Soft Tissues: Pericytoma with t(7;12)(p22;q13) ACTB/GLI1

2005-03-01   Anna Dahlén , Fredrik Mertens , Nils Mandahl , Ioannis Panagopoulos 

1.Department of Clinical Genetics, University Hospital, SE-221 85 Lund, Sweden

Clinics and Pathology

Phenotype stem cell origin

Unknown

Embryonic origin

The cellular origin is unknown, but it presumably derives from the mesoderm. The tumor cells display cytoarchitectural, immunohistochemical and ultrastructural features highly suggestive of pericytic differentiation, and it seems likely that these lesions fall within the spectrum of myopericytic neoplasms.

Etiology

Unknown.

Epidemiology

Presumably rare, but differential diagnostic problems may have hampered the distinction of these tumors in the past. Tumors that fall within the differential diagnosis include cellular examples of solitary fibrous tumors (also known as hemangiopericytoma), myofibroma(tosis), monophasic synovial sarcoma, mesenchymal chondrosarcoma, and metastatic endometrial stromal sarcoma. Affects both men and woman of all ages. No familial cases are known.

Clinics

Seems to present as a solitary pain-less nodule. The locations reported so far have been the tongue (3 cases), the stomach (1 case) and the calf (1 case).

Pathology

Pericytomas with t(7;12) display a multilobulated, infiltrative growth pattern, and are composed of uniform spindle-shaped pericytic cells that are consistently arranged around small, thin-walled arborizing vessels. The spindle cells present small amounts of eosinophilic cytoplasm, and ovoid-to-tapered nuclei with vesicular chromatin and often a single nucleolus. No significant atypia or pleomorphism is present, and mitotic figures are rare.

Treatment

Preoperative chemotherapy has not proven efficient. Surgical excision seems to be the treatment of choice.

Prognosis

Based on a limited follow-up (22-120 months), pericytomas with t(7;12) are seemingly benign or low-malignant tumors. No signs of recurrence or metastasis have been reported.

Cytogenetics

Atlas Image
Representative G-banded partial karyotype of the t(7;12)(p22;q13)

Cytogenetics morphological

The recurrently observed t(7;12)(p22;q13) is a specific translocation characteristic for the tumor type.

Cytogenetics molecular

Metaphase FISH mapping analysis on one case revealed that the breakpoints were located to BAC probes RP11-1275H24, and RP11-93G19 on 7p22, and to BAC probes 181L23, and 772E1 on 12q13. The probes gave split signals on the respective derivatives. On the normal chromosomes, intact signals were seen.

Probes

BAC probes RP11-1275H24 (AC092171; substantially larger than the 85 kb reported by the NCBI), and RP11-93G19 (BAC ends: AQ321651, AQ321650) spanning the ACTB locus, and BAC probes 181L23 (AC022506), and 772E1 (AC063917) spanning the GLI1 locus.

Genes Involved and Proteins

Note

The t(7;12)(p22;q13), fuses the ACTB gene in 7p22, to the GLI1 gene in 12q13.

Gene name

ACTB (Actin, beta)

Location

7p22.1

Dna rna description

Six exons, spans approximately 3.4 kb of genomic DNA in the centromere-to-teleomere orientation. The translation initiation codon ATG is located to exon 2, and the stop codon to exon 6. The ACTB mRNA is approximately 1.8 kb. ACTB is abundantly expressed in all mammalian and avian non-muscle cells.

Protein description

The open reading frame encodes a 374 amino acid protein, with an estimated molecular weight of approximately 41.7 kDa. The ACTB protein is located in the cytoplasm where it is a component (together with actin g) of the cytoskeleton.

Gene name

GLI1 (glioma-associated oncogene homolog 1)

Location

12q13.3

Dna rna description

Twelve exons, spans approximately 12 kb of genomic DNA in the centromere-to-telomere orientation. The translation initiation codon is located in exon 2, and the stop codon in exon 12. The GLI1 mRNA transcript is 3.6 kb.

GLI proteins function as direct effectors of sonic hedgehog-signaling during embryogenesis. GLI1 (also GLI2 and GLI3) are therefore likely to be involved in the tissue-specific proliferation of the central nervous system, the zones of polarizing activity in the developing limb, and of the gut. In the adult human, GLI1 expression has been demonstrated in the testes, myometrium and Fallopian tubes.

Protein description

The open reading frame encodes an 1106 amino acid protein, with an estimated molecular weight of approximately 118 kDa. The GLI protein is a DNA binding transcription factor, also the last known step in the sonic hedgehog-signaling pathway. The GLI1 protein contains five DNA-binding zinc fingers between amino acids 235 and 393 (encoded by exons 7-10), and a transactivating domain constituted by amino acids 1020-1091 (encoded by exon 12).

Result of the chromosomal anomaly

Note

To date, five cases of pericytoma with t(7;12) have been reported. All of them expressed an ACTB-GLI1 transcript, and two of them also expressed a reciprocal GLI1-ACTB fusion transcript. The genomic breakpoints of these fusions have been characterized, revealing that the respective breakpoints shared short common oligomers.

Detection protocole

A detailed description of a protocol for the detection of ACTB-GLI1 and GLI1-ACTB chimeras has been reported.

Note

The function of the ACTB-GLI1 chimera is unknown, but it is suggested that the strong ACTB promoter causes an over-expression of GLI1 sequences important for transcriptional activation of downstream target genes.

Description

The ACTB-GLI1 fusion protein contains the N-terminal of ACTB and the C-terminal of GLI1, including the DNA-binding zinc finger motifs (encoded by exons 7-10) and transactivating motifs (exon 12).

Highly cited references

Pubmed IDYearTitleCitations
346432882022Primary cutaneous epithelioid mesenchymal neoplasm with ACTB-GLI1 fusion: a case report.0
356107152022Correction to: Malignant epithelioid neoplasm of the ileum with ACTB-GLI1 fusion mimicking an adnexal mass.0
353876382022Malignant epithelioid neoplasm of the ileum with ACTB-GLI1 fusion mimicking an adnexal mass.0
315671942019Pericytoma With t(7;12) and ACTB-GLI1 Fusion: Reevaluation of an Unusual Entity and its Relationship to the Spectrum of GLI1 Fusion-related Neoplasms.8
321320202020An Unbalanced Chromosome Translocation Between 7p22 and 12q13 Leads to ACTB-GLI1 Fusion in Pericytoma.0
306339252019New fusion sarcomas: histopathology and clinical significance of selected entities.22
293093072018A Distinct Malignant Epithelioid Neoplasm With GLI1 Gene Rearrangements, Frequent S100 Protein Expression, and Metastatic Potential: Expanding the Spectrum of Pathologic Entities With ACTB/MALAT1/PTCH1-GLI1 Fusions.24
269800272016Translocation t(7;12) as the sole chromosomal abnormality resulting in ACTB-GLI1 fusion in pediatric gastric pericytoma.12
225752612012Pericytoma with t(7;12) and ACTB-GLI1 fusion arising in bone.15

Bibliography

Pubmed IDLast YearTitleAuthors
155555712004Molecular genetic characterization of the genomic ACTB-GLI fusion in pericytoma with t(7;12).Dahlén A et al
38422061985The human beta-actin multigene family.Kedes L et al
21054561990The GLI gene encodes a nuclear protein which binds specific sequences in the human genome.Kinzler KW et al
95242011998Characterization of the promoter region and genomic organization of GLI, a member of the Sonic hedgehog-Patched signaling pathway.Liu CZ et al
29940621985Molecular structure of the human cytoplasmic beta-actin gene: interspecies homology of sequences in the introns.Nakajima-Iijima S et al
38371821985Evolution of the functional human beta-actin gene and its multi-pseudogene family: conservation of noncoding regions and chromosomal dispersion of pseudogenes.Ng SY et al
110015842000The sonic hedgehog-patched-gli pathway in human development and disease.Villavicencio EH et al

External Links

Citation

Anna Dahlén ; Fredrik Mertens ; Nils Mandahl ; Ioannis Panagopoulos

Soft Tissues: Pericytoma with t(7;12)(p22;q13) ACTB/GLI1

Atlas Genet Cytogenet Oncol Haematol. 2005-03-01

Online version: http://atlasgeneticsoncology.org/solid-tumor/5192/soft-tissues-pericytoma-with-t(7;12)(p22;q13)-actb-gli1