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. 2008 May 28:3:13.
doi: 10.1186/1749-8104-3-13.

Regulation of survival in adult hippocampal and glioblastoma stem cell lineages by the homeodomain-only protein HOP

Arianna De Toni  1 , Marie Zbinden, Jonathan A Epstein, Ariel Ruiz i Altaba, Alain Prochiantz, Isabelle Caillé
Affiliations

Regulation of survival in adult hippocampal and glioblastoma stem cell lineages by the homeodomain-only protein HOP

Arianna De Toni et al. Neural Dev. .

Abstract

Background: Homeodomain proteins play critical roles in shaping the development of the embryonic central nervous system in mammals. After birth, neurogenic activities are relegated to stem cell niches, which include the subgranular layer of the dentate gyrus of the hippocampus. Here, we have analyzed the function of HOP (Homeodomain only protein) in this stem cell niche and in human glioblastomas.

Results: We find that HOP is strongly expressed by radial astrocytes of the dentate gyrus in mice, which are stem cells that give rise to hippocampal granular neurons throughout adulthood. Deletion or down-regulation of HOP results in a decrease of apoptosis of these stem cells without changes in proliferation, and in an increase in the number of newly formed granule neurons. We also find that human glioblastomas largely lack HOP expression and that reintroduction of HOP function in glioma cells cultured as gliomaspheres leads to enhanced apoptosis in a subset of cases. In these cells, HOP function decreases clonogenicity.

Conclusion: These data suggest that HOP participates in the regulation of the adult mouse hippocampal stem cell niche by negatively affecting cell survival. In addition, HOP may work as a tumor suppressor in a subset of glioblastomas. HOP function thus appears to be critical in the adult brain in a region of continued plasticity, and its deregulation may contribute to disease.

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Figures

Figure 1
Figure 1
HOP is expressed by SGL radial astrocytes. (a) In situ hybridization shows HOP mRNA expression in numerous DG cells with a prominent labeling in the SGL (arrow), the neurogenic region for the production of granule cells destined to the granule cell layer (GCL). (b) Immunohistochemical detection of HOP protein in the DG, especially in the SGL. WT, wild type. (c) HOP immunohistochemical staining is absent in knock out (KO) mice, demonstrating HOP antibody specificity. (d) Western blot shows an 8 kDa protein from hippocampal wild-type extracts, which is absent in the knock out extracts. (e-h) Double-staining with HOP and GFAP antibodies, illustrating the co-expression of the two proteins. (h) Higher magnification of the boxed area in (e-g) with orthogonal projections along the z confocal stack at the x and y levels indicated by the intersecting white lines. (i-l) Double-staining with HOP and 3PGDH antibodies, showing that HOP immunoreactive cells are 3PGDH+. (l) Higher magnification of the boxed area with orthogonal projections. (m-p) Double-staining with HOP and DCX, showing that they are expressed by different SGL cells. (p) Higher magnification of the boxed area with orthogonal projections. The y projection shows, in particular, that DCX+ processes are closely juxtaposed to HOP+ processes but are distinct. Scale bars: (a-f, e-g, i-k, m-p), 50 μm; (h, l, p), 10 μm.
Figure 2
Figure 2
HOP does not regulate the proliferation of SGL astrocytic stem cells. (a-c) After a 2 h pulse of BrdU, mice were processed for HOP/BrdU immunocytochemistry. Some HOP immunoreactive cells incorporate BrdU. Scale bar: 10 μm. (d, e) After a 2 h pulse of BrdU, mice were processed for GFAP/BrdU ICC and the double-labeled SGL cells were counted under a confocal microscope (n = 5). The data are presented as the number of GFAP/BrdU cells per mm of SGL. The number of GFAP/BrdU cells is unchanged in the HOP knock out mice compared to the wild type (d) even when growth factors (EGF + bFGF, 20 μg/ml) were infused into the lateral ventricle to stimulate the proliferation of DG progenitors (n = 5) (e). (f-h) HOP (g) or control (f) siRNA coupled to the cell permeant peptide Penetratin (20 μM) were infused for three days above the DG to locally silence HOP expression. A strong reduction of HOP expression is seen after HOP siRNA infusion. (h) The number of GFAP/BrdU cells is not significantly different between the two conditions (n = 5). Scale bars: 50 μm.
Figure 3
Figure 3
HOP regulates apoptosis of SGL astrocytic stem cells. (a) Apoptotic cells are detected in the SGL (arrows) with a TUNEL fluorescent assay. These cells are relatively rare (asterisks). Scale bar: 50 μm. (b) The number of TUNEL positive apoptotic cells in the SGL was counted across the entire DG (36 slices per mouse). A significant decrease of 48.2% is observed in knock out (KO) mice compared to wild type (WT) (n = 5, Mann-Whitney U test, *p = 0.001). (c-h) Double labeling for HOP and TUNEL shows that a majority of the TUNEL positive SGL cells are HOP immunoreactive (arrows). The arrowhead in (c-e) indicates a HOP negative TUNEL positive SGL cells (probably a D/type2 cell). The asterisk in (c-e) shows a TUNEL positive cell in the granule cell layer (probably a granular neuron). (i) Higher magnification of (h) with orthogonal projections along the z confocal stack at the x and y levels indicated by the intersecting white lines. Scale bars: 10 μm.
Figure 4
Figure 4
HOP influences neuronal production. (a-c) Wild-type (WT) and knock out (KO) mice were injected three times with BrdU (30 mg/kg) three weeks before perfusion and double staining was performed with NeuN and BrdU to visualize newly formed neurons in the granule cell layer. Double-labeled cells were counted under a confocal microscope (a, b) and the data are presented as the number of NeuN/BrdU positive cells per mm of SGL (c). The number of newly formed NeuN/BrdU neurons is significantly higher (2.5-fold) in knock out mice than in wild type (n = 6, Mann-Whitney U test, *p < 0.01). (d) HOP or control siRNA were infused above the DG for three days before three injections of BrdU. Three weeks later, the number of newly formed NeuN/BrdU neurons was significantly higher (1.7-fold) in the HOP siRNA infused mice (n = 5, Mann-Whitney U test, *p < 0.01). Scale bars: 50 μm.
Figure 5
Figure 5
HOP in gliomas and gliomaspheres. (a) Expression levels of HOP in control cortical tissues (black bars), fresh glioma samples (blue bars), culture of gliomaspheres (red bars) or U87 cells (green bars). The data are expressed as the relative ratio of HOP expression over that of GAPDH times 105. (b) Mouse HOP tagged with hemagglutinin (HOP-HA) and coupled to Penetratin was added to the medium of gliomaspheres from GBM-6 cells at 1 μM and the HA staining was developed. Cells are counterstained with Hoechst. Scale bar: 5 μm.
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References

    1. Chen F, Kook H, Milewski R, Gitler AD, Lu MM, Li J, Nazarian R, Schnepp R, Jen K, Biben C, Runke G, Mackay JP, Novotny J, Schwartz RJ, Harvey RP, Mullins MC, Epstein JA. Hop is an unusual homeobox gene that modulates cardiac development. Cell. 2002;110:713–723. doi: 10.1016/S0092-8674(02)00932-7. - DOI - PubMed
    1. Shin CH, Liu ZP, Passier R, Zhang CL, Wang DZ, Harris TM, Yamagishi H, Richardson JA, Childs G, Olson EN. Modulation of cardiac growth and development by HOP, an unusual homeodomain protein. Cell. 2002;110:725–735. doi: 10.1016/S0092-8674(02)00933-9. - DOI - PubMed
    1. Chen Y, Petersen S, Pacyna-Gengelbach M, Pietas A, Petersen I. Identification of a novel homeobox-containing gene, LAGY, which is downregulated in lung cancer. Oncology. 2003;64:450–458. doi: 10.1159/000070306. - DOI - PubMed
    1. Lemaire F, Millon R, Muller D, Rabouel Y, Bracco L, Abecassis J, Wasylyk B. Loss of HOP tumour suppressor expression in head and neck squamous cell carcinoma. Br J Cancer. 2004;91:258–261. - PMC - PubMed
    1. Asanoma K, Matsuda T, Kondo H, Kato K, Kishino T, Niikawa N, Wake N, Kato H. NECC1, a candidate choriocarcinoma suppressor gene that encodes a homeodomain consensus motif. Genomics. 2003;81:15–25. doi: 10.1016/S0888-7543(02)00011-3. - DOI - PubMed

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