Molecular characteristics

What causes autosomal dominant mental retardation-56?
Autosomal dominant mental retardation-56 is caused by a change in one of the two copies of the CLTC gene.

A gene (i.e. a small piece of our genetic code or DNA) is an instruction to assemble a sequence of several amino acids in the correct order to produce a protein, which is a structure essential for the formation and proper functioning of our body. If you think about the CLTC gene as a sequence of letters in a sentence, which code for words, this specific CLTC genetic variant is a change of a single letter (e.g. A) for another letter (e.g. G), resulting in a change of an amino acid for another amino acid in the protein. This genetic change disrupts the information encoded by CLTC, which becomes misinterpreted.

The CLTC gene is thought to be important for brain development and function. Thus, it is thought that the disturbance of this processes may result in the patient’s intellectual characteristics.

The clinical consequences of other CLTC variants is still to be investigated.

What is needed to confirm the diagnosis of Autosomal dominant mental retardation-56?
The diagnosis of Autosomal dominant mental retardation-56 is confirmed by performing genetic testing in an affected individual, which enables the detection of a disease-causing change in the CLTC gene.

The individual’s characteristics are usually not sufficient to raise the suspicion of Autosomal dominant mental retardation-56 (for example, because they overlap with the characteristics observed in other genetic disorders). Thus, the DNA sequence of multiple genes, including the CLTC gene, will be analysed using a multi-gene panel or exome sequencing.

The genetic testing can be arranged by a clinical geneticist and involves the collection of a sample of blood or saliva from the affected individual (and eventually the parents). Analysing the DNA of the patient and comparing it with the parents’ DNA may facilitate the detection of a disease-causing change in the CLTC gene that is not present in the healthy parents (i.e. a “de novo” change).