Preventing Common Hereditary Disorders through Time-Separated Twinning

Biomedical advances have led to a relaxation of natural selection in the human population of developed countries. In the absence of strong purifying selection, spontaneous and frequently deleterious mutations tend to accumulate in the human genome and gradually increase the genetic load; that is, the frequency of potentially lethal genes in the gene pool. Gradual increase in incidence of many complex disorders suggests deleterious impact of the genetic load on human well-being. Recent advances in in vitro fertilization (IVF) combined with artificial twinning and transgenerational embryo cryoconservation offer the possibility of preventing significant accumulation of genetic load and reducing the incidence of hereditary disorders. Many complex diseases such as type 1 and 2 diabetes, autism, bipolar disorder, allergies, Alzheimer’s disease, and some cancers show significantly higher concordance in monozygotic (MZ) twins than in fraternal twins (dizygotic, DZ) or parent-child pairs, suggesting their etiology is strongly influenced by genetics. Preventing these diseases based on genetic data alone is frequently impossible due to the complex interplay between genetic and environmental factors. We hypothesize that the incidence of complex diseases could be significantly reduced in the future through a strategy based on time-separated twinning. This strategy involves the collection and fertilization of human oocytes followed by several rounds of artificial twinning. If preimplantation genetic screening (PGS) reports no aneuploidy or known Mendelian disorders, one of the MZ siblings would be implanted and the remaining embryos cryoconserved. Once the good health of the adult MZ sibling(s) is established, subsequent parenthood with the cryoconserved co-twins could substantially lower the incidence of hereditary disorders with complex etiology and virtually eradicate simple Mendelian disorders. The proposed method of artificial twinning has the potential to alleviate suffering and reduce the negative social impact induced by dysgenic effects associated with known and unknown genetic factors. Time-separated twinning has the capacity to prevent further accumulation of the genetic load and to provide source of isogenic embryonic stem cells for future regenerative therapies.