How cute! Image Source

There is still no scientific consensus on whether lobsters feel pain or not (but people are actively working on the question). However, the Swiss federal government has recently asserted its empathy for these little creatures and declared it illegal to cook them alive. I am not Swiss, neither am I a big fan of seafood but I have to admit that the Lobster deserves recognition for more that its taste. To understand why, let’s first take a look at how aging works in humans.

Telomeres are biological timers

Most cells of our body (at the exception of reproductive cells and some other specific cell types) contain 23 pairs of chromosomes of various sizes. These chromosomes are fully duplicated at each cell division (or mitosis) to ensure the stability of the genomic information over time. This mechanism, called DNA replication, allows each dividing cell to transfer the totality of its genome to two daughter cells. 

DNA replication is an incredibly complex mechanism involving many regulatory steps. It requires multiple proteins acting together to open the DNA double-helix and “scan” the chromosome, reading its nucleotide sequence while synthetizing a perfect copy of it in real time. 

Because of some characteristics of this “scanning” mechanism that I will not detail here, the replication complex is unable to copy the DNA regions located at the extremities of chromosomes. As a consequence, a small part of each chromosome is lost during each replication cycle.

As you can imagine, the loss of genetic material at each division could have dramatic consequences for the cell. To solve this problem, the chromosome ends are composed of short nucleotide sequences repeated multiple times (between 500 and 3000 times in humans). These patterns form what we call the telomeres of the chromosome, which serve as a buffers to prevent the loss of critical genetic information during replication. 

Image source

Telomeres also have other purposes. Notably, they are recognized by multiple proteins which prevent the fusion of chromosomes together (as we saw in this article, cells do not like free DNA ends). Telomeres are thus progressively consumed over time like genetic fuses or timers. 

This progressive loss of the telomeres is not the only reason behind aging but, as they become too short, the genome loses in stability which leads to cellular dysfunctions. This instability is normally detected by the cell which, in consequence, enters senescence and dies. However, in some cases this could lead to cancers or other diseases. 

The maximum number of divisions that a cell can undergo before entering senescence is thus “determined” in advance by the size of its telomeres and is called the Hayflick limit.

So what’s the deal with lobsters? 

Lobster cells produce a specific enzyme called telomerase which is able to regenerate the telomeres by adding new repeats at their extremity, thus allowing the cells to divide virtually forever. This enzyme also exists in Human but is only produced in stem cells, hair follicles and some immune cells whereas it is ubiquitous in the cells of our crustacean friend. This explains why some lobsters could live up to 50 years and reach the terrifying weight of 20 kg (44 lb) when they don't end up in your delicious sandwich. So does that mean that they are immortal? No.

Even though they are able to hunt and reproduce until the end of their lives (old individuals are apparently even more fertile than younger ones), lobsters most of the time die of diseases or predation. And when they don’t, approximately 10% of them dies of exhaustion during moulting. One interesting characteristics of the lobster is indeed that they keep growing during their whole lives, which means that they needs to regularly change their rigid exoskeleton. Sadly for them, this process consumes a ridiculous amount of metabolic energy and it gets worst as the animal gets bigger, which ends up killing them… Sad story.

What does that mean for us Humans?

Researchers have shown that artificially forcing human cells to produce telomerase could make them immortal and avoid senescence. While this could be useful in a lab, trying to apply this method to a Human is very risky. Indeed, while the telomerase protects cells from some replication-associated mutations, it is also found active in up to 90% of cancers. The mechanism of senescence indeed allows the body to clear out cells that may have accumulated too many mutations over time, blocking it could thus mean taking the risk to keep alive dangerously mutated cells. 

Telomerase might thus not give us the key to immortality, but this could be for the best, let’s remember that in the end even the glorious Lobster dies alone at the bottom of the ocean for wanting to become too big for its own skin.

Sources and further reading:

• Longevity in lobsters in linked to telomerase expression
• If you want to learn more about the Hayflick limit
• Expressing telomerase in normal human cells increases their life-span
• Changing life-style could increase the length of telomeres in cancer patients 
• Telomerase as a therapeutic target
• The Guinness World Record page for the biggest lobster ever captured
• A good article on the same subject
• Starting next March, you will have to treat your meal in a humane way (at least in Switzerland)
• A nice review article on the dual role of telomerase in cancer

Check out my previous articles

•  [CRISPR 101] What is CRISPR?
• My introduction