The mechanism that removes unfit cells before you’re born
- November 28, 2023
- Posted by: OptimizeIAS Team
- Category: DPN Topics
No Comments
The mechanism that removes unfit cells before you’re born
Subject : Science and Tech
Section: Biotech
Context:
- In 2016, Manvendra Singh re-analysed previously published gene expression data from an early human embryo, and spotted a new group of cells that hadn’t been seen before.
- These cells didn’t become a part of the later stages of the embryo and were elim-inated early in development .
Important findings of the Study:
- A new group of cells were found that had died before being developed into the later stages of an embryo.
- These cells were non-committed and found among cells of inner cell mass.
- The inner cell mass or embryoblast is a structure in the early development of an embryo which is not yet implanted along the lines of uterus of the mother.
- Human embryonic stem cells express a gene called HERVH.
- HERVH is a virus-like gene that helps maintain pluripotency.
- Pluripotency is seen in cells that has the ability to make other types of cells in the human body.
- Most of the cells of inner cell mass express HERVH, except non-committed cells eventually dies.
Stage of development of embryo:
- The development of the human body entails growth from a one-celled zygote to an adult human after fertilization.
- Fertilization occurs when the sperm cell enters and fuses with an egg cell (ovum).
- The genetic material of the sperm and egg then combines to form the single-cell- zygote.
- Zygote than undergoes the processes of cell division and cellular differentiation leading to the formation of the embryo that occurs during the early stages of development.
- An embryo is an initial stage of development of a multicellular organism.
- The mass of cells that form the early embryo gets implanted inside the mother’s womb and then grows bigger.
- The cells then start to differentiate into different types of cells that makes up the skin, muscles, nerves, etc.
- Over time, it develops into organs such as heart, lungs, the brain, and so forth.
- In the early stages of the human embryo (before implantation in the womb), the cells arrange themselves in a particular way.
- A blob of cells gathers towards one side of the embryo and the other cells arrange themselves around the blob, the cells that are collected on one side are called the Inner cell mass.
- Inner cell mass contains pluripotent cells.
What are Jumping Genes?
- Transposable elements (TEs) or jumping genes are Deoxyribonucleic acid (DNA) sequences that move from one location of the genome to another.
- These elements were first identified by geneticist Barbara McClintock in 1948.
- They are abundantly found in almost all organisms both prokaryotes and eukaryotes.
- Prokaryotes are unicellular organisms that do not contain well bounded nucleus and other membrane-bound organelles. Example: Monera and archaebacteria.
- Eukaryotes are those organisms that contain well bounded nucleus and membrane-bound organelles and can be either unicellular or multicellular. Example: protists, fungi, plants, and animals.
- TEs make up 50% of the human genome and up to 90% of the maize genome.
- These genes are dangerous little pieces of DNA that can get inserted into different regions of the genome and can damage DNA or cell death.
Role of HERVH:
- HERVH itself is a transposon but without the ability to jump.
- It protects early embryonic cells from dying because it does not contain another set of mutagenic transposons that causes DNA damage.
- It plays a role in the pluripotency of stem cells, so it has major implications for regenerative medicine.
- It could play a role in the fitness of the early embryo.
- The good non-committed cells expressing HERVH are reducing, leading to less healthy embryos.
A small price to pay:
- In the early embryo, when the cells form the inner cell mass and other cells surround it, the latter forms the placenta.
- The placenta is a structure that is attached to the wall of the uterus, near the developing fetus, and helps move oxygen and nutrients from the mother to the fetus.
- The cells that form the placenta also express transposon activity but are more tolerant of the transposons, and do not die.
- But the placenta is discarded after childbirth, so the cost of the placenta is the least to the organism.
The transposon activity in the early embryo could affect its fitness, with implications for infertility treatment and in-vitro fertilization (IVF) techniques.