Prdm5 Regulates Collagen Gene Transcription by Association with RNA Polymerase II in Developing Bone

PRDM family members are transcriptional regulators involved in tissue specific differentiation. PRDM5 has been reported to predominantly repress transcription, but a characterization of its molecular functions in a relevant biological context is lacking. We demonstrate here that Prdm5 is highly expressed in developing bones; and, by genome-wide mapping of Prdm5 occupancy in pre-osteoblastic cells, we uncover a novel and unique role for Prdm5 in targeting all mouse collagen genes as well as several SLRP proteoglycan genes. In particular, we show that Prdm5 controls both Collagen I transcription and fibrillogenesis by binding inside the Col1a1 gene body and maintaining RNA polymerase II occupancy. In vivo, Prdm5 loss results in delayed ossification involving a pronounced impairment in the assembly of fibrillar collagens. Collectively, our results define a novel role for Prdm5 in sustaining the transcriptional program necessary to the proper assembly of osteoblastic extracellular matrix

Mice carrying a hypomorphic Evi1 allele are embryonic viable but exhibit severe congenital heart defects

The ecotropic viral integration site 1 (Evi1) oncogenic transcription factor is one of a number of alternative transcripts encoded by the Mds1 and Evi1 complex locus (Mecom). Overexpression of Evi1 has been observed in a number of myeloid disorders and is associated with poor patient survival. It is also amplified and/or overexpressed in many epithelial cancers including nasopharyngeal carcinoma, ovarian carcinoma, ependymomas, and lung and colorectal cancers. Two murine knockout models have also demonstrated Evi1's critical role in the maintenance of hematopoietic stem cell renewal with its absence resulting in the death of mutant embryos due to hematopoietic failure. Here we characterize a novel mouse model (designated Evi1(fl3)) in which Evi1 exon 3, which carries the ATG start, is flanked by loxP sites. Unexpectedly, we found that germline deletion of exon3 produces a hypomorphic allele due to the use of an alternative ATG start site located in exon 4, resulting in a minor Evi1 N-terminal truncation and a block in expression of the Mds1-Evi1 fusion transcript. Evi1(deltaex3/deltaex3) mutant embryos showed only a mild non-lethal hematopoietic phenotype and bone marrow failure was only observed in adult Vav-iCre/+, Evi1(fl3/fl3) mice in which exon 3 was specifically deleted in the hematopoietic system. Evi1(deltaex3/deltaex3) knockout pups are born in normal numbers but die during the perinatal period from congenital heart defects. Database searches identified 143 genes with similar mutant heart phenotypes as those observed in Evi1(deltaex3/deltaex3) mutant pups. Interestingly, 42 of these congenital heart defect genes contain known Evi1-binding sites, and expression of 18 of these genes are also effected by Evi1 siRNA knockdown. These results show a potential functional involvement of Evi1 target genes in heart development and indicate that Evi1 is part of a transcriptional program that regulates cardiac development in addition to the development of blood

Regulation of Retinoid Receptors by Retinoic Acid and Axonal Contact in Schwann Cells

Background: Schwann cells (SCs) are the cell type responsible for the formation of the myelin sheath in the peripheral nervous system (PNS). As retinoic acid (RA) and other retinoids have a profound effect as regulators of the myelination program, we sought to investigate how their nuclear receptors levels were regulated in this cell type. Methodology/Principal Findings: In the present study, by using Schwann cells primary cultures from neonatal Wistar rat pups, as well as myelinating cocultures of Schwann cells with embryonic rat dorsal root ganglion sensory neurons, we have found that sustained expression of RXR-c depends on the continuous presence of a labile activator, while axonal contact mimickers produced an increase in RXR-c mRNA and protein levels, increment that could be prevented by RA. The upregulation by axonal contact mimickers and the transcriptional downregulation by RA were dependent on de novo protein synthesis and did not involve changes in mRNA stability. On the other hand, RAR-b mRNA levels were only slightly modulated by axonal contact mimickers, while RA produced a strong transcriptional upregulation that was independent of de novo protein synthesis without changes in mRNA stability. Conclusions/Significance: All together, our results show that retinoid receptors are regulated in a complex manner i

Identification of molecular signatures specific for distinct cranial sensory ganglia in the developing chick

Background The cranial sensory ganglia represent populations of neurons with distinct functions, or sensory modalities. The production of individual ganglia from distinct neurogenic placodes with different developmental pathways provides a powerful model to investigate the acquisition of specific sensory modalities. To date there is a limited range of gene markers available to examine the molecular pathways underlying this process. Results Transcriptional profiles were generated for populations of differentiated neurons purified from distinct cranial sensory ganglia using microdissection in embryonic chicken followed by FAC-sorting and RNAseq. Whole transcriptome analysis confirmed the division into somato- versus viscerosensory neurons, with additional evidence for subdivision of the somatic class into general and special somatosensory neurons. Cross-comparison of distinct ganglia transcriptomes identified a total of 134 markers, 113 of which are novel, which can be used to distinguish trigeminal, vestibulo-acoustic and epibranchial neuronal populations. In situ hybridisation analysis provided validation for 20/26 tested markers, and showed related expression in the target region of the hindbrain in many cases. Results One hundred thirty-four high-confidence markers have been identified for placode-derived cranial sensory ganglia which can now be used to address the acquisition of specific cranial sensory modalities.</p

Mice carrying a hypomorphic Evi1 allele are embryonic viable but exhibit severe congenital heart defects

10.1371/journal.pone.0089397PLoS ONE92e8939

DNA methylation of developmental genes in pediatric medulloblastomas identified by denaturation analysis of methylation differences

DNA methylation might have a significant role in preventing normal differentiation in pediatric cancers. We used a genomewide method for detecting regions of CpG methylation on the basis of the increased melting temperature of methylated DNA, termed denaturation analysis of methylation differences (DAMD). Using the DAMD assay, we find common regions of cancer-specific methylation changes in primary medulloblastomas in critical developmental regulatory pathways, including Sonic hedgehog (Shh), Wingless (Wnt), retinoic acid receptor (RAR), and bone morphogenetic protein (BMP). One of the commonly methylated loci is the PTCH1-1C promoter, a negative regulator of the Shh pathway that is methylated in both primary patient samples and human medulloblastoma cell lines. Treatment with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (5-aza-dC) increases the expression of PTCH1 and other methylated loci. Whereas genetic mutations in PTCH1 have previously been shown to lead to medulloblastoma, our study indicates that epigenetic silencing of PTCH1, and other critical developmental loci, by DNA methylation is a fundamental process of pediatric medulloblastoma formation. This finding warrants strong consideration for DNA demethylating agents in future clinical trials for children with this disease