chromosome 6p deletion

Chromosome 6p deletion: A reason for no pain, no hunger and no sleep

An 8-year-old girl is the first unique case of chromosome 6p deletion. She can not feel pain, hunger and requirement of sleep. It is a congenital condition in which some of the parts of chromosome 6 deleted during the process of cell division.

23 pairs of chromosomes are present in humans. The chromosome numbers vary from organism to organism. it is the complex network of DNA and protein which helps DNA to fit inside the cell nucleus.

How DNA fits inside the nucleus? Read the article: DNA packaging in eukaryotes

Two arms, centromere and telomere are three different parts of the chromosome. Each part has a different function to do.

The centromere helps chromosomes to arrange properly during the process of replication, the two arms (“p” arm and “q” arm) have genetic information in the form of genes and the telomeres are the cap of the chromosomes which protects the genetic information of the chromosomes.

Depending upon the location of the centromere the chromosomes are divided into several categories such as acrocentric, metacentric or submetacentric. The chromosome 6 is a medium submetacentric chromosome having the “p” arm slightly shorter than the “q” arm.

Take a look at the different forms of chromosome 6 depending upon its length:

Chromosome 6p deletion
Image credit: atlasgeneticsoncology.org

 

Any abnormality is occurred due to the mutations in the genome. These mutations are might be chromosomal aberrations or gene mutations.

Read further: Role of Telomeres in ageing

Deletion, duplication, translocation, single nucleotide polymorphisms are some the types of gene mutations while chromosomal mutations are structural or numerical.

The structural mutations are deletion, duplication, translocation, insertion or triplication whereas trisomy, tetrasomy, monosomy or pentasomy are some of the types of numerical aberration.

In the case of structural chromosomal aberrations, the structure of the chromosome changed while in the numerical chromosomal aberration, the total number of the chromosomes changed.

For more detail on mutation read the article: Different types of Genetic mutations

For example, trisomy of chromosome number 21 is observed in the down syndrome. Instead of  2 times, the chromosome 21 occurred 3 times in the individual which results in severe mental retardation and growth-related problem.

Chromosome 6p deletion

The cry-do-cat syndrome is a type of structural aberration in which some portion of the “p” arm of the chromosome 5 deleted.

Similarly, 6p deletion is such type of structural aberration which is very rare in the entire world. Now let’s understand some of the basics about chromosome 6. 

Read some of the interesting articles:

Genetic information on chromosome 6

Chromosome 6 contains more than 1000 genes (~1200-1300 genes) with more than 170 million base pairs. The majority of the genes present on chromosome 6 are associated with the immune system. The genes for major histocompatibility complex are present on it.

Read the article on Genetics of the immune system:

The major histocompatibility genes are HLA-A, HLA-B, HLA-C, HLA-DQA1, HLA-DQB1, HLA-DQ, HLA-DRA, HLA-DRB1, HLA-DRB3, HLA-DRB4, HLA-DRB5, HLA-DPA1, HLA- DPB1, HLA-Cw present on the “p” arm of chromosome 6. See the image which shows the location of the HLA genes on the p arm of chromosome 6:

Chromosome 6p deletion

The total size of the chromosome 6 is 170Mb in which the short “p” arm contains 60Mb portion and the long “q” arm contains the 110Mb portion of the total size.

Chromosome 6 is involved in some of the well-known diseases such as maple syrup urine disease, Parkinson disease, polycystic kidney disease and Rheumatoid arthritis.

Also ring chromosome, del 6q, del 6q16, del 6p22 and insertion in the proximal end on the p arm are some of the common types of the structural chromosomal aberration associated with chromosome 6. 

Chromosome 6p Deletion

An 8-year-old girl named Olivia Farnsworth is the first unique case of chromosome 6p deletion. The story of her came in light when she was hit by the car and injured badly. However, she has not felt any pain and did not shade a single tear.

After the diagnosis of a condition, her mother said that she does not need to sleep or eat. Furthermore, she confessed that she never feel danger, pain, hunger and need of sleep also she feels fewer emotions as compared with other girls.

The doctors named her as a first “Bionic girl” for her superhuman capability. Tons of articles are available on the Internet which covered the story of Olivia Farnsworth but none of the articles explained which part of chromosome 6 or how many genes from chromosome 6 are deleted.

The cytological analysis reveals that the major portion of the “p” arm was deleted from the single copy of chromosome 6 in case of Olivia.

The major portion of chromosome 6 is associated with the immunes system. The immune system gives power to the organism to resist any pathological condition. We can feel the pain when a signal to the brain is given from the site of cut or damage.

This power is given by the immune system to our body. The major genes which code for the proteins of the immune system are located on chromosome 6, more specifically on the “p” arm.

The genes for the major histocompatibility complex are located on the p arm of chromosome 6. So hypothetically, it is possible that some of the genes from this “HLA genes clouds” may be deleted which give the insane immune resistance power to Olivia.

Interestingly, the other genes which are present on the chromosomes 6 mainly associated with diabetes, developmental delay, distinctive facial features, intellectual disability and other mantle problem but not with hunger, pain or sleep.

The severity of the phenotype depends on the size of the deleted fragment. Further, the condition is congenital and not inherited to the next generation.

Read articles on DNA extraction:

  1. Proteinase K DNA extraction method
  2. Phenol chloroform DNA extraction: Basics, preparation of chemicals and protocol
  3. Different types of DNA extraction methods
  4. Role of alcohol in DNA extraction

Other 6p deletions are in CCD (Cleido Cranial Dysplasia) del 6p12.3, deletion of 6p22 and terminal deletion of 6p arm are some of the other 6p deletion reported.

In all these deletions, the major phenotypic abnormalities are associated with developmental delay, mental retardation and intellectual disability.

Though more than 100 cases like Olivia are reported, she is the only person in the world who has all three phenotypes of “no pain, no sleep and no hunger”. Additionally, approximately, 3000 cases are reported worldwide in which chromosome 6 deletion is involved (but none of the cases is like Olivia).

“1 in 200 children is born with chromosomal abnormalities worldwide”

Chromosome 6p deletion
Genes located on chromosome 6. Image credit: public.ornl.gov

Is she superhuman?

Most people think so but she is not. It is not a power; it is a limitation.

Feel of pain and hunger is the first line of defence for our body. The pain is the signal for the danger that some portion of our body is hurt. Also, hunger is a signal for the requirement of energy for our body.

When we feel hunger, we eat. Suppose if we can not feel hunger, the carbohydrate, protein and energy level of our body decreases and we can not feel it. We might be unconscious or dies due to hunger.

Imagine the condition in which we are injured badly and we even don’t know about it. What will happen?

Further, due to lack of sleep, the working efficiency of our brain can be decreased. 

“If we do not sleep for a longer time, we can not differentiate between reality and illusion.”

So scientifically, it is not a superpower. Still, she is different from us. We can say that she is the “naturally genetically modified organism”. Nonetheless, the reason for the less hunger and sleeplessness is not cleared.

Conclusion

Chromosome 6p deletion case of Olivia is the unique and only case in the world.

I personally believe that mutation or any other alteration gives the survival power to the organism and Olivia is the example of it. In future, we can hope that Non-oxygen depended GMO can be created. And, that will change the fate of the human race.

Read Further,