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We previously identified Wiz in a mouse screen for epigenetic modifiers. Due to its known association with G9a/GLP, Wiz is generally considered a transcriptional repressor. Here, we provide evidence that it may also function as a transcriptional activator. Wiz levels are high in the brain, but its function and direct targets are unknown. ChIP-seq was performed in adult cerebellum and Wiz peaks were found at promoters and transcription factor CTCF binding sites. RNA-seq in Wiz mutant mice identified genes differentially regulated in adult cerebellum and embryonic brain. In embryonic brain most decreased in expression and included clustered protocadherin genes. These also decreased in adult cerebellum and showed strong Wiz ChIP-seq enrichment. Because a precise pattern of protocadherin gene expression is required for neuronal development, behavioural tests were carried out on mutant mice, revealing an anxiety-like phenotype. This is the first evidence of a role for Wiz in neural function. DOI: http://dx.doi.org/10.7554/eLife.15082.001

Background Microrchidia proteins (MORCs) are involved in epigenetic gene silencing in a variety of eukaryotic organisms. Deletion of MORCs result in several developmental abnormalities and their dysregulation has been implicated in developmental disease and multiple cancers. Specifically, mammalian MORC3 mutations are associated with immune system defects and human cancers such as bladder, uterine, stomach, lung, and diffuse large B cell lymphomas. While previous studies have shown that MORC3 binds to H3K4me3 in vitro and overlaps with H3K4me3 ChIP-seq peaks in mouse embryonic stem cells, the mechanism by which MORC3 regulates gene expression is unknown. Results In this study, we identified that mutation in Morc3 results in a suppressor of variegation phenotype in a Modifiers of murine metastable epialleles Dominant (MommeD) screen. We also find that MORC3 functions as an epigenetic silencer of transposable elements (TEs) in mouse embryonic stem cells (mESCs). Loss of Morc3 results in upregulation of TEs, specifically those belonging to the LTR class of retrotransposons also referred to as endogenous retroviruses (ERVs). Using ChIP-seq we found that MORC3, in addition to its known localization at H3K4me3 sites, also binds to ERVs, suggesting a direct role in regulating their expression. Previous studies have shown that these ERVs are marked by the repressive histone mark H3K9me3 which plays a key role in their silencing. However, we found that levels of H3K9me3 showed only minor losses in Morc3 mutant mES cells. Instead, we found that loss of Morc3 resulted in increased chromatin accessibility at ERVs as measured by ATAC-seq. Conclusions Our results reveal MORC3 as a novel regulator of ERV silencing in mouse embryonic stem cells. The relatively minor changes of H3K9me3 in the Morc3 mutant suggests that MORC3 acts mainly downstream of, or in a parallel pathway with, the TRIM28/SETDB1 complex that deposits H3K9me3 at these loci. The increased chromatin accessibility of ERVs in the Morc3 mutant suggests that MORC3 may act at the level of chromatin compaction to effect TE silencing.

Pleural mesothelioma is a cancer of serosal surfaces caused by environmental exposure to asbestos. Clinical outcome remains poor and while trials of new treatments are ongoing it remains an understudied cancer. Mesothelioma cell lines can readily be grown from primary tumour and from tumour cells shed into pleural effusion with the latter representing a particularly valuable source of DNA in clinical settings, procurable without the need for additional invasive procedures. However, it is not well understood how accurately patient-derived cultured tumour cells represent the molecular characteristics of their primary tumour. We used whole-genome sequencing of primary tumour and matched cultured cells to comprehensively characterize mutations and structural alterations. Most cases had complex rearranged genomes with evidence of chromoanagenesis and rearrangements reminiscent of chromoplexy. Many of the identified driver mutations were structural, indicating that mesothelioma is often caused by structural alterations and catastrophic genomic events, rather than point mutations. Because the majority of genomic changes detected in tumours were also displayed by the genomes of cultured tumour cells, we conclude that low-passage cultured tumour cells are generally suitable for molecular characterization of mesothelioma and may be particularly useful where tissue samples with high tumour cell content are not available. However, the subclonal compositions of the cell lines did not fully recapitulate the subclonal diversity of the primary tumours. Furthermore, longitudinal acquisition of major alterations in subclonal cell populations was observed after long-term passaging. These two factors define limitations of tumour-derived cell lines as genomic substrate for clinical purposes.

The interplay between 3D chromatin architecture and gene silencing is incompletely understood. Here, we report a novel point mutation in the non-canonical SMC protein SMCHD1 that enhances its silencing capacity at endogenous developmental targets and at the facioscapulohumeral muscular dystrophy associated macro-array, D4Z4. Heightened SMCHD1 silencing perturbs developmental Hox gene activation, causing a homeotic transformation in mice. Paradoxically, the mutant SMCHD1 appears to enhance insulation against another epigenetic regulator complex, PRC2, while depleting long range chromatin interactions akin to what is observed in the absence of SMCHD1. These data suggest that SMCHD1’s role in long range chromatin interactions is not directly linked to gene silencing or insulating the chromatin, refining the model for how the different levels of SMCHD1-mediated chromatin regulation interact to bring about gene silencing in normal development and disease.

16 páginas, 1 tabla, 3 figuras., Mesenteric infection by the parasitic blood fluke Schistosoma bovis is a common veterinary problem in Africa and the Middle East and occasionally in the Mediterranean Region. The species also has the ability to form interspecific hybrids with the human parasite S. haematobium with natural hybridisation observed in West Africa, presenting possible zoonotic transmission. Additionally, this exchange of alleles between species may dramatically influence disease dynamics and parasite evolution. We have generated a 374 Mb assembly of the S. bovis genome using Illumina and PacBio-based technologies. Despite infecting different hosts and organs, the genome sequences of S. bovis and S. haematobium appeared strikingly similar with 97% sequence identity. The two species share 98% of protein-coding genes, with an average sequence identity of 97.3% at the amino acid level. Genome comparison identified large continuous parts of the genome (up to several 100 kb) showing almost 100% sequence identity between S. bovis and S. haematobium. It is unlikely that this is a result of genome conservation and provides further evidence of natural interspecific hybridization between S. bovis and S. haematobium. Our results suggest that foreign DNA obtained by interspecific hybridization was maintained in the population through multiple meiosis cycles and that hybrids were sexually reproductive, producing viable offspring. The S. bovis genome assembly forms a highly valuable resource for studying schistosome evolution and exploring genetic regions that are associated with species-specific phenotypic traits., This work was supported by grants from the QIMR Berghofer Medical Research Institute (Chenhall Estate) and the Australian Infectious Diseases Research Centre. NDY was supported by a National Health and Medical Research Council (NHMRC) CDF1, PKK by an NHMRC ECRF and DPM by an NHMRC SPRF (APP1102926). The work has been supported by NHMRC project grant APP1102322.

Background Foodborne infections caused by lung flukes of the genus Paragonimus are a significant and widespread public health problem in tropical areas. Approximately 50 Paragonimus species have been reported to infect animals and humans, but Paragonimus westermani is responsible for the bulk of human disease. Despite their medical and economic importance, no genome sequence for any Paragonimus species is available. Results We sequenced and assembled the genome of P. westermani, which is among the largest of the known pathogen genomes with an estimated size of 1.1 Gb. A 922.8 Mb genome assembly was generated from Illumina and Pacific Biosciences (PacBio) sequence data, covering 84% of the estimated genome size. The genome has a high proportion (45%) of repeat-derived DNA, particularly of the long interspersed element and long terminal repeat subtypes, and the expansion of these elements may explain some of the large size. We predicted 12,852 protein coding genes, showing a high level of conservation with related trematode species. The majority of proteins (80%) had homologs in the human liver fluke Opisthorchis viverrini, with an average sequence identity of 64.1%. Assembly of the P. westermani mitochondrial genome from long PacBio reads resulted in a single high-quality circularized 20.6 kb contig. The contig harbored a 6.9 kb region of non-coding repetitive DNA comprised of three distinct repeat units. Our results suggest that the region is highly polymorphic in P. westermani, possibly even within single worm isolates. Conclusions The generated assembly represents the first Paragonimus genome sequence and will facilitate future molecular studies of this important, but neglected, parasite group.

Position-effect variegation of transgene expression is sensitive to the chromatin state. We previously reported a forward genetic screen in mice carrying a variegated α-globin GFP transgene to find novel genes encoding epigenetic regulators. We named the phenovariant strains "Mommes" for modifiers of murine metastable epialleles. Here we report positional cloning of mutations in two Momme strains which result in suppression of variegation. Both strains harbour point mutations in the erythroid transcription factor, Klf1. One (D11) generates a stop codon in the zinc finger domain and a homozygous null phenotype. The other (D45) generates an amino acid transversion (H350R) within a conserved linker between zinc fingers two and three. Homozygous MommeD45 mice have chronic microcytic anaemia which models the phenotype in a recently described family. This is the first genetic evidence that the linkers between the zinc fingers of transcription factors have a function beyond that of a simple spacer.

Introduction Interactions between tumor cells and the immune system play a critical role in regulating tumor development. Immune-based therapies have shown variable responses in diffuse large B-cell lymphoma (DLBCL) which suggests that the immune cell composition of the tumor microenvironment (TME) influences response to these agents. However, the key determinants of the immune TME are poorly understood. We have recently shown that indolent lymphomas can be stratified as immunologically 'hot' or 'cold' (Tobin et al J. Clin Oncol, in press) and sought to test for this in DLBCL. Also, given that beta-2-microglobulin (B2M) has a key role in antigen presentation and its loss is a frequent immune evasion mechanism in DLBCL, we determined the effect of B2M expression on the nature and magnitude of immune infiltration in the tumor microenvironment of DLBCL. Methods Ninety-seven de novo systemic DLBCL FFPE biopsies underwent targeted exon re-sequencing of B2M (Illumina) in addition to quantitative gene expression of Β2M, immune effector (CD4, CD8, CD56, CD137), immunosuppressive macrophage markers (CD68, CD163) and immune checkpoints (TIM3, LAG3, PD1 and PDL1) (Nanostring Technologies). B2M promoter methylation by mass array, immunohistochemistry for the above markers and high throughput T-cell receptor β sequencing (Adaptive Biotechnologies) were performed on a subset of cases. Genomic findings were validated in a whole exome and transcriptome cohort of approximately 1000 DLBCL samples (Reddy et al Cell 2017). Results Β2MMut were detected in 14/97 (14.4%) samples and had lower Β2M gene expression compared to Β2MWT (p = 0.0094) and all of these showed B2M protein loss. However, 29/40 (72%) of B2MWT samples tested also had B2M protein loss. There was no differential methylation of B2M promoter regions observed compared to lymph node controls. Results indicate that mechanisms other than mutation and methylation status contribute to loss of B2M surface expression and that a more comprehensive assessment of B2M expression within tumor tissues is achieved by B2M digital gene quantification. Consistent with this, there were no significant differences in expression of intra-tumoral immune markers between B2MMut and B2MWT tissues, whereas gene expression of B2M was significantly associated and positively correlated with the gene expression of CD4, CD8, CD56, CD137, CD68, CD163, PD1, PDL1, LAG3 and TIM3 (all p Next, we tested the discovery cohort for relationships with the TCR repertoire. High B2M gene expression was significantly associated with reduced TCR diversity (p = 0.0101) compared to low B2M gene expression, suggesting that clonal T cell expansions are more likely with intact antigen presentation. The validation cohort also demonstrated that B2M gene expression correlated with immune cell infiltration and additionally showed that B2M positively correlated with the gene expression of HLA Class I//II molecules and a range of regulatory, transport and assembly molecules involved in the antigen presentation machinery pathway. However, no differential survival benefit was observed in patients with high versus low B2M. Conclusions In summary, digital gene expression is a robust measure of B2M quantification in the TME. Our data show that high B2M gene expression reflects an immunologically active or 'hot' tumor microenvironment in DLBCL characterised by higher levels of immune cell infiltration. These findings indicate that B2M gene expression level could be used as a biomarker of an active intra-tumoral immune response in DLBCL. Further studies are required to determine if B2M gene expression may have a role in stratifying the selection of patients in whom immune-based therapies are more likely to be effective. Disclosures Gould: NovoNordisk: Other: Travel funding - domestic flights to attend education, May 2018. Keane:MSD: Consultancy; BMS: Research Funding; Celgene: Consultancy; Gilead: Consultancy; Roche: Consultancy, Other: Travel Grant. Hertzberg:Takeda: Consultancy, Honoraria; MSD: Consultancy; Roche: Consultancy, Honoraria. Gandhi:Gilead: Honoraria, Research Funding; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Other: Travel Support; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria.

The number of reports of paternal epigenetic influences on the phenotype of offspring in rodents is increasing but the molecular events involved remain unclear. Here, we show that haploinsufficiency for the histone 3 lysine 9 methyltransferase Setdb1 in the sire can influence the coat colour phenotype of wild type offspring. This effect occurs when the allele that directly drives coat colour is inherited from the dam, inferring that the effect involves an “in trans” step. The implication of this finding is that epigenetic state of the sperm can alter the expression of genes inherited on the maternally derived chromosomes. Whole genome bisulphite sequencing revealed that Setdb1 mutant mice show DNA hypomethylation at specific classes of transposable elements in the sperm. Our results identify Setdb1 as a paternal effect gene in the mouse and suggest that epigenetic inheritance may be more likely in individuals with altered levels of epigenetic modifiers.

We have used a forward genetic screen to identify genes required for transgene silencing in the mouse. Previously these genes were found using candidate-based sequencing, a slow and labor-intensive process. Recently, whole-exome deep sequencing has accelerated our ability to find the causative point mutations, resulting in the discovery of novel and sometimes unexpected genes. Here we report the identification of translation initiation factor 3, subunit H (eIF3h) in two modifier of murine metastable epialleles (Mommes) lines. Mice carrying mutations in this gene have not been reported previously, and a possible involvement of eIF3h in transcription or epigenetic regulation has not been considered.

We have recently shown that transcription initiation RNAs (tiRNAs) are derived from sequences immediately downstream of transcription start sites. Here, using cytoplasmic and nuclear small RNA high-throughput sequencing datasets, we report the identification of a second class of nuclear-specific approximately 17- to 18-nucleotide small RNAs whose 3' ends map precisely to the splice donor site of internal exons in animals. These splice-site RNAs (spliRNAs) are associated with highly expressed genes and show evidence of developmental stage- and region-specific expression. We also show that tiRNAs are localized to the nucleus, are enriched at chromatin marks associated with transcription initiation and possess a 3'-nucleotide bias. Additionally, we find that microRNA-offset RNAs (moRNAs), the miR-15/16 cluster previously linked to oncosuppression and most small nucleolar RNA (snoRNA)-derived small RNAs (sdRNAs) are enriched in the nucleus, whereas most miRNAs and two H/ACA sdRNAs are cytoplasmically enriched. We propose that nuclear-localized tiny RNAs are involved in the epigenetic regulation of gene expression.

Summary This study describes the esophageal cancer methylation landscape and its impact on gene expression. Genes aberrantly methylated suggest a mechanism that could lead to genomic instability and chromothripsis. A CpG island methylator phenotype-like subtype with potentially worse clinical outcome was also identified., The incidence of esophageal adenocarcinoma (EAC) has risen significantly over recent decades. Although survival has improved, cure rates remain poor, with

Background Phenotypic variability among inbred littermates reared in controlled environments remains poorly understood. Metastable epialleles refer to loci that intrinsically behave in this way and a few examples have been described. They display differential methylation in association with differential expression. For example, inbred mice carrying the agouti viable yellow (Avy) allele show a range of coat colours associated with different DNA methylation states at the locus. The availability of next-generation sequencing, in particular whole genome sequencing of bisulphite converted DNA, allows us, for the first time, to search for metastable epialleles at base pair resolution. Results Using whole genome bisulphite sequencing of DNA from the livers of five mice from the Avy colony, we searched for sites at which DNA methylation differed among the mice. A small number of loci, 356, were detected and we call these inter-individual Differentially Methylated Regions, iiDMRs, 55 of which overlap with endogenous retroviral elements (ERVs). Whole genome resequencing of two mice from the colony identified very few differences and these did not occur at or near the iiDMRs. Further work suggested that the majority of ERV iiDMRs are metastable epialleles; the level of methylation was maintained in tissue from other germ layers and the level of mRNA from the neighbouring gene inversely correlated with methylation state. Most iiDMRs that were not overlapping ERV insertions occurred at tissue-specific DMRs and it cannot be ruled out that these are driven by changes in the ratio of cell types in the tissues analysed. Conclusions Using the most thorough genome-wide profiling technologies for differentially methylated regions, we find very few intrinsically epigenetically variable regions that we term iiDMRs. The most robust of these are at retroviral elements and appear to be metastable epialleles. The non-ERV iiDMRs cannot be described as metastable epialleles at this stage but provide a novel class of variably methylated elements for further study. Electronic supplementary material The online version of this article (doi:10.1186/s13072-015-0047-z) contains supplementary material, which is available to authorized users.

Background We recently identified a novel protein, Rearranged L-myc fusion (Rlf), that is required for DNA hypomethylation and transcriptional activity at two specific regions of the genome known to be sensitive to epigenetic gene silencing. To identify other loci affected by the absence of Rlf, we have now analysed 12 whole genome bisulphite sequencing datasets across three different embryonic tissues/stages from mice wild-type or null for Rlf. Results Here we show that the absence of Rlf results in an increase in DNA methylation at thousands of elements involved in transcriptional regulation and many of the changes occur at enhancers and CpG island shores. ChIP-seq for H3K4me1, a mark generally found at regulatory elements, revealed associated changes at many of the regions that are differentially methylated in the Rlf mutants. RNA-seq showed that the numerous effects of the absence of Rlf on the epigenome are associated with relatively subtle effects on the mRNA population. In vitro studies suggest that Rlf’s zinc fingers have the capacity to bind DNA and that the protein interacts with other known epigenetic modifiers. Conclusion This study provides the first evidence that the epigenetic modifier Rlf is involved in the maintenance of DNA methylation at enhancers and CGI shores across the genome. Electronic supplementary material The online version of this article (doi:10.1186/s12915-015-0128-2) contains supplementary material, which is available to authorized users.

The word 'epimutation' is often used in a manner that can be misinterpreted. The strict definition of epimutation is a heritable change in gene activity that is not associated with a DNA mutation but rather with gain or loss of DNA methylation or other heritable modifications of chromatin. Unfortunately, there is a growing tendency in the cancer field to use the word in situations in which underlying DNA sequence changes have occurred.

stress-sensitive reporter predicts longevity in isogenic populations of Caenorhabditis elegans. Nat Genet 2005; 37:894–98. 6 Orgel LE. The maintenance of the accuracy of protein synthesis and its relevance to ageing: a correction. Proc Natl Acad Sci U S A 1970;67:1476. 7 Fraga MF, Ballestar E, Paz MF et al. Epigenetic differences arise during the lifetime of monozygotic twins. Proc Natl Acad Sci U S A 2005;102:10604–09. 8 Childs DZ, Metcalf CJ, Rees M. Evolutionary bet-hedging in the real world: empirical evidence and challenges revealed by plants. Proc R. Soc Lond B Biol Sci 2010;277: 3055–64. 9 Martin GM. Epigenetic gambling and epigenetic drift as an antagonistic pleiotropic mechanism of aging. Aging Cell 2009;8:761–64. 10 Martin GM. Stochastic modulations of the pace and patterns of ageing: impacts on quasi-stochastic distributions of multiple geriatric pathologies. Mech Ageing Dev 2011; doi:10.1016/j.mad.2011.09.001. 11 Salk JJ, Salipante SJ, Risques RA et al. Clonal expansions in ulcerative colitis identify patients with neoplasia. Proc Natl Acad Sci U S A 2009;106:20871–76.

Position-effect variegation of transgene expression is sensitive to the chromatin state. We previously reported a forward genetic screen in mice carrying a variegated a-globin GFP transgene to find novel genes encoding epigenetic regulators. We named the phenovariant strains "Mommes" for Modifiers of murine metastable epi-alleles. Here we report positional cloning of mutations in two Momme strains which result in suppression of variegation; i.e. an increased percentage of GFP+ circulating red blood cells. Both strains harbour point mutations in the erythroid specific transcription factor, Klf1. One (D11) generates a stop codon in the zinc finger domain. D11 homozygous mice die in utero of anaemia at 14.5DPC. The other (D45) generates an amino acid transversion (H350R) within a conserved linker between zinc fingers two and three. Homozygous MommeD45 mice have mild compensated microcytic anaemia which models the phenotype in a recently described human family. Mice Carrying the H350R mutation were interbred with Klf1+/- mice. Klf1H350R/- mice have severe perinatal haemolytic anaemia and marked splenomegaly. Furthermore blood haemoglobin content, haematocrit and red blood cell size (MCV) were significantly reduced in Klf1H350R/- mice compared to wildtype and D45 homozygous offspring of the same age. Analysis of Klf1H350R/- by flow cytometry showed an increase in circulating immature red blood cells. In the bone marrow, a lack of mature red blood cells was observed. Flow cytometric analysis of the spleen from Klf1H350R/- animals revealed an expansion of erythroid cells and a relative reduction in B and T Cells. Gel shifts assays of a recombinant Klf1 zinc finger protein with the H350R mutation showed normal binding to the b -globin promoter sequence but weak binding to the Alas2 intronic enhancer site. Furthermore b -globin gene expression was near normal whereas expression of other known Klf1 target genes was decreased. We will discuss how H350R disrupts function from ChIP-seq and RNA-seq in primary fetal liver tissue. Previous studies of the linkers in C2H2 zinc finger transcription factors have revealed their necessity as structural and regulatory components for the C2H2 class of transcription factors. Our results thus far show that the second linker of Klf1 has a role in maintaining the integrity of Klf1 function (at a subset of Klf1-occupied sites,) and does not act just as a spacer for the zinc fingers. Disclosures Perkins: Novartis Oncology: Honoraria.

Transposable elements (TEs) have been active in the mammalian genome for millions of years and the silencing of these elements in the germline is important for the survival of the host. Mice carrying reporter transgenes can be used to model transcriptional silencing. A mutagenesis screen for modifiers of epigenetic gene silencing produced a line with a mutation in Trim33; the mutants displayed increased expression of the reporter transgene. ChIP-seq of Trim33 in testis revealed 9,109 peaks, mostly at promoters. This is the first report of ChIP-seq for Trim33 in any tissue. Comparison with ENCODE datasets showed that regions of high read density for Trim33 had high read density for histone marks associated with transcriptional activity and mapping to TE consensus sequences revealed Trim33 enrichment at RLTR10B, the LTR of one of the youngest retrotransposons in the mouse genome, MMERVK10C. We identified consensus sequences from the 266 regions at which Trim33 ChIP-seq peaks overlapped RLTR10B elements and found a match to the A-Myb DNA-binding site. We found that TRIM33 has E3 ubiquitin ligase activity for A-MYB and regulates its abundance. RNA-seq revealed that mice haploinsufficient for Trim33 had altered expression of a small group of genes in the testis and the gene with the most significant increase was found to be transcribed from an upstream RLTR10B. These studies provide the first evidence that A-Myb has a role in the actions of Trim33 and suggest a role for both A-Myb and Trim33 in the arms race between the transposon and the host. This the first report of any factor specifically regulating RLTR10B and adds to the current literature on the silencing of MMERVK10C retrotransposons. This is also the first report that A-Myb has a role in the transcription of any retrotransposon., Author Summary Almost half of the genomes of humans and mice are made up of transposable elements. During host evolution, subsets of these elements have periods of transpositional activity during which they spread throughout the genome. This is dependent on the transcriptional activity of these elements in the cells that contribute to the germline. Hosts have evolved pathways to silence their expression. A number of Trim family proteins have been found to have a role in silencing transposable elements, and it was previously shown that Trim33 shared this function in liver. However, the function of Trim33 in other tissues is poorly understood. Here we report a role for Trim33 in silencing a specific subset of retrotransposons that contain RLTR10B LTRs, in the germline. We also show the transcription factor, A-Myb, is responsible for activating transcription of these elements and it is likely that a subset of RLTR10Bs have recently evolved Myb DNA binding sites to capitalise on the critical role that the A-Myb transcription factor has in germ cells. Suppression of A-Myb activity by Trim33 provides a plausible mechanism by which the host keeps transposons in check.

Background Piwi interacting RNA, or piRNA, is a class of small RNA almost exclusively expressed in the germline where they serve essential roles in retrotransposon silencing. There are two types, primary and secondary piRNA, and the latter is a product of enzymatic cleavage of retrotransposons' transcripts directed by the former. Recently, a new class of 19nt long RNA was discovered that is specific to testis and appears to be linked to secondary piRNA biogenesis. Results We locate clusters of the testis-specific 19mers, which we call piRNA-related 19mers (pr19RNA), and characterise the transcripts from which they are derived. Most pr19RNA clusters were associated with retrotransposons and unannotated antisense transcripts overlapping piRNA clusters. At these loci the abundance of 19mers was found to be greater than that of secondary piRNAs. Conclusion We find that pr19RNAs are distinguished from other RNA populations by their length and flanking sequence, allowing their identification without requiring overlapping piRNAs. Using such sequence features allows identification of the source transcripts, and we suggest that these likely represent the substrates of primary piRNA-guided RNA cleavage events. While pr19RNAs appear not to bind directly to Miwi or Mili, their abundance relative to secondary piRNAs, in combination with their precise length, suggests they may be more than by-products of secondary piRNA biogenesis.

With the advent of easy access to the human genome sequence, molecular biology techniques to target respirome-specific genes have begun to be exploited in the study of human disorders and in particular human cancers. In some recent publications it would appear that some investigators have inappropriately targeted pseudogenes rather than functional genes. The high transcription level and generally small size of many of the genes in the respirome make them prone to duplications in the form of processed pseudogenes within the human genome. Such genes can be challenging to analyse using standard molecular genetics approaches. In this presentation, we offer an analysis of pseudogenes that have been identified to have significant homology with some elements of the respirome. Other sequence elements such as Alu repeats, which present similar research obstacles, are also discussed.

Background We have used a sensitized ENU mutagenesis screen to produce mouse lines that carry mutations in genes required for epigenetic regulation. We call these lines Modifiers of murine metastable epialleles (Mommes). Results We report a basic molecular and phenotypic characterization for twenty of the Momme mouse lines, and in each case we also identify the causative mutation. Three of the lines carry a mutation in a novel epigenetic modifier, Rearranged L-myc fusion (Rlf), and one gene, Rap-interacting factor 1 (Rif1), has not previously been reported to be involved in transcriptional regulation in mammals. Many of the other lines are novel alleles of known epigenetic regulators. For two genes, Rlf and Widely-interspaced zinc finger (Wiz), we describe the first mouse mutants. All of the Momme mutants show some degree of homozygous embryonic lethality, emphasizing the importance of epigenetic processes. The penetrance of lethality is incomplete in a number of cases. Similarly, abnormalities in phenotype seen in the heterozygous individuals of some lines occur with incomplete penetrance. Conclusions Recent advances in sequencing enhance the power of sensitized mutagenesis screens to identify the function of previously uncharacterized factors and to discover additional functions for previously characterized proteins. The observation of incomplete penetrance of phenotypes in these inbred mutant mice, at various stages of development, is of interest. Overall, the Momme collection of mouse mutants provides a valuable resource for researchers across many disciplines.