https://www.nature.com/articles/s41421-022-00511-1
Engineered chromosomal fusion with no discernable fitness effect.
Abstract
Chromosomes occupy discrete spaces in the interphase cell nucleus, called chromosome territory. The structural and functional relevance of chromosome territory remains elusive. We fused chromosome 15 and 17 in mouse haploid embryonic stem cells (haESCs), resulting in distinct changes of territories in the cognate chromosomes, but with little effect on gene expression, pluripotency and gamete functions of haESCs. The karyotype-engineered haESCs were successfully implemented in generating heterozygous (2n = 39) and homozygous (2n = 38) mouse models. Mice containing the fusion chromosome are fertile, and their representative tissues and organs display no phenotypic abnormalities, suggesting unscathed development. These results indicate that the mammalian chromosome architectures are highly resilient, and reorganization of chromosome territories can be readily tolerated during cell differentiation and mouse development.
The chromosome number in naturally evolved house mice Mus musculus domesticus , which have populated in Western Europe and North Africa, ranges from 2n = 40 to 2n = 22[16]
So Bill, does this single species of mouse share a common ancestor? Were individuals of this species magically poofed into existence?
(Chromosome territory reorganization through artificial chromosome fusion is compatible with cell fate determination and mouse development | Cell Discovery),17,18. Some of their chromosomes are metacentric, i.e., the centromere is at the middle of each chromosome due to fusions of two telocentric chromosomes, which are commonly found in the laboratory mouse (e.g., C57BL/6)19. In addition, Muntjac deer (Muntiacus, Muntiacinae, Cervidae) have evolved quite diverse karyotypes (e.g., 2n = 46 of M. reevesi and 2n = 6/7 of M. muntjak vaginalis ) through chromosome translocation, tandem fusion, and pericentric inversion20,21,22. Recently, deliberate artificial chromosome engineering has succeeded in generating single-chromosomal Saccharomyces cerevisiae and Schizosaccharomyces pombe strains, which show drastic changes in global chromosome structures, but grow as robustly as the naturally evolved strains23,24,25. These lines of evidence suggest that chromosome architecture in eukaryotes is highly resilient, and chromosome territories could be self-organizing representations of the genome, or simply be a manifestation of random chromatin collisions driven by intrinsic interactions between chromatin loci and/or geometric constraints within the nucleus.