Can humans create life? In terms of creating life from scratch, Dr Craig Venter, a multi-millionaire pioneer in genetics, and his team have managed to create a completely new "synthetic" life form constructed entirely with synthetic DNA in May 2010. Eight years later, Chinese scientists created a functional single-chromosome eukaryotic cell from budding yeast haploid cells containing 16 chromosomes. This work has been published in Nature with Yangyang Shao as the first author, a postdoctoral fellow at the CAS Center for Excellence in Molecular Plant Sciences/Institute of Plant Physiology and Ecology.
Eukaryotic genomes are generally organized in multiple chromosomes. Humans have 23 pairs of chromosomes, for example, the budding yeast diploid cells have 32 and the worms Caenorhabditis elegans have 12 chromosomes. The advantages of a eukaryotic cell with multiple chromosomes instead of a single one are not clear. Shao and collaborators created a single chromosome yeast and explore the consequences of chromosome-number reduction. Unexpectedly, the fusion has little effect on cell fitness. The fusion of 16 chromosomes into 1 considerably altered the chromosome structure, but had slight impact on global gene expression. Chromosome fusion strains show small defects in sexual reproduction, which may explain the advantages of having more chromosomes.
Subsequently, Shao and collaborators circularized the artificially created
yeast single-linear-chromosome SY14 to evaluate the possibility for a
eukaryotic cell to have a ring instead of a linear chromosome, which apparently
has not been found in nature. The single circular chromosome yeast without
telomeres shows no cell senescence upon telomerase inactivation, and is a
long-lived cell in some sense.
Beyond the current findings, these engineered strains would be of considerable value for future investigations of telomere biology, centromere/kinetochore biology, meiotic recombination, and the relationship between nuclear organization and function. Since human and yeast share 1/3 homologous genes, these strains would also be useful in studying aging and telomere associated diseases.