The good, the bad, and the healthy: how spindlechromosomal complex transfer can improve the future.

• Author: Baffi, Nicole

1. INTRODUCTION

   A child who will develop a mitochondrial disease by age ten is born every fifteen minutes. (1) Mitochondrial diseases can affect the nervous system and skeletal muscles, cause heart and cardiac abnormalities, and cause organ malfunction. (2) Principally, mitochondrial diseases are caused by mitochondrial DNA CmtDNA") mutations, which are genetically inherited through the mother. (3) These mtDNA mutations cause mitochondrial dysfunction, which is at the core of many common illnesses such as Alzheimer's disease, Parkinson's disease, diabetes, arthritis, cancer, and aging. (4) The severity of mitochondrial diseases varies according

   to the percentage of mutated mtDNA present in the mother's egg. (5) Since each egg contains numerous mitochondria, some mutated and others not, the percentage of mutated mtDNA passed genetically to a child is unpredictable. (6) Due to the erratic nature of mtDNA mutations, it has been difficult for scientists and researchers to identify mutated mtDNA within a mother's egg. (7) Therefore, developing methods to prevent mutated mtDNA from genetically transferring to a mother's offspring has been challenging.

   Until the advent of a recent germline (8) therapy technique, called spindle-chromosomal complex transfer, (9) there had been no way to identify and remove mutated mtDNA from a mother's egg, thereby preventing the transfer of mutated mtDNA to her offspring. (10) Therefore, children born to a mother with a genetic history evidencing mtDNA diseases, or who carries mutated mtDNA, could be born with a disease, develop one later in life, or not be affected at all. With the technological advancement of spindle-chromosomal complex transfer, a child can be born without the inherited mutated mtDNA, and thus be healthy. (11)

   This paper argues that new biomedical technology, whose purpose is to prevent children from suffering with a disease associated with mtDNA, should not be unduly hindered by regulations, institutional review boards, lack of funding, or restrictions on human clinical trials. Although research and testing should be reviewed and regulated to ensure it is performed in good faith, the technology should not be stifled, thereby preventing its advancement and utilization. Less restrictive regulations should be applied to spindle-chromosomal complex transfer to allow for widespread utilization and access to this beneficial technology.

   Part II will provide factual background about mitochondria: what it is, its role in cell function, and genetic diseases associated with mutated mtDNA. Part II will also provide factual background about spindle-chromosomal complex transfer, its processes, requirements, and potential outcome. Part III will discuss the current legal background surrounding egg donation and research involving gene therapy. Part IV will address ethical and legal concerns continually arising out of research involving human subjects and gene manipulation. Part V will discuss clinical trials in relation to regulation processes and ethical principles. Finally, Part VI will propose a bill aimed at allowing for funding, gamete donation, and gene therapy, which will enable spindle-chromosomal complex transfer technology to proceed and be available to those who wish to utilize this biotechnology.

2. MITOCHONDRIAL DNA AND SPINDLE-CHROMOSOMAL COMPLEX TRANSFER: THE FACTS

   Mitochondria are important, complex organelles which provide cellular energy for cell growth and cell death. (12) Considered the "power plant of the cell," they contain enzymes responsible for each cell's activity, (13) and affect how cells convert food into energy. (14) Mitochondria are "responsible for providing more than 90% of the energy needed by the body to sustain life and support growth." (15) They are located in almost every cell of our body and contain their own genome: mtDNA. (16) Since each cell contains numerous mitochondria, "a cell may harbor several thousand mtDNA copies." (17) Unfortunately, not all copies of mtDNA contained within our cells are normal. (18) Since all human mtDNA contain the same enzymes, (19) the distinctions between humans are due to the varying percentages of mtDNA mutations. (20)

   Many humans have mutations in their mitochondrial DNA. (21) For most, the mutations are in the lower percentages: not high enough to cause a mitochondrial disease. (22) Yet, there are many individuals with higher percentages who will develop or already have a disease associated with mutated mtDNA. (23) Mitochondrial diseases are illnesses resulting from a deficiency of any protein located within the mitochondria and involved in energy metabolism. (24) Since mitochondria are the "key regulators of cell survival and death," (25) most diseases and illnesses with problems related to energy deficiencies are attributable to mitochondrial dysfunction. (26) When mitochondria dysfunction, less energy is produced causing cell injury followed by cell death. (27) The repetition of this process causes systems within the body to fail and compromises the life of the suffering individual. (28) Symptoms of a mitochondrial disease may present at any age or be evident from birth or infancy. (29) Currently, there are more than 150 mutations of mtDNA that have been identified and associated with human disorders. (30) There are over forty identified diseases associated with mutated mtDNA. (31)

   These diseases are usually categorized by the organs they affect and the symptoms they cause. (32) The number of organs affected differs among those with mitochondrial disease. (33) In some people, one organ can be affected, in others all. (34) The severity of the disease can range from mild to fatal, affecting the cells of the brain, heart, nerves, kidneys, muscles, eyes, ears, and many other organs. (35) Mitochondrial diseases are among the most common genetically inherited diseases. (36) They primarily affect children, and currently have no cure or effective treatments. (37)

   Mutations in mtDNA are transferred genetically and can further mutate in future generations. They are genetically inherited, either through autosomal recessive (38) or maternal manner. (39) Maternal inheritance is the most common, since all embryonic mtDNA is derived from the mother. (40) Thus, a woman will pass on mutated mtDNA through her egg's cytoplasm. (41) However, a man will not pass on mutated mtDNA because sperm mitochondria are only a small portion of the zygote's cohort, eliminated shortly after fertilization. (42) Since "[s]perm lose their mitochondria when they penetrate the egg," (43) it follows that transmission of mutated mtDNA can be prevented by eliminating defective mitochondria from the woman's egg prior to fertilization. (44)

   Researchers have made progress toward eliminating mitochondrial disease with the development of a new technology which has proven safe and effective in non-human primates. Shoukhrat Mitalipov and his team at the Oregon National Primate Research Center have successfully transferred the nuclear genetic material from a mother's egg containing mtDNA mutations into an enucleated (45) healthy donor egg with normal mtDNA. (46) The nucleus in the mother's egg is removed, leaving behind her mtDNA which, if inherited by her offspring, could cause mitochondrial disease. (47) The nucleus removed from the mother's egg is then transplanted into a donor's egg, which has also had its nucleus removed and only contains normal mtDNA. (48) The resulting egg to be fertilized is thus a combination of the mother's nuclear DNA and the donor's mtDNA. (49) This method is called spindle-chromosomal complex transfer ("spindle transfer"), (50) and is a type of germline therapy. (51) Researchers have discovered that mtDNA can be sufficiently replaced in mature oocytes, without disturbing subsequent fertilization or development, (52) enabling offspring to be born free of mutated mtDNA. (53) Even though the process of spindle transfer is both complicated and technical, the potential benefit is deserving of the research efforts.

   When using a mature oocyte, DNA visibility is problematic because the nucleus cannot be seen, thereby complicating the removal of the oocyte's nucleus. (54) However, with the development of cloning processes and techniques, researchers were able to enucleate mature oocytes in a routine manner: staining DNA with fluorophores (55) and visualizing the DNA with ultraviolet light. (56) This enucleation technique was found to be applicable in isolating the mature oocyte's spindle-chromosomal complexes and transferring them to a spindle-free donor oocyte. (57) Researchers then used a karyoplast fusion technique, using an extract from the Sendai virus, (58) which produced reconstructed oocytes which maintained the spindle-chromosomal complexes transferred from the mature oocyte. (59) The use of a virus as the vector enables genetic materials to be introduced and absorbed by the cells, (60) thereby fusing them together. These reconstructed oocytes were then fertilized using intracytoplasmic sperm injection and in vitro embryo culture. (61) After analyzing the spindle transfer embryonic stem cells, the results revealed normal karyotypes with no detectable chromosomal abnormalities. (62) Finally, researchers tested the "in vivo developmental potential" of the embryos, transferring them into the reproductive tract of recipient female monkeys. (63) The resulting pregnancies were remarkable. The monkeys born as a result of this process are healthy, and their weight and gestational lengths are normal for their species. (64)

   The overall results suggest that "spindle-chromosomal complexes can be efficiently isolated and transplanted into enucleated oocytes." (65) The births of these healthy offspring demonstrate that this process can successfully mitigate mtDNA defects. (66) If this technology could be utilized with humans, it would require oocytes from both the mother and donor. The donor's egg would have to contain...