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Dynamic changes in localization of chromobox (CBX) family members during the maternal to embryonic transition
Author(s) -
RuddockD'Cruz Nancy T.,
Prashadkumar Sivachelvi,
Wilson Katrina J.,
Heffernan Corey,
Cooney Melissa A.,
French Andrew J.,
Jans David A.,
Verma Paul J.,
Holland Michael K.
Publication year - 2008
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20752
Subject(s) - biology , heterochromatin , heterochromatin protein 1 , cytoplasm , cell nucleus , nuclear protein , microbiology and biotechnology , chromatin , nuclear export signal , nuclear localization sequence , histone , euchromatin , embryonic stem cell , genetics , gene , transcription factor
The Chromobox domain (Cbx) gene family, consisting of Polycomb and Heterochromatin Protein 1 genes, is involved in transcriptional repression, cell cycle regulation and chromatin remodeling. We report the first study of gene expression and protein localization of the Cbx genes in in vitro produced bovine embryos. All but one gene (Cbx6) were expressed. This was confirmed by immunolocalization for HP1α, β, γ, and Pc2, 3. HP1β was found in the nuclei of embryos from the two‐cell stage onwards, whereas HP1γ showed diffuse cytoplasmic/nuclear localization at the two‐ and eight‐cell stages, and predominantly nuclear localization at the four‐cell stage and the 16‐cell stage onwards. Leptomycin B (LMB), a specific inhibitor of the nuclear export protein CRM‐1 (chromosomal regional maintenance‐1), was found to increase nuclear localization of HP1γ at the eight‐cell stage, and to prevent progression past this stage of embryogenesis. This indicates that HP1γ possesses a CRM‐1‐dependent nuclear export pathway which may represent part of the basis of HP1γ's ability to shuttle between the nucleus and the cytoplasm in dynamic fashion. HP1α was expressed in embryonic nuclei at all stages, but was found to relocalise from euchromatin to heterochromatin during the maternal to embryonic transition (MET). In contrast, Pc2 and Pc3 were evenly distributed between cytoplasm and nucleus until the eight‐ and sixteen‐cell stages or the morula stage, respectively, before relocating preferentially to the cytoplasm. Collectively, the results suggest that dynamic changes of the nuclear‐cytoplasmic and subnuclear distribution of members of the Cbx family may be central to the MET. Mol. Reprod. Dev. 75: 477–488, 2008. © 2007 Wiley‐Liss, Inc.