Exogenous Expression of Human Protamine 1 (hPrm1) Remodels Fibroblast Nuclei into Spermatid-like Structures

• In vitro protaminization of somatic cell nuclei
• Conversion of interphase somatic nuclei into “spermatid-like” structures
• Protaminization of somatic nuclei that is reversed upon injection into enucleated oocytes
• A simplified model of nuclear remodeling and reprogramming in vitro

SummaryProtamines confer a compact structure to the genome of male gametes. Here, we find that somatic cells can be remodeled by transient expression of protamine 1 (Prm1). Ectopically expressed Prm1 forms scattered foci in the nuclei of fibroblasts, which coalescence into spermatid-like structures, concomitant with a loss of histones and a reprogramming barrier, H3 lysine 9 methylation. Protaminized nuclei injected into enucleated oocytes efficiently underwent protamine to maternal histone TH2B exchange and developed into normal blastocyst stage embryos in vitro. Altogether, our findings present a model to study male-specific chromatin remodeling, which can be exploited for the improvement of somatic cell nuclear transfer.

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