Heterochromatin protein 1 (HP1) is a highly conserved family of eukaryotic proteins required for heterochromatic gene silencing and euchromatic gene transcription regulation. In addition, HP1 is involved in chromatin organization and protection of chromosome integrity during cell division. Here, we present a cytological and molecular analysis of the effects of HP1 knockdown in Eyprepocnemis plorans, a grasshopper species polymorphic for supernumerary heterochromatic chromosomes. Our results revealed contrasting effects of HP1 knockdown on gene activity. While the Bub1 gene decreased in expression level in HP1 knockdown animals, NOR activity, rRNA and, contrarily to previous reports in Drosophila, Hsp70 gene expression remained unchanged. Furthermore, HP1 knockdown resulted in abnormal chromatin condensation, chromosomal bridges, higher frequency of macrospermatids, loss of muscle mass and hemolymph amount as well as a low number of dividing cells and survival reduction. All these phenotypes are very likely due to the chromatin condensation disruption observed for almost all kinds of chromatin.
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Acknowledgements We thank T. López for technical assistance and Karl Meunier for language revision. This study was supported by a grant from the Spanish Ministerio de Ciencia e Innovación (CGL2009-11917) and Plan Andaluz de Investigación (CVI-6649), and was partially performed by FEDER funds. M Ruiz-Estévez was supported by a FPU fellowship from the Spanish Ministerio de Ciencia e Innovación. M. Bakkali wishes to thank the Spanish Ministerio de Ciencia e Innovación both for the grant (BFU2010-16438) and for the Ramón y Cajal Fellowship.
- Eyprepocnemis plorans
- Heterochromatin protein 1