Histone modifications and chromosome elimination in Bengalese finch

DEL PRIORE LUCIA; PIGOZZI M.I.

CHROMOSOMA

SPRINGER

Lugar: Berlin; Año: 2014 vol. 123 p. 293 - 302

0009-5915

We report here that a germline-restricted chromosome(GRC) is regularly present in males and females of theBengalese finch (Lonchura domestica). While the GRC is euchromaticin oocytes, in spermatocytes this chromosome iscytologically seen as entirely heterochromatic and presumablyinactive. The GRC is observed in the cytoplasm of secondaryspermatocytes, indicating that its elimination from the nucleusoccurs during the first meiotic division. By immunofluorescenceon microspreads, we investigated the presence of histone H3modifications throughoutmalemeiosis, as well as in postmeioticstages. We found that the GRC is highly enriched in di- andtrimethylated histone H3 at lysine 9 during prophase I, inagreement with the presumed inactive state of this chromosome.At metaphase I, dimethylated histone H3 is no longer detectableon theGRC and its chromatin ismore faintly stained withDAPI.The condensed GRC is underphosphorylated at serine 10 comparedto the regular chromosomes during metaphase I, beingphosphorylated later at this site after the first meiotic division.From these results, we proposed that trimethylation of histoneH3 at lysine 9 on the GRC chromatin increases during metaphaseI. This hypermethylated state at lysine 9 may preclude thephosphorylation of the adjacent serine 10 residue, providing anexample of cross-talk of histone H3 modifications as describedin experimental systems. The differential underphosphorylationof the GRC chromatin before elimination is interpreted as acytologically detectable byproduct of deficient activity ofAurora B kinase, which is responsible for the phosphorylationof H3 at serine 10 during mitosis and meiosis.