Repression of transcription by HoxC11 upon phorbol ester stimulation

Transcript analysis reveals a specific HOX signature associated with positional identity of human endothelial cells

The distinct topographic Hox expression patterns observed in vascular smooth muscle cells (VSMCs) of the adult cardiovascular system suggest that these transcriptional regulators are critical for maintaining region-specific physiological properties of blood vessels. To test this proposition, we expanded the vascular Hoxc11 expression domain normally restricted to the lower limbs by utilizing an innovative integrated tetracycline regulatory system and Transgelin promoter elements to induce Hoxc11 expression universally in VSMCs of transgenic mice. Ectopic Hoxc11 expression in carotid arteries, aortic arch and descending aorta resulted in drastic vessel wall remodeling involving elastic laminae fragmentation, medial smooth muscle cell loss, and intimal lesion formation. None of these alterations were observed upon induction of Hoxc11 transgene expression in the femoral artery, i.e. the natural Hoxc11 activity domain, although this vessel was greatly enlarged, comparable to the topographically restricted vascular changes seen in Hoxc11^−/− mice. To begin defining Hoxc11-controlled pathways of vascular remodeling, we performed immunolabeling studies in conjunction with co-transfection and chromatin immunoprecipitation (ChIP) assays using mouse vascular smooth muscle (MOVAS) cells. The results suggest direct transcriptional control of two members of the matrix metalloproteinase (Mmp) family, including Mmp2 and Mmp9 that are known as key players in the inception and progression of vascular remodeling events. In summary, the severe vascular abnormalities resulting from the induced dysregulated expression of a Hox gene with regional vascular patterning functions suggest that proper Hox function and regulation is critical for maintaining vascular functional integrity.

Major form of NUP98/HOXC11 fusion in adult AML with t(11;12)(p15;q13) translocation exhibits aberrant trans-regulatory activity

Three adult patients with de novo acute myeloid leukemia of distinct subtypes harboring t(11;12)(p15;q13) have been investigated to characterize the genes involved in that translocation. Through molecular cytogenetics, a chromosome break was detected at the 3' part of nucleoporin 98 (NUP98) gene at 11p15. Using rapid amplification of cDNA end, we identified the partner gene at 12q13, HOXC11. Molecular analysis showed that exon 12 of NUP98 was fused in-frame to exon 2 of HOXC11 in all three cases with t(11;12)(p15;q13). Therefore, this type of fusion may represent the major form of the NUP98-HOXC11 chimera so far reported. Moreover, two out of three cases had a confirmed deletion of the 3' part of NUP98 gene and more telomeric region of 11p harboring a group of tumor-suppressor genes. Interestingly, the NUP98-HOXC11 protein when assayed in a GAL4 reporter system, showed an aberrant trans-regulatory activity as compared to the wild-type HOXC11 in both COS-7 and HL-60 cells. Therefore, NUP98-HOXC11 may contribute to the leukemogenesis by interfering with the cellular mechanism of transcriptional regulation.