An international team of researchers from Singapore and the United Kingdom has identified an enzyme that regulates the production of sperm and egg cells in human reproduction. The discovery improves our understanding of a process which can often go wrong, resulting in miscarriage or infants born with chromosomal irregularities.
Meiosis: dividing pollen mother cells. Image credit: Josef Reischig / CC BY-SA 3.0.
The research team, headed by Dr. Prakash Arumugam of the National University of Singapore and Bioinformatics Institute, looked at a process known as meiosis, which unlike normal cell division (mitosis) has two rounds of nuclear division, to ensure that when sex cells fuse with each other, they have two copies of each chromosome – one from each parent.
“Meiosis is a specialized form of cell division in sexually reproducing organisms by which haploid daughter cells are produced from diploid germ cells. This is different from mitotic cycle in which daughter cells produced have the same DNA content as their parental cells,” the authors explained.
“Understanding how meiosis is regulated is of great importance to understanding the causes of aneuploidy and genetic disorders in humans,” they said.
When the cells have too many or too few (aneuploidy), babies are born with Down syndrome (three copies of chromosome 21); Patau syndrome (three copies of chromosome 13) and other conditions.
Aneuploidy is also a leading cause of miscarriage, and with an estimated 1 in 7 pregnancies resulting in miscarriage.
In order to identify the ‘genetic switch’ that regulates segregation and mis-segration, Dr. Arumugam and his colleagues – Dr. Jin Huei Wong of Bioinformatics Institute and Dr. Gary Kerr of the University of Salford – investigated PP2ACdc55, an enzyme involved in diverse cellular processes.
Using fluorescent tagging, they tracked the enzyme’s presence on yeast models – which offer a number of commonalities in the processes of meiosis in humans.
Prior studies by the team showed that PP2ACdc55 played an essential role in controlling the timing of metaphase to anaphase during meiosis, in other words preventing cells from prematurely exiting meiosis.
By creating random mutations in the Cdc55 gene, the scientists analyzed the resulting 987 mutant yeast strains, characterized the mutations and worked to identify the role of the gene by looking at the effect of the mutations on the resulting colonies.
The resulting data suggests that PP2ACdc55 plays a pivotal role in chromosome segregation, although we are still a way from knowing how the processes go wrong.
The team’s findings were published July 26, 2016 in the journal Scientific Reports.
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Gary W. Kerr et al. 2016. PP2ACdc55’s role in reductional chromosome segregation during achiasmate meiosis in budding yeast is independent of its FEAR function. Scientific Reports 6, article number: 30397; doi: 10.1038/srep30397
