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A neocentromere on human chromosome 3 without detectable alpha-satellite DNA forms morphologically normal
A Wandall1, L Tranebjaerg, N Tommerup
1Department of Medical Genetics, IMBG, University of Copenhagen, Panum, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. al.wandall@imbg.ku.dk
Chromosoma
|January 23, 1999
Summary
A neocentromere formed on chromosome 3q26 in a father and daughter, lacking typical DNA but forming functional kinetochores. This neocentromere proved stable, unlike the original centromere on a marker chromosome.
Area of Science:
- Genetics
- Cell Biology
- Epigenetics
Background:
- Centromeres are crucial for chromosome segregation during cell division.
- Neocentromeres, or newly formed centromeres, can arise in regions lacking canonical centromeric DNA.
- The formation and stability of neocentromeres are not fully understood.
Observation:
- A neocentromere was identified at the 3q26 region in a familial case (father and daughter) involving a chromosome 3 with a deleted centromere.
- The 3q26 neocentromere lacked detectable alpha-satellite DNA, a hallmark of canonical centromeres.
- Immunostaining showed weak positivity with anticentromere (CREST) antibodies at the 3q26 neocentromere.
Findings:
- Electron microscopy revealed that the 3q26 neocentromere assembled microtubule-associated kinetochores with normal morphology and size, comparable to those on other large chromosomes.
- The deleted centromere formed a small marker chromosome with strong anticentromere antibody reactivity but reduced kinetochore size.
- The neocentromere at 3q26 exhibited remarkable stability under stress conditions that induced kinetochore loss in the original centromere on the marker chromosome.
Implications:
- This study demonstrates the formation of a functional neocentromere in a familial setting, highlighting the plasticity of centromere formation.
- The findings suggest that epigenetic factors, rather than solely DNA sequences, play a critical role in neocentromere establishment and function.
- The stability of the 3q26 neokinetochore provides insights into the mechanisms maintaining centromere integrity and function, even in the absence of standard centromeric DNA.