Chromosome transplantation: a possible approach to treat human X-linked disorders.

Abstract Many human genetic diseases are associated to gross mutations such as aneuploidies, deletions, duplications or inversions. For these “structural” disorders conventional gene therapy, based on viral vectors and/or on programmable nuclease-mediated homologous recombination, is still unsatisfactory. To correct this type of disorders, Chromosome Transplantation (CT), defined as the perfect substitution of an endogenous defective chromosome with an exogenous normal one, could be applied. CT re-establishes a normal diploid cell, leaving no marker of the procedure, as we have recently shown in mouse pluripotent stem cells. To prove the feasibility of the CT approach in human cells we used induced pluripotent stem cells (hiPSCs) reprogrammed from the Lesch-Nyhan (LN) disease patients, taking advantage of their mutation in the X-linked HPRT gene, making the LN cells selectable and distinguishable from the resistant corrected normal cells. Here we demonstrate, for the first time, that CT is feasible in hiPSCs: normal exogenous X chromosome was first transferred using an improved chromosome transfer system and the extra sex chromosome was spontaneously lost. These CT cells were functionally corrected and maintained their pluripotency and differentiation capability. By inactivation of the autologous HPRT gene, CT paves the way to the correction of hiPSCs from several X-linked disorders.