Geneticists have successfully identified an enzyme that may be linked to Downs’ Syndrome, as well as a key component of miscarriages.
The enzyme, PP2ACdc55, regulates the production of sperm and egg cells in human reproduction and the discovery may improve the understanding of the process that can lead to miscarriage, or infants born with Downs’ Syndrome and other chromosomal irregularities.
Scientists at the University of Salford looked at a process called meiosis. Unlike normal cell division (mitosis), meiosis has two rounds of nuclear division. This ensures that when sex cells fuse with each other, they have two copies of each chromosome, one from each parent.
When cells have too many or too few chromosomes this is known as aneuploidy. For instance, babies born with Downs’ Syndrome have three copies of chromosome 21, whereas Patau Syndrome is when three copies of chromosome 13 are present. Aneuploidy is also the leading cause of miscarriage, with an estimated one in seven pregnancies resulting in miscarriage. “Understanding how meiosis is regulated is of great importance to understanding the causes of aneuploidy and genetic disorders in humans,” said Dr Gary Kerr and colleagues, writing in the journal Scientific Reports.
In order to identify the ‘genetic switch’ which regulates segregation and mis-segreation of cells that can lead to aneuploidy, the team investigated PP2ACdc55, an enzyme known to play a role in preventing cells from prematurely exiting meiosis. Using fluorescent tagging, they tracked the enzyme’s presence on yeast model – which mimics the processes of meiosis in humans.
The team created random mutations in the Cdc55 gene, allowing them to analyse the resulting 987 mutant yeast strains, characterize the mutations and then work backwards to identify the role of the gene by looking at the effect of the mutations on the resulting colonies.
As a result, the data suggested the PP2ACdc55 enzyme does play an essential role in chromosome segregation however, scientists are still a way from knowing exactly how the processes are affected to lead to aneuploidy.