Overview

• Using long-read sequencing, the team produced the first complete sequences of three common fusions—two 13;14 and one 14;21.
• The shared fusion site lies within the SST1 macrosatellite repeat near acrocentric short arms previously missing from the reference genome.
• Imaging and genomic assays show SST1 regions can meet in the nucleolus, and an inverted SST1 orientation on chromosome 14 permits attachment by chromosome 13 or 21.
• Although fused chromosomes carry two centromeres, epigenetic control typically silences one, stabilizing segregation during cell division.
• The study links carriage in about 1 in 800 people to elevated risks of infertility, miscarriage and trisomy, and reports a human‑specific SST1 arrangement plus individuals lacking the permissive region on chromosome 14.