What Causes Chimerism?

Chimerism typically arises from the fusion of multiple embryos during early development or the exchange of cells between twin embryos in utero. Different types of chimerism have slightly different causes and symptoms.

Tetragametic Chimerism

Tetragametic chimerism is a rare condition where an individual possesses cells from at least four genetically distinct parents. It occurs during fertilization when two separate eggs are fertilized by two different sperm, resulting in the formation of fraternal twins. Subsequently, the embryos fuse in early development, leading to a single individual with cells from both embryos.

1. Tetragametic chimeras have two different sets of DNA, with one set originating from each twin. This can result in a mosaic of traits throughout the body.
2. Diagnosis occurs incidentally during genetic testing, such as when discrepancies are found between different tissue samples or during paternity testing.
3. Tetragametic chimerism can lead to variations in physical appearance, organ function, and genetic markers across different parts of the body.
4. While tetragametic chimerism is usually benign, it can complicate medical diagnoses and forensic investigations due to discrepancies in DNA profiles from different tissues.
5. The existence of tetragametic chimerism raises ethical questions regarding individual identity, reproductive rights, and legal parentage.

Microchimerism

Microchimerism occurs when a small number of cells carrying different genetic material from another individual persist within the body of a host organism. Microchimerism can occur naturally during pregnancy when fetal cells cross the placenta and enter the maternal circulation, leading to maternal-fetal microchimerism. It can also arise from blood transfusions, organ transplantation, or maternal cells entering the fetus during pregnancy. There are two main types of microchimerism:

• Maternal-Fetal Microchimerism: Fetal cells (from the fetus) persisting in the mother’s body after pregnancy.
• Fetal-Maternal Microchimerism: Maternal cells (from the mother) persisting in the fetus or newborn.

Microchimerism has been implicated in both beneficial and detrimental effects on health. It may contribute to immune tolerance during pregnancy and enhance maternal immune responses. However, it has also been associated with autoimmune diseases, transplant rejection, and certain cancers. Microchimerism is detected the through various techniques, including PCR-based methods to identify specific genetic markers unique to the microchimeric cells.

Also Read: Genome Editing – Definition, Techniques & Applications

Twin Chimerism

Twin chimerism occurs when twins exchange cells with each other while still in the womb, leading to a blend of their genetic material. This can result in an individual having cells with different DNA, potentially causing variations in traits or characteristics. Twin chimerism shows how interactions between siblings during development can influence an individual’s biological makeup. It highlights the complexity of human biology and the unique ways in which genetic diversity can manifest within individuals.

Artifical Chimerism

Artificial chimeras can be created through laboratory manipulation, such as:

1. Cell Transplantation: Genetically modified cells or tissues can be transplanted into an organism, integrating with the host’s cells and contributing to its genetic makeup.
2. Genetic Engineering: Techniques such as gene editing can be used to introduce specific genetic alterations into an organism’s cells, resulting in chimerism with both modified and unmodified cells.

Chimera genetics refers to an organism containing cells with different genetic compositions. In genetics, human chimeras are individuals with cells from two or more genetically distinct sources. Identification of chimerism in humans involves genetic testing of multiple tissues or cells to detect variations in DNA profiles.

Chimerism can occur naturally through processes like twinning or fusion of embryos, and artificially through procedures like organ transplantation or gene therapy. Chimerism has applications in various fields like forensics, transplantation, and reproductive medicine. In this article, we will study the meaning of chimera, its formation, chimera in humans and its identification in detail.