A common symptom of polyQ diseases is the progressive degeneration of nerve cells, usually affecting people later in life. Although these diseases share the same repeated codon (CAG) and some symptoms, the repeats are found in different, unrelated genes. In all cases, the expanded CAG repeats are translated into an uninterrupted sequence of glutamine residues, forming a polyQ tract, and the accumulation of polyQ proteins damages key cellular functions such as the ubiquitin-proteasome system. However different polyQ-containing proteins damage different subsets of neurons, leading to different symptoms. , ten neurological and neuromuscular disorders were known to be caused by an increased number of CAG repeats. The non-PolyQ diseases do not share any specific symptoms and are unlike the PolyQ diseases. In some of these diseases, such as Fragile X syndrome, the pathology is caused by lack of the normal function of the protein encoded by the affected gene. In others, such as Myotonic Dystrophy Type 1, the pathology is caused by a change in protein expression or function mediated through changes in the messenger RNA produced by the expression of the affected gene. In yet others, the pathology is caused by toxic assemblies of RNA in the nuclei of cells.
Trinucleotide repeat disorder
Lysosomal storage disease
Ribosomopathy
Lipid storage disorder
Trinucleotide repeat expansion
Creatine transporter defect
Cerebral creatine deficiency
Peroxisomal disorder