Proteins Can Be Produced for Research, Diagnosis, & Commerce
المؤلف:
Peter J. Kennelly, Kathleen M. Botham, Owen P. McGuinness, Victor W. Rodwell, P. Anthony Weil
المصدر:
Harpers Illustrated Biochemistry
الجزء والصفحة:
32nd edition.p453-454
2025-10-27
74
A practical goal of recombinant DNA research is the production of materials for biomedical applications. This technology has two distinct merits: (1) it can supply large amounts of material that could not be obtained by conventional purification methods (eg, interferon, tissue plasminogen activating factor, etc.); and (2) it can provide human proteins (eg, insulin and growth hormone). The advantages in both cases are obvious. Although the primary aim is to supply products—generally proteins—for treatment (insulin) and diagnosis (AIDS testing) of human and other animal diseases and for disease prevention (hepatitis B; COVID-19 vaccines), there are other potential commercial applications, especially in agriculture. An example of the latter is the attempt to engineer plants that are more resistant to drought or temperature extremes, more efficient at fixing nitrogen, or that produce seeds containing the complete complement of essential amino acids (rice, wheat, corn, etc.).
Direct Sequencing of Genomic DNA & Exomes
As noted earlier, recent advances in DNA-sequencing technology, the so-called NGS, or high-throughput sequencing (HTS) platforms, have dramatically reduced the per base cost of DNA sequencing. The initial sequence of the human genome costs roughly $350,000,000 (US). The cost of sequencing of the same 3 × 109 bp diploid human genome using the new NGS plat forms is estimated to be less than 0.03% of the original. Thus, human genome sequencing for less than or equal to $1000 (US), and exomes for less than or equal to $500 (US) is readily available. This dramatic reduction in cost has stimulated various international initiatives to sequence the entire genomes/ exomes of hundreds of thousands of individuals of various racial and ethnic backgrounds in order to determine the true extent of DNA/genome polymorphisms present within the human population. The resulting cornucopia of genetic information, and the ever-decreasing cost of genomic DNA sequencing is dramatically increasing our ability to diagnose and, ultimately treat human disease. Obviously, when personal genome sequencing does become commonplace, dramatic changes in the practice of medicine will result because therapies will ultimately be custom tailored to the exact genetic makeup of each individual.
Gene Therapy & Stem Cell Biology
Diseases caused by deficiency of a single-gene product are all theoretically amenable to replacement therapy. The strategy is to clone a normal copy of the relevant gene (eg, the gene that codes for adenosine deaminase) into a vector that will readily be taken up and incorporated into the genome of a host cell. Bone marrow precursor cells are being investigated for this purpose because they presumably will resettle in the marrow and replicate there. The introduced gene would begin to direct the expression of its protein product, and this would correct the deficiency in the host cell.
As an alternative to “replacing” defective genes to cure human disease, many scientists are investigating the feasibility of identifying and characterizing pluripotent stem cells that have the ability to differentiate into any cell type in the body. Recent results in this field have shown that adult human somatic cells can readily be converted into apparent induced pluripotent stem cells (iPSCs) by transfection with cDNAs encoding a handful of DNA-binding transcription factors. These and other new developments in the fields of gene therapy and stem cell biology promise exciting new potential therapies for curing human disease. Finally, generating iPSCs from diseased patient cells also offer the opportunity to create authentic human cell–based models for laboratory studies of the molecular basis of human disease.
Transgenic Animals
The somatic cell gene replacement therapy described earlier would obviously not be passed on to offspring. Other strategies to alter germ cell lines have been devised but have been tested only in experimental animals. A certain percentage of genes injected into a fertilized mouse ovum will be incorporated into the genome and found in both somatic and germ cells. Hundreds of transgenic animals have been established, and these are useful for analysis of tissue-specific effects on gene expression and effects of overproduction of gene products (eg, those from the growth hormone gene or oncogenes) and in discovering genes involved in development, a process that heretofore has been difficult to study in mammals. The transgenic approach has been used to correct a genetic deficiency in mice. Fertilized ova obtained from mice with genetic hypogonadism were injected with DNA containing the coding sequence for the gonadotropin-releasing hormone (GnRH) precursor protein. This gene was expressed and regulated normally in the hypothalamus of a certain number of the resultant mice, and these animals were in all respects normal. Their off spring also showed no evidence of GnRH deficiency. This is, therefore, evidence of somatic cell expression of the transgene and of its maintenance in germ cells.
الاكثر قراءة في مواضيع عامة في الاحياء الجزيئي
اخر الاخبار
اخبار العتبة العباسية المقدسة
