Knock-down of methyl CpG-binding protein 2 (MeCP2) causes alterations in cell proliferation and nuclear lamins expression in mammalian cells.
BACKGROUND
MeCP2 (CpG-binding protein 2) is a nuclear multifunctional protein involved in several cellular processes, like large-scale chromatin reorganization and architecture, and transcriptional regulation. In recent years, a non-neuronal role for MeCP2 has emerged in cell growth and proliferation. Mutations in the MeCP2 gene have been reported to determine growth disadvantages in cultured lymphocyte cells, and its functional ablation suppresses cell growth in glial cells and proliferation in mesenchymal stem cells and prostate cancer cells. MeCP2 interacts with lamin B receptor (LBR) and with Heterochromatin Protein 1 (HP1) at the nuclear envelope (NE), suggesting that it could be part of complexes involved in attracting heterochromatin at the nuclear periphery and in mediating gene silencing. The nuclear lamins, major components of the lamina, have a role in maintaining NE integrity, in orchestrating mitosis, in DNA replication and transcription, in regulation of mitosis and apoptosis and in providing anchoring sites for chromatin domains.In this work, we inferred that MeCP2 might have a role in nuclear envelope stability, thereby affecting the proliferation pattern of highly proliferating systems.


RESULTS
By performing knock-down (KD) of MeCP2 in normal murine (NIH-3 T3) and in human prostate transformed cells (PC-3 and LNCaP), we observed a strong proliferation decrease and a defect in the cell cycle progression, with accumulation of cells in S/G2M, without triggering a strong apoptotic and senescent phenotype. In these cells, KD of MeCP2 evidenced a considerable decrease of the levels of lamin A, lamin C, lamin B1 and LBR proteins. Moreover, by confocal analysis we confirmed the reduction of lamin A levels, but we also observed an alteration in the shape of the nuclear lamina and an irregular nuclear rim.


CONCLUSIONS
Our results that indicate reduced levels of NE components, are consistent with a hypothesis that the deficiency of MeCP2 might cause the lack of a key "bridge" function that links the peripheral heterochromatin to the NE, thereby causing an incorrect assembly of the NE itself, together with a decreased cell proliferation and viability.
Department of Theoretical and Applied Sciences, Insubria University, via A, da Giussano 10, Busto Arsizio, 21052, Italy. feba0612@libero.it
Federica
F
Babbio
Ilaria
I
Castiglioni
Chiara
C
Cassina
Marzia Bruna
MB
Gariboldi
Christian
C
Pistore
Elena
E
Magnani
Gianfranco
G
Badaracco
Elena
E
Monti
Ian Marc
IM
Bonapace
D000818:Animals; D059447:Cell Cycle Checkpoints; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002470:Cell Survival; D006801:Humans; D034904:Lamin Type A / Q000378:metabolism*; D034921:Lamin Type B / Q000378:metabolism*; D051783:Methyl-CpG-Binding Protein 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D009685:Nuclear Envelope / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D000097682:Lamin B Receptor
D034904:Lamin Type A; D034921:Lamin Type B; D051783:Methyl-CpG-Binding Protein 2; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D000097682:Lamin B Receptor; C440308:lamin C