ZIC2 (Holoprosencephaly 5) Repeat Expansion Testing
Description
Pathogenic GCN repeat expansions within exon 3 of the ZIC2 gene have been associated with autosomal dominant holoprosencephaly 5 syndrome (HPE5). The pathogenic repeat expansions lead to an extended polyalanine tract that can impair DNA binding and the transcriptional activities of the protein 1.
Pathogenicity is dependent upon GCN repeat length according to the following ranges 1-2:
Normal Alleles | Mutable Normal Alleles | Intermediate/Uncertain Alleles | Reduced Penetrance Alleles | Full Penetrance Alleles |
15 | - | 16-24 | - | 25 or more |