Epigenetic DNA Modifications Are Correlated With B Chromosomes and Sex in the Cichlid Astatotilapia latifasciata

Supernumerary B chromosomes are dispensable elements found in several groups of eukaryotes, and their impacts in host organisms are not clear. The cichlid fish Astatotilapia latifasciata presents one or two large metacentric B chromosomes. These elements affect the transcription of several classes of RNAs. Here, we evaluated the epigenetic DNA modification status of B chromosomes using immunocytogenetics and assessed the impact of B chromosome presence on the global contents of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) and the molecular mechanisms underlying these variations. We found that the B chromosome of A. latifasciata has an active pattern of DNA epimarks, and its presence promotes the loss of 5mC in gonads of females with B chromosome (FB+) and promotes the loss of 5hmC in the muscle of males with the B element (MB+). Based on the transcriptional quantification of DNA modification genes (dnmt, tet, and tdg) and their candidate regulators (idh genes, microRNAs, and long non-coding RNAs) and on RNA-protein interaction prediction, we suggest the occurrence of passive demethylation in gonads of FB+ and 5hmC loss by Tet inhibition or by 5hmC oxidation in MB+ muscle. We suggest that these results can also explain the previously reported variations in the transcription levels of several classes of RNA depending on B chromosome presence. The DNA modifications detected here are also influenced by sex. Although the correlation between B chromosomes and sex has been previously reported, it remains unexplained. The B chromosome of A. latifasciata seems to be active and impacts cell physiology in a very complex way, including at the epigenetic level

X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The X1X1X2X2/X1X2Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X1X1X2X2/X1X2Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B . n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X1X1X2X2/X1X2Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X1X1X2X2/X1X2Y system may represent sex chromosomes turnover events in Gymnotiformes

Chromosomal And Electric Signal Diversity In Three Sympatric Electric Knifefish Species (Gymnotus, Gymnotidae) From The Central Amazon Floodplain

This article examines recent government reforms in China to identify changes and lessons of the Chinese reform experience. The article provides a review of major government reform concepts and analyzes eight Chinese reform cases in four areas of government: personnel, structure, strategy, and process. These reforms have expanded the objectives and scopes of the past administrative reforms to include new governance concepts of promoting managerial competency, organizational capacity, accountability and transparency, and citizen participation. The reforms have not only reported positive lessons of local innovation and international connection but have also identified limitations and concerns about social and political stability. Implications about reform findings and challenges are provided for future studies of Chinese government reforms. © 2012 SAGE Publications

Additional file 7 of First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

Additional file 7. Fasta file containing A. latifasciata pld6 sequences from the transcriptome

Additional file 3 of First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

Additional file 3. PDF file containing the pld6 B-mutation alignment

Additional file 2 of First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

Additional file 2. PDF file containing reverse transcriptase and transposase alignment information

Additional file 4 of First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

Additional file 4. Spreadsheet of FEL and FUBAR selection site analysis

Chromosomal diversity in three species of electric fish (Apteronotidae, Gymnotiformes) from the Amazon Basin

Cytogenetic studies were carried out on samples of Parapteronotus hasemani, Sternarchogiton preto and Sternarchorhamphus muelleri (Apteronotidae, Gymnotiformes) from the Amazon basin. The first two species exhibited both a 2n = 52 karyotype, but differed in their karyotypic formulae, distribution of constitutive heterochromatin, and chromosomal location of the NOR. The third species, Sternarchorhamphus muelleri, was found to have a 2n = 32 karyotype. In all three species the DAPI and chromomycin A3 staining results were consistent with the C-banding results and nucleolar organizer region (NOR) localization. The 18S rDNA probe confirmed that there was only one pair of ribosomal DNA cistron bearers per species. The telomeric probe did not reveal interstitial telomeric sequences (ITS). The karyotypic differences among these species can be used for taxonomic identification. These data will be useful in future studies of these fishes and help understanding the phylogenetic relationships and chromosomal evolution of the Apteronotidae

Additional file 6 of First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

Additional file 6. PDF file containing Table S03Pld6 NCBI ID accession numbers

Additional file 5 of First characterization of PIWI-interacting RNA clusters in a cichlid fish with a B chromosome

Additional file 5. PDF file containing Table S01 Small RNA sequencing Table S02 Primer sequences