DNA GENDER CHANGE NOW POSSIBLE BY BMT-RECIPIENT Y CHROMOSOME KNOCKED OUT AND X CHROMOSOME DOUBLED IN HUMANS
It is widely known that the blood karyotype of bone marrow transplant recipients reflects that of the donor and not that of the recipient. XX recpients of BMT from XY donors have a blood genotype that can become 100% XY. Likewise, XY recipients of BMT from XX donors have a blood genotype that can become 100% XX. This change of genotype is not limited to the blood. It can affect other tissues. (1-3) Some authors have noted a change in genotype from XY to XX in up to 96% of buccal swabs from the cheek (1, 3) and 72.9% of fingernails (3). The buccal results further demonstrate why DNA sex testing in sports is not valid since the buccal smear for sex testing has traditionally been commonplace. The fingernail results demonstrate the inadequacy of the use of DNA for sex testing in forensics. The finding of donor karyotype in recipient hair also underscores the limitations of DNA gender testing in forensics. The finding of donor cells in recipient brain tissue (4) suggests that donor cells may cross the brain-blood barrier, and suggests that any recpient tissue may acquire the DNA type of bone marrow transplant donors. That a Y chromosome can re-populate the endometrium AND contribute to the FUNCTION of the uterus in a formerly XX individual, attests to the fact that one's DNA type has a high degree of plasticity and is not as fixed as previously thought. (5)
But recently, it has been found that bone marrow transplants not only can cause the recipient's DNA to change to that of the donor, but that bone marrow transplants and stem cell transfer may actually cause a knockout of a recipient's Y chromosome AND a duplication of a recipient's single X chromosome resulting in the recipient's genotype changing from XY to XX. (6, 7, 8). This is not likely to be part of the disease process (as the change only occurs AFTER the transplant). This is suggested to be a normal process and the mechanism for a bone marrow transplant from an XX donor knocking out a recipient's Y chromosome is provided below
Although this is a good explanation as to why the recipient Y chromosome gets knocked out the duplication of the X chromosome requires another explanation. I suggest that it is adaptive and preferential non-disjunction to avoid the deleterious consequences of an XO karyotype. XO cells undergo a high rate of apoptosis when compared with XY or XX cells.
Since a bone marrow transplant from an XX donor has been shown (see above) to be able to REPLACE recpient XY cells in virtually any tissue (including hair, neurons, and fingernails), it is also likely that bone marrow transplantation or stem cel transfer can ALSO cause the recipient DNA itself to change in any of these tissues by not only knocking out the recpient's Y chromosomes but also by causing the recipient's single X chromosomes to double. This effectively doesn't only cause the recpient to take on the donor's genotype but actually changes the recipient's genotype from XY to XX.
(1) Tran SD, Pillemer SR, Dutra A, Barrett AJ, Brownstein MJ, Key S et al. Differentiation of human bone marrow-derived cells into buccal epithelial cells in vivo: a molecular analytical study. Lancet 2003; 361: 1084–1088. | Article | PubMed | ISI
(2) Abkowitz JL. Can human hematopoietic stem cells become skin, gut, or liver cells? [Letter]. N Engl J Med 2002; 346: 770–772. | Article | PubMed | ISI
(3) Körbling M, Katz RL, Khanna A, Ruifrok AC, Rondon G, Albitar M et al. Hepatocytes and epithelial cells of donor origin in recipients of peripheral-blood stem cells. N Engl J Med 2002; 346: 738–746. | Article | PubMed | ISI
(4) http://www.ncbi.nlm.nih.gov/pubmed/15121406
(5) http://www.ncbi.nlm.nih.gov/pubmed/15238594
(6) http://jco.ascopubs.org/content/28/36/e750
(7) http://www.ncbi.nlm.nih.gov/pubmed/20979181
