In animal brains, there is a gene called the brain-derived neurotrophic factor (BDNF) that is important for neurons in the hippocampus to grow and connect to each other, processes that are the basis of memory and learning. The gene produces a growth factor that makes neurons grow which plays a key role in the initial development of the brain: Mice born without BDNF have developmental deficits and die soon after birth. BDNF is also secreted by neurons in adult brains when synaptic junctions between neurons require strengthening (something called "synaptic plasticity") which again are processes that underly memory and learning. Just in case this is not enough, BDNF production has been linked to exercise and to treating depression.

(Quick recap of The Central Dogma of genetics as it's about to feature in our story: DNA stores the genetic material which is then transcribed into RNA that is then translated into proteins. This DNA->RNA->Protein is at the heart of genetics and molecular biology as it summarizes how genetic material is transmitted between generations (via DNA) and how the DNA controls the cell's processes via the RNA and proteins.)

There's been a weird twist in the BDNF story: when the BDNF gene is transcribed into RNA it makes two different types of RNA, a long one and a short one, differing in the tail length of the RNA that's produced. This is not uncommon in genetics as lots of genes produce more than one type of RNA that end up producing variants of the same protein product. The weird thing about BDNF is that both RNA types end up producing the exact same protein. The question is why does it do that? Why does BDNF need two types of RNA to produce the same exact product when only one would suffice?

The answer seems to be transportation. A paper recently published in the journal Cell shows that the long version of the BDNF RNA is transported down the long axons of nerve cells. Nerve cells can be quite long and the long BDNF RNA has anchors that transport proteins dock to and move the RNA towards the tips of the nerve cells. There, the same exact BDNF protein is made but it is at the tip of the nerve instead near the main body of the nerve cell. Neat!