Dyslexia – Genetic Connections

Dyslexia is a learning disorder that causes difficulty in reading or interpreting words. Children with dyslexia have problems with relating speech sounds to letters. The question is ‘why’? What causes the brain changes that challenge kids with reading problems.

This article digs into what researchers have learned about dyslexia through examining the genes that are likely to be altered in kids with dyslexia.

Is Dyslexia Genetic?

Dyslexia is known to run in families. The heritability, or genetic component, is estimated to be about 50%. This means that while genetics plays a big role in the susceptibility to dyslexia, but that there are also other factors involved. Researchers have found many different genetic variants that add a little to the risk of being dyslexic, showing that dyslexia is influenced by multiple genes instead of just one ‘dyslexia gene’.

Researchers estimate that 5 – 12% of individuals are affected by dyslexia. It is diagnosed in childhood and mainly occurs in children with normal or above-average IQ.[ref]

What is going on in the brain with dyslexia?

Genetic studies can help to point to the physiological cause of dyslexia. Two of the genes (KIA/A0319 and DCDC2) identified as playing a role in dyslexia are involved in neuron migration.  A recent study (Oct. 2016) points to a connection between these genes and cilia, hair-like structures that are present on most neurons.[ref]

In other words, physical changes in the neurons happen in some people with the identified genetic variants. Not everyone with the variants will end up having dyslexia, though. Instead, it is a risk factor that seems to need another component.

It isn’t all genetics… environment matters too.

A recent study looked at the interactions between genetics and environment in children with dyslexia combined with ADHD. The study found that one of the DCDC2 gene variants has associations with both dyslexia and ADHD. Environmental factors also came into play: smoking in the home added to the correlation.[ref]

Other environmental factors that interact with genetics in increasing susceptibility may include:[ref][ref][ref]

  • birth weight
  • socio-economic status
  • maternal smoking during pregnancy
  • gestational iodine deficiency
  • early life stressors

Note that all of those environmental factors cause stress, either physical or mental, in the baby or child.

Stress and the cortico-limbic system

Recent research points to the important role of chronic early life stress on dyslexia. The brain has a vast potential to change and respond to environmental circumstances. These changes can occur in utero – but the brain is capable of changing throughout life. The biggest times of brain growth are early childhood years.

Stress – whether physical or mental – causes physiological changes. Hormones, including cortisol, can release due to stressors and affect the brain. The Hypothalamic-Pituitary-Adrenal (HPA) axis is the pathway linking stress hormone released from the adrenals and the effects on the brain.[ref]

Researchers hypothesize that early life stress causes release physiological changes in the brain. In children with certain KIAA03190 genetic variants, maternal stress during pregnancy was linked with significantly poorer reading ability.[ref]

Not all stress is bad, of course. At a moderate level and intermittent, stress increases attention, motivation, and neuronal synaptic plasticity. However, chronic or excessive stress causes cellular metabolic changes that could shift the brain from growth and plasticity towards stress protection.[ref]

 


Genetic variants (SNPs) and Dyslexia:

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Please note that most of these SNPs are not found in 23andMe v5 data, so if you aren’t seeing your data below, that may be the reason.

KIAA0319 gene:

The KIAA0319 gene encodes a protein involved in cell-to-cell interactions. In animal models, knocking out the KIAA0319 gene causes animals to have impaired, rapid auditory processing and spatial learning problems. Most of these fairly common variants are found in a quarter of the population or more. Thus, they don’t cause dyslexia on their own, but rather increase the susceptibility to it.

Check your genetic data for rs4504469 (23andMe v4; AncestryDNA)

  • T/T: protective against dyslexia in Asian populations, but linked to a higher risk of dyslexia in European populations.[ref][ref]
  • C/T: protective against dyslexia in Asian populations, but linked to a higher risk of dyslexia in European populations.
  • C/C: typical

Members: Your genotype for rs4504469 is .

Check your genetic data for rs9461045 (23andMe v4; AncestryDNA):

  • T/T: reduced expression of the KIA/A0319 gene, associated with a risk for dyslexia[ref]
  • C/T: reduced expression of the KIA/A0319 gene, associated with a risk for dyslexia
  • C/C: typical

Members: Your genotype for rs9461045 is .

Check your genetic data for rs2038137 (23andMe v4)

  • T/T: slightly increased risk of dyslexia[ref]
  • G/T: typical risk
  • G/G: typical risk

Members: Your genotype for rs2038137 is .

Check your genetic data for rs761100 (23andMe v4, v5; AncestryDNA):

  • C/C: slightly higher risk of dyslexia[ref]
  • A/C: typical risk
  • A/A: typical risk

Members: Your genotype for rs761100 is .

Check your genetic data for rs6935076 (23andMe v4, AncestryDNA):

  • T/T: slightly increased risk of dyslexia (OR = 1.25)[ref]
  • C/T: slightly increased risk of dyslexia (OR = 1.25)
  • C/C: typical

Members: Your genotype for rs6935076 is .

 

DCDC2 gene:

The DCDC2 gene encodes a protein important in the formation of neurons in the brain.

Check your genetic data for rs793862 (23andMe v4; AncestryDNA):

  • A/A: 3 to 5x greater risk of dyslexia[ref]
  • A/G: increased risk of dyslexia
  • G/G: typical risk

Members: Your genotype for rs793862 is .

Check your genetic data for rs807701 (23andMe v4; AncestryDNA):

  • G/G: 2 to 5x increased risk of dyslexia; even great risk if combined with rs793862[ref][ref]
  • A/G: increased risk of dyslexia
  • A/A: typical risk

Members: Your genotype for rs807701 is .

 


Lifehacks:

Check thyroid TPO-antibodies:
A recent study found that children with dyslexia were significantly more likely to have autoimmune thyroid issues than the normal control group.[ref]

Get the lead out:
Boys with elevated blood levels of lead have a pronounced ‘negative impact on executive function’. This wasn’t true, though, for girls.[ref]

What doesn’t seem to work: 
It is often just as important to know which interventions have been shown in clinical trials not to work.

  • EPA, a component of fish oil, has been tested in clinical trials. There was no difference between the EPA and placebo groups for reading skills, spelling, decoding fluency, and reading-related language skills.[ref]
  • A clinical trial involving applied kinesiology, physical manipulation, massage, homeopathy, and herbal remedies found that dyslexia and literacy performance did not statistically improve.[ref]

 


Related Articles and Genes:

Genetics and Anxiety
Did you know that about 1 in 5 people will deal with an anxiety disorder at some point in life? From generalized anxiety to separation anxiety to panic disorder – there are underlying physiological and genetic factors involved.

GABA: Genetic variants that impact this inhibitory neurotransmitter
GABA (gamma-Aminobuyteric acid) is a neurotransmitter that acts to block or inhibit a neuron from firing. It is an essential way that the brain regulates impulses, and low GABA levels are linked with several conditions including anxiety and PTSD.

ABCC11 gene: Ear wax and no body odor
The ABCC11 gene determines both the type of earwax a person has and whether they have no armpit or body odor.

Genetics and Double Eyelashes
Ever wonder why Elizabeth Taylor had such compelling eyes? It turns out that she probably carried a mutation for doubled eyelashes, also known as distichiasis.




Author Information:   Debbie Moon
Debbie Moon is the founder of Genetic Lifehacks. She holds a Master of Science in Biological Sciences from Clemson University and an undergraduate degree in engineering from Colorado School of Mines. Debbie is a science communicator who is passionate about explaining evidence-based health information. Her goal with Genetic Lifehacks is to bridge the gap between the research hidden in scientific journals and everyone's ability to use that information. To contact Debbie, visit the contact page.