Table 5.

HTT Technical Considerations

Technical IssueComment [Reference]
Sequence of repeat CAG; however, an interrupted repeat, [(CAG)n-CAA-CAG], is present on the majority of alleles [Wright et al 2019]; for clinical implications see Genotype-Phenotype Correlations.
Methods to detect expanded allele (see Table 6 ) Conventional PCR, triplet-primed PCR (TP-PCR) [Jama et al 2013], and Southern blotting [Bean & Bayrak-Toydemir 2014] have been described.
Somatic instability Alleles with an abnormal number of CAG repeats may display somatic instability of the repeat [Telenius et al 1994].
Germline instability Although expansion & contraction of repeat length can occur w/maternal or paternal transmission, expansion occurs far more commonly in paternal transmission, w/large expansions (i.e., >7 CAG repeats) occurring almost exclusively through paternal transmission [Semaka et al 2013a]. Most individuals w/juvenile-onset HD inherit the expanded allele from their fathers [Nahhas et al 2005].

From: Huntington Disease

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