While dyslexia is known to run in families, the role of genetics in dyslexia is still being determined. Here is a quick look at some of the genes thought to be involved in dyslexia, which affects around 10% of the population.
Two of the genes (KIAA0319 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 which 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 was associated with both dyslexia and ADHD, with smoking in the environment adding to the correlation. [ref]
Genes Involved in Dyslexia:
KIAA0319 is involved in cell to cell interactions. In animal models, knocking out KIAA0319 causes animals to have impaired, rapid auditory processing and spatial learning problems. Most of these are fairly common variants and are found in a quarter of the population or more.
- rs4504469 (T) – found to be protective against dyslexia in Asian populations, but linked to higher risk of dyslexia in European populations. [ref] [ref]
- rs9461045 (T) – reduced expression of the KIAA0319 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]
DCDC2 gene – from Genetics Home Reference “This gene encodes a doublecortin domain-containing family member. The doublecortin domain has been demonstrated to bind tubulin and enhance microtubule polymerization. This family member is thought to function in neuronal migration where it may affect the signaling of primary cilia. Mutations in this gene have been associated with 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 this to be significantly associated 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 an mTor inhibitor can differentially regulate DCDC2 (in podocytes – kidney cells).