The construction and application of human artificial chromosomes (HACs) has so far proved a formidable challenge due to a persistent obstacle known as uncontrolled multimerization—the pervasive joining of similar molecules. This phenomenon has long thwarted efforts to develop HACs that are large, stable, and structurally well-defined, however, scientists have now overcome this challenge.

This breakthrough, published in Science, holds promise for advancing chromosome engineering and precise genome editing across a spectrum of organisms, including mammals. Artificial chromosomes, capable of accommodating large numbers of engineered genes, have emerged as potent tools in genetic manipulation, with prior applications in bacteria and yeast allowing the writing and rewriting of genomes. Their success in these organisms hints at their potential to reshape genetic landscapes within human cell lines as an alternative to other established approaches.

While HACs date back nearly a quarter-century, their practical utility has been hampered by the challenge of multimerization and uncontrolled rearrangement during their formation, limiting their efficacy in human applications. Craig Gambogi and colleagues now present a new strategy to avoid unintended multimerization.

A circular artificial chromosome is first assembled within budding yeast, followed by its transfer into human cell lines through a process of cell fusion. Remarkably, the resultant HACs evade multimerization, remaining as singular entities within the human cells. In comparison with previous iterations, these newly engineered HACs boast a formidable size, clocking in at approximately 750 kilobase pairs of DNA. This provides sufficient capacity for the intricate multi-domain chromatin necessary for inheritance across cellular divisions.

R. Kelly Dawe underscores in a related Perspective, “Future applications of HACs will likely focus on introducing long genes or multigene clusters into cell lines or individuals.” 

“It may soon be possible to include artificial chromosomes as a part of an expanding toolkit to address global challenges related to healthcare, livestock, and the production of food and fiber.”