Chinese researchers have announced the world’s first engineered mammal using reprogrammed genes. The remarkable breakthrough hints at the significance of chromosomal rearrangement in evolution and the creation of new species.
The results have the potential to lead to cures for diseases and conditions like infertility, cancers and even childhood leukaemia.
The Beijing-based Chinese Academy of Sciences research unit used the CRISPR gene-editing tool to break down and reorder individual chromosomal segments into new gene packages, resulting in a genetically altered mouse, Xiao Zhu, or ‘Little Bamboo’.
Healthy laboratory house mice have an array or karyotype of 40 chromosomes and have maintained this genetic make-up after more than a century of breeding in artificial conditions.
These karyotype changes only occur organically 3.2 to 3.5 times every million years in rodents and less frequently in primates, at roughly 1.6 changes per million years.
While incredibly infrequent, even a single small change in an animal’s make-up can result in significant changes within a species.
For example, gorillas, humans and some 200 other species of primates all share a common ancestor. Despite rather distinct differences in appearance and intelligence, gorillas and humans are separated by minute chromosomal differences: gorillas have two distinct chromosomes, while humans have two fused ones in their place.
In years gone by, scientists had enjoyed moderate success replicating these chromosomal alterations, but only in very basic single-cell organisms like yeast.
Li Wei, a lead author of the study that was published in the academic journal Science, explained how the genomes in mammals are vastly more complex than yeast, and recreating any change had been a challenging puzzle for geneticists to solve.
The research team altered the rodent’s genetic make-up by stitching together a long chromosomal strand. Scientists observed that some errors in this practice led to undesired results, with several subjects showing adverse effects, mal adaptations and sometimes death.
Li and his team shortened each chromosome and reduced the number of chromosome pairs from 20 to 19, creating a new karyotype in lab mice and, in a world-first, they found the subjects to exhibit normal behaviour healthy and disease-free.
Their breakthrough was hugely important for the synthetic biology industry, said Li and his team. Li also said that the work went a long way to further understanding the mechanisms responsible for growth and development at a molecular scale.
Because the genetic alterations carry over from generation to generation, some scientists are hopeful Li and the Academy’s work can aid in discovering treatments and cures for infertility and cancer.
However, it should be noted that CRISPR gene-editing on human beings is still illegal in China.