The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://http://dspace.unitus.it:80 2013-05-21T21:06:40Z 2013-05-21T21:06:40Z Bongiorni, Silvia Pugnali, Margherita Volpi, Silvia Bizzaro, Davide Singh, Prim B. Prantera, Giorgio http://hdl.handle.net/2067/1615 2011-06-29T16:34:09Z 2008-12-31T23:00:00Z

Title: Epigenetic Marks For Chromosome Imprinting During Spermatogenesis In Coccids Authors: Bongiorni, Silvia; Pugnali, Margherita; Volpi, Silvia; Bizzaro, Davide; Singh, Prim B.; Prantera, Giorgio Abstract: The establishment of sex-specific epigenetic marks during gametogenesis is one of the key feature of genomic imprinting. By immunocytological analysis, we thoroughly characterized the chromatin remodeling events that take place during gametogenesis in the mealybug Planococcus citri, in which an entire haploid set of (imprinted) chromosomes undergoes facultative heterochromatinization in male embryos. Building on our previous work, we have investigated the interplay of several epigenetic marks in the regulation of this genome-wide phenomenon. We characterized the germline patterns of histone modifications, Me(3)K9H3, Me(2)K9H3, and Me (3)K20H4, and of heterochromatic proteins, PCHET2 (HP1-like) and HP2-like during male and female gametogenesis. We found that at all stages in oogenesis chromatin is devoid of any detectable epigenetic marks. On the other hand, spermatogenesis is accompanied by a complex pattern of redistribution of epigenetic marks from euchromatin to heterochromatin, and vice versa. At the end of spermatogenesis, sperm heads are decorated by all the molecules we tested, except for PCHET2. However, only Me(3)K9H3 and Me(2)K9H3 are still detectable in the male pronucleus. We suggest that the histone H3 lysine 9 methylation is the signal used to establish the malespecific imprinting on the paternal genome, thus allowing it to be distinguished from the maternal genome in the developing embryo. Description: L'articolo è disponibile sul sito dell'editore: http://www.springerlink.com

2008-12-31T23:00:00Z Volpi, Silvia Bongiorni, Silvia Prantera, Giorgio http://hdl.handle.net/2067/1643 2011-06-30T09:35:14Z 2006-12-31T23:00:00Z

Title: HP2-like protein: a new piece of the facultative heterochromatin puzzle Authors: Volpi, Silvia; Bongiorni, Silvia; Prantera, Giorgio Abstract: In Drosophila melanogaster, the two chromosomal proteins HP1 and HP2 colocalize on heterochromatic and euchromatic sites in polytene chromosomes. Mutations in the HP2 gene act as dominant suppressors of position effect variegation, demonstrating a role for HP2 in the formation or maintenance of heterochromatin. In this paper, we investigated whether a putative homolog of the D. melanogaster HP2 is involved in the facultative heterochromatinization process in mealybugs. Using an antibody raised against the Drosophila HP2, we identified in the mealybug Planococcus citri a cross-reactive epitope, which we refer to as HP2-like. We investigated the HP2-like pattern during the male embryo development where the entire paternal haploid chromosome set becomes heterochromatic. The HP2 antibody heavily decorates the chromocenters, where it localizes with HP1, and marks the chromatin before it acquires the full cytological characteristics of the male-specific heterochromatin. In euchromatic chromosomes, HP2-like is mainly concentrated at telomeric sites. The interplay between HP2-like and HP1-like was studied by dsRNA interference experiments. Extinguishing HP1-like expression by RNAi does not prevent the association of HP2-like with facultative heterochromatin, implying that HP2-like binds to chromatin in a HP1- independent manner. Our results confirm and extend the structural and functional conservation of proteins involved in heterochromatin assembly. Description: L'articolo è disponibile sul sito dell'editore: http://www.springerlink.com

2006-12-31T23:00:00Z Bongiorni, Silvia Pasqualini, Barbara Taranta, Monia Singh, Prim B. Prantera, Giorgio http://hdl.handle.net/2067/1642 2011-06-29T16:50:24Z 2006-12-31T23:00:00Z

Title: Epigenetic regulation of facultative heterochromatinisation in Planococcus citri via the Me(3)K9H3/HP1/Me(3)K20H4 pathway Authors: Bongiorni, Silvia; Pasqualini, Barbara; Taranta, Monia; Singh, Prim B.; Prantera, Giorgio Abstract: Using RNA interference (RNAi) we have conducted a functional analysis of the HP1-like chromobox gene pchet2 during embryogenesis of the mealybug Planococcus citri. Knocking down pchet2 expression results in decondensation of the male-specific chromocenter that normally arises from the developmentally-regulated facultative heterochromatinisation of the paternal chromosome complement. Together with the disappearance of the chromocenter the staining levels of two associated histone modifications, tri-methylated lysine 9 of histone H3 [Me(3)K9H3] and tri-methylated lysine 20 of histone H4 [Me(3)K20H4], are reduced to undetectable levels. Embryos treated with double-stranded RNA (dsRNA) targeting pchet2 also exhibit chromosome abnormalities, such as aberrant chromosome condensation, and also the presence of metaphases that contain ‘lagging’ chromosomes. We conclude that PCHET2 regulates chromosome behavior during metaphase and is a crucial component of a Me(3)K9H3-HP1-Me(3)K20H4 pathway involved in the facultative heterochromatinisation of the (imprinted) paternal chromosome set. Description: L'articolo è disponibile sul sito dell'editore: http://jcs.biologists.org.

2006-12-31T23:00:00Z