Dynamic sex chromosome expression in Drosophila male germ cells
Sharvani Mahadevaraju, Justin M. Fear, Miriam Akeju, Brian J. Galletta, Mara Pinheiro, Camila C. Avelino, Diogo Cavalcanti Cabral-de-Mello, Katie Conlon, Stefania Dell’Orso, Zelalem Demere, Kush Mansuria, Carolina A. Mendonça, Octavio M. Palacios‐Gimenez, Eli Ross, Max Savery, Kevin Yu, Harold E. Smith, Vittorio Sartorelli, Haiwang Yang, Nasser M. Rusan, Maria D. Vibranovski, Erika Matunis, Brian Oliver
Abstract
Abstract Given their copy number differences and unique modes of inheritance, the evolved gene content and expression of sex chromosomes is unusual. In many organisms the X and Y chromosomes are inactivated in spermatocytes, possibly as a defense mechanism against insertions into unpaired chromatin. In addition to current sex chromosomes, Drosophila has a small gene-poor X-chromosome relic (4 th ) that re-acquired autosomal status. Here we use single cell RNA-Seq on fly larvae to demonstrate that the single X and pair of 4 th chromosomes are specifically inactivated in primary spermatocytes, based on measuring all genes or a set of broadly expressed genes in testis we identified. In contrast, genes on the single Y chromosome become maximally active in primary spermatocytes. Reduced X transcript levels are due to failed activation of RNA-Polymerase-II by phosphorylation of Serine 2 and 5.