Biological/Biochemical Features and Molecular Genetics of Specific Language Impairment ( SLI )

Abstract

Common learning disorders include attention‐deficit hyperactivity disorder, dyslexia, specific language impairment (SLI), speech–sound disorder and dyspraxia. They are influenced by genes and several research groups to attempt to identify susceptibility genes of learning disorders through the sequential analysis of genetic linkage and association. This review highlights the genetic contribution to SLI and the current molecular genetic researches aimed at identifying susceptibility and candidate genes for SLI. Currently, four susceptibility loci and three candidate genes ( CMIP , ATP2C2 and CNTNAP2 ) associated with SLI have been found. This review also summarises the biological/biochemical features of SLI. The success of dietary intervention of nutritional supplements (i.e. thiamine and some fatty acids) to improve learning abilities in SLI and dyslexia suggests that a greater understanding of biochemical abnormalities may provide a useful addition with other treatment procedures for these learning disorders. Key Concepts: Learning disorders may cause the learner to receive and process some information inaccurately. People with learning disorders may have problems of basic psychological processes involved in understanding or in using language, spoken or written, that may manifest itself in an imperfect ability to listen, think, speak, read, write, spell or do mathematical calculations. Individuals with specific language impairment (SLI) seem to have problems in pragmatics, such as discourse maintenance, use and range of speech acts and narrative abilities. Genetic factors are important in specific language impairment. Molecular genetic researches should be aimed to identify susceptibility genes for SLI. Molecular advances in SLI will help to set the research agendas for future studies to follow. The association and linkage studies of learning disorders may help us to understand the biological basis of normal learning variation, and shed light on more fundamental questions regarding the origin of human speech and language.

Genome-Wide Studies of Specific Language Impairment

“…In summary, five regions have consistently been associated with SLI, using GWLA, and targeted association studies have enabled identification of risk variants and candidate genes within three of these regions [ 13 , 47 ] (see Table 1 ).…”

Biochemical and genetic analyses of childhood attention deficit/hyperactivity disorder

“…Especially, EFAs should be taken with diet as precursors because of the animals and humans lack the ability to synthesize them. There is some evidence that the insufficiency in PUFA metabolism may contribute to the biological predisposition to learning disorders as dyslexia or ADHD [Richardson and Ross, 2000; Caylak, 2010/2011, 2011a, b]. It was found that plasma EFA levels were significantly lower in the children with hyperactivity than normal children [Mitchell et al, 1987].…”

“…It has considered that they have major role in the structure and function of this organ. There is some evidence that the insufficiency in PUFA metabolism may contribute to the biological predisposition to learning disorders as dyslexia, specific language impairment (SLI), speech–sound disorder (SSD), dyspraxia, and ADHD [Richardson and Ross, 2000; Caylak, 2010/2011, 2011a, b]. In addition, EFA deficiency impairs ADHD‐related behaviors in sensory and motivational processes [Richardson, 2006].…”

The Brave New World of Epigenetics: Embracing Complexity in the Study of Speech and Language Disorders

“…Genetics offers a delimited but critical window into understanding the complex causal mechanisms associated with developmental speech and language disorders. Some isolated cases aside, recent findings have highlighted that specific language impairment (SLI) and speech sound disorders (SSD) do not follow single-gene Mendelian modes of transmission or causality [1][2][3]. These disorders, like many speech and language disorders, are now thought to result from multiplex interactions across various genetic and environmental factors.…”