found to have significantly fewer short chain fatty acids (P < 0.01) and more saturated fatty acids (P < 0.05) compared to controls, suggesting an overall metabolic stress and/or decreased expression of key enzymes (e.g. fatty acid synthase, stearoyl-CoA desaturase). The concentration of Na(+), K(+), assessed by atomic absorption spectrophotometry, and serum albumin, determined by bromocresol green dye and scanning densitometry, were similar in transgenic and control goats during the first several weeks of lactation. However, as lactation progressed, a significant increase in Na and serum albumin concentrations and a decrease in K(+) concentration were found in the milk of transgenic goats, while control animals remained unchanged (P < 0.01). These findings suggest that: (a) high expression of recombinant proteins may be associated with a slow-down in other synthetic activities at the mammary epithelium, as evidenced by a reduced casein expression and a decreased de-novo synthesis of fatty acids; (b) the development of permeable tight junctions may be the main mechanism involved in the premature cessation of milk secretion observed in these transgenic goats.
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13
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Hallén E, Wedholm A, Andrén A, Lundén A. Effect of β-casein, κ-casein and β-lactoglobulin genotypes on concentration of milk protein variants. J Anim Breed Genet 2008; 125:119-29. [DOI: 10.1111/j.1439-0388.2007.00706.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Kim MO, Kim SH, Lee SR, Shin MJ, Min KS, Lee DB, Lee SW, Kim KS, Kim SJ, Ryoo ZY. Ectopic expression of tethered human follicle-stimulating hormone (hFSH) gene in transgenic mice. Transgenic Res 2006; 16:65-75. [PMID: 17103026 DOI: 10.1007/s11248-006-9031-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Accepted: 07/27/2006] [Indexed: 12/21/2022]
Abstract
To determine whether the mammary gland can be used to secrete large quantities of a bioactive heterodimeric protein into milk, we used a bovine beta-casein promoter to target and express human follicle-stimulating hormone (hFSH) in the mammary gland into the milk of transgenic mice. We also identified the effects of hFSH leaked into the bloodstream. Transgenic mice produced a high level (up to 300 mIU/ml) of recombinant hFSH in the mammary gland. Human FSH was expressed in the mammary gland and brain, as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. In vitro bioactivity was also identified by cyclic AMP (cAMP) assay. The highest activity was showed in the transgenic mice line 11. However, hFSH leaked into the bloodstream was a powerful factor in the generation of breast and ovarian tumors from the transgenic mice line 11. These results suggest that change of endogenous hormones (FSH and progesterone) may affect the morphology and blood cell counts of peripheral blood and, especially, provoke breast and ovarian tumors.
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MESH Headings
- Animals
- Base Sequence
- Blood Cell Count
- Caseins/genetics
- Cattle
- DNA Primers/genetics
- Enzyme-Linked Immunosorbent Assay
- Female
- Follicle Stimulating Hormone, Human/blood
- Follicle Stimulating Hormone, Human/genetics
- Follicle Stimulating Hormone, Human/metabolism
- Gene Expression
- Humans
- Immunohistochemistry
- Mammary Glands, Animal/anatomy & histology
- Mammary Glands, Animal/metabolism
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Inbred ICR
- Mice, Transgenic
- Milk/metabolism
- Ovary/anatomy & histology
- Promoter Regions, Genetic
- Recombinant Proteins/blood
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- Myoung Ok Kim
- School of Life Sciences and Biotechnology, College of Natural Sciences, Kyungpook National University, 1370 Sankyuk-dong, Buk-ku, Daegu, 702-701, Korea
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15
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Maga EA, Shoemaker CF, Rowe JD, Bondurant RH, Anderson GB, Murray JD. Production and Processing of Milk from Transgenic Goats Expressing Human Lysozyme in the Mammary Gland. J Dairy Sci 2006; 89:518-24. [PMID: 16428620 DOI: 10.3168/jds.s0022-0302(06)72114-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The potential for applying biotechnology to benefit animal agriculture and food production has long been speculated. The addition of human milk components with intrinsic antimicrobial activity and positive charge to livestock milk by genetic engineering has the potential to benefit animal health, as well as food safety and production. We generated one line of transgenic goats as a model for the dairy cow designed to express human lysozyme in the mammary gland. Here we report the characterization of the milk from 5 transgenic females of this line expressing human lysozyme in their milk at 270 microg/mL or 68% of the level found in human milk. Milk from transgenic animals had a lower somatic cell count, but the overall component composition of the milk and milk production were not different from controls. Milk from transgenic animals had a shorter rennet clotting time and increased curd strength. Milk of such nature may be of benefit to the producer by influencing udder health and milk processing.
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Affiliation(s)
- E A Maga
- Department of Animal Science, University of California, Davis 95616, USA.
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Coates CJ, Kaminski JM, Summers JB, Segal DJ, Miller AD, Kolb AF. Site-directed genome modification: derivatives of DNA-modifying enzymes as targeting tools. Trends Biotechnol 2005; 23:407-19. [PMID: 15993503 DOI: 10.1016/j.tibtech.2005.06.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 04/14/2005] [Accepted: 06/14/2005] [Indexed: 01/11/2023]
Abstract
The modification of mammalian genomes is an important goal in gene therapy and animal transgenesis. To generate stable genetic and biochemical changes, the therapeutic genes or transgenes need to be incorporated into the host genome. Ideally, the integration of the foreign gene should occur at sites that ensure their continual expression in the absence of any unwanted side effects on cellular metabolism. In this article, we discuss the opportunities provided by natural DNA-modifying enzymes, such as transposases, recombinases and integrases, to mediate the stable integration of foreign genes into host genomes. In addition, we discuss the approaches that have been taken to improve the efficiency and to modify the site-specificity of these enzymes.
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Affiliation(s)
- Craig J Coates
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
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Palmer CA, Lubon H, McManaman JL. Transgenic mice expressing recombinant human protein C exhibit defects in lactation and impaired mammary gland development. Transgenic Res 2003; 12:283-92. [PMID: 12779117 DOI: 10.1023/a:1023398926763] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
To determine if the production of recombinant human protein C (rHPC) could be increased in milk, we created two lines of mice homozygous for the mouse whey acidic protein (WAP)/human protein C (HPC) transgene. Females of both lines had normal growth, activity and fertility, but failed to lactate normally and were unable to raise litters. Histological analyses of mammary glands from lactating homozygous females showed barely distended alveoli filled with dense-staining milk. Epithelial cells within these alveoli had distinct, centrally located nuclei and contained intracellular lipid droplets. Hemizygous animals derived from these lines were able to lactate and raised normal sized litters. Northern blot analysis showed that the 6.4 homozygous (6.4H) line expressed the transgene at higher levels then corresponding hemizygous (6.4) animals, but the 4.2 homozygous (4.2H) line expressed the transgene at lower levels than the 4.2 hemizygous line. The 6.4H line also had increased rHPC levels in the milk as revealed by western blot analysis. The 4.2H, 6.4, and 6.4H lines showed decreased and/or delayed expression of WAP, beta-casein, and alpha-lactalbumin mRNA's compared to wild type animals during lactogenesis. The 4.2 line showed decreased mRNA expression for beta-casein and alpha-lactalbumin, but normal or higher expression of WAP during lactogenesis. Elevated levels of some proteins were detected in the milk of transgenic mice. From these results, it is concluded that expression of rHPC induced a lactational phenotype that involves abnormal morphological, biochemical, and functional differentiation of mammary epithelial cells. However, the induction of this phenotype does not appear to be directly related to the level of rHPC mRNA expression, thus suggesting that the basis of this phenotype may involve secondary, rather than primary, effects of rHPC on mammary gland development.
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Affiliation(s)
- Carol A Palmer
- Department of Genetics, George Washington University, Washington, DC 20037, USA.
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18
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Kappeler SR, Farah Z, Puhan Z. 5'-flanking regions of camel milk genes are highly similar to homologue regions of other species and can be divided into two distinct groups. J Dairy Sci 2003; 86:498-508. [PMID: 12647956 DOI: 10.3168/jds.s0022-0302(03)73628-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The concentrations of individual casein and whey proteins in camel milk differ markedly to respective protein concentrations in bovine milk. The ratio of beta-casein to kappa-casein is considerably higher in camel milk. beta-Lactoglobulin is absent, but whey acidic protein and peptidoglycan recognition protein have been detected. Genomic sequences upstream to milk-protein genes, which are known to regulate the expression of milk proteins to a great extent, were determined for 10 camel milk-protein genes and compared to respective sequences in other mammals. Multiple sequence alignment showed closest relationships to homologous sequences from other mammals. Comparison of milk protein regulative regions revealed two distantly related groups with pronouncedly different transcription factor site probabilities. The GC-content in sequences of the first group was considerably higher than in sequences of the second group and combined occurrence of CAAT and TATAA boxes was rare, suggesting that the first group represented mostly the housekeeping gene type, probably regulated by cellular signal transduction pathways, whereas the second group helped to regulate genes specifically expressed in terminally differentiated cells of the lactating alveolar epithelium. A core region of the composite response element, which primarily controls milk protein gene activity, was found by a search for elements conserved within all 5'-flanking sequences analyzed, and it is assumed, that the presence of this element determines gene expression in the lactating mammary gland, and binding sites for general activator and repressor factors, surrounding the milk protein gene specific element, are important for regulation of gene activity.
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Affiliation(s)
- S R Kappeler
- Laboratory of Dairy Science, Institute of Food Science, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland.
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Brophy B, Smolenski G, Wheeler T, Wells D, L'Huillier P, Laible G. Cloned transgenic cattle produce milk with higher levels of beta-casein and kappa-casein. Nat Biotechnol 2003; 21:157-62. [PMID: 12548290 DOI: 10.1038/nbt783] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2002] [Accepted: 12/05/2002] [Indexed: 11/08/2022]
Abstract
To enhance milk composition and milk processing efficiency by increasing the casein concentration in milk, we have introduced additional copies of the genes encoding bovine beta- and kappa-casein (CSN2 and CSN3, respectively) into female bovine fibroblasts. Nuclear transfer with four independent donor cell lines resulted in the production of 11 transgenic calves. The analysis of hormonally induced milk showed substantial expression and secretion of the transgene-derived caseins into milk. Nine cows, representing two high-expressing lines, produced milk with an 8-20% increase in beta-casein, a twofold increase in kappa-casein levels, and a markedly altered kappa-casein to total casein ratio. These results show that it is feasible to substantially alter a major component of milk in high producing dairy cows by a transgenic approach and thus to improve the functional properties of dairy milk.
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Affiliation(s)
- Brigid Brophy
- AgResearch, Ruakura Research Centre, Hamilton, New Zealand
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21
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Simulating Patterns of Change in Rates of Secretion of Protein into Milk. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003. [DOI: 10.1007/978-1-4419-9019-8_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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22
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Opsahl ML, McClenaghan M, Springbett A, Reid S, Lathe R, Colman A, Whitelaw CBA. Multiple effects of genetic background on variegated transgene expression in mice. Genetics 2002; 160:1107-12. [PMID: 11901126 PMCID: PMC1462007 DOI: 10.1093/genetics/160.3.1107] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BLG/7 transgenic mice express an ovine beta-lactoglobulin transgene during lactation. Unusually, transgene expression levels in milk differ between siblings. This variable expression is due to variegated transgene expression in the mammary gland and is reminiscent of position-effect variegation. The BLG/7 line was created and maintained on a mixed CBA x C57BL/6 background. We have investigated the effect on transgene expression of backcrossing for 13 generations into these backgrounds. Variable transgene expression was observed in all populations examined, confirming that it is an inherent property of the transgene array at its site of integration. There were also strain-specific effects on transgene expression that appear to be independent of the inherent variegation. The transgene, compared to endogenous milk protein genes, is specifically susceptible to inbreeding depression. Outcrossing restored transgene expression levels to that of the parental population; thus suppression was not inherited. Finally, no generation-dependent decrease in mean expression levels was observed in the parental population. Thus, although the BLG/7 transgene is expressed in a variegated manner, there was no generation-associated accumulated silencing of transgene expression.
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Affiliation(s)
- Margaret L Opsahl
- Roslin Institute (Edinburgh), Division of Molecular Biology, Roslin, Midlothian, EH25 9PS, United Kingdom
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23
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de Groot N, van Kuik-Romeijn P, Lee SH, de Boer HA. Over-expression of the murine pIgR gene in the mammary gland of transgenic mice influences the milk composition and reduces its nutritional value. Transgenic Res 2001; 10:285-91. [PMID: 11592708 DOI: 10.1023/a:1016684111840] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The polymeric immunoglobulin receptor (pIgR) transports dimeric IgA (dIgA) across epithelial cells lining mucosal and glandular tissues, including the mammary gland. Four transgenic mouse lines were generated, overexpressing the murine pIgR gene in the epithelial cells of their mammary glands under control of the regulatory sequences of the bovine alphas1-casein gene. Ten to 270-fold over-expression of the IgA receptor was achieved. The pIgR transgenic line 3644, having the highest pIgR transgene expression, had a markedly altered milk composition compared to non-transgenic mice. In the other three transgenic lines the milk composition, other than SC levels, were not changed. In the milk of line 3644 a protein of 31 kD was lacking and a new protein of 11 kD appeared at relatively high levels. The 31 kD protein was identified as k-casein and the 11 kD protein as serum amyloid A-1 (SAA1). The nutritional value of the milk of females from transgenic line 3644 was dramatically impaired as shown by the retarded growth and development of the pups, leading to death two weeks after birth.
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Affiliation(s)
- N de Groot
- Medical Biotechnology Department, Leiden University, The Netherlands.
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24
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Van Cott KE, Lubon H, Gwazdauskas FC, Knight J, Drohan WN, Velander WH. Recombinant human protein C expression in the milk of transgenic pigs and the effect on endogenous milk immunoglobulin and transferrin levels. Transgenic Res 2001; 10:43-51. [PMID: 11252382 DOI: 10.1023/a:1008963817646] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Colostrum and milk are natural vehicles for acquiring passive immunity and are valuable tools for decreasing neonatant mortality from diarrheal disease. The effects of recombinant human protein C (rhPC) expression levels on endogenous immunoglobulin and transferrin content of the milk of different lineages of transgenic pigs were studied. The levels of rhPC in the milk ranged from 40 to 1200 microg/ml. Transgenic pigs with rhPC expression levels less than 500 microg/ml had no significant differences in milk protein composition with respect to nontransgenic pigs. A line of transgenic pigs having rhPC expression levels of 960-1200 microg/ml had two- to three-fold higher IgG, IgM, and secretory IgA concentrations compared to other transgenic and nontransgenic pig groups (P < 0.05), and four- to five-fold higher transferrin levels than nontransgenic pigs (P < 0.05). Changes in milk protein composition were not associated with mastitis or other pathologic disruption of epithelial cell junctions as indicated by normal casein and albumin levels in milk. Since IgG, IgM, secretory IgA, and transferrin are transported into the milk by transcytosis, higher levels of these proteins indicate that transcyctosis in the mammary epithelial cell was likely upregulated in pigs having high rhPC expression levels. This study is the first that shows a statistically significant example that mammary tissue specific expression of a heterologous protein can enhance endogenous phenotypic characteristics of milk.
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Affiliation(s)
- K E Van Cott
- Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24061, USA
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25
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Kolb AF. Selection-marker-free modification of the murine beta-casein gene using a lox2272 [correction of lox2722] site. Anal Biochem 2001; 290:260-71. [PMID: 11237328 DOI: 10.1006/abio.2000.4984] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gene targeting and site-specific recombination strategies allow the precise modification of the eukaryotic genome. Many of the recombination strategies currently used, however, will introduce a selection marker gene at the modified site. DNA sequences of prokaryotic origin like vector sequences, selection marker, and reporter genes have been shown to markedly influence the regulation of the modified genomic loci. In order to avoid the insertion of excess sequences, a biphasic recombination strategy involving homologous recombination and Cre-recombinase-mediated cassette exchange (RMCE) was devised and used to insert a foreign gene into the beta-casein gene in murine embryonic stem cells. The incompatibility of the heterospecific lox sites used for the recombinase-mediated cassette exchange was found to be critical for the success of the strategy. The frequently used mutant site lox511, which differs from the natural loxP site by a single point mutation, proved unsuitable for this approach. A mutant lox site carrying two point mutations, however, was highly effective and 90% of the selected cell clones carried the desired modification. This biphasic recombination strategy allows for the efficient and precise modification of gene loci without the concomitant introduction of a selectable marker gene.
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Affiliation(s)
- A F Kolb
- Cell Physiology Group, Hannah Research Institute, Ayr, KA6 5HL, Scotland, United Kingdom.
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26
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Clark AJ, Neil C, Gusterson B, McWhir J, Binas B. Deletion of the gene encoding H-FABP/MDGI has no overt effects in the mammary gland. Transgenic Res 2000; 9:439-44. [PMID: 11206972 DOI: 10.1023/a:1026552629493] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Heart fatty acid binding protein (H-FABP) is expressed abundantly in the mammary gland. A number of in vitro studies have shown that H-FABP is functionally indistinguishable from a factor isolated from this organ, termed mammary derived growth inhibitor (MDGI), which specifically inhibits the proliferation of mammary tissue. We have previously shown that over-expression of H-FABP/MDGI in the mammary gland of transgenic mice has no discernable effects on cell proliferation or differentiation. In this report we describe knockout mouse in which the H-FABP/MDGI gene has been specifically disrupted. The mice exhibit no overt phenotype in the mammary gland, and we conclude that this gene does not play a specific role in regulating the normal development or function of this tissue.
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Affiliation(s)
- A J Clark
- Department of Gene Expression and Development, Roslin Institute, Midlothian, Scotland, UK.
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27
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Brandt R, Eisenbrandt R, Leenders F, Zschiesche W, Binas B, Juergensen C, Theuring F. Mammary gland specific hEGF receptor transgene expression induces neoplasia and inhibits differentiation. Oncogene 2000; 19:2129-37. [PMID: 10815804 DOI: 10.1038/sj.onc.1203520] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The epidermal growth factor receptor (EGFR) is overexpressed in about 48% of human breast cancer tissues. To analyse the role of the EGFR in mammary tumor development we generated transgenic mice expressing the human EGFR under the control of either the MMTV-LTR (MHERc) or the beta-lactoglobulin promoter (BLGHERc). The BLGHERc-transgene was expressed exclusively in the female mammary gland, whereas the MHERc transgene was expressed more promiscuously in other organs, such as ovary, salivary gland and testis. Female virgin and lactating transgenic mice of both strains have impaired mammary gland development. Virgin EGFR transgenic mice developed mammary epithelial hyperplasias, whereas in lactating animals progression to dysplasias and tubular adenocarcinomas was observed. In both strains the number of dysplasias increased after multiple pregnancies. The transgene expression pattern was heterogeneous, but generally restricted to regions of impaired mammary gland development. Highest EGFR transgene expression was observed in adenocarcinomas. By using a whole mount organ culture system to study the differentiation potential of the mammary epithelium, we observed a reduced number of fully developed alveoli and a decrease in whey acidic protein expression. Taken together, EGFR overexpression results in a dramatic effect of impaired mammary gland development in vitro as well as in vivo, reducing the differentiation potential of the mammary epithelium and inducing epithelial cell transformation.
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Affiliation(s)
- R Brandt
- Schering Research Laboratories, Berlin, Germany
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28
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Abstract
The production of recombinant proteins is one of the major successes of biotechnology. Animal cells are required to synthesize proteins with the appropriate post-translational modifications. Transgenic animals are being used for this purpose. Milk, egg white, blood, urine, seminal plasma and silk worm cocoon from transgenic animals are candidates to be the source of recombinant proteins at an industrial scale. Although the first recombinant protein produced by transgenic animals is expected to be in the market in 2000, a certain number of technical problems remain to be solved before the various systems are optimized. Although the generation of transgenic farm animals has become recently easier mainly with the technique of animal cloning using transfected somatic cells as nuclear donor, this point remains a limitation as far as cost is concerned. Numerous experiments carried out for the last 15 years have shown that the expression of the transgene is predictable only to a limited extent. This is clearly due to the fact that the expression vectors are not constructed in an appropriate manner. This undoubtedly comes from the fact that all the signals contained in genes have not yet been identified. Gene constructions thus result sometime in poorly functional expression vectors. One possibility consists in using long genomic DNA fragments contained in YAC or BAC vectors. The other relies on the identification of the major important elements required to obtain a satisfactory transgene expression. These elements include essentially gene insulators, chromatin openers, matrix attached regions, enhancers and introns. A certain number of proteins having complex structures (formed by several subunits, being glycosylated, cleaved, carboxylated...) have been obtained at levels sufficient for an industrial exploitation. In other cases, the mammary cellular machinery seems insufficient to promote all the post-translational modifications. The addition of genes coding for enzymes involved in protein maturation has been envisaged and successfully performed in one case. Furin gene expressed specifically in the mammary gland proved to able to cleave native human protein C with good efficiency. In a certain number of cases, the recombinant proteins produced in milk have deleterious effects on the mammary gland function or in the animals themselves. This comes independently from ectopic expression of the transgenes and from the transfer of the recombinant proteins from milk to blood. One possibility to eliminate or reduce these side-effects may be to use systems inducible by an exogenous molecule such as tetracycline allowing the transgene to be expressed only during lactation and strictly in the mammary gland. The purification of recombinant proteins from milk is generally not particularly difficult. This may not be the case, however, when the endogenous proteins such as serum albumin or antibodies are abundantly present in milk. This problem may be still more crucial if proteins are produced in blood. Among the biological contaminants potentially present in the recombinant proteins prepared from transgenic animals, prions are certainly those raising the major concern. The selection of animals chosen to generate transgenics on one hand and the elimination of the potentially contaminated animals, thanks to recently defined quite sensitive tests may reduce the risk to an extremely low level. The available techniques to produce pharmaceutical proteins in milk can be used as well to optimize milk composition of farm animals, to add nutriceuticals in milk and potentially to reduce or even eliminate some mammary infectious diseases.
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Affiliation(s)
- L M Houdebine
- Unite de Biologie du Développement et Biotechnologie, Institut National de la Recherche Agronomique, Jouy-en-Josas, France.
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29
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Abstract
While the technique of homologous recombination, or gene targeting, has led to the generation of transgenic mice of great value to biomedical research, similar approaches are only being developed in other species. With the exception of recent reports on the generation of gene-targeted sheep, the technology in domestic animals is still in its infancy (45). The development of techniques for generating large animals with deleted or modified genes will result in the generation of animals of great value to society. While the technical difficulties to achieve gene targeting in domestic species are significant, they are not insurmountable. Potential applications in both the bovine and porcine species are described with particular emphasis on the generation of cattle resistant to bovine spongiform encephalopathy (BSE) and pigs that can be of use in xenotransplantation.
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Affiliation(s)
- J A Piedrahita
- Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station 77843, USA
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30
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Bobe G, Beitz DC, Freeman AE, Lindberg GL. Effect of milk protein genotypes on milk protein composition and its genetic parameter estimates. J Dairy Sci 1999; 82:2797-804. [PMID: 10629828 DOI: 10.3168/jds.s0022-0302(99)75537-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effects of kappa-casein (CN) and beta-lactoglobulin (LG) genotypes on milk protein concentration and composition were estimated for the US Holstein-Friesian population using a single-trait, mixed, linear animal model on 592 individual milk samples from 233 cows. Both milk protein genotypes had no statistically significant effect on the total milk protein concentration; however, substitution of the kappa-CN A allele additively increased the proportion of kappa-CN, and substitution of the beta-LG B allele additively increased the proportion of beta-LG in total milk protein. In response, proportions of the other milk proteins, mainly alpha S1-CN, were decreased. For proportions of alpha S1-CN, kappa-CN, and beta-LG in total milk protein, kappa-CN and beta-LG genotypes explain more than 50 and 25% of the heritability and repeatability estimates, respectively. We concluded that kappa-CN and beta-LG genotypes affect the phenotypic and genetic variation of milk protein composition but do not significantly affect milk protein concentration. A possible explanation for our conclusion is that altered gene sequences in the promoter region of kappa-CN B and beta-LG A, linked closely to the respective genotypes, favor the transcription or translation of their own protein at the expense of the synthesis of other milk proteins, in particular of alpha S1-CN.
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Affiliation(s)
- G Bobe
- Department of Animal Science, Iowa State University, Ames 50011-3150, USA
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31
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McClenaghan M, Hitchin E, Stevenson EM, Clark AJ, Holt C, Leaver J. Insertion of a casein kinase recognition sequence induces phosphorylation of ovine beta-lactoglobulin in transgenic mice. PROTEIN ENGINEERING 1999; 12:259-64. [PMID: 10235627 DOI: 10.1093/protein/12.3.259] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have shown that the cellular mechanisms of the mammary gland can be used to produce a phosphorylated form of a normally unphosphorylated milk protein. This was achieved by the insertion of a beta-casein DNA sequence coding for a group of mammary gland casein kinase recognition sites into ovine beta-lactoglobulin. Transgenic mice carrying this modified gene were generated and lactating females were shown to produce a novel beta-lactoglobulin in their milk. The infrared spectrum, reactivity to antiphosphoserine antibody and reduction of electrophoretic mobility on treatment with alkaline phosphatase showed that the novel protein recovered from the milk whey (serum) was phosphorylated and molecular mass determination by mass spectrometry was consistent with the phosphorylation of one or two residues. A similar level of phosphorylation was measured by quantitative infrared spectroscopy. Centrifugation of the milk to pellet the casein micelles showed that most of the phosphorylated beta-lactoglobulin was in the whey and hence not incorporated into casein micelles.
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32
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Lubon H. Transgenic animal bioreactors in biotechnology and production of blood proteins. BIOTECHNOLOGY ANNUAL REVIEW 1999; 4:1-54. [PMID: 9890137 DOI: 10.1016/s1387-2656(08)70066-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The regulatory elements of genes used to target the tissue-specific expression of heterologous human proteins have been studied in vitro and in transgenic mice. Hybrid genes exhibiting the desired performance have been introduced into large animals. Complex proteins like protein C, factor IX, factor VIII, fibrinogen and hemoglobin, in addition to simpler proteins like alpha 1-antitrypsin, antithrombin III, albumin and tissue plasminogen activator have been produced in transgenic livestock. The amount of functional protein secreted when the transgene is expressed at high levels may be limited by the required posttranslational modifications in host tissues. This can be overcome by engineering the transgenic bioreactor to express the appropriate modifying enzymes. Genetically engineered livestock are thus rapidly becoming a choice for the production of recombinant human blood proteins.
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Affiliation(s)
- H Lubon
- Plasma Derivatives Department, American Red Cross, Rockville, Maryland, USA.
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33
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Abstract
The secretion of milk depends on the activity of a large number of membrane transport systems located on the apical and basolateral membranes of mammary secretory cells. It follows that a thorough knowledge of individual mammary tissue membrane transport systems is required if we are to fully understand the process of milk secretion. The distribution of the transporters between the apical and basolateral poles of the mammary epithelium must be asymmetrical given that the mammary gland is capable of vectorial transport. This is particularly evident in the case of glucose and amino acid transport systems: the transport mechanisms for these compounds are predominantly situated in the blood-facing aspect of the secretory cells. In addition. it is apparent that there is a polarized distribution of transport systems (carriers and channels) which accept sodium, potassium, chloride, phosphate, and calcium as substrates.
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Affiliation(s)
- D B Shennan
- Hannah Research Institute, Ayr, Scotland, United Kingdom.
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34
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Karatzas CN, Turner JD. Toward altering milk composition by genetic manipulation: current status and challenges. J Dairy Sci 1997; 80:2225-32. [PMID: 9313168 DOI: 10.3168/jds.s0022-0302(97)76171-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The implementation of large-scale genome mapping and sequencing has improved the understanding of animal genetics. A large number of gene sequences are now available to serve as regulatory elements or genes of interest. Although the central thrust of this work is focused on understanding disease states, the manipulation of normal metabolic processes is feasible. To date, the genetic manipulation of livestock has been limited to the permanent addition of genes of clinical interest. This study explores the utility of genetically engineered cattle as a means of altering milk composition to improve the functional properties of milk, increasing marketability. Improvements would include increasing the concentration of valuable components in milk (e.g., casein), removing undesirable components (e.g., lactose), or altering composition to resemble that of human milk as a means of improving human neonatal nutrition. The protracted time lines of genetically modifying dairy cattle has prompted the development of animal models. A model for dwarf goats is discussed in terms of circumventing the lengthy time lines involved in generating transgenic cattle and allowing for an accelerated expansion of research in molecular genetics of dairy animals. Thus, the genetic manipulation of dairy cattle is feasible and could have significant impacts on milk quality, attributes of novel dairy products, and human health.
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35
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Dobie KW, Lee M, Fantes JA, Graham E, Clark AJ, Springbett A, Lathe R, McClenaghan M. Variegated transgene expression in mouse mammary gland is determined by the transgene integration locus. Proc Natl Acad Sci U S A 1996; 93:6659-64. [PMID: 8692874 PMCID: PMC39082 DOI: 10.1073/pnas.93.13.6659] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Mice carrying an ovine beta-lactoglobulin (BLG) transgene secrete BLG protein into their milk. To explore transgene expression stability, we studied expression levels in three BLG transgenic mouse lines. Unexpectedly, two lines exhibited variable levels of transgene expression. Copy number within lines appeared to be stable and there was no evidence of transgene rearrangement. In the most variable line, BLG production levels were stable within individual mice in two successive lactations. Backcrossing demonstrated that genetic background did not contribute significantly to variable expression. Tissue in situ hybridization revealed mosaicism of transgene expression within individual mammary glands from the two variable lines; in low expressors, discrete patches of cells expressing the transgene were observed. Transgene protein concentrations in milk reflected the proportion of epithelial cells expressing BLG mRNA. Furthermore, chromosomal in situ hybridization revealed that transgene arrays in both lines are situated close to the centromere. We propose that mosaicism of transgene expression is a consequence of the chromosomal location and/or the nature of the primary transgene integration event.
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Affiliation(s)
- K W Dobie
- Centre for Genome Research, University of Edinburgh, United Kingdom
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