MeCP2: The Genetic Driver of Rett Syndrome Epigenetics.

Mutations in methyl CpG binding protein 2 (MeCP2) are the major cause of Rett syndrome (RTT), a rare neurodevelopmental disorder with a notable period of developmental regression following apparently normal initial development. Such MeCP2 alterations often result in changes to DNA binding and chromatin clustering ability, and in the stability of this protein. Among other functions, MeCP2 binds to methylated genomic DNA, which represents an important epigenetic mark with broad physiological implications, including neuronal development. In this review, we will summarize the genetic foundations behind RTT, and the variable degrees of protein stability exhibited by MeCP2 and its mutated versions. Also, past and emerging relationships that MeCP2 has with mRNA splicing, miRNA processing, and other non-coding RNAs (ncRNA) will be explored, and we suggest that these molecules could be missing links in understanding the epigenetic consequences incurred from genetic ablation of this important chromatin modifier. Importantly, although MeCP2 is highly expressed in the brain, where it has been most extensively studied, the role of this protein and its alterations in other tissues cannot be ignored and will also be discussed. Finally, the additional complexity to RTT pathology introduced by structural and functional implications of the two MeCP2 isoforms (MeCP2-E1 and MeCP2-E2) will be described. Epigenetic therapeutics are gaining clinical popularity, yet treatment for Rett syndrome is more complicated than would be anticipated for a purely epigenetic disorder, which should be taken into account in future clinical contexts.

Deciphering the Enigma of the Histone H2A.Z-1/H2A.Z-2 Isoforms: Novel Insights and Remaining Questions.

The replication independent (RI) histone H2A.Z is one of the more extensively studied variant members of the core histone H2A family, which consists of many replication dependent (RD) members. The protein has been shown to be indispensable for survival, and involved in multiple roles from DNA damage to chromosome segregation, replication, and transcription. However, its functional involvement in gene expression is controversial. Moreover, the variant in several groups of metazoan organisms consists of two main isoforms (H2A.Z-1 and H2A.Z-2) that differ in a few (3-6) amino acids. They comprise the main topic of this review, starting from the events that led to their identification, what is currently known about them, followed by further experimental, structural, and functional insight into their roles. Despite their structural differences, a direct correlation to their functional variability remains enigmatic. As all of this is being elucidated, it appears that a strong functional involvement of isoform variability may be connected to development.

Protamine-like proteins have bactericidal activity. The first evidence in Mytilus galloprovincialis.

The major acid-soluble protein components of the mussel Mytilus galloprovincialis sperm chromatin consist of the protamine-like proteins PL-II, PL-III and PL-IV, an intermediate group of sperm nuclear basic proteins between histones and protamines. The aim of this study was to investigate the bactericidal activity of these proteins since, to date, there are reports on bactericidal activity of protamines and histones, but not on protamine-like proteins. We tested the bactericidal activity of these proteins against Gram-positive bacteria: Enterococcus faecalis and two different strains of Staphylococcus aureus, as well as Gram-negative bacteria: Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhmurium, Enterobacter aerogenes, Enterobacter cloacae, and Escherichia coli. Clinical isolates of the same bacterial species were also used to compare their sensitivity to these proteins. The results show that Mytilus galloprovincialis protamine-like proteins exhibited bactericidal activity against all bacterial strains tested with different minimum bactericidal concentration values, ranging from 15.7 to 250 µg/mL. Furthermore, these proteins were active against some bacterial strains tested that are resistant to conventional antibiotics. These proteins showed very low toxicity as judged by red blood cell lysis and viability MTT assays and seem to act both at the membrane level and within the bacterial cell. We also tested the bactericidal activity of the product obtained from an in vitro model of gastrointestinal digestion of protamine-like proteins on a Gram-positive and a Gram-negative strain, and obtained the same results with respect to undigested protamine-like proteins on the Gram-positive bacterium. These results provide the first evidence of bactericidal activity of protamine-like-proteins.

Protamine-like proteins' analysis as an emerging biotechnique for cadmium impact assessment on male mollusk Mytilus galloprovincialis (Lamarck 1819).

Here we report the industrial pollution effects due to cadmium on the reproductive health of Mytilus galloprovincialis. Mussels were removed from the biofouling of a Conatex panel after one year exposition at a polluted site near a disposal metallurgical factory. A high cadmium bioaccumulation was observed in the testis of mussels housed at the polluted site, with respect to a control site, as determined by inductively coupled plasma-mass spectrometry, along with a 10 fold increase in metallothionein 20 kDa gene (mt20) expression levels determined by qPCR. Furthermore, mussels transferred into laboratory tanks from the reference site, and exposed to 1.5, 5 and 10 µM CdCl2, revealed a 1.7, 3.2 and 4.5 fold expression increase in the testis mt20, respectively, and a positive correlation with cadmium bioaccumulation was found. To evaluate a potential detrimental risk of such alterations on spermatozoa, we carried out electrophoretic analyses on their protamine-like proteins. As determined by AU-PAGE, after 1.5 µM CdCl2 exposure, protamine-like proteins also display major alterations with respect to those obtained after 5 and 10 µM CdCl2 exposure. All protamine-like proteins isolated from the polluted biofouling were in an aggregated form and displayed the same reduced DNA binding affinity of the protamine-like proteins obtained after 1.5 µM CdCl2 as demonstrated EMSA with sperm genomic DNA. Our results contribute to the studies concerning cadmium induced testis alterations and highlight protamine-like proteins' analysis as an emerging biotechnique for cadmium impact assessment on Mytilus galloprovincialis, for the sensitivity of the in vivo and in vitro changes of protamine-like proteins' state and their DNA binding affinity.

Trichostatin A decreases the levels of MeCP2 expression and phosphorylation and increases its chromatin binding affinity.

MeCP2 binds to methylated DNA in a chromatin context and has an important role in cancer and brain development and function. Histone deacetylase (HDAC) inhibitors are currently being used to palliate many cancer and neurological disorders. Yet, the molecular mechanisms involved are not well known for the most part and, in particular, the relationship between histone acetylation and MeCP2 is not well understood. In this paper, we study the effect of the HDAC inhibitor trichostatin A (TSA) on MeCP2, a protein whose dysregulation plays an important role in these diseases. We find that treatment of cells with TSA decreases the phosphorylation state of this protein and appears to result in a higher MeCP2 chromatin binding affinity. Yet, the binding dynamics with which the protein binds to DNA appear not to be significantly affected despite the chromatin reorganization resulting from the high levels of acetylation. HDAC inhibition also results in an overall decrease in MeCP2 levels of different cell lines. Moreover, we show that miR132 increases upon TSA treatment, and is one of the players involved in the observed downregulation of MeCP2.