XL 4q12 DC consists of a green-labeled probe hybridizing proximal to the FIP1L1 gene region at 4q12, an orange-labeled probe hybridizing to the CHIC2 gene region at 4q12 and another green-labeled probe hybridizing to the PDGFRA gene region at 4q12.

Probe maps are created in accordance with the intended purpose of the product. Solid colored bars do not necessarily indicate that the probe fully covers the indicated genomic region. Therefore, caution is advised when interpreting results generated through off-label use. Probe map details based on UCSC Genome Browser GRCh37/hg19. Map components not to scale. Further information is available on request.

The category ´myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB or FGFR1, or with PCM1/JAK2´ of the revised 4th edition of the WHO classification defines three particular groups with rearrangements in PDGFRA, PDGFRB or FGFR1 and a provisional entity with PCM1/JAK2 rearrangement. The clinical manifestations within this category are numerous and heterogeneous and include myeloproliferative neoplasms, myelodysplastic syndromes as well as de novo or secondary mixed phenotype acute leukemias and lymphomas. Neoplasms with eosinophilia are associated with dysregulated tyrosine kinases, usually as a result of gene fusions. It is of great importance to identify the genes involved because aberrant tyrosine kinases react to tyrosine kinase inhibitors with varying sensitivity. Patients with PDGFRA and PDGFRB rearrangements are responsive to imatinib, whereas FGFR1-related diseases are non-responsive. PDGFRA rearrangements are usually associated with chronic eosinophilic leukemia (CEL). The most frequent PDGFRA-related aberration is the interstitial deletion of the CHIC2 gene with breakpoints in the FIP1L1 and PDGFRA genes. The deletion of a fragment of about 800kb is resulting in the FIP1L1-PDGFRA fusion gene, a constitutively activated tyrosine kinase transforming hematopoietic cells. In FISH assays, the detection of CHIC2 deletion at 4q12 is a surrogate for the direct detection of the FIP1L1-PDGFRA fusion gene. Translocations with other partner genes, resulting in aberrant tyrosine kinase activity, are known.
Involvement of PDGFRA can be detected by FISH using break apart strategies.

Clinical Applications

• Myeloproliferative Neoplasm (MPN)

XL 4q12 DC hybridized to lymphocytes. Two normal interphases and one metaphase are shown.

• Cools et al (2003) N Engl J Med 348:1201-1214
• Pardanani et al (2003) Blood 102:3093-3096
• Swerdlow et al (2017) WHO classification of tumors of haematopoietic and lymphoid tissues (revised 4th edition)

• Utility and performance of bacterial artificial chromosomes-on-beads assays in chromosome analysis of clinical prenatal samples, products of conception and blood samples.
• A child with multiple congenital anomalies due to partial trisomy 7q22.1 → qter resulting from a maternally inherited balanced translocation: a case report and review of literature.
• Distinct roles of ATM and ATR in the regulation of ARP8 phosphorylation to prevent chromosome translocations.
• Heterogeneous MYCN amplification in neuroblastoma: a SIOP Europe Neuroblastoma Study.
• Immense random colocalization, revealed by automated high content image cytometry, seriously questions FISH as gold standard for detecting EML4-ALK fusion.
• Fluorescence in situ hybridisation assays designed for del(7q) detection uncover more complex rearrangements in myeloid leukaemia cell lines
• Detection of t(7;12)(q36;p13) in paediatric leukaemia using dual colour fluorescence in situ hybridisation.
• A rare case of t(11;22) in a mantle cell lymphoma like B-cell neoplasiaresulting in a fusion of IGL and CCND1: case report.
• Genomic DNA-chip hybridization in t(11;14)-positive mantle cell lymphomas shows a high frequency of aberrations and allows a refined characterization of consensus regions.