Trinucleotide Repeat Disorder

Genetic disorders are widespread and affect many people on daily basis. Many are passed from one generation to the next. Trinucleotide repeat disorder also known as trinucleotide repeat expansion disorders, codon reiteration or triplet repeat expansion disorders is a set of genetic disorders caused by a kind of mutation where trinucleotide repeat in certain genes that exceed the normal and stable threshold of genes [Trinucleotide repeat expansion]. This kind of mutation is as a result of unstable microsatellite repeat that occur in all genomic systems.

Trinucleotide repeat expansion disorders cause several human diseases and occur during multiple stages of human development and growth in different cell types.  This disorder is sensitive and can be severe to the gender of the parent gene. Anita Harding, a British neurologist was the first to identify the relationship between trinucleotide repeat expansion and diseases that cause many neurological dysfunctions. Today, there are more than 14 known trinucleotide repeat disorders.  The trinucleotide repeat disorders are classified into three groups and they include;

1. The common repeat is the triplet CAG which occurs when presented in the coding area of a gene codes for the amino acid glutamine. It leads to disorders commonly referred to as the polyglutamine [polyQ] disorders. These disorders include Huntington disease [HD], Spinobulbar muscular atrophy [SBMA], Dentatorubro-Pallidoluysian Atrophy and Spinocerebellar Ataxia.
2. The second category of repeat expansion disorder either do not include the CAG triplet or the CAG triplet I is not within the coding region of the gene. Hence, they are known as the Non-polyglutamine disorders and include Fragile X syndrome, Myotonic dystrophy, Spinocerebellar Ataxia, Fragile XE Mental Retardation and Friedreich Ataxia.
3. This category is a sunset of the Non-polyglutamine repeat disorders and entails diseases linked to expansion of a polyglutamine tract.

The common symptom of trinucleotide repeat disorder is a progressive degeneration of the nerve cells and this feature affects many people.  Despite these diseases sharing the same repeated codon [CAG] and a number of symptoms, the repeats for polyglutamine diseases are present on different chromosomes. Surprisingly, non-polyglutamine diseases do not exhibit any symptoms.

Genetic disorders are usually fatal especially if they are caused by central nervous system. Some of the common trinucleotide repeat expansion disorders such as Huntington disease, spinal cerebellar ataxia and myotonic dystrophy can be treated through symptomatic intervention and supportive measures. RNA interference [RNAi], a method of inhibiting target genes expression also presents an exclusive tool for therapy by attacking the main problem causing the disorder directly. Due to the slow development nature of trinucleotide repeat diseases, some of the changes that impact cell functions and morphology may be as a result of secondary or tertiary responses to the chief effects of mutant proteins.

Some of these disorders associated with trinucleotide repeat expansion disorder may result to weight gain and other complications. Transduction of the hypothalamus among other brain regions or direct treatment of the periphery may enhance loss of muscle weight and motor behaviors. All in all, it is wise to consult an experienced and certified specialists more so a neurologist and find better ways to prevent ad lessen the effect of trinucleotide repeat disorder symptoms.

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References

http://www.nature.com/gt/journal/v13/n6/full/3302664a.html

http://en.wikipedia.org/wiki/Trinucleotide_repeat_disorder

http://web.stanford.edu/group/hopes/cgi-bin/wordpress/2010/06/trinucleotide-repeat-disorders/