Anti-MBD1 monoclonal antibody, clone 200C383.2.

Background: Epigenetic mechanisms, including DNA methylation, histone modification, and microRNAs, play pivotal roles in stem cell biology. Methyl-CpG binding protein 1 (MBD1), an important epigenetic regulator of adult neurogenesis, controls the proliferation and differentiation of adult neural stem/progenitor cells (aNSCs). We recently demonstrated that MBD1 deficiency in aNSCs leads to altered expression of several noncoding microRNAs (miRNAs). Methodology/Principal Findings: Here we show that one of these miRNAs, miR-195, and MBD1 form a negative feedback loop. While MBD1 directly represses the expression of miR-195 in aNSCs, high levels of miR-195 in turn repress the expression of MBD1. Both gain-of-function and loss-of-function investigations show that alterations of the MBD1-miR-195 feedback loop tip the balance between aNSC proliferation and differentiation. Conclusions/Significance: Therefore the regulatory loop formed by MBD1 and miR-195 is an important component of the epigenetic network that controls aNSC fate.

Dmp1 (Dmtf1) encodes a Myb-like transcription factor implicated in tumor suppression through direct activation of the Arf-p53 pathway. The human DMP1 gene is frequently deleted in non-small cell lung cancers, especially those that retain wild-type INK4 alpha/ARF and/or p53. To identify novel genes that are regulated by Dmp1, transcriptional profiles of lung tissue from Dmp1-null and wild-type mice were generated using the GeneChip Microarray. Comparative analysis of gene expression changes between the two groups resulted in identification of numerous genes that may be regulated by Dmp1. Notably, amphiregulin (Areg), thrombospondin-1 (Tsp-1), JunB, Egr1, adrenomedullin (Adm), Bcl-3 and methyl-CpG binding domain protein 1 (Mbd1) were downregulated in the lungs from Dmp1-null mice while Gas1 and Ect2 genes were upregulated. These target genes were chosen for further analyses since they are involved in cell proliferation, transcription, angiogenesis/metastasis, apoptosis, or DNA methylation, and thus could account for the tumor suppressor phenotype of Dmp1. Dmp1 directly bound to the genomic loci of Areg, Tsp-1, JunB and Egr1. Significant upregulation or downregulation of the novel Dmp1 target genes was observed upon transient expression of Dmp1 in alveolar epithelial cells, an effect which was nullified by the inhibition of de novo mRNA synthesis. Interestingly, these genes and their protein products were significantly downregulated or upregulated in the lungs from Dmp1-heterozygous mice as well. Identification of novel Dmp1 target genes not only provides insights into the effects of Dmp1 on global gene expression, but also sheds light on the mechanism of haploid insufficiency of Dmp1 in tumor suppression.