MicroRNAs (miRNAs) are small non-coding RNAs that function as guide molecules in RNA silencing. Targeting most protein-coding transcripts, miRNAs are involved in nearly all developmental and pathological processes in animals. The biogenesis of miRNAs is under tight temporal and spatial control, and their dysregulation is associated with many human diseases, particularly cancer. In animals, miRNAs are ∼22 nucleotides in length, and they are produced by two RNase III proteins--Drosha and Dicer. miRNA biogenesis is regulated at multiple levels, including at the level of miRNA transcription; its processing by Drosha and Dicer in the nucleus and cytoplasm, respectively; its modification by RNA editing, RNA methylation, uridylation and adenylation; Argonaute loading; and RNA decay. Non-canonical pathways for miRNA biogenesis, including those that are independent of Drosha or Dicer, are also emerging.

Regulation of microRNA biogenesis

MeCP2isachromosomal protein whichbinds toDNA that ismethylated atCpG.Insitu immunofluorescence inmouse cells hasshownthattheprotein ismost concentrated inpericentromeric heterochromatin, suggesting that MeCP2mayplay arole intheformation ofInert chromatin. Herewe haveIsolated a minimal methyl-CpG binding domaln (MBD) fromMeCP2.MBD Is85aminoacids Inlength, andbindsexclusively to DNA thatcontains one or more symmetrically methylated CpGs.MBD hasnegligable non-specific affinity forDNA,confirming thatnon-specific and methyl-CpG specific binding domainsofMeCP2are distinct. Invitrofootprlnting Indicates thatMBDbinding can protect a 12nucleotide regionsurrounding a methyl-CpG pair, withan approximate dissociation constant of10-9M.

Dissection ofthemethyl-CpG binding domainfromthe chromosomal protein MeCP2

Rett syndrome (RTT) is a severe neurological disorder caused by mutations in the X-linked gene MECP2 (methyl-CpG-binding protein 2). Two decades of research have fostered the view that MeCP2 is a multifunctional chromatin protein that integrates diverse aspects of neuronal biology. More recently, studies have focused on specific RTT-associated mutations within the protein. This work has yielded molecular insights into the critical functions of MeCP2 that promise to simplify our understanding of RTT pathology.

https://birdlab.bio.ed.ac.uk/bird/sites/sbsweb2.bio.ed.ac.uk.bird/files/Lyst%20and%20Bird2.pdf

Rett syndrome: a complex disorder with simple roots

The development and progression of diabetic kidney disease (DKD), a highly prevalent complication of diabetes mellitus, are influenced by both genetic and environmental factors. DKD is an important contributor to the morbidity of patients with diabetes mellitus, indicating a clear need for an improved understanding of disease aetiology to inform the development of more efficacious treatments. DKD is characterized by an accumulation of extracellular matrix, hypertrophy and fibrosis in kidney glomerular and tubular cells. Increasing evidence shows that genes associated with these features of DKD are regulated not only by classical signalling pathways but also by epigenetic mechanisms involving chromatin histone modifications, DNA methylation and non-coding RNAs. These mechanisms can respond to changes in the environment and, importantly, might mediate the persistent long-term expression of DKD-related genes and phenotypes induced by prior glycaemic exposure despite subsequent glycaemic control, a phenomenon called metabolic memory. Detection of epigenetic events during the early stages of DKD could be valuable for timely diagnosis and prompt treatment to prevent progression to end-stage renal disease. Identification of epigenetic signatures of DKD via epigenome-wide association studies might also inform precision medicine approaches. Here, we highlight the emerging role of epigenetics and epigenomics in DKD and the translational potential of candidate epigenetic factors and non-coding RNAs as biomarkers and drug targets for DKD. This Review describes the current understanding of the role of epigenetics and epigenomics in diabetic kidney disease (DKD) and how epigenetic mechanisms might contribute to metabolic memory. The authors also discuss how epigenetic factors and non-coding RNAs could be used as biomarkers and drug targets for DKD diagnosis, prognosis and treatment.

/pdf/epigenetics-and-epigenomics-in-diabetic-kidney-disease-and-2uchrsutac.pdf

Epigenetics and epigenomics in diabetic kidney disease and metabolic memory

Methyl-CpG binding protein 2 (MeCP2) has crucial roles in transcriptional regulation and microRNA processing. Mutations in the MECP2 gene are found in 90% of patients with Rett syndrome, a severe developmental disorder with autistic phenotypes. Duplications of MECP2-containing genomic segments cause the MECP2 duplication syndrome, which shares core symptoms with autism spectrum disorders. Although Mecp2-null mice recapitulate most developmental and behavioural defects seen in patients with Rett syndrome, it has been difficult to identify autism-like behaviours in the mouse model of MeCP2 overexpression. Here we report that lentivirus-based transgenic cynomolgus monkeys (Macaca fascicularis) expressing human MeCP2 in the brain exhibit autism-like behaviours and show germline transmission of the transgene. Expression of the MECP2 transgene was confirmed by western blotting and immunostaining of brain tissues of transgenic monkeys. Genomic integration sites of the transgenes were characterized by a deep-sequencing-based method. As compared to wild-type monkeys, MECP2 transgenic monkeys exhibited a higher frequency of repetitive circular locomotion and increased stress responses, as measured by the threat-related anxiety and defensive test. The transgenic monkeys showed less interaction with wild-type monkeys within the same group, and also a reduced interaction time when paired with other transgenic monkeys in social interaction tests. The cognitive functions of the transgenic monkeys were largely normal in the Wisconsin general test apparatus, although some showed signs of stereotypic cognitive behaviours. Notably, we succeeded in generating five F1 offspring of MECP2 transgenic monkeys by intracytoplasmic sperm injection with sperm from one F0 transgenic monkey, showing germline transmission and Mendelian segregation of several MECP2 transgenes in the F1 progeny. Moreover, F1 transgenic monkeys also showed reduced social interactions when tested in pairs, as compared to wild-type monkeys of similar age. Together, these results indicate the feasibility and reliability of using genetically engineered non-human primates to study brain disorders.

Autism-like behaviours and germline transmission in transgenic monkeys overexpressing MeCP2

https://www.cell.com/developmental-cell/pdf/S1534-5807(14)00073-2.pdf

Tian Lin Cheng

Papers

MeCP2 Suppresses Nuclear MicroRNA Processing and Dendritic Growth by Regulating the DGCR8/Drosha Complex