(C) The proportions of rod nuclei with two or more chromocenters were scored in retinas of two and one littermate at two age points, P30 and P53 (C1). [7-10], while expression of rescues the Rett phenotype. More effective rescue was achieved through embryonic, Umibecestat (CNP520) compared to early postnatal expression [11-13], whereas targeted expression in postmitotic neurons resulted in asymptomatic mice [12,14]. mutant mice exhibit abnormalities in the number of synapses , the morphology of neuronal processes [16,17], neuronal maturation , and the neurophysiological activity of these cells [18,19]. These effects are associated with particular neuron types. For instance, brain stem GABA-ergic neurons are affected, but glycinergic ones are not . Glutamatergic neurons of the brain and their synapses are also affected through the expression level of brain-derived neurotrophic factor Umibecestat (CNP520) (BDNF)  which is usually regulated by MECP2 in a neuronal activity-dependent manner FGF18 [17,22,23]. The results listed above conform to the conclusion that MECP2 deficiency leads to subtle changes in the expression levels of genes causing diverse and widespread phenotypic changes . There is growing evidence that both expression in Lbr-TER mice does not increase MECP2 expression. In (Solovei et al. ); LBR staining is not shown on this panel. (C) In R7E mice, rods de-differentiate, partially restore the conventional architecture of their nuclei, and drop their rod identity. This process is usually accompanied by increased expression of MECP2 which becomes abundant in Umibecestat (CNP520) chromocenters (three such nuclei are marked by approaches, and therefore, one cannot wholly exclude that microglia cells express MECP2 at a level not detectable microscopically. Open in a separate window Physique 2 Microglial cells (A) have no detectable MECP2 compared to astroglia (B) and neurons (C). (A, B) MECP2 detection in brain cortex, cerebellum, spinal cord, and retina combined with microglial (A) and astroglial (B) cell type-specific staining. Overlays of 4′,6-diamidino-2-phenylindole (DAPI) staining (in the right column images trace the shape of the nuclei of interest. (C) Neurons from cerebellum C Purkinje cells (C1) and granular cells (C2) demonstrate strong MECP2 staining in chromocenters and moderate staining of the nucleoplasm in a single confocal section. Scale bars: (A,B) 10?m, (C) 5?m. Retinas of knockout mice, decline in visual acuity, which was observed in late postnatal development, is usually caused by general silencing of the cortical circuitry . However, major morphological characteristics of retinas in MECP2-deficient mice have not been yet reported. We dissected retinas of and littermates. Other 14 markers for retinal cell types, synapses, and neurotransmitters are shown in Additional file 2. (B) Comparable distribution of a histone modification common of euchromatin (H3ac) in and littermate retinas; nuclei with conventional (ganglion and INL cells) and inverted (rods) architecture are shown. (C) The proportions of rod nuclei with two or more chromocenters were scored in retinas of two and one littermate at two age points, P30 and P53 (C1). At P53, nearly all nuclei have a single chromocenter. Average proportions of rods with two or less chromocenters were Umibecestat (CNP520) not significantly different between the two genotypes. Errors bars are the 95% confidence intervals. Rod nuclei with two (C2) and one Umibecestat (CNP520) (C3) chromocenter. Scale bars: (A) 25?m, (B) 5?m, (C) 2?m. Nuclear architecture of neuronal nuclei in double knockout mouse . In contrast, double knockout of and affects neither rod nuclear morphology  nor MECP2 binding patterns (this study), suggesting that cells in a tissue context might have more redundancy in epigenetic mechanisms than cultured cells. Although even a complete loss of MECP2 does not prevent chromocenter formation in mouse cells , observations on astroglial cells and neurons differentiated from embryonic stem cells showed that the number of chromocenters was significantly higher in MECP2-null cells compared to wild-type cells . The other way around, ectopic expression of MECP2 induces clustering and fusion of chromocenters, a process which takes place during myotube differentiation . These findings prompted us to assess rod chromocenter numbers in adult mice of both genotypes. Chromocenter fusion in nuclei of mouse rods is usually a slow process. A significant proportion of rods at ca. 1?month still have two or more chromocenters; their fusion in all rods is completed only at 2C2.5?months of age ( [30,41]; c.f. Physique?.