Scientists have made a groundbreaking feat of generating a new type of embryonic stem cell that contains only a single copy of the human genome. Normal stem cells typically carry two copies of the human genome. Remarkably, the new embryonic stem cells are able to divide exactly like their normal stem cell counterparts.
The feat is especially noteworthy because typical human cells inherit two sets of chromosomes, one set from the father and the other set from the mother. Each set contains 23 chromosomes. Therefore, the typical human cell contains 46 chromosomes. This arrangement is the bedrock for the “diploid” tag attached to the human cell.
However, the reproductive cells (sperm and egg) have a different arrangement. They contain only one set of chromosomes. Consequently, scientists call reproductive cells “haploid” cells.
Naturally, the diploid cells are able to divide to form new cells in a complex process called cell division. Conversely, a haploid cell type is only able to combine with another haploid cell type to form a diploid cell (haploid sperm combines with haploid egg to form a diploid zygote that develops into a new individual). Therefore, haploid cells are not able to divide to form new haploid cells.
In the lab, scientists have generated embryonic stem cells from human egg cells. However, these generated embryonic stem cells were diploid in nature. In this research, the team of scientists sought to change that.
To begin, they triggered unfertilized human egg cells into dividing. Next, they highlighted the DNA with a fluorescent dye. Finally, from the resulting soup of diploid cells and haploid stem cells, they isolated the latter, which were fewer in number.
Later on, the researchers then demonstrated the ability of these isolated haploid stem cells to divide and subsequently differentiate into other cell types. These include pancreatic, heart and nerve cells. The important distinction was that the isolated haploid cells were able to divide and differentiate while retaining a single set of chromosomes.
According to researchers, the implications of this discovery are immense and varied centering in the fields of human genetics and medical research. First off, it would help provide more insight into the happenings of human development and provide compelling reasons why we reproduce sexually instead of from a single parent.
Also, the ability of the human cells to retain their haploid nature whilst being able to reproduce will be very influential in carrying out more comprehensive and successful genetic edits and genetic screening. To put it simply, it will facilitate genetic analysis in cancer research, precision and regenerative medicine.
This is because it is much easier isolate and understand specific gene abnormalities in haploid cells where genes appear singly than in diploid cells where genes appear in twos. In diploid cells, one gene might be abnormal while the analogous gene might be normal. Consequently, the normal, healthy gene will modulate the biological effect of the mutated or deficient gene, leading to a nightmare for scientists and researchers.
Furthermore, since the isolated haploid stem cells were genetic matches of the egg cells from which they were derived, it is overwhelmingly possible to develop cell-based therapies for diseases in which genetically identical cells offer a therapeutic advantage. Examples of such diseases are diabetes and blindness.
The haploid stem cells might also be useful for reproductive purposes since their genetic content is equivalent to the genetic content of germ cells.
The scientists published their findings in the journal Nature.