Dyslexia is known to run in families however genetics’ role in dyslexia is still being determined. Take a quick look at some of the genes thought to be involved in dyslexia, affecting around 10% of the population.
Two of the genes (KIA/A0319 and DCDC2) identified as probably 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]
A recent study looked at the interactions between genetics and environment when it comes to dyslexia being combined with ADHD. The study found that one of the DCDC2 gene variants has associations with both dyslexia and ADHD, with smoking in the environment adding to the correlation.[ref]
Genes Involved in Dyslexia:
KIA/A0319 is involved in cell to cell interactions. In animal models, knocking out KIA/A0319 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.
- rs4504469 (T) – found as a protectant against dyslexia in Asian populations, but linked to a higher risk of dyslexia in European populations.[ref][ref]
- rs9461045 (T) – reduced expression of the KIA/A0319 gene, associated with a risk for dyslexia[ref]
- rs2038137 (T) – slightly increased risk of dyslexia for homozygous[ref]
- rs6935076 (T) – slightly increased risk of dyslexia (OR = 1.25)[ref]
From the Genetics Home Reference “This gene encodes a doublecortin domain-containing family member. The doublecortin domain has demonstrated to bind tubulin and enhance microtubule polymerization. This family member seems to function in neuronal migration where it may affect the signaling of primary cilia. Mutations in this gene have associations to reading disability (RD) type 2, also referred to as developmental dyslexia.”
- rs793862 (A) – 3 to 5x greater risk of dyslexia[ref]
- rs807701 (G) – 2 to 5x increased risk of dyslexia if homozygous; even great risk if combined with rs793862[ref][ref]
- rs7765678 (C) – protective against dyslexia[ref]
- rs807724 (C) – A Chinese study found a significant association with reading comprehension and fluency.[ref]
More to read:
Recent studies have looked into the differences between the types of dyslexia caused by these two genes. A study from April 2016, Knockdown of Dyslexia-Gene Ccd2 Interferes with Speech Sound Discrimination in Continuous Streams, gives details on the differences.
Visual motion discrimination has been linked to DCDC2 polymorphisms.
A rabbit trail to go down:
A recent study found that a mTor inhibitor can differentially regulate DCDC2 (in podocytes – kidney cells).
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