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Sahoo A, Das PK, Dasu VV, Patra S. Insulin evolution: A holistic view of recombinant production advancements. Int J Biol Macromol 2024; 277:133951. [PMID: 39032893 DOI: 10.1016/j.ijbiomac.2024.133951] [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: 04/23/2024] [Revised: 06/29/2024] [Accepted: 07/16/2024] [Indexed: 07/23/2024]
Abstract
The increased prevalence of diabetes and the growing popularity of non-invasive methods of recombinant human insulin uptake, such as oral insulin, have increased insulin demand, further limiting the affordability of insulin. Over 40 years have passed since the development of engineered microorganisms that replaced the animal pancreas as the primary source of insulin. To stay ahead of the need for insulin in the present and the future, a few drawbacks with the existing expression systems need to be alleviated, including the inclusion body formation, the use of toxic inducers, and high process costs. To address these bottlenecks and improve insulin production, a variety of techniques are being used in bacteria, yeasts, transgenic plants and animals, mammalian cell lines, and cell-free expression systems. Different approaches for the production of insulin, including two-chain, proinsulin or mini-proinsulin, preproinsulin coupled with fusion protein, chaperone, signal peptide, and purification tags, are explored in upstream, whereas downstream processing takes into account the recovery of intact protein in its bioactive form and purity. This article focuses on the strategies used in the upstream and downstream phases of the bioprocess to produce recombinant human insulin. This review also covers a range of analytical methods and tools employed in investigating the genuity of recombinant human insulin.
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Affiliation(s)
- Ansuman Sahoo
- Biochemical Engineering Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Prabir Kumar Das
- Biochemical Engineering Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Veeranki Venkata Dasu
- Biochemical Engineering Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, 781039, Assam, India.
| | - Sanjukta Patra
- Enzyme & Microbial Technology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, 781039, Assam, India
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Monzani PS, Sangalli JR, Sampaio RV, Guemra S, Zanin R, Adona PR, Berlingieri MA, Cunha-Filho LFC, Mora-Ocampo IY, Pirovani CP, Meirelles FV, Wheeler MB, Ohashi OM. Human proinsulin production in the milk of transgenic cattle. Biotechnol J 2024; 19:e2300307. [PMID: 38472101 DOI: 10.1002/biot.202300307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 01/16/2024] [Accepted: 01/24/2024] [Indexed: 03/14/2024]
Abstract
BACKGROUND The worldwide growing demand for human insulin for treating diabetes could be supplied by transgenic animals producing insulin in their milk. METHODS AND RESULTS Pseudo-lentivirus containing the bovine β-casein promoter and human insulin sequences was used to produce modified adult fibroblasts, and the cells were used for nuclear transfer. Transgenic embryos were transferred to recipient cows, and one pregnancy was produced. Recombinant protein in milk was evaluated using western blotting and mass spectrometry. One transgenic cow was generated, and in milk analysis, two bands were observed in western blotting with a molecular mass corresponding to the proinsulin and insulin. The mass spectrometry analysis showed the presence of human insulin more than proinsulin in the milk, and it identified proteases in the transgenic milk that could convert proinsulin into insulin and insulin-degrading enzyme that could degrade the recombinant protein. CONCLUSION The methodologies used for generating the transgenic cow allowed the detection of the production of recombinant protein in the milk at low relative expression compared to milk proteins, using mass spectrometry, which was efficient for detecting recombinant protein with low expression in milk. Milk proteases could act on protein processing converting recombinant protein to functional protein. On the other hand, some milk proteases could act in degrading the recombinant protein.
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Affiliation(s)
- Paulo S Monzani
- Center for Biological and Health Sciences, University of Northern Paraná, Londrina, Paraná, Brazil
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Juliano R Sangalli
- Department of Veterinary Medicine, University of São Paulo, Pirassununga, São Paulo, Brazil
| | - Rafael V Sampaio
- Department of Veterinary Medicine, University of São Paulo, Pirassununga, São Paulo, Brazil
| | - Samuel Guemra
- Center for Biological and Health Sciences, University of Northern Paraná, Londrina, Paraná, Brazil
| | - Renato Zanin
- Laffranchi Agriculture, Tamarana, Paraná, Brazil
| | - Paulo R Adona
- Center for Biological and Health Sciences, University of Northern Paraná, Londrina, Paraná, Brazil
| | - Maria A Berlingieri
- Center for Biological and Health Sciences, University of Northern Paraná, Londrina, Paraná, Brazil
| | - Luiz F C Cunha-Filho
- Center for Biological and Health Sciences, University of Northern Paraná, Londrina, Paraná, Brazil
| | - Irma Y Mora-Ocampo
- Department of Biological Sciences, State University of Santa Cruz (UESC), Ilhéus, Bahia, Brazil
| | - Carlos P Pirovani
- Department of Biological Sciences, State University of Santa Cruz (UESC), Ilhéus, Bahia, Brazil
| | - Flávio V Meirelles
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Matthew B Wheeler
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Otavio M Ohashi
- Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil
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Evaluation of the α-casein (CSN1S1) locus as a potential target for a site-specific transgene integration. Sci Rep 2022; 12:7983. [PMID: 35568783 PMCID: PMC9107462 DOI: 10.1038/s41598-022-12071-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 04/29/2022] [Indexed: 11/25/2022] Open
Abstract
Transgenic animals are an important tool in biotechnology, including the production of recombinant proteins in the milk. Traditionally, expression constructs are based on hybrid vectors bearing mammary gland specific regulatory elements from the α-casein (Csn1s1), β-casein (Csn2), whey acidic protein (WAP), or β-lactoglobulin (BLG) genes. Overexpression from the randomly integrated vectors typically provides high levels of expression, but has drawbacks due to unpredictable genome localization. CRISPR-Cas9 targeted transgene integration into the endogenous casein locus could alleviate the need for extensive animal screening to achieve high and reproducible expression levels. We decided to evaluate such a “precise” integration approach, placing the human granulocyte–macrophage colony-stimulating factor (hGMCSF) gene under control of the mouse endogenous alpha-S1-casein (Csn1s1) promoter. We designed two types of transgene integrations: a knock-in in the second exon of the Csn1s1 (INS-GM) and a full-size Csn1s1 replacement with hGMCSF (REP-GM) which was never tested before. The INS-GM approach demonstrated low transgene expression and milk protein levels (0.4% of Csn2 transcripts; 2–11 µg/ml hGMCSF). This was probably caused by the absence of the 3’-polyadenylation signal in the hGMCSF transgene. REP-GM animals displayed high transgene expression, reaching and slightly exceeding the level of the endogenous Csn1s1 (30–40% of Csn2 transcripts), but yielded less hGMCSF protein than expected (0.2–0.5 mg/ml vs 25 mg/ml of Csn1s1), indicating that translation of the protein is not optimal. Homozygous inserts leading to the Csn1s1 knock-out did not have any long standing effects on the animals’ health. Thus, in our experimental design, site-specific transgene integration into the casein locus did not provide any significant advantage over the overexpression approach.
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Current advances and future prospects in production of recombinant insulin and other proteins to treat diabetes mellitus. Biotechnol Lett 2022; 44:643-669. [DOI: 10.1007/s10529-022-03247-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 03/16/2022] [Indexed: 12/14/2022]
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Smirnov AV, Shnaider TА, Korablev AN, Yunusova AM, Serova IA, Battulin NR. A hypomorphic mutation in the mouse Csn1s1 gene generated by CRISPR/Cas9 pronuclear microinjection. Vavilovskii Zhurnal Genet Selektsii 2021; 25:331-336. [PMID: 34901729 PMCID: PMC8627868 DOI: 10.18699/vj21.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/28/2021] [Accepted: 02/08/2021] [Indexed: 11/19/2022] Open
Abstract
Caseins are major milk proteins that have an evolutionarily conserved role in nutrition. Sequence variations in the
casein genes affect milk composition in livestock species. Regulatory elements of the casein genes could be used to direct
the expression of desired transgenes into the milk of transgenic animals. Dozens of casein alleles have been identified for
goats, cows, sheep, camels and horses, and these sequence variants are associated with altered gene expression and milk
protein content. Most of the known mutations affecting casein genes’ expression are located in the promoter and 3’-untranslated regions. We performed pronuclear microinjections with Cas9 mRNA and sgRNA against the first coding exon of
the mouse Csn1s1 gene to introduce random mutations in the α-casein (Csn1s1) signal peptide sequence at the beginning
of the mouse gene. Sanger sequencing of the founder mice identified 40 mutations. As expected, mutations clustered
around the sgRNA cut site (3 bp from PAM). Most of the mutations represented small deletions (1–10 bp), but we detected
several larger deletions as well (100–300 bp). Functionally most mutations led to gene knockout due to a frameshift or a
start codon loss. Some of the mutations represented in-frame indels in the first coding exon. Of these, we describe a novel
hypomorphic Csn1s1 (Csn1s1c.4-5insTCC) allele. We measured Csn1s1 protein levels and confirmed that the mutation has a
negative effect on milk composition, which shows a 50 % reduction in gene expression and a 40–80 % decrease in Csn1s1
protein amount, compared to the wild-type allele. We assumed that mutation affected transcript stability or splicing by an
unknown mechanism. This mutation can potentially serve as a genetic marker for low Csn1s1 expression.
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Affiliation(s)
- A V Smirnov
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - T А Shnaider
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - A N Korablev
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - A M Yunusova
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - I A Serova
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - N R Battulin
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia Novosibirsk State University, Novosibirsk, Russia
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Chen Q, Zhao FQ, Ren Y, Han J, Liu J, Li Y, Liu H. Parenterally Delivered Methionyl-Methionine Dipeptide During Pregnancy Enhances Mammogenesis and Lactation Performance Over Free Methionine by Activating PI3K-AKT Signaling in Methionine-Deficient Mice. J Nutr 2020; 150:1186-1195. [PMID: 32006013 DOI: 10.1093/jn/nxaa005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/23/2019] [Accepted: 01/07/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Pregnancy-induced hypoaminoacidemia, l-methionine (Met) included, disturbs embryogenesis and may also affect breast function. Supplementation with the dipeptide l-methionyl-Met (Met-Met) may improve lactation performance. OBJECTIVE We compared the effects of supplemental Met or Met-Met during pregnancy on mammogenesis and lactogenesis and investigated underlying mechanisms. METHODS In experiment 1, 9-wk-old ICR mice (n = 72, ∼30 g) were divided into 3 groups. During the first 17 days of pregnancy (DP), the Control group was fed a diet with Met (8.2 g/kg) and saline was intraperitoneally injected, the Met group was fed a Met-devoid diet and 35% of the Met (92-mmo l Met) as contained in the Control diet was intraperitoneally injected, and the Met-Met group was fed the same diet and 70-mmo l Met plus 11-mmo l Met-Met was intraperitoneally injected. All animals were fed the Control diet after DP17 and during lactation. Mammogenesis, lactogenesis, transcriptome at DP17, and milk performance during lactation were examined. In experiment 2, 9-wk-old ICR mice (n = 55, ∼30 g) at DP0 were injected through the teat with adeno-associated virus for overexpression/inhibition of phosphoinositide-3-kinase regulatory subunit 1 (Pik3r1), divided into the Control, Met, and Met-Met groups and received the same treatment as experiment 1 to examine mammogenesis and lactogenesis at DP17. RESULTS In experiment 1, compared with the Met group, the Met-Met group showed higher (P < 0.05) mammary epithelium percentage (42%) and αS1-casein expression (84%) at DP17, milk yield (34%) and energy concentrations (8.7%) during lactation; transcriptomic analysis illustrated activated phosphatidylinositol-3 kinase (PI3K)/protein kinase B (AKT) signaling in the mammary glands of the Met-Met group (P-adj < 0.001). In experiment 2, overexpression of Pik3r1 enhanced (P < 0.05) the protective effect of Met-Met over Met on mammogenesis and β-casein expression. CONCLUSION Met-Met is more effective than Met in promoting mammogenesis and lactogenesis mainly by activation of PI3K-AKT signaling in Met-deficient mice.
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Affiliation(s)
- Qiong Chen
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Feng-Qi Zhao
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China.,Department of Animal and Veterinary Sciences, University of Vermont, Burlington, VT, USA
| | - Yifei Ren
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Jialiang Han
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Jianxin Liu
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Yang Li
- Obstetrical Department, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, PR China
| | - Hongyun Liu
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
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Production of biologically active human factor IX-Fc fusion protein in the milk of transgenic mice. Biotechnol Lett 2020; 42:717-726. [PMID: 32002712 DOI: 10.1007/s10529-020-02808-1] [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: 08/20/2019] [Accepted: 01/13/2020] [Indexed: 10/25/2022]
Abstract
OBJECTIVE To investigate the feasibility of producing human IgG1 Fc fragment fused factor IX (FIX-Fc) in the milk of transgenic animals, for an alternative possible solution to the unmet need of FIX-Fc products for hemophilia B treatment. RESULTS Six founder lines of transgenic mice harboring FIX-Fc cassette designed to be expressed specifically in the mammary gland were generated. FIX-Fc protein was secreted into the milk of transgenic mice with preserved biological activity (with the highest value of 6.2 IU/mL), similar to that of the non-fused FIX transgenic milk. RT-PCR and immunofluorescence analysis confirmed that FIX-Fc was specifically expressed in the mammary gland. The blood FIX clotting activities were unchanged, and no apparent health defects were observed in the transgenic mice. Moreover, the stability of FIX protein in milk was increased by the Fc fusion. CONCLUSIONS It is feasible to produce biologically functional FIX-Fc in the mammary gland of transgenic mice. Our preliminary results provide a foundation for the potential scale-up production of FIX-Fc in the milk of dairy animals.
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Kalmykov VA, Kusov PA, Deykin AV. Development of a Multiplex PCR Test System for the Determination of a Transgene Based on the pBC1 Plasmid and Its Derivatives for the Expression of Recombinant Proteins in Mus musculus Milk. DOKL BIOCHEM BIOPHYS 2019; 485:153-156. [PMID: 31201639 DOI: 10.1134/s1607672919020212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Indexed: 11/23/2022]
Abstract
A multiplex PCR test system for identification of the regulatory sequences of genetic constructs for transformation (promotor, insulator, and terminator) in the Mus musculus genome and for transgenic animal selection by genotyping with horizontal agarose gel electrophoresis detection was developed. The proposed system was validated by genotyping mouse strains producing human lactoferrin, heat shock protein HSP 70, firefly luciferase, and lysozyme, which were obtained by microinjections of linearized DNA into murine zygote pronucleus with random transgene integration into the genome using the pBC1 plasmid for expression of the gene of interest in milk of transformed animals (milk expression vector kit).
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Affiliation(s)
- V A Kalmykov
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Moscow, Russia
| | - P A Kusov
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Moscow, Russia.,Skolkovo Institute of Science and Technology, 143025, Skolkovo, Moscow oblast, Russia
| | - A V Deykin
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Moscow, Russia. .,Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, 125315, Moscow, Russia.
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Kong S, Li L, Zhu W, Xin L, Ruan J, Zhang Y, Yang S, Li K. Genetic characteristics of polycistronic system‑mediated randomly‑inserted multi‑transgenes in miniature pigs and mice. Mol Med Rep 2017; 17:37-50. [PMID: 29115474 PMCID: PMC5780143 DOI: 10.3892/mmr.2017.7842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Accepted: 06/28/2017] [Indexed: 11/24/2022] Open
Abstract
Multi-transgenic technology is superior to single transgenic technology in biological and medical research. Multi-transgene insertion mediated by a polycistronic system is more effective for the integration of polygenes. The multi-transgene insertion patterns and manners of inheritance are not completely understood. Copy number quantification is one available approach for addressing this issue. The present study determined copy numbers in two multi-transgenic mice (K3 and L3) and two multi-transgenic miniature pigs (Z2 and Z3) using absolute quantitative polymerase chain reaction analysis. For the F0 generation, a given transgene was able to exhibit different copy number integration capacities in different individuals. For the F1 generation, the most notable characteristic was that the copy number proportions were different among pedigrees (P<0.05). The results of the present study demonstrated that transgenes within the same vector exhibited the same integration trend between the F0 and F1 generations. In conclusion, intraspecific consistency and intergenerational copy numbers were compared and the integration capacity of each specific transgene differed in multi-transgenic animals. In particular, the copy number of one transgene may not be used to represent other transgenes in polycistronic vector-mediated multi-transgenic organisms. Consequently, in multi-transgenic experimental animal disease model research or breeding, copy numbers provide an important reference. Therefore, each transgene in multi-transgenic animals must be separately screened to prevent large copy number differences, and inconsistent expression between transgenes and miscellaneous data, in subsequent research.
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Affiliation(s)
- Siyuan Kong
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
| | - Li Li
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
| | - Wenjuan Zhu
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
| | - Leilei Xin
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
| | - Jinxue Ruan
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
| | - Yubo Zhang
- Animal Functional Genomics Group, Agricultural Genomes Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, Guangdong 518120, P.R. China
| | - Shulin Yang
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
| | - Kui Li
- State Key Laboratory of Animal Nutrition, Key Laboratory of Farm Animal Genetic Resource and Germplasm Innovation of Ministry of Agriculture, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China
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Intron V, not intron I of human thrombopoietin, improves expression in the milk of transgenic mice regulated by goat beta-casein promoter. Sci Rep 2015; 5:16051. [PMID: 26527459 PMCID: PMC4630608 DOI: 10.1038/srep16051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 09/25/2015] [Indexed: 11/29/2022] Open
Abstract
Introns near 5′ end of genes generally enhance gene expression because of an enhancer /a promoter within their sequence or as intron-mediated enhancement. Surprisingly, our previous experiments found that the vector containing the last intron (intron V) of human thromobopoietin (hTPO) expressed higher hTPO in cos-1 cell than the vector containing intron I regulated by cytomegalovirus promoter. Moreover, regulated by 1.0 kb rat whey acidic protein promoter, hTPO expression was higher in transgenic mice generated by intron V-TPOcDNA than in transgenic mice generated by TPOcDNA and TPOgDNA. However, it is unknown whether the enhancement of hTPO expression by intron I is decreased by uAUG7 at 5′-UTR of hTPO in vivo. Currently, we constructed vectors regulated by stronger 6.5kb β-casein promoter, including pTPOGA (containing TPOcDNA), pTPOGB (containing TUR-TPOcDNA, TUR including exon1, intron I and non-coding exon2 of hTPO gene), pTPOGC (containing ΔTUR-TPOcDNA, nucleotides of TUR from uAUG7 to physiological AUG were deleted), pTPOGD (containing intron V-TPOcDNA) and pTPOGE (containing TPOgDNA), to evaluate the effect of intron I on hTPO expression and to further verify whether intron V enhances hTPO expression in the milk of transgenic mice. The results demonstrated that intron V, not intron I improved hTPO expression.
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