To characterize the role of miR-449a in brain tumour stem cells (BTSC), murine (m)BTSC were derived from SVZ stem/progenitor cells of naïve Pten/p53 or Rb/p53 mice, recombined in vitro [7] and expanded in EGF and FGF-enriched serum-free stem cell medium [38]. The gene discussed is PTEN; the disease is brain neoplasm.