Christopher Cogle and his colleagues from Gainesville, Florida, in 2004 reported a retrospective study of autopsy (postmortem) specimens from three women who underwent stem cell transplantation for leukemia using hematopoietic stem cells (HSCs) from their brothers, up to six years before death. In all three stem cell recipients, the brain cells showed a Y chromosome. The findings of a male sex chromosome in the brain cells (neurons) supported the concept that bone marrow cells can migrate to the brain and transform into neural cells. Such cells could therefore participate in the repair of brain tissue.