title: Dissociation of the X chromosome from the synaptonemal complex in the XY body of the rodent Galea musteloides.
abstract: The XY body from spermatocytes of the rodent Galea musteloides shows progressive changes of the synaptonemal complex (SC) axes and the X-chromatin during pachynema. There is a gross thickening of the X-axis and the formation of a large X chromosome loop at mid and late pachytene stages. The SC proteins synaptonemal complex protein 3 (SYCP3), synaptonemal complex protein 1, and synaptonemal complex central element protein 3 and the proteins breast cancer 1, MutL homolog 1 (MLH1), and radiation-repair 51 (related to meiotic processes), the cohesin structural maintenance of chromosome 3, the centromeric protein (with CREST antibody), and the silenced chromatin (with phosphorylated (139ph) H2A histone family, member X (γ-H2AX) antibody) were analyzed in this XY body. The thick X-axis, including the interstitial loop, becomes formed by four to six laminae showing a cross-striation with a periodicity of about 20 nm. The whole length of the gross X-axis shows no significant changes during pachynema, but the interstitial chromatin of the X chromosome and the X centromere are included in the large loop, and it becomes separated from the SC. A conventional SC formed by the Y-axis, a central region and a thin lateral element originally corresponding to the X-axis, remains undisturbed up to the end of pachynema. A single MLH1 focus develops either at the distal or the proximal region of the loop end attached to the conventional SC. The chromatin surrounding the thickened axis is labeled with γ-H2AX. It is shown that most of the SYCP3 protein associated with the X chromosome loop is not involved in the SC maintenance, but it is located with the cohesin axis separated from the SC proper.
authors.affiliation: 2da. UA de Biología Celular, Histología, Embriología y Genética, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 Piso 10 (C1121ABG), Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Roberta B
authors.initials: RB
authors.lastname: Sciurano
authors.forename: I Mónica
authors.initials: IM
authors.lastname: Rahn
authors.forename: Juan C
authors.initials: JC
authors.lastname: Cavicchia
authors.forename: Alberto J
authors.initials: AJ
authors.lastname: Solari
mesh_terms: D000818:Animals; D002503:Centromere / Q000235:genetics / Q000648:ultrastructure; D002843:Chromatin / Q000235:genetics / Q000648:ultrastructure; D019143:Evolution, Molecular; D020868:Gene Silencing; D006168:Guinea Pigs; D008297:Male; D009685:Nuclear Envelope; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D049471:Pachytene Stage; D012377:Rodentia / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013573:Synaptonemal Complex / Q000235:genetics / Q000648:ultrastructure*; D014960:X Chromosome / Q000235:genetics / Q000648:ultrastructure*
chemical_list: D002843:Chromatin; D009687:Nuclear Proteins
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