How to breed more intelligent humans? This is a difficult question, one which raises numerous issues, both ethical and scientific. Would you give your eyesight away to become brighter? As crazy as this question may sound, a blinding mutation might increase intelligence.
The CORD7 (cone-rod dystrophy 7) mutation of the RIMS1 gene produces progressive blindness in humans, and a previous study found that people carrying this mutation showed increased intelligence, particularly in childhood.
Now, the question is to understand how a mutation which effectively causes a negative effect in the eye can have a positive effect on cognition. To address this question, a team of researchers led by Tobias Langenhan and Manfred Heckmann investigated the functional implications of this mutation at the neuron level in flies 1.
The investigators introduced the corresponding mutation to CORD7 in flies by CRISPR and observed the effects of the mutation at the cell level since testing fly intelligence might not be a good proxy for the cognitive effects in humans. What they discovered was that the mutation increased synaptic transmission, that is, it made for more efficient “thinking”. The mutation makes neurons release more neurotransmitters at the synapsis –the region of contact between neurons through which information is transmitted in the form of small chemical signals, the neurotransmitters– that way the intensity of the message transmitted is stronger. However, in the retina, this excess of neurotransmitter release and intense transmission “burns” receptor cells in their retina, leading to blinding. This is how this blinding mutation to the RIMS1 gene appears to increase intelligence in humans.
Back to the opening question, you may still not want to exchange your eyesight for intelligence, but maybe in the future there might be away of tinkering with CORD7 without causing blindness. However, the ethics and feasibility of the process are a question for the future.