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Two different Philadelphia chromosomes in a cell line from an AML-M0 patient
J R González García1, O M Garcés Ruíz, J L Delgado Lamas
1División de Genética, Centro Médico Nacional de Occidente, Institituto Mexicano del Seguro Social, Guadalajara, Jalisco, Mexico.
Cancer Genetics and Cytogenetics
|October 23, 1997
Summary
A second Philadelphia (Ph) chromosome, common in leukemia, was investigated. Findings suggest it may arise from new translocations or mitotic crossing over, not just duplication.
Area of Science:
- Cytogenetics
- Molecular Biology
- Hematology
Background:
- The Philadelphia (Ph) chromosome, a result of the t(9;22) translocation, is a hallmark of certain leukemias.
- Secondary Ph chromosomes are frequent in leukemias with existing 9;22 translocations.
- Previous studies suggested the second Ph chromosome is a duplication of the derivative chromosome 22.
Observation:
- A unique case of acute myelogenous leukemia presented a cell line with two distinct Ph chromosomes.
- This distinctness was identified via chromosome 22 centromeric heteromorphism.
- The presence of two different Ph chromosomes raised questions about their origin and genetic content.
Findings:
- Fluorescent in situ hybridization (FISH) confirmed the presence of the bcr-abl fusion gene in two separate Ph chromosomes.
- Two bcr-abl positive signals were detected in 60% of analyzed interphase nuclei.
- This indicates the second Ph chromosome is indeed a true Philadelphia chromosome.
Implications:
- The origin of the second Ph chromosome may involve mechanisms beyond simple duplication.
- Potential mechanisms include mitotic crossing over or novel chromatid translocations.
- Understanding these mechanisms is crucial for leukemia diagnosis and treatment strategies.