PABPN1 Repeat Expansion Testing
Description
Pathogenic GCN repeat expansions within the first exon of the PABPN1 gene have been associated with autosomal dominant oculopharyngeal muscular dystrophy (OPMD). The pathogenic repeat expansions lead to the expression of a toxic polyalanine tract that can form aggregates and have a negative effect on genes involved in mRNA processing.
Pathogenicity is dependent upon GCN repeat length according to the following ranges 1-2:
Normal Alleles | Mutable Normal Alleles | Intermediate or Uncertain Alleles | Reduced Penetrance Alleles | Full Penetrance Alleles |
10 | - | - | 11* | 12-18 |
*Biallelic 11 repeat expansions are associated with full penetrance.
Note: As OPMD is typically adult onset, PABPN1 repeat expansions are not reported in minors in comprehensive analyses.