Advancing Human Artificial Chromosomes at the Dawn of Synthetic Genomics.

Human artificial chromosomes (HACs) are engineered, chromosome-scale DNA molecules that replicate and segregate autonomously in mammalian cells, offering a unique platform for large, stable, nonintegrating genetic delivery. The first generation of HACs emerged prior to synthetic genomics efforts, and their development has aided understanding of chromosome structure and centromere function. In parallel, microbial synthetic genomics demonstrated that entire viral, bacterial, and yeast chromosomes can be designed, synthesized, assembled, and functionally validated, establishing core principles for genome-scale engineering. Recent advances in large DNA assembly, long-read sequencing, and epigenetic centromere specification now position HACs within this broader synthetic genomics framework. We review and integrate lessons from microbial systems with advances in mammalian chromosome biology and discuss how HACs are becoming increasingly precise and customizable platforms. Current efforts promise to expand their potential for gene and cell therapy, functional genomics, humanized models, and the rational construction of synthetic mammalian genomes.