Formation of the sea urchin male pronucleus in vitro: Membrane‐independent chromatin decondensation and nuclear envelope‐dependent nuclear swelling

Collas, Philippe; Poccia, Dominic

doi:10.1002/mrd.1080420114

Cited by 34 publications

(24 citation statements)

References 26 publications

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“…In spite of the complexity of this mechanism, we could not observe any difference between the nucleons versus normal sperm nuclei swelling patterns, being practically twin patterns (Figure 3). Studies in different animal species and particular sea urchin sperm show that male pronuclear development in vitro is a two-step process involving membrane-independent chromatin decondensation and nuclear envelope-dependent pronuclear swelling [13].…”

Section: Discussionmentioning

confidence: 99%

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Nucleons, I: A Model for Studying the Mechanism of Sperm Nucleus Swelling in Vitro

Delgado¹,

Sánchez-Vázquez²,

Reyes³

et al. 1999

Archives of Andrology

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Section: Discussionmentioning

confidence: 99%

“…Studies may shed light upon the following chromatin decondensation mechanisms: (1) role of the perinuclear theca, lamin, and calicin [33,40,53], (2) sperm structure integrity, membrane influence, and the requirement of being alive or dead [1,13,20,23,26], and (3) clinical semen analysis to predict the sperm fertilizing ability [12,19,27,47].…”

mentioning

confidence: 99%

Nucleons, I: A Model for Studying the Mechanism of Sperm Nucleus Swelling in Vitro

Delgado¹,

Sánchez-Vázquez²,

Reyes³

et al. 1999

Archives of Andrology

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“…To determine whether Ca 2ϩ was required for lamin solubilization in interphase fertilized egg cytosol, sperm nuclei were incubated in cytosol containing 5 mM of the Ca 2ϩ chelator BAPTA (a concentration that inhibits NE growth associated with completion of male pronuclear formation in vitro) (32) and lamin B solubilization was examined by immunofluorescence. BAPTA blocked lamin solubilization and chromatin decondensation ( Fig.…”

Section: Phosphorylation and Solubilization Of Lamin B In Interphasementioning

confidence: 99%

“…Phosphorylation of lamin B was directly demonstrated by rapid (1 min) 32 P incorporation into sperm lamin B (Fig. 1C, upper panel), immediately followed by the release of phosphorylated lamin into the cytosol (Fig.…”

Section: Phosphorylation and Solubilization Of Lamin B In Interphasementioning

confidence: 99%

Protein Kinase C-mediated Interphase Lamin B Phosphorylation and Solubilization

Collas¹,

Thompson²,

Fields³

et al. 1997

Journal of Biological Chemistry

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Disassembly of the sperm nuclear envelope at fertilization is one of the earliest events in the development of the male pronucleus. We report that nuclear lamina disassembly in interphase sea urchin egg cytosol is a result of lamin B phosphorylation mediated by protein kinase C (PKC). Lamin B of permeabilized sea urchin sperm nuclei incubated in fertilized egg G 1 phase cytosolic extract is phosphorylated within 1 min of incubation and solubilized prior to sperm chromatin decondensation. Phosphorylation is Ca 2؉ -dependent. It is reversibly inhibited by the PKC-specific inhibitor chelerythrine, a PKC pseudosubstrate inhibitor peptide, and a PKC substrate peptide, but not by inhibitors of PKA, p34 cdc2 or calmodulin kinase II. Phosphorylation is inhibited by immunodepletion of cytosolic PKC and restored by addition of purified rat brain PKC. Sperm lamin B is a substrate for rat brain PKC in vitro, resulting in lamin B solubilization. Two-dimensional phosphopeptide maps of lamin B phosphorylated by the cytosolic kinase and by purified rat PKC are virtually identical. These data suggest that PKC is the major kinase required for interphase disassembly of the sperm lamina.The nuclear lamina consists of a polymeric network of intermediate filament molecules, the nuclear lamins, underlying the inner nuclear membrane. The lamina is a dynamic structure, undergoing expansion during interphase of the cell cycle, and depolymerization at mitosis upon breakdown of the nuclear envelope (NE) 1 (1). Mitotic disassembly and reassembly of the lamina is regulated by reversible lamin phosphorylation and dephosphorylation (1). Interphase lamin phosphorylation has also been reported (2-6), but its significance is not fully understood.Several lamin kinases have been identified that promote mitotic lamina solubilization or inhibit lamina assembly in vitro. They include cyclin B/p34 cdc2 (7), S6 kinase II (8), protein kinase C (PKC) (4, 9), and the cAMP-dependent protein kinase PKA (10). Down-regulation of PKA has also been shown to be essential for mitotic lamina disassembly (11). Although not a lamin kinase, Ca 2ϩ /calmodulin-dependent kinase II (CaM kinase II) is also involved in mitotic NE breakdown in sea urchin embryos (12). PKC has also been shown to phosphorylate chicken lamin B 2 in interphase, a process thought to regulate lamin import into the nucleus (13). These observations imply that multiple kinases regulate the dynamics of the nuclear lamina during the cell cycle. The transformation of the sea urchin sperm nucleus into a pronucleus at fertilization provides an opportunity to investigate NE assembly/disassembly during interphase. Sea urchin eggs are fertilized in G 1 phase of the first cell cycle after completion of both meiotic divisions. At fertilization, the sperm NE vesiculates and a new NE reforms around the male pronucleus as the sperm chromatin decondenses (14). Male pronuclear formation has been duplicated in a cell-free system by incubating detergent-permeabilized sperm nuclei in fertilized egg extracts (15)(16)(1...

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“…Basal levels of Ca# + are required for membrane fusion [22,23]. NEs formed in 12 mM EGTA, in which Ca# + levels were measured at less than 100 nM, but not in 5 mM BAPTA [bis-(o-aminophenoxy)ethane-N,N,Nh,Nh-tetra-acetic acid], indicating that extremely low levels of Ca# + are required.…”

Section: Bacterial Pi-plc Induces Ne Formationmentioning

confidence: 99%