Human tail, butterfly wings, & repetitive behaviour | Last Week in Science (3rd March 2024)

Colors of butterfly wings

As soon as you read Biology in high school, you learn that the genes code for proteins which form via an intermediate molecule RNA. But then we now know that more number of genes code for RNA that never form proteins. This RNA must be doing something. The past few decades have shown that this RNA that is not coding for protein or non coding RNA plays an important role in deciding the formation of other proteins or as to say whether and when a specific gene is active to form the protein. When we talk about visible features and say that genes might be responsible then mostly it is the protein that is being formed from that gene is responsible. But that may not be true in the case of butterfly wing colors.

Who doesn't like looking at butterflies flapping their beautiful wings as they move from one flower to the other? Have you wondered what makes the butterfly have such colorful wings? By studying white butterflies, scientists found that it is not the protein but an RNA that decides whether the color pigments will form or not in the butterfly. This RNA molecule is a long non coding RNA or lncRNA. LncRNAs are known to be involved in many functions in the body and play important roles in the development of many diseases. But the current study is the first example where a visible trait is getting affected because of an lncRNA.

Reference: Surprise RNAs solve mystery of how butterfly wings get their colorful patterns

Tale of the tail

With the myriad functions the tail serves for organisms that have one, it is still a mystery as to why and how the common ancestor of apes and humans lost their tail.  One of the hypothesis for why our ancestor lost the tail is that the bipedal walking - walking on two limbs was easier without a tail. But a lot of animals have a tail and can still walk on two limbs. Certain AI models for robotics have even shown that a tail actually helps in stability while moving on two limbs. Although, we do not know the why but a group of scientists may have found the how.

Researchers in New York studied one of the genes - TBXT, which is involved in tail development in various species including mice and cats. They found that in apes including humans the TBXT gene is altered in a way that it forms a shorter RNA as compared to the RNA that gets formed from TBXT gene in other primates that have a tail. So, the code of the DNA is first transcribed into an RNA molecule which further forms a protein. A shorter RNA being formed means a shorter protein being formed in apes which could be the reason for loss of the tail. The scientists then introduced this altered TBXT gene of apes in mice to test whether the mice lost their tail. And they indeed lose their tails. I wonder now whether these mice can be trained to walk on two limbs like humans.

Reference: How humans lost their tails — and why the discovery took 2.5 years to publish 

Beyond the role of glue

Half of the cells in the brain are not neurons but glia. The glial cells have been known to be the supporting cells for neurons till now. An increasing number of studies are showing that glia are much more than being the glue for neurons.

Repetitive behavior or doing an action again and again is present in disease conditions, like moving objects around to be in a specific order as seen in Obsessive Compulsive Disorder, repeated movement of limbs in Huntington's and Autism. A particular protein was found to be reduced in the brain of individuals with these conditions. In a surprising finding, the scientists found that this protein forms not in neurons but astrocytes - a type of glial cells. When they removed this protein from mice then repetitive behavior in the form of excessive self grooming, excessive licking of the water source in the cage, or excessive exploring of a familiar object stopped. Although, they still need to find how astrocytes are controlling neurons and thus the repetitive behavior, but this finding may soon lead to a better understanding of diseases like OCD and autism. 

Reference: Non-neuronal brain cells modulate behaviour