20q12, Red
20q13.12, Green
The 20q12 probe, labelled in red, covers a 331kb region within the PTPRT gene and includes the D20S108 marker. The 20q13.1 probes, labelled in green (141kb and 174kb), cover the MYBL2 gene and includes the D20S150 marker.
Deletions of the long arm of chromosome 20 are a common chromosomal abnormality associated with myeloid malignancies, in particular myeloproliferative neoplasms (MPN), myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML)1.
Deletion of the long arm of chromosome 20 [del(20q)] is observed in 10% of patients with polycythemia vera (PV) and in other MPNs2. Additionally, it can be seen in 4% of MDS cases and in 1-2% of AML cases2. The prognosis for MDS where del(20q) is the sole abnormality is good; however, the presence of secondary abnormalities may be indicative of disease progression3.
FISH is particularly useful in confirming the presence and extent of the abnormality in poor cytogenetic sample preparations.
Potential target genes have been investigated in the region of overlap between the AML/MDS and MPD common deleted region at band 20q12. Five genes were expressed in both bone marrow and CD34+ cells. Of these genes, three were previously identified: L(3)MBTL1 regulates chromatin structure during mitosis; SRSF6 encodes a serine rich protein important to regulation of alternative splicing of mRNA; and MYBL2, a member of the MYB transcription factor family, is involved in cell cycle control2,4,5.
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