- Scientists have identified 1,016 specific genes and 205 regions in DNA associated with intelligence.
- The study deepens our understanding of neurobiology of cognitive functions, and genetically linked psychiatric and neurological disorders.
Intelligence — a construct that includes problem solving abilities, language acquisition and spatial manipulation — is at the forefront of genetic research. Scientists usually believe that intelligence can be measured and captured by psychometric tests. At present, we don’t know how genes and environment interact to produce smart decisions and why the average IQ increased worldwide during the 20th century.
Recently an international team of researchers conducted 2 different studies on a large scale to discover more about human intelligence and how our brain functions. They found 939 new genes and 190 new genetic loci (a fixed location on a chromosome) linked with intelligence.
The study builds upon previous research (2017), in which scientist identified 40 new genes associated with intelligence. These genes are predominately expressed in brain tissue, and pathway analysis shows the involvement of genes controlling cell development. Let’s find out what they have done new this time.
Scientists conducted a genome-wide association meta analysis on 269,867 people (from 14 European cohorts) who participated in neurocognitive tests. They measured participants’ intelligence and matched scores with genetic variation of participants’ DNA — known as single nucleotide polymorphisms. This way, scientists observed which mutations are linked with high intelligence.
The team detected more than 9 million mutations in the given samples, from which they identified 1,016 specific genes and 205 regions in DNA associated with intelligence. Out of these 1,016 specific genes, 77 had been already identified in previous researches.
Reference: Nature Genetics | doi:10.1038/s41588-018-0152-6
Also, they discovered direct relationships between higher intelligence and longer lifespan. The genes that make us smarter also protect us from Alzheimer’s disease, hyperactivity disorder, schizophrenia and depressive symptoms.
However, these genes are responsible for increased instances of autism spectrum disorder, which includes repetitive behaviors, poor social skills, speech and nonverbal communication.
This research increases our knowledge of neurobiology of cognitive functions, and genetically linked psychiatric and neurological disorders.
Researchers performed another large-scale genome-wide association meta analysis – this time on 449.484 people, and detected 136 independent genome-wide significant loci (12 of them had been previously detected), implicating 599 genes.
These genes are linked with neuroticism — one of the Big Five personality traits in psychology. It’s a big step towards understanding what exactly causes conditions like anxiety, depression and schizophrenia.
Functional follow-up implicated enrichment in different parts of the brain and involvement of certain types of cells, including serotonergic neurons, medium spiny neurons and dopaminergic neuroblasts. Furthermore, gene set analyses implicated 3 particular pathways: neurogenesis, behavioral response to cocaine processes, and axon part.
Reference: Nature Genetics | doi:10.1038/s41588-018-0151-7
The team also showed that the genetic signal of neuroticism partially originates in 2 different subclusters – ‘worry’ and ‘depressed affect’. The Mendelian randomization analysis showed both unidirectional and bidirectional impacts between neuroticism and various psychiatric traits.
This research offers new leads and testable functional hypotheses to unravel the neurobiology of neuroticism, its subtypes, and its genetically linked traits.
The team also reported that they used a newly built statistical method, known as MAGMA, to estimate aggregate association on the basis of all single-nucleotide polymorphisms in a gene. In simple language, it helps to associate genetic data with specific parts of the brain.