Mahadevaraju, S., Fear, J.M., Akeju, M., Galletta, B.J., Pinheiro, M.M.L.S., Avelino, C.C., Cabral-de-Mello, D.C., Conlon, K., Dell'Orso, S., Demere, Z., Mansuria, K., Mendonça, C.A., Palacios-Gimenez, O.M., Ross, E., Savery, M., Yu, K., Smith, H.E., Sartorelli, V., Yang, H., Rusan, N.M., Vibranovski, M.D., Matunis, E., Oliver, B. (2021). Dynamic sex chromosome expression in Drosophila male germ cells.  Nat. Commun. 12(1): 892.

FBrf0248088

Research paper

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 (4th) that re-acquired autosomal status. Here we use single cell RNA-Seq on fly larvae to demonstrate that the single X and pair of 4th 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.

PMC7873209 (PMC) (EuropePMC)