Goat Farming

Human Diseases and Ailments: Transgenic Goat Milk for the rescue

January 7, 2024

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Human Diseases and Ailments: Transgenic Goat Milk for the rescue

ABSTRACT

Transgenic animals are those which carry a known sequence of recombinant DNA in its cells, and which passes that DNA onto its offspring. Among various methods to introduce a foreign DNA in order to make a transgene, DNA microinjection, Transposons mediated gene transfer, Transfer of DNA into gametes, Using retroviral vectors, Using embryonic stem cells are important. Among all the transgenic mammalian bioreactors already produced, goats (Capra hircus) have represented an excellent model for transgenesis, since the production of founder animals and operating costs are significantly easier to manage compared to cattle. Recently transgenic goat milk has been used to produce human lysozyme. Lysozyme in milk can diminish bacterial growth, increasing the safety and storage time of milk and milk products. Other important therapeutic uses of transgenic goat milk included the production of human α-fetoprotein (hαFP), malaria vaccine antigen (Stowers et al., 2002), antithrombin III, Lactoferrin (Lactoferrin (LTF) which is antiviral, antitumor, antibacterial, antifungal, antiinflammatory and immunoregulatory properties), human factor IX (Deficiencies in human factor IX (hF IX) which lead to the hemorrhagic disorders of hemophilia B. Transgenic technology, a revolutionary breakthrough in biotechnology, has found a unique application in the realm of dairy production through the creation of transgenic goats capable of producing enhanced milk. This article explores the science behind transgenic goat milk, its potential benefits for human health, and the implications for the dairy industry.

Introduction – What are Transgenic Organisms?

A genetically engineered or “transgenic” animal is an animal that carries a known sequence of recombinant DNA in its cells, and which passes that DNA onto its offspring. Recombinant DNA refers to DNA fragments that have been joined together in a laboratory. The resultant recombinant DNA “construct” is usually designed to express the protein(s) that are encoded by the gene(s) included in the construct, when present in the genome of a transgenic animal. Because the genetic code for all organisms is made up of the same four deoxynucleotide building blocks, this means that a gene makes the same protein whether it is made in an animal, a plant, or a microbe. Transgenic animals look and behave normally, and differ from their non-modified counterparts only in the expression of an additional protein. The transgenic animals thus created are also called genetically modified organisms (GMOs) as their genome as been modified by using external techniques. Genetic engineering is a useful technology because it enables animals to produce novel proteins.

Conventional animal breeding is constrained to selection based on naturally-occurring variations in the proteins that are present in a species, and this limits the range and extent of genetic improvement. Genetically-engineered animals are being produced for two distinct applications: human medicine and agriculture. Most commercial transgenic animal research is in the field of human medicine. Many therapeutic proteins for the treatment of human disease require animal-cell specific modifications to be effective, and at the present time they are almost all produced in mammalian cell-based bioreactors. The manufacturing capacity for therapeutic proteins cannot keep pace with the rapid progress in drug discovery and development, and this has resulted in unmet needs and dramatically rising costs. Genetically engineered animals may provide an important source of these protein drugs in the future, because the production of recombinant proteins in the milk, blood, or eggs of transgenic animals presents a much less-expensive approach to producing therapeutic proteins in animal cells.

Methods and principle to produce transgenic organisms

The production of transgenic farm animals is extraordinarily labor and cost intensive and depends upon advanced techniques in molecular biology, cell culture, reproductive biology and biochemistry. The transfer of the foreign DNA is only one step in this process. Critical steps involved in the production of transgenic farm animals are; Identification – of the gene (genome analysis); Cloning of the gene; Production of a suitable gene construct; Transfer of the gene; Proof of integration of the foreign gene; Proof of expression (mRNA, protein); Demonstration of transmission (inheritance); Selective breeding. There are variety of methods to introduce a foreign DNA and make a transgene, some of them include – DNA microinjection- it is one of the first technique that was used to create a transgene, the DNA is directly injected into the pronuclei of embryos. The technique is relatively easy and had maximum success in mouse; the technique is also useful in rat, rabbit, pig, sheep, goat and cow. However, the yield of transgenic animals is lower due to low reproduction rates in bovine. Transposons mediated gene transfer – Transposons containing at least one gene coding for a transposase enzyme and motifs located on both ends could trigger transposition and integration. Retrotranposons that are first transcribed RNA and then back to DNA which can integrate within the genome are the choice for transposons mediated gene transfer. To become a vector for gene transfer, a transposon must be genetically modified, for this the transposase is deleted to make space for foreign. Generally a plasmid is used capable of expressing the transposase gene and is injected with recombinant vector which allow the integration of foreign gene with the vector and the plasmid later on degrades rapidly. Transfer of DNA into gametes – one approach to create transgenic is to insert the foreign DNA into gametes. This has been shown that when the spermatozoa are incubated with foreign DNA they rapidly take up that DNA and produce transgenic spermatozoa. These can be later on fertilized in vivo or in vitro to produce transgenic organism. The results of such transfer are inconsistent however utilizing this method transgenic fish, chicken, rabbit pig, sheep has been created. Using retroviral vectors- Use of retroviruses to introduce a transgene has been advocated however the method is laborious and less efficient than the DNA microinjection method. Although the method has been laborious and less efficient it remains the method of choice for the production of transgenic chickens. Using embryonic stem cells – Gene replacement by homologous recombination is performed in routine in bacteria and yeast. It can be achieved in somatic mammalian cells although with a relatively poor efficiency. For unknown reasons, homologous recombination is more frequent in pluripotent embryonic cells. This approach is very attractive since it can lead to specific gene inactivation, to targeted point mutation in an animal genome or to the replacement of a given gene by a non-related one. Although laborious this protocol has become popular and genes are frequently inactivated in mouse.

Transgenic goats

Since later times, the mammary gland of mammals was considered as a bioreactor that could be used to extract protein / therapeutic materials. Of all the transgenic mammalian bioreactors already produced, goats (Capra hircus) have represented an excellent model for transgenesis, since the production of founder animals and operating costs are significantly easier to manage compared to cattle. Since milk represents a source of raw material, unprocessed, safe, abundant, renewable, easy to obtain and well accepted by the public it becomes a possible medium that makes mammary gland as target tissue for transgenesis. Therefore transgenic goats have been created rapidly that produces substances which are of human therapeutic use. In 1994, Ebert and co-workers reported the induction of human tissue plasminogen activator in the mammary gland of transgenic goats. In 1999, the world’s first cloned transgenic goats weren born as part of a research program conducted by LSU Agricultural Center and Genzyme Transgenic Corp. The goat was named Millie, gave milk that containes a therapeutic protein that can be extracted to make drug for patients undergoing coronary bypass surgery. The drug works in conjunction with heparin, which prevents blood from clotting. One spectacular example of transgenic goat milk include the production of protein fibers of spider silk. The protein fibers of spider silk are known for being natural materials with high tensile strength and toughness. Due to these properties, these fibers have been the target of studies for more than 40 years (Swanson et al., 2009). Some research has utilized transgenesis for the expression of recombinant proteins of spider silk from mammalian epithelial cells and from the milk of transgenic goats for potential uses in ballistic protection, aircrafts, medical devices, and automotive material, among others (Karatzas et al., 1999).

Transgenic Goat milk as a remedy for ailments

Recently transgenic goat milk has been used to produce human lysozyme. Lysozyme shows antimicrobial properties and catalyzes the cleavage of glycosidic bonds between the C-1 of N-acetylmuramic acid (Mur2Ac) and the C-4 of N-acetyl-D-glucosamine (GlcNAc) in peptidoglycans of bacterial cell walls (Maga et al., 2006). The levels of lysozyme in the milk of dairy animals are 1600 to 3000 times less than that found in human milk. Lysozyme in milk can diminish bacterial growth, increasing the safety and storage time of milk and milk products. Secondly, the lysozyme inhibits the growth of bacteria by destroying the bacterial cell wall, causing the contents of the cell to leak out. Because of its antibacterial activities lysozyme is thought to help protect breastfeeding children against diarrheal diseases. A study carried out by in 2013 showed that consumption of transgenic goat milk containing the human lysozyme helped in lowering the incidence of diarrhoea in young piglets. The pigs that consumed the transgenic goat milk recovered from clinical diseases much earlier than the control group. This showed that the transgenic goat milk may act as a therapeutic remedy for intestinal disorders especially in young ones. Other important therapeutic uses of transgenic goat milk included the production of human α-fetoprotein (hαFP), which can be used in autoimmune diseases (Parker et al., 2004), malaria vaccine antigen (Stowers et al., 2002), antithrombin III (individuals with a deficiency of antithrombin run the risk of developing fatal blood clot) (sold as Atryn®), Tissue plasminogen activator (Human tissue plasminogen activator (htPA) is a serum protease that converts the pro-enzyme plasminogen into plasmin, a fibrinolytic enzyme capable of initiating the degradation of proteins of the extracellular matrix), Lactoferrin (Lactoferrin (LTF) show various biological activities such as antiviral, antitumor, antibacterial, antifungal, antiinflammatory and immunoregulatory properties), human factor IX (Deficiencies in human factor IX (hF IX) are linked to chromosome X defects, which lead to the hemorrhagic disorders of hemophilia B), Human granulocyte colony-stimulating factor (Human Granulocyte ColonyStimulating Factor (hG-CSF) is a hematopoetic growth factor that acts on the maturation of neutrophils, stimulating their phagocytic and chemotactic activities, it is widely utilized in different forms of neutropenia, chemotherapeutically induced leukopenia and allogenic transplants, Human growth hormone (hGH) (hGH is one of the principal hormones required for post-natal growth and is absolutely essential for normal body development) etc.