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Isodicentric Y chromosomes and secondary microchromosomes
H Rivera1, L M Ayala-Madrigal, M Gutiérrez-Angulo
1División de Genética, Instituto Mexicano del Seguro Social, Guadalajara, Jal., Mexico. hrivera@cencar.udg.mx
Genetic Counseling (Geneva, Switzerland)
|July 23, 2003
Summary
Mosaic patients with isodicentric Yp chromosomes and microchromosomes often go undiagnosed. These microchromosomes arise from the excision of one centromere from Y-isodicentrics, requiring FISH for detection.
Area of Science:
- Genetics
- Cytogenetics
- Molecular Biology
Background:
- Investigating chromosomal abnormalities in patients with mosaicism.
- Understanding the origin and structure of Y-chromosome anomalies.
Observation:
- Two mosaic patients presented with both an isodicentric Yp (idic(Yp)) and a microchromosome.
- Fluorescence in situ hybridization (FISH) using the DYZ3 alphoid repeat probe confirmed two alphoid clusters in the isodicentrics.
- The microchromosomes were found to contain a Y-centromere.
Findings:
- Microchromosomes associated with Y-chromosome abnormalities likely originate from the functional dicentricity of isodicentric Y-chromosomes.
- These microchromosomes represent the excision of one centromere and adjacent chromatin from the parent isodicentric Y-chromosome.
- Previous observations support this mechanism for microchromosome formation.
Implications:
- The rarity of reported cases suggests a high rate of underdiagnosis for this specific chromosomal abnormality.
- FISH analysis is crucial for detecting these microchromosomes, as they may be missed in standard cytogenetic assessments.
- Improved diagnostic methods are needed to accurately identify individuals with Y-chromosome microchromosomes and associated mosaicism.