Loss of pericentromeric DNA methylation pattern in human glioblastoma is associated with altered DNA methyltransferases expression and involves the stem cell compartment.

Cancer is generally characterized by loss of CG dinucleo- tides methylation resulting in a global hypomethylation and the consequent genomic instability. The major contribu- tion to the general decreased methylation levels seems to be due to demethylation of heterochromatin repetitive DNA sequences. In human immunodeficiency, centromeric instability and facial anomalies syndrome, demethylation of pericentromeric satellite 2 DNA sequences has been correlated to functional mutations of the de novo DNA methyltransferase 3b (DNMT3b), but the mechanism responsible for the hypomethylated status in tumors is poorly known. Here, we report that human glioblastoma is affected by strong hypomethylation of satellite 2 pericen- tromeric sequences that involves the stem cell compartment. Concomitantly with the integrity of the DNMTs coding sequences, we report aberrations in DNA methyltrasferases expression showing upregulation of the DNA methyltrans- ferase 1 (DNMT1) and downregulation of the de novo DNA methyltransferase 3a (DNMT3a). Moreover, we show that DNMT3a is the major de novo methyltransferase expressed in normal neural progenitor cells (NPCs) and its forced re-expression is sufficient to partially recover the methylation levels of satellite 2 repeats in glioblastoma cell lines. Thus, we speculate that DNMT3a decreased expres- sion may be involved in the early post-natal inheritance of an epigenetically altered NPC population that could be responsible for glioblastoma development later in adult life