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General Comment |
Fu G, et al reported that Mouse Oocytes and Early Embryos Express Multiple Histone H1 Subtypes.
They report that oocytes and embryos contain mRNA encoding H1(). A PCR-based test indicated that the poly(A) tail did not lengthen during meiotic maturation, although it did so beginning at the 4-cell stage. Antibodies raised against histone H1() stained the nucleus of wild-type prophase-arrested oocytes but not of mice lacking the H1() gene. Following fertilization, H1() was detected in the nuclei of 2-cell embryos and less strongly at the 4-cell stage. No signal was detected in H1() -/- embryos. Radiolabelling revealed that species co-migrating with the somatic H1 subtypes H1a and H1c were synthesized in maturing oocytes and in 1- and 2-cell embryos. Beginning at the 4-cell stage in both wild-type and H1() -/- embryos, species co-migrating with subtypes H1b, H1d and H1e were additionally synthesized. These results establish that histone H1() constitutes a portion of the linker histone complement in oocytes and early embryos, and that changes in the pattern of somatic H1 synthesis occur during early embryonic development. Taken together with previous results, these findings suggest that multiple H1 subtypes are present on oocyte chromatin and that following fertilization changes in the histone H1 complement accompany the establishment of regulated embryonic gene expression.
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