The shared ancestry between the C9orf72 hexanucleotide repeat expansion and intermediate-length alleles using haplotype sharing trees and HAPTK

Using haplotype sharing trees and majority-based ancestral haplotypes, we demonstrate that the C9orf72 hexanucleotide repeat expansion and alleles with ≥18–20 repeats share large haplotype blocks, indicating very recent shared ancestry. This was in sharp contrast to the shorter alleles, suggesting that expansions might be formed from the longer repeat alleles.