Medical Biotechnology Chapter 11
Testing for Down’s Syndrome and sex “Karyotyping”
Screening for genetic abnormalities • Fluorescent in situ hybridization (FISH) used to detect: • Extra chromosomes • Missing parts of chromosomes • DNA swapping across different chromosomes • Chronic myelogenous leukemia • DNA exchange between chromosome 9 and 22 ACCATG GTATAC *TGGTAC *CATATG Fluorescent DNA probes
Allele specific oligonucleotide analysis (ASO) • Analyze DNA from cells of 8-32-cell-stage-old embryo created by in vitro fertilization • Allows individuals to select health embryos before implantation
Single nucleotide polymorphisms Oligonucleotide probes that react with sequence of normal bA gene or disease bS gene
GAGGACTCCTCTTCA Normal gene sequence Disease gene sequence CTCCTGAGGAGAAGT GAGGACTCCTCTTCA GAGGACTCCACTTCA GAGGACTCCTCTTCA CTCCTGAGGTGAAGT CTCCTGAGGAGAAGT CTCCTGAGGAGAAGT DNA Cell Extract DNA nucleus pcr amplify primer primer dot blot Add probe for normal gene Add probe for disease gene Probe for normal gene Probe for disease gene
SNPs are abundant • Estimated that 1 SNP occurs every 1000-3000 bp along the DNA of every chromosome • Over 1.4 million SNPS identified to date on human chromosome. • When SNPs occur in a gene that codes for a body function, a disease can result. • Pharmaceutical companies are cataloguing the chromosomal locations of SNPs
stopped Identifying sets of disease genes by microarrays
Testing issues • Should we test people for genetic conditions for which no cure exists? • What are the accepted consequences if a parent learns their unborn child has a genetic defect? • What are the psychological consequences of a false results that indicates that a healthy person has a disease gene or a gene defect? • How do we ensure privacy and confidentiality?
Drug delivery • Getting drug to target organs and tissue • Oral drug to treat arthritis in knee is not very efficient • Drug solubility may be an issue • Microspheres Insulin delivered as a powder through an inhaler
Nanomedicine 10-9 meters 1 meter • Nanometer is one billionth of a meter • May be used for delivery of small sensors to target sites in body • Unclogging arteries • Detect and destroy cancer cells
Artificial blood • Cell-free solutions containing molecules that can bind and transport oxygen like hemoglobin • Benefits • Disease-free alternative to real blood • Constant supply • Universal donor type • Disadvantages • Cannot perform all the functions of a red blood cell-only oxygen delivery • Source of iron • Carbon dioxide removal
A B A,B O Out of 100 donors . . . . .
stopped Gene therapy • Delivery of therapeutic genes into the body to correct disease conditions created by faulty gene • How is it done? 1 2 4 3
Severe combined immune deficiency Mutation in gene encoding adenine deaminase enzyme Shows up as incompetent T-cells which prevent B-cells from making antibodies
Challenges • How long will introduced genes remain in body? • What vectors to use? • Viruses (adenovirus, influenza virus, herpes, HIV • Will depend on what tissues you want to target
Cell and tissue transplantation • Parkinson’s disease • Loss of brain cells that produce dopamine which is the chemical that nerve cells use to communicate with each other • Results in tremors, loss of balance, dexterity, etc. • Tissue damage • Adult neurons do not regenerate like fetal neurons • Fetal neuron transplants into damaged tissue has resulted in partial recovery of neurological damage • Recent studies indicate that not many survive at the site of damage due to inflammatory response of host and those that do, end up differentiating into olfactory bulb neurons instead of medium-sized spiny neurons
Cell and tissue transplantation Drill hole in skull
Xenotransplantation • Transplanting organs from one species into another • May someday become an alternative to human-to-human transplantation • 1984 baboon heart transplanted into a 12-year-old human girl • Girl died after 3 weeks as a result of organ rejection • Can be avoided by matching immune system of donor and acceptor • Major histocompatibility complex • Human leucocyte antigen (HLA) present on all of our cells
Pigs genetically engineered to lack a sugar-producing gene that causes human bodies to reject pig organs
Stem cells • Embryonic stem cells • Infant and adult stem cells • Present in small numbers in • Bone marrow • Peripheral blood • Skin epithelium • Umbilical cord blood • Dental pulp of infant’s teeth • May be obtained by reprogramming somatic cells • Introduction of retroviruses carrying reprogramming genes into fibroblasts
Embryonic Stem Cells Subject stem cells to specific conditions to encourage differentiation into one of many cell types
What stages of early embryonic development are important for generating embryonic stem cells? Embryonic stem cells, as their name suggests, are derived from embryos. Specifically, embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro in an in vitro fertilization clinic and then donated for research purposes with informed consent of the donors. They are not derived from eggs fertilized in a woman's body. The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst.
Current NIH-supported research • Umbilical cord stem cells are able to repopulate the bone marrow of a small child, but only a small number of cells are obtained from each umbilical cord. • Now seeking methods to expand cells in culture to generate larger numbers for use in clinical applications.
NIH Supported Research • Stem cells found in dental pulp of “baby teeth” have the potential to become cells expressing molecular markers characteristic of dentin, bone, fat, and nerve cells. • Advance: These cells could possibly be used to repair damaged teeth, regenerate bone, treat nerve injury or disease.
Using stem cells Step 1- Define the problem. Brain and spinal cord injuries result in damage to neurons. Damaged neurons are not replaced by the right kind of newborn neurons Parkinson’s Disease is a genetic defect that results in dead nerve cells that do not produce sufficient amounts of dopamine needed for normal nerve signaling
Possible solution: introduce stem cells to affected area of the brain Step 2: Determine source of stem cells • Blastocyst embryonic stem cells. • pluripotent stem cells-most universal type • Fetal stem cells. • pluripotent stem cells • Umbilical cord blood stem cells. • multipotent stem cells-can become many different types of cells but natural fate is to become blood and immune cells • Adult stem cells. • multipotent adult stem cells but best to use ones that are destined for specific functions (dopamine production in brain) Stem cells from another normal individual or stem cells from patient? Step 3: Determine source of stem cells
Step 4: If source is from another individual, match the stem cells with the transplant recipient If source is from patient’s previously collected and stored stem cells, use these If patient has Parkinson’ Disease, then introduce good copy of gene in chromosome of stem cells
STEP 5: Introduce stem cells at site of injury or where function needs to be restored
STEP 5: Make the transplanted cells perform the function The implanted cells must survive and differentiate into the proper nerve cells (medium –sized spiny neurons in case of injury or dopamine-producing cells in case of Parkinson’s Disease patient. Some patients reported a lessening in the severity of their symptoms. Some patients who underwent the procedure experienced severe side effects, including involuntary muscle twitching and jerking.
Cloning • Can refer to a gene, a cell, or an entire organism • Reproductive vs. therapeutic cloning • Goal of reproductive cloning is to create a baby • Goal of therapeutic cloning is to provide stem cells that are a genetic match to a patient who requires a transplant. • Differences are diagrammed in Table 11.3 of text
Regulations and ethics related to stem cell • Regs are in a state of flux in this country • Ethical issues and regulations are intertwined • In Chapter 12, pages 314-315 a historical perspective is provided. • Your generation will likely play a significant role not only in the development of the technology but also the rules governing the application of the technology
Learning Objectives After completing this chapter you should be able to: • Provide examples of model organisms and explain why they are important. • Describe different karyotyping techniques that can detect chromosome abnormalities and molecular techniques for genetic testing. • Provide examples of why pharmacogenomics can change how many genetic disease conditions may be treated in the future. • Discuss how monoclonal antibodies may be used for treating disease. • Understand the purpose of gene therapy, and compare and contrast different gene therapy strategies and recognize limitation of gene therapy. • Define regenerative medicine and provide examples of how cell and tissue transplantation and organ engineering can be used. • Understand what stem cells are and describe how they can be isolated. Provide examples of possible therapies that may be developed from stem cells in the future. • Compare and contrast therapeutic cloning and reproductive cloning. • Briefly explain how molecular biology techniques and the Human Genome Project are being used to create human disease gene maps.
Summary • What is meant by “model organisms” in the context of detecting and diagnosing human disease? • What is karyotyping and what is its purpose? • How will pharmacogenomics change how many genetic disease conditions may be treated in the future? • How can monoclonal antibodies be used for treating disease? • What is purpose of gene therapy? What are its different forms? What are its limitations? • Describe how cell and tissue transplantation and organ engineering can be used in regenerative medicine
Summary • How are stem cells obtained? Provide examples of possible therapies that may be developed from stem cells in the future. • What is the difference between therapeutic cloning and reproductive cloning. • How are molecular biology techniques and the Human Genome Project being used to create human disease gene maps?