Dicentric chromosome 13 and centromere inactivation

Area of Science:

• Cytogenetics
• Human Genetics
• Molecular Biology

Background:

• Investigating chromosomal abnormalities in children with dysmorphic findings.
• Examining cases suggestive of both trisomy 13 and 13q- syndrome.

Observation:

• A child presented with dysmorphic features indicating potential trisomy 13 and 13q- syndrome.
• Karyotype analysis revealed two distinct dicentric chromosomes involving chromosome 13.

Findings:

• One dicentric chromosome showed a duplication of 13q, while the other exhibited a deletion of 13q.
• Leukocyte studies indicated a loss of cells with the smaller, deleted dicentric chromosome over time.
• Fibroblasts consistently contained the smaller, deleted dicentric chromosome.
• Q-band polymorphisms suggested both dicentric chromosomes were of paternal origin.
• The smaller dicentric chromosome likely arose from the larger one through a bridge-breakage-fusion cycle.
• The presence of two active centromeres in either dicentric chromosome could not be confirmed.

Implications:

• Understanding the stability and behavior of dicentric chromosomes in different cell types.
• Elucidating the role of the bridge-breakage-fusion cycle in generating chromosomal abnormalities.
• Contributing to the diagnosis and understanding of rare chromosomal disorders like trisomy 13 and 13q- syndrome.