title: The RNA binding protein SAM68 transiently localizes in the chromatoid body of male germ cells and influences expression of select microRNAs.
abstract: The chromatoid body (CB) is a unique structure of male germ cells composed of thin filaments that condense into a perinuclear organelle after meiosis. Due to the presence of proteins involved in different steps of RNA metabolism and of different classes of RNAs, including microRNAs (miRNAs), the CB has been recently suggested to function as an RNA processing centre. Herein, we show that the RNA binding protein SAM68 transiently localizes in the CB, in concomitance with the meiotic divisions of mouse spermatocytes. Precise staging of the seminiferous tubules and co-localization studies with MVH and MILI, two well recognized CB markers, documented that SAM68 transiently associates with the CB in secondary spermatocytes and early round spermatids. Furthermore, although SAM68 co-immunoprecipitated with MVH in secondary spermatocytes, its ablation did not affect the proper localization of MVH in the CB. On the other hand, ablation of the CB constitutive component MIWI did not impair association of SAM68 with the CB. Isolation of CBs from Sam68 wild type and knockout mouse testes and comparison of their protein content by mass spectrometry indicated that Sam68 ablation did not cause overall alterations in the CB proteome. Lastly, we found that SAM68 interacts with DROSHA and DICER in secondary spermatocytes and early round spermatids and that a subset of miRNAs were altered in Sam68(-/-) germ cells. These results suggest a novel role for SAM68 in the miRNA pathway during spermatogenesis.
authors: Section of Anatomy, Department of Public Health and Cell Biology, University of Rome Tor Vergata, Rome, Italy.
authors: Valeria
authors: V
authors: Messina
authors: Oliver
authors: O
authors: Meikar
authors: Maria Paola
authors: MP
authors: Paronetto
authors: Sara
authors: S
authors: Calabretta
authors: Raffaele
authors: R
authors: Geremia
authors: Noora
authors: N
authors: Kotaja
authors: Claudio
authors: C
authors: Sette
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005854:Germ Cells / Q000378:metabolism* / Q000648:ultrastructure; D047468:Immunoprecipitation; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D046529:Microscopy, Electron, Transmission; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013087:Spermatids / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C513253:Khdrbs1 protein, mouse; D035683:MicroRNAs; D016601:RNA-Binding Proteins