The methyl-CpG binding protein 2 (MeCP2) is a ubiquitous transcription factor predominantly expressed in the brain and mutated in Rett syndrome (OMIM #321750), a progressive neurodevelopmental disorder. Neuronal MeCP2 genome-wide binding tracks methyl-CpG density and its absence results in large-scale changes in chromatin structures, suggesting a global regulatory role. In mouse cells MeCP2 accumulates at pericentric heterochromatin (PCH), composed by major satellite DNA of different chromosomes that aggregate during development to form chromocenters, structures possibly critical for the establishment of silent compartments1. Several proteins and ncRNAs [e.g. HP1? and maj sat forward transcript (MSFT)] seem to be relevant for establishment and maintenance of PCH. Recently, we established a versatile model of murine embryonic stem cells lacking MeCP2 (MeCP2-/y), capable to differentiate to neurons and astroglia. There, we highlighted a crucial role of MeCP2 in the PCH re-organization during neural differentiation, supporting the view of MeCP2 as a multifunctional chromatin organizing factor2. To unravel the molecular mechanism by which MeCP2 regulates the PCH re-organization we investigated the expression and the spatial distribution of MSFT and HP1? during neural differentiation of wt and MeCP2-/y cells. MSFT expression increases during differentiation of both wt and MeCP2-/y cells, without significant changes among the two cell lines. On the other hand, RNA-FISH analyses revealed the presence of very strong MSFT signals at chromocenters of wt cells, whereas the fluorescence intensity appeared weaker in MeCP2-/y nuclei. Noteworthy, the foci number in wt nuclei is significantly greater compared to MeCP2-/y nuclei at each time point of differentiation. Furthermore, MeCP2 co-localizes with MSFT and physically associates with it in differentiated wt cells. These data suggest an involvement of MeCP2 in the localization of MSFT at chromocenters, while in mutated nuclei this phenomenon is partially impaired. Moreover, MeCP2 co-localizes with HP1? at chromocenters, suggesting possible functional interactions in PCH organization. A deeper analysis of HP1? sub-nuclear distribution in MeCP2-/y cells is currently under investigation. Our preliminary results allow to hypothesise that MeCP2 may cooperate with MSFT and, possibly, HP1?, at chromocenters for the pericentric heterochromatin structural organization. 1 Della Ragione, F., et al.. (2012). Front Genet Sep 11;3:181. 2 Bertulat, B., De Bonis, M.L., Della Ragione, F. et al., (2012). PLoS One 7(10).
Relationships between MeCP2 and pericentric heterochromatin factors during neural differentiation
DELLA RAGIONE F;MATARAZZO MR;D'ESPOSITO M
2014
Abstract
The methyl-CpG binding protein 2 (MeCP2) is a ubiquitous transcription factor predominantly expressed in the brain and mutated in Rett syndrome (OMIM #321750), a progressive neurodevelopmental disorder. Neuronal MeCP2 genome-wide binding tracks methyl-CpG density and its absence results in large-scale changes in chromatin structures, suggesting a global regulatory role. In mouse cells MeCP2 accumulates at pericentric heterochromatin (PCH), composed by major satellite DNA of different chromosomes that aggregate during development to form chromocenters, structures possibly critical for the establishment of silent compartments1. Several proteins and ncRNAs [e.g. HP1? and maj sat forward transcript (MSFT)] seem to be relevant for establishment and maintenance of PCH. Recently, we established a versatile model of murine embryonic stem cells lacking MeCP2 (MeCP2-/y), capable to differentiate to neurons and astroglia. There, we highlighted a crucial role of MeCP2 in the PCH re-organization during neural differentiation, supporting the view of MeCP2 as a multifunctional chromatin organizing factor2. To unravel the molecular mechanism by which MeCP2 regulates the PCH re-organization we investigated the expression and the spatial distribution of MSFT and HP1? during neural differentiation of wt and MeCP2-/y cells. MSFT expression increases during differentiation of both wt and MeCP2-/y cells, without significant changes among the two cell lines. On the other hand, RNA-FISH analyses revealed the presence of very strong MSFT signals at chromocenters of wt cells, whereas the fluorescence intensity appeared weaker in MeCP2-/y nuclei. Noteworthy, the foci number in wt nuclei is significantly greater compared to MeCP2-/y nuclei at each time point of differentiation. Furthermore, MeCP2 co-localizes with MSFT and physically associates with it in differentiated wt cells. These data suggest an involvement of MeCP2 in the localization of MSFT at chromocenters, while in mutated nuclei this phenomenon is partially impaired. Moreover, MeCP2 co-localizes with HP1? at chromocenters, suggesting possible functional interactions in PCH organization. A deeper analysis of HP1? sub-nuclear distribution in MeCP2-/y cells is currently under investigation. Our preliminary results allow to hypothesise that MeCP2 may cooperate with MSFT and, possibly, HP1?, at chromocenters for the pericentric heterochromatin structural organization. 1 Della Ragione, F., et al.. (2012). Front Genet Sep 11;3:181. 2 Bertulat, B., De Bonis, M.L., Della Ragione, F. et al., (2012). PLoS One 7(10).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
