A C. elegans LSD1 Demethylase Contributes to Germline Immortality by Reprogramming Epigenetic Memory

Microarray-based expression profiling of mixed stage populations taken from generation 1,13 and 26 spr-5 mutant animals as well as wild-type animals reveals a large class of spermatogenesis-expressed genes whose expression coordinately increased from generations 1 to 13 and then decreased from generations 13 to 26 in spr-5(by101) mutants. These results suggest that a failure to reset spermatogenesis acquired H3K4me2 may result in the progressive sterility that is observed in spr-5 mutants.

Mean FPKM value of all remanei control samples

This is the mean value of the N=26 RNASeq FPKM expression values for this gene in all life-stages of this species of all samples in the SRA that are wildtype controls that do not appear to have undergone any experimental conditions or treatment that would affect gene expression.

Median FPKM value of all remanei control samples

This is the median value of the N=26 RNASeq FPKM expression values for this gene in all life-stages of this species of all samples in the SRA that are wildtype controls that do not appear to have undergone any experimental conditions or treatment that would affect gene expression.

Expression data from mir-35-41(nDf50) mutant embryos grown at 20 degrees, compared to wild type

Gene expression in early animal embryogenesis is in large part controlled post-transcriptionally. Maternally-contributed microRNAs may therefore play important roles in early development. We have elucidated a major biological role of the nematode mir-35 family of maternally-contributed, essential microRNAs. We show that this microRNA family regulates the sex determination pathway at multiple levels, acting both upstream and downstream of her-1 to prevent aberrantly activated male developmental programs in hermaphrodite embryos. The predicted target genes that act downstream of the mir-35 family in this process, sup-26 and nhl-2, both encode RNA binding proteins, thus delineating a previously unknown post-transcriptional regulatory subnetwork within the well-studied sex determination pathway of C. elegans. Repression of nhl-2 by the mir-35 family is not only required for proper sex determination but also for viability, showing that a single microRNA target site can be essential. Since sex determination in C. elegans requires zygotic gene expression to read the sex chromosome karyotype, early embryos must remain gender-nave; our findings show that the mir-35 family microRNAs act in the early embryo to function as a developmental timer that preserves navet and prevents premature deleterious developmental decisions. The mir-35 family of microRNAs is essential for development. The mir-35-41(nDf50) allele deleted 7 of 8 mir-35 family members, and presents a hypomorphic phenotype in which embryonic lethality is temperature sensitive. To characterize the molecular phenotype associated with loss of mir-35 family function, we profiled gene expression in mir-35-41(nDf50) mutant embryos at both permissive (20) and restrictive (25) temperatures. (Refer to A microRNA family exerts maternal control on sex determination in C. elegans)

Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult C. elegans

Reports that low-intensity microwave radiation can induce heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by very slight heating. This study used a microwave exposure system (1.0 GHz, 0.5 W power input; SAR 0.9-3 mW kg-1 for 6-well plates) that minimises the temperature differential between sham and exposed conditions to 0.1C. Comparable measurement and simulation studies of SAR distribution within this exposure system are presented. We compared 5 Affymetrix gene-arrays of pooled triplicate RNA populations from sham-exposed L4/adult worms against 5 gene-arrays of pooled RNA from microwave-exposed worms (taken from the same source population in each run). Few genes showed consistent expression changes across all 5 comparisons, and all such expression changes appeared modest after applying standard normalisation procedures ( 30% up- or down-regulated). The number of statistically significant differences in gene expression (846) was less than the false-positive rate expected by chance (1131). As one example, an apparent up-regulation of the vit-3 vitellogenin gene by microwave exposure was not mirrored by similar changes affecting the other co-regulated members of the same vit gene family. We conclude that the pattern of gene expression in L4/adult C elegans is not substantially perturbed by low-intensity microwave radiation, and that the minor changes observed in this study may well be explicable as false positives. As a check on the sensitivity of the Affymetrix gene-arrays used, we also compared RNA samples from N2 worms subjected to a sub-heat-shock treatment (28C) against controls kept at 26 C (but using only 2 gene arrays per condition). After similar normalisation, many more genes (3712) showed substantial expression changes (i.e. > 2-fold at p < 0.05), including a group of six heat-shock genes which were strongly but unexpectedly down-regulated (by > 10-fold). However, further replication and confirmation by real-time RT-PCR would be needed to establish how many of these changes might also be false positives. Experimenter name: Adam Dawe Experimenter phone: +27 21 959 2364 adam@sanbi.ac.za Experimenter institute: South African National Bioinformatics Institute Experimenter address: University of Western Cape, Old Chemistry Building, University of Western Cape, Modderdam Road, Bellville 7530, Capetown Experimenter zip/postal_code: 7530 Experimenter country: South Africa Keywords: Microwave radiation, gene expression, gene arrays, Caenorhabditis elegans