Disorders in the development of language and speech in children receive little attention and the cause is usually unknown. Lot Snijders Blok describes in her thesis errors in five new genes that underlie these disorders. Two of them are even named after her. But there are many more mutated genes that cause such disorders. "We need to do genetic diagnostic testing much more often in children who are seriously behind in talking.”
In the Netherlands, seven percent of children struggle with a language and speech development disorder. This is a relatively unknown disorder, especially compared to, for example, ADHD, autism or dyslexia. And yet it often occurs together with these disorders. In some of these children, the language disorder is severe: they do not develop properly and end up in special education. It is then useful to determine the cause. And that is often in the genes.
Clinical geneticist in training Lot Snijders Blok from the Radboudumc dug into the DNA of dozens of families and tracked down five new genes with errors that cause language disorders. "These are genes that regulate all kinds of processes in the body and are important for such things as brain development. These genes are not responsible for the development of language and speech, but errors in these genes can disrupt this development. We expect that there are many more genes that cause such disorders."
Han Brunner, professor of clinical genetics, puts the new errors in DNA in a broader perspective: "People like to think in boxes. They would prefer that an error in a particular gene leads to a particular disease. But in doing so, we are underestimating the complexity of genetics. There is always more going on with these children than just the language or speech disorder, and we must therefore not view it separately from the development of the rest of the brain. I think the genetic errors we find provide the basis for a pediatrician to not just do something about the language disorder, but to take a more holistic approach."
The genetic errors found cannot yet be fixed. So why is it important to look for a genetic cause? Lot: "There is a lot of doubt among these parents as to whether their child's retardation might be due to the upbringing, or whether they have fallen short in their child's guidance. It is a real relief when we find a genetic cause for the problems. Parents who would like to have more children also want to know how great the chance is that their next child will have the same disorder. We can find that out if we also analyze the parents' DNA."
In addition, a genetic cause gives direction to treatment. "Based on the DNA research, we estimate what to expect in a child. Are the disorders mild or severe? Will the child ever learn to talk at all? Or would it be better to start immediately with a particular treatment, such as learning supportive gestures? And we know that some genetic errors are also associated with other disorders, such as heart defects. You want to catch that in time."
Two disorders with your name
Genetic diagnostics therefore need to be put on the map better among care providers. "I often hear that speech therapists, for example, think that the disorder is not hereditary because language problems do not run in the family. But especially in children with healthy parents without developmental problems, a new mutation can very well arise and DNA testing is of added value. I find it very interesting if a child develops completely differently from the parents, especially then I want to know everything about the DNA."
The disorders caused by two of the described genes have now been named after the researcher. In Snijders Blok-Fisher syndrome, children carry an error in the gene POU3F3. In Snijders Blok-Campeau syndrome, the error is in the gene CHD3. In both cases, a delay in general development occurs and problems with language and speech may arise.
On October 15 at 12.30, Lot Snijders Blok defends her thesis titled 'Let the genes speak! De novo variants in developmental disorders with speech and language impairment'. The live stream can be followed via this link.
At the Department of Genetics of the Radboudumc a clinical study is running, for which Lot Snijders Blok is looking for children with severe speech and language developmental disorders with a normal IQ and both of whose parents do not have this disorder. More information about this GENTOS study can be found here.
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