Genetic research into dyslexia
Encyclopedia
The genetic research into dyslexia has its roots in the work of Galaburda and Kemper, 1979, and Galaburda et al. 1985, from the examination of post-autopsy brains of people with dyslexia. When they observed anatomical differences in the language center
in a dyslexic brain, they showed microscopic cortical
malformations known as ectopias and more rarely vascular
micro-malformations, and in some instances these cortical malformations appeared as a microgyrus
. These studies and those of Cohen et al. 1989 suggested abnormal cortical development which was presumed to occur before or during the sixth month of foetal brain development.
have been identified, including at the two regions first related to dyslexia: ROBO1 on chromosome 3, DCDC2
and KIAA0319
, on chromosome 6 and DYX1C1
on chromosome 15.
A 2007 review reported that no specific cognitive processes are known to be influenced by the proposed susceptibility genes. Some studies have already started to include neurophysiological (e.g., event-related potential) and imaging (e.g., functional MRI) procedures in their phenotype
characterisation of patients. Such samples are an important prerequisite for the identification of those processes that are most proximal to the effects of particular genes and their associated biological pathways.
Language center
The term language center refers to the areas of the brain which serve a particular function for speech processing and production.- Current scientific consensus :...
in a dyslexic brain, they showed microscopic cortical
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
malformations known as ectopias and more rarely vascular
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
micro-malformations, and in some instances these cortical malformations appeared as a microgyrus
Microgyrus
A microgyrus is an area of the cerebral cortex that includes only four cortical layers instead of six.Microgyria are believed by some to be part of the genetic lack of prenatal development which is a cause of, or one of the causes of, dyslexia....
. These studies and those of Cohen et al. 1989 suggested abnormal cortical development which was presumed to occur before or during the sixth month of foetal brain development.
Genes and chromosomes associated with dyslexia
Molecular studies have linked several forms of dyslexia to genetic markers. Several candidate genesGênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
have been identified, including at the two regions first related to dyslexia: ROBO1 on chromosome 3, DCDC2
DCDC2
DCDC2 is a gene that has been identified with the development of dyslexia . Precisely how it contributes to the disorder remains unclear. It is thought that the gene may affect the migration of nerve cells in the brain as it develops ....
and KIAA0319
KIAA0319
KIAA0319 is a protein which in humans is encoded by the KIAA0319 gene.- Clinical significance :Variants of the KIAA0319 gene have been associated with developmental dyslexia....
, on chromosome 6 and DYX1C1
DYX1C1
Dyslexia susceptibility 1 candidate gene 1 protein is a protein that in humans is encoded by the DYX1C1 gene. This protein contains 420-amino acids with 3 tetratricopeptide repeat domains, thought to mediate protein–protein interactions....
on chromosome 15.
A 2007 review reported that no specific cognitive processes are known to be influenced by the proposed susceptibility genes. Some studies have already started to include neurophysiological (e.g., event-related potential) and imaging (e.g., functional MRI) procedures in their phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
characterisation of patients. Such samples are an important prerequisite for the identification of those processes that are most proximal to the effects of particular genes and their associated biological pathways.