title: Identification of GPM6A and GPM6B as potential new human lymphoid leukemia-associated oncogenes.
abstract: BACKGROUND
  Previously, we found that the Graffi murine leukemia virus (MuLV) is able to induce a wide spectrum of hematologic malignancies in vivo. Using high-density oligonucleotide microarrays, we established the gene expression profiles of several of these malignancies, thereby specifically focusing on genes deregulated in the lymphoid sub-types. We observed over-expression of a variety of genes, including Arntl2, Bfsp2, Gfra2, Gpm6a, Gpm6b, Nln, Fbln1, Bmp7, Etv5 and Celsr1 and, in addition, provided evidence that Fmn2 and Parm-1 may act as novel oncogenes. In the present study, we assessed the expression patterns of eight selected human homologs of these genes in primary human B-cell malignancies, and explored the putative oncogenic potential of GPM6A and GPM6B.
  
  
  METHODS
  The gene expression levels of the selected human homologs were tested in human B-cell malignancies by semi-quantitative RT-PCR. The protein expression profiles of human GPM6A and GPM6B were analyzed by Western blotting. The localization and the effect of GPM6A and GPM6B on the cytoskeleton were determined using confocal and indirect immunofluorescence microscopy. To confirm the oncogenic potential of GPM6A and GPM6B, classical colony formation assays in soft agar and focus forming assays were used. The effects of these proteins on the cell cycle were assessed by flow cytometry analysis.
  
  
  RESULTS
  Using semi-quantitative RT-PCR, we found that most of the primary B-cell malignancies assessed showed altered expression patterns of the genes tested, including GPM6A and GPM6B. Using confocal microscopy, we found that the GPM6A protein (isoform 3) exhibits a punctate cytoplasmic localization and that the GPM6B protein (isoform 4) exhibits a peri-nuclear and punctate cytoplasmic localization. Interestingly, we found that exogenous over-expression of both proteins in NIH/3T3 cells alters the actin and microtubule networks and induces the formation of long filopodia-like protrusions. Additionally, we found that these over-expressing NIH/3T3 cells exhibit anchorage-independent growth and enhanced proliferation rates. Cellular transformation (i.e., loss of contact inhibition) was, however, only observed after exogenous over-expression of GPM6B.
  
  
  CONCLUSIONS
  Our results indicate that several human homologs of the genes found to be deregulated in Graffi MuLV experimental mouse models may serve as candidate biomarkers for human B-cell malignancies. In addition, we found that GPM6A and GPM6B may act as novel oncogenes in the development of these malignancies.
authors.affiliation: Laboratoire de Biologie Moléculaire, Département des Sciences Biologiques, Centre BioMed, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, QC, H3C-3P8, Canada, charfi.cyndia@courrier.uqam.ca.
authors.forename: Cyndia
authors.initials: C
authors.lastname: Charfi
authors.forename: Elsy
authors.initials: E
authors.lastname: Edouard
authors.forename: Eric
authors.initials: E
authors.lastname: Rassart
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion / Q000235:genetics; D002453:Cell Cycle / Q000235:genetics; D049109:Cell Proliferation; D002648:Child; D003599:Cytoskeleton / Q000378:metabolism; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D015973:Gene Expression Regulation, Leukemic; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D041681:NIH 3T3 Cells; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D015513:Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: C484158:GPM6A protein, human; C484160:GPM6B protein, human; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D015513:Oncogene Proteins; D049452:Green Fluorescent Proteins