1 Department of Veterinary and Animal Sciences, University of Massachusetts,
Amherst, MA 01003, USA
2 Hematech, LLC, 4401 Technology Drive, Sioux Falls, SD 57106, USA
3 Institute of Medical Biochemistry, University of Oslo, PO Box 1112 Blindern,
0317 Oslo, Norway
Author for correspondence (e-mail:
philippe.collas{at}basalmed.uio.no)
Accepted 28 May 2003
![]() |
Summary |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: Chromatin, Embryo, Mouse, Nuclear envelope, Nuclear transplantation
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
We have chosen to examine molecular markers of the nuclear envelope, of a nonionic detergent-, nuclease- and salt-resistant `nuclear matrix' structure, and of the interface between the nuclear envelope and chromatin. There is increasing evidence that the nuclear envelope is more than just a barrier around chromosomes: it also plays a crucial role in maintaining the integrity of genome function via interactions with the nuclear matrix and chromatin.
The nuclear envelope consists of two concentric membranes, nuclear pores
and the nuclear lamina, a meshwork of intermediate filaments called A- and
B-type lamins (reviewed in Gruenbaum et
al., 2000). A-type lamins include lamins A and C, which are splice
variants of the LMNA gene in humans and are expressed in
differentiated somatic cells (Guilly et
al., 1990
). B-type lamins include lamins B1 and B2, products of
the LMNB1 and LMNB2 genes, respectively, and are
ubiquitously expressed (Gruenbaum et al.,
2000
). Lamins mediate interactions between the inner nuclear
membrane and chromatin or DNA and play a functional role in the nucleus.
Disorganization of the lamina with dominant negative lamin mutants alters
replication (Ellis et al.,
1997
; Spann et al.,
1997
; Moir et al.,
2000
) and improper assembly of the lamina at the end of mitosis
leads to cell death (Steen and Collas,
2001
). Intranuclear lamin foci also co-localize with RNA splicing
factors, suggesting that lamins might contribute to organizing the RNA
processing machinery (Jagatheesan et al.,
1999
). Moreover, the discovery that mutations in the LMNA
gene cause life-threatening hereditary disorders affecting skeletal, cardiac
and adipose tissues (reviewed in Vigouroux
and Bonne, 2002
) suggests a role for the nuclear envelope in the
regulation of gene expression. Interestingly, Lmna null mice display
phenotypes reminiscent of those created by lamin A/C mutations in humans
(Sullivan et al., 1999
).
The nuclear and mitotic apparatus (NuMA) protein is a 240-kDa
intranuclear protein that is distributed into each daughter cell during
mitosis by association with the spindle apparatus
(Zeng, 2000
;
He et al., 1995
;
Compton and Cleveland, 1994
).
In interphase, NuMA is a major structural component of the nuclear matrix
(Harborth and Osborn, 1999
;
Compton and Cleveland, 1994
).
Mutational analyses have shown that functional NuMA is required during mitosis
for the terminal phases of chromosome separation and/or nuclear reassembly to
occur (Compton and Cleveland,
1993
;Compton and Cleveland,
1994
).
A-kinase anchoring protein 95 (AKAP95) is a 95-kDa protein that binds the
cAMP-dependent protein kinase at mitosis
(Coghlan et al., 1994;
Eide et al., 1998
) and is
implicated in recruiting components required for chromosome condensation in
human cultured cells (Collas et al.,
1999
) and in mouse female pronuclei
(Bomar et al., 2002
). In
interphase, AKAP95 is a nuclear protein that primarily associates with the
nuclear matrix, although a small proportion also co-fractionates with
nuclease-soluble chromatin (Collas et al.,
1999
). The role of AKAP95 in the nucleus remains elusive but
recent data localizing AKAP95 preferentially to transcriptionally silent
(hypoacetylated) chromatin in HeLa and mouse cumulus cells (P.N.M. et al.,
unpublished) suggest that AKAP95 might interface the chromatin with the
nuclear envelope. The growing evidence that AKAPs can anchor several signaling
molecules (Feliciello et al.,
2001
; Smith and Scott,
2002
; Tasken et al.,
2001
) raises the possibility that AKAP95 might function in
integrating multiple signaling pathways in the nucleus.
Here, we characterize the dynamics of A- and B-type lamins and NuMA, and variations in intranuclear anchoring properties of AKAP95 following NT in the mouse. We show that some of these structural and functional proteins constitute markers of incomplete somatic nuclear remodeling by NT. Partial remodeling is manifested by the identification of structural abnormalities in nuclei of NT embryos.
![]() |
Materials and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Oocyte and embryo collection
Metaphase II (MII) oocytes and fertilized pronuclear stage embryos were
collected from superovulated B6D2F1 mice 14 and 20 hours after injections of
human chorionic gonadotrophin (hphCG) injection, respectively. Cumulus cells
were dispersed with 300 U ml-1 hyaluronidase and oocytes or embryos
were cultured in Potassium Simplex Optimized Media (KSOM; Specialty Media) at
38°C in an atmosphere of 5% CO2 in air. Oocytes were
micromanipulated at 15 hphCG.
Intracytoplasmic sperm injection
Intracytoplasmic sperm injection (ICSI) was performed as described
(Bomar et al., 2002;
Wakayama et al., 1998b
).
Briefly, sperm heads thawed after storage in liquid nitrogen were washed in
PBS containing 3 mg ml-1 bovine serum albumin (BSA) and 10%
polyvinylpyrrolidone. ICSI was performed at 19°C in PBS containing 3%BSA
using a piezoelectric drill. After a 15-minute recovery at 35°C, oocytes
were cultured in KSOM.
NT and oocyte activation
NT with cumulus cell donor nuclei was done as described
(Wakayama et al., 1998a) with
minor alterations. Cells obtained from four to eight cumulus-oocyte complexes
were washed in
-Modified Eagle's Medium (
-MEM; Gibco-BRL),
resuspended in 100 µl
-MEM and cultured until use. MII oocyte
enucleation was carried out by aspiration of a translucid cytoplasmic area
containing the metaphase plate in Flushing Holding Medium (FHM; Specialty
Media) containing 5 µg ml-1 cytochalasin B. Enucleated oocytes
were washed and returned to culture. After
2 hours, cumulus cells were
transferred to FHM containing 10% polyvinyl pyrrolidone, lysed in a pipette
attached to a piezoelectric micromanipulator and a single nucleus was injected
into an enucleated oocyte. Oocytes were cultured in KSOM for at least 1 hour
before artificial activation.
Recipient oocytes were activated for 6 hours with 10 mM SrCl2 in Ca2+-free CZB medium (Specialty Media) containing 5 µg ml-1 cytochalasin B to prevent polar body extrusion. For inhibition of transcription or protein synthesis in NT embryos, activation medium contained 5 µg ml-1 actinomycin D (ActD; Sigma) or 20 µg ml-1 cycloheximide (CHX; Sigma), respectively. At the end of treatment, embryos were washed and cultured in KSOM. Parthenogenetic activation of MII oocytes was carried out as for NT embryos in the presence of 5 µg ml-1 cytochalasin B to maintain diploidy.
Immunological procedures
Proteins from cells, oocytes and embryos (n>200) were resolved
by 10% SDS-PAGE, transferred to nitrocellulose
(Bomar et al., 2002) and probed
with the following antibodies: anti-AKAP95 (1:250 dilution) and rabbit
anti-lamin-B (1:1,000), anti-lamin-A/C (1:500) and anti-NuMA (1:500). Blots
were incubated with peroxidaseconjugated secondary antibodies and developed by
enhanced chemiluminescence (Amersham). For immunofluorescence analysis, cells,
oocytes and embryos were settled onto poly-L-lysine-coated coverslips. Samples
were either fixed with 3% paraformaldehyde and permeabilized with 0.1% Triton
X-100 (Bomar et al., 2002
) or
extracted with 0.1% Triton X-100, 1 mg ml-1 DNase I, 100 µg
ml-1 RNase A containing 100 mM NaCl or 300 mM NaCl in Tris-HCl
buffer (pH 7.2) for 30 minutes before fixation
(Martins et al., 2000
).
Proteins were blocked in PBS containing 2% BSA and 0.01% Tween-20. Primary
antibodies (1:100 dilution) and TRITC- or FITC-conjugated secondary antibodies
were incubated each for 30 minutes. DNA was stained with 0.1 µg
ml-1 Hoechst 33342 or 0.1 µg ml-1 propidium iodide as
indicated.
Microscopy and image analysis
Observations were made on an Olympus BX60 microscope and photographs were
taken with a JVC CCD camera and processed using Adobe Photoshop.
Quantification of fluorescence signals was performed with AnalySIS and data
expressed as the mean±s.d. of relative fluorescence intensities.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Immunofluorescence analysis of preimplantation embryos is shown in
Fig. 1B. In fertilized embryos,
lamin B was detected at the nuclear periphery at all stages examined. Lamin
A/C, however, was not detected up to the blastocyst stage, as expected from a
marker of differentiated cells. AKAP95 labeling was restricted to the female
pronucleus (FPN), the smaller of the two pronuclei, as detected by Hoechst
labeling (Fig. 1C), confirming
our earlier observations (Bomar et al.,
2002). Intranuclear localization of AKAP95 was observed in nuclei
of all blastomeres in subsequent developmental stages. Similar to AKAP95, NuMA
labeling occurred only in the FPN at the pronuclear stage
(Fig. 1B,C) and in nuclei of
all blastomeres thereafter. Detection of lamin B, NuMA and AKAP95, but not of
lamin A/C, in pronuclear stage embryos was confirmed on western blots
(Fig. 1D). The blotting data
indicate that the lack of immunofluorescence labeling of lamin A/C in
preimplantation embryos was not due to antigen masking but rather to the
absence of the protein. Because A-type lamins are expressed in differentiated
somatic cells, we rationalized that they constitute a potential marker of
nuclear remodeling by NT.
Dynamics of nuclear lamins, NuMA and AKAP95 following NT
The dynamics of lamin B, lamin A/C, AKAP95 and NuMA were examined during
morphological remodeling associated with transplantation of cumulus cell
nuclei into enucleated oocytes. Reconstituted embryos were activated with
SrCl2 for 6 hours starting 2 hours after NT. Donor nuclei
underwent premature chromatin condensation (PCC) within 3 hours of injection
into oocytes in all embryos examined (n=20), as shown by DNA staining
with Hoechst 33342 (Fig. 2,
PCC). By 7 hours after injection, embryos contained fully expanded nuclei
(Fig. 2, NT PN). Notably, in
all experiments conducted in this study, 89% of activated NT embryos displayed
more than one reconstituted nucleus, but each of these nuclei was similar to
those shown in Fig. 2. This
observation is largely consistent with previous reports of NT in the mouse
(e.g. Wakayama et al., 1998a
;
Wakayama et al., 1999
) but
reasons for the formation of multiple nuclei following NT remain
unexplored.
|
PCC and interphase one-cell-stage NT embryos and, as controls,
parthenogenetic pronuclei were analysed by immunofluorescence
(Fig. 2). AKAP95 was associated
with PCC, a property consistent with the chromosome association of AKAP95 in
mitotic somatic cells and blastomeres
(Collas et al., 1999;
Bomar et al., 2002
). Lamins A/C
and B were not detected on chromosomes, probably as a result of their
dispersal in the egg cytoplasm (data not shown). Likewise, NuMA was absent
from the condensed chromosomes and showed signs of association with polar
structures on either side of the chromosome plate. At the one-cell stage, all
markers were detected in the nuclei of reconstructed embryos
(Fig. 2, NT Int.). Lamin B was
detected in NT nuclei and parthenogenetic pronuclei. Remarkably, lamins A/C
were also detected at the nuclear envelope of NT embryos, which contrasted
with their absence from the pronuclear envelope of parthenotes (Part PN) or
fertilized embryos (Fig. 1B).
NuMA also displayed consistently strong intranuclear labeling in NT embryos,
which contrasted with the weak labeling detected in parthenogenetic pronuclei
(Fig. 2). Weaker NuMA labeling
in parthenogenetic nuclei could not be accounted for by a reduced DNA content,
because parthenotes were diploidized with cytochalasin B after activation.
Rather, it probably reflected a lower concentration of protein in these nuclei
(see below). Lastly, AKAP95 decorated the nuclear interior except nucleoli in
nuclei of NT embryos and parthenotes, consistent with its localization in
fertilized embryos. We concluded from these observations that reconstituted
nuclei of NT embryos express strong lamin A/C and NuMA immunoreactivity, two
characteristics of the somatic donor cells.
Misregulation of A-type lamin expression in NT embryos
We determined whether the assembly of lamin A/C in nuclei of NT embryos
resulted from (i) retargeting of somatic lamins disassembled upon PCC, (ii)
translation and assembly of lamins from a pool of maternal lamin A/C mRNA or
(iii) de novo transcription of the somatic Lmna gene in reconstituted
NT nuclei. To distinguish between these possibilities, mouse NT embryos were
activated with SrCl2 as described in Materials and Methods,
activated in the presence of the protein synthesis inhibitor cycloheximide
(CHX) or activated in the presence of the RNA polymerase II inhibitor
actinomycin D (ActD) to inhibit transcription. The results are shown in
Fig. 3. Activation with 20
µg ml-1 CHX or 5 µg ml-1 ActD, both compatible
with nuclear reformation, inhibited lamin A/C assembly. This argues that lamin
A/C assembly resulted from transcription of the somatic Lmna gene
rather than from retargeting from a somatic pool brought into the oocyte
during the NT procedure. Lamin B assembly was not affected by CHX or ActD,
suggesting that lamin B was retargeted to chromosomes from a disassembled
somatic pool and/or from a maternal pool of lamins. Essentially no NuMA was
seen after CHX exposure but 40% NuMA immunoreactivity was detected in NT
nuclei after ActD treatment. This suggests that NuMA reassembled as a result
of translation from maternal mRNA and of de novo transcription from the
transplanted genome. AKAP95 detection was not altered in CHX- or ActD-treated
NT embryos, suggesting that a large proportion at least of nuclear AKAP95 is
presumably of somatic origin. Therefore, because lamins A/C and NuMA appear to
be abnormally transcribed in NT nuclei, we propose that they constitute two
markers of incomplete nuclear remodeling in the oocyte.
|
Different anchoring of AKAP95 in nuclei of fertilized and NT
embryos
The next marker of nuclear remodeling examined was the intranuclear
anchoring properties of AKAP95 in reconstituted nuclei of one-cell-stage NT
embryos. AKAP95 was the only marker investigated that was detected in somatic
donor nuclei, on PCC chromosomes and in NT nuclei with a labeling intensity
similar to that of parthenotes and fertilized embryos, and, as such, it did
not appear to be a valuable marker of nuclear remodeling by NT. Nevertheless,
the strength of AKAP95 association with intranuclear ligands (the nature of
which remains to be explored) was examined by in situ extraction of ICSI
embryos, NT embryos, parthenotes and cumulus cells with 0.1% Triton X-100, 1
mg ml-1 DNase I and 100 µg ml-1 RNase A together with
100 mM NaCl or 300 mM NaCl. In ICSI female pronuclei, nearly all AKAP95 and
all detectable DNA were extracted under 100 mM NaCl
(Fig. 4, FPN); male pronuclei
do not harbor any AKAP95 (Bomar et al.,
2002). Similarly, in parthenotes
90% of AKAP95 and DNA was
extracted under 100 mM NaCl, and
98% of AKAP95 was removed under 300 mM
NaCl. By contrast, a significant proportion of AKAP95 and DNA (
50%) was
resistant to extraction even under 300 mM NaCl in nuclei of NT embryos
(Fig. 4). Resistance of AKAP95
and DNA to extraction in NT nuclei resembled that of cumulus cell nuclei
(Fig. 4B). Notably, no
detectable lamin B extraction occurred in ICSI, parthenote or NT nuclei
regardless of extraction conditions (Fig.
4), suggesting that alterations in AKAP95 and DNA distributions
did not result merely from gross changes in nuclear architecture. These
results imply that NT nuclei are characterized by tight anchoring of AKAP95 to
intranuclear ligands and restricted DNA accessibility to DNase I. They also
suggest that nuclei produced by somatic NT display structural abnormalities as
a result of incomplete morphological remodeling of donor nuclei and/or
transcriptional misregulation of somatic genes.
|
Passage through first mitosis does not rescue nuclear anomalies in NT
embryos
Mitosis involves extensive morphological remodeling of the nucleus,
including breakdown of the nuclear envelope, condensation of chromosomes and
reformation of a new nuclear envelope as the separated sets of chromosomes
decondense. We rationalized that, although passage through PCC did not allow a
complete remodeling of the somatic nucleus, passage through mitosis might
enable completion of nuclear remodeling. To test this hypothesis, we examined
lamin A/C immunolabeling and the resistance of AKAP95 to in situ extraction
with 0.1% Triton X-100, 1 mg ml-1 DNase I and 100 µg
ml-1 RNase A in 300 mM NaCl in two-cell-stage NT and ICSI embryos.
In contrast to ICSI embryos, two-cell-stage NT embryos displayed lamin A/C
labeling in each blastomere (Fig.
5A), whereas lamin B distribution was similar in ISCI and NT
two-cell-stage embryos (data not shown). Furthermore, as in one-cell-stage
embryos, more AKAP95 and DNA were resistant to detergent, nuclease and salt
extraction in nuclei of NT embryos than in ICSI embryos
(Fig. 5B,C). In addition, both
lamin A/C labeling and enhanced resistance to extraction of DNA and AKAP95
were detected in later-stage preimplantation NT embryos (data not shown). We
concluded from these observations that passage of NT embryos through first
mitosis does not further remodel donor somatic nuclei, at least based on lamin
A/C labeling and intranuclear AKAP95 anchoring properties.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
We tested the hypothesis that passage through mitosis might restore nuclear abnormalities detected and further remodel the donor nucleus. This hypothesis was rejected on the basis that first mitosis did not eliminate perinuclear lamin A/C labeling, nor did it readjust the strength of intranuclear AKAP95 anchoring. Together with the apparent lack of Lmna gene inactivation in nuclei reconstituted after PCC, this finding implies that mitotic chromosome condensation per se is not sufficient to elicit inactivation of the Lmna gene in the subsequent cell cycle. A second implication is that PCC or first embryonic mitotic chromosome condensation does not significantly reset the overall chromatin organization of the parent cell to remodel it into an embryonic pattern, at least based on nuclease sensitivity of DNA and AKAP95 anchoring. We do not, however, exclude the possibility that progressive remodeling occurs with each blastomere division, such that embryonic chromatin organization is obtained later in development.
A significant observation is that the Lmna gene most likely
remains active in nuclei of pre-implantation NT embryos, as judged by
inhibition of transcription and translation after NT. This resulted in the
assembly of differentiated cell-specific A-type lamins. The lack of
immunodetection of A-type lamins in fertilized preimplantation embryos
contradicts a previous report where these epitopes were recognized in the
mouse embryo at least until the 8-cell stage
(Prather et al., 1991).
Reasons for this discrepancy are unclear but might involve the source of
antibodies used. Through interactions with chromatin and components of the RNA
processing machinery, nuclear lamins have been suggested to participate in the
regulation of transcription (Jagatheesan
et al., 1999
). Thus, assembly of the correct set of lamins is
probably crucial for proper nuclear function in NT embryos. One hypothesis is
that aberrant assembly of A-type lamins might lead to sequestration of
transcriptional regulators important for the activation of developmental
genes. Alternatively, because A-type lamins bind DNA (Stierlé et al.,
2003), its untimely presence in the nuclear envelope might affect chromatin
modifications, replication or transcription in these areas. Although
technically challenging, it would be interesting to determine whether the low
proportion of NT embryos developing to term and remaining healthy after birth
are those not harboring lamins A/C during preimplantation development or
whether, on the contrary, this anomaly is compatible with normal development
and health.
Like Lmna, the NuMA gene apparently also remains active
in nuclei of one-cell stage NT embryos, resulting in apparent NuMA
overexpression in NT pronuclei. Owing to its involvement in the formation and
maintenance of the mitotic spindle
(Compton and Cleveland, 1994;
Compton, 1998
), NuMA
overexpression might lead to abnormal chromosome segregation and aneuploidy.
Moreover, the suggested involvement of NuMA with various nuclear functions
(Gribbon et al., 2002
;
Barboro et al., 2002
) suggests
that misregulated NuMA levels in NT embryos might also affect functions
important for normal development. This hypothesis remains to be tested.
We observed that AKAP95, a component of the matrix-chromatin interface in somatic cells, was more strongly associated with its as-yet-unidentified ligands in nuclei of NT embryos than in fertilized embryos or parthenogenetic pronuclei. This association might impose constraints on DNA organization or result from altered chromatin conformation in NT embryos. In any event, because most chromatin-bound AKAP95 remains associated with DNase-I-resistant DNA, which is mostly transcriptionally silent, we propose that increased resistance of AKAP95 to extraction by nucleases and salt reflects an enhanced proportion of heterochromatin in early NT embryos. This, in turn, raises the speculative hypothesis that expression of developmentally important genes might be affected. It will be interesting to identify and investigate the transcriptional regulation of genes involved in placental development, maintenance of late pregnancy and post-natal survival of cloned animals.
![]() |
Acknowledgments |
---|
![]() |
Footnotes |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Barboro, P., D'Arrigo, C., Diaspro, A., Mormino, M., Alberti, I., Parodi, S., Patrone, E. and Balbi, C. (2002). Unraveling the organization of the internal nuclear matrix: RNA-dependent anchoring of NuMA to a lamin scaffold. Exp. Cell Res. 279, 202-218.[CrossRef][Medline]
Barnes, F. L., Collas, P., Powell, R., King, W. A., Westhusin, M. and Sheperd, D. (1993). Influence of recipient oocyte cell cycle stage on DNA synthesis, nuclear envelope breakdown, chromosome constitution and development in nuclear transplant bovine embryos. Mol. Reprod. Devel. 36, 33-41.[Medline]
Bomar, J., Moreira, P., Balise, J. J. and Collas, P.
(2002). Differential regulation of maternal and paternal
chromosome condensation in mitotic zygotes. J. Cell
Sci. 115,
2931-2940.
Chaudhary, N. and Courvalin, J.-C. (1993). Stepwise reassembly of the nuclear envelope at the end of mitosis. J. Cell Biol. 122, 295-306.[Abstract]
Cibelli, J. B., Campbell, K. H., Seidel, G. E., West, M. D. and Lanza, R. P. (2002). The health profile of cloned animals. Nat. Biotechnol. 20, 13-14.[CrossRef][Medline]
Coghlan, V. M., Langeberg, L. K., Fernandez, A., Lamb, N. J. and
Scott, J. D. (1994). Cloning and characterization of AKAP 95,
a nuclear protein that associates with the regulatory subunit of type II
cAMP-dependent protein kinase. J. Biol. Chem.
269,
7658-7665.
Collas, P. and Robl, J. M. (1991). Relationship between nuclear remodeling and development in nuclear transplant rabbit embryos. Biol. Reprod. 45, 455-465.[Abstract]
Collas, P., Le Guellec, K. and Tasken, K.
(1999). The A-kinase anchoring protein, AKAP95, is a multivalent
protein with a key role in chromatin condensation at mitosis. J.
Cell Biol. 147,
1167-1180.
Compton, D. A. (1998). Focusing on spindle
poles. J. Cell Sci. 111,
1477-1481.
Compton, D. A. and Cleveland, D. W. (1993). NuMA is required for the proper completion of mitosis. J. Cell Biol. 120, 947-957.[Abstract]
Compton, D. A. and Cleveland, D. W. (1994). NuMA, a nuclear protein involved in mitosis and nuclear reformation. Curr. Opin. Cell Biol. 6, 343-346.[Medline]
Eide, T., Coghlan, V., Orstavik, S., Holsve, C., Solberg, R., Skalhegg, B. S., Lamb, N. J., Langeberg, L., Fernandez, A., Scott, J. D. et al. (1998). Molecular cloning, chromosomal localization, and cell cycle-dependent subcellular distribution of the A-kinase anchoring protein, AKAP95. Exp. Cell Res. 238, 305-316.[CrossRef][Medline]
Ellis, D. J., Jenkins, H., Whitfield, W. G. and Hutchison, C.
J. (1997). GST-lamin fusion proteins act as dominant negative
mutants in Xenopus egg extract and reveal the function of the lamina
in DNA replication. J. Cell Sci
110,
2507-2518.
Feliciello, A., Gottesman, M. E. and Avvedimento, E. V. (2001). The biological functions of A-kinase anchor proteins. J. Mol. Biol. 308, 99-114.[CrossRef][Medline]
Gribbon, C., Dahm, R., Prescott, A. R. and Quinlan, R. A. (2002). Association of the nuclear matrix component NuMA with the Cajal body and nuclear speckle compartments during transitions in transcriptional activity in lens cell differentiation. Eur. J. Cell Biol. 81, 557-566.[Medline]
Gruenbaum, Y., Wilson, K. L., Harel, A., Goldberg, M. and Cohen, M. (2000). Review: nuclear lamins - structural proteins with fundamental functions. J. Struct. Biol. 129, 313-323.[CrossRef][Medline]
Guilly, M.-N., Kobl, J.-P., Gosti, F., Godeau, F. and Courvalin, J.-C. (1990). Lamins A and C are not expressed at early stages of human lymphocyte differentiation. Exp. Cell Res. 189, 145-147.[Medline]
Harborth, J. and Osborn, M. (1999). Does NuMA have a scaffold function in the interphase nucleus? Crit. Rev. Eukaryotic Gene Expr. 9, 319-328.[Medline]
Hashizume, K., Ishiwata, H., Kizaki, K., Yamada, O., Takahashi, T., Imai, K., Patel, O. V., Akagi, S., Shimizu, M., Takahashi, S. et al. (2002). Implantation and placental development in somatic cell clone recipient cows. Cloning Stem Cells 4, 197-209.[CrossRef][Medline]
He, D., Zeng, C. and Brinkley, B. R. (1995). Nuclear matrix proteins as structural and functional components of the mitotic apparatus. Int. Rev. Cytol. 162, 1-74.
Jagatheesan, G., Thanumalayan, S., Muralikrishna, B., Rangaraj,
N., Karande, A. A. and Parnaik, V. K. (1999). Colocalization
of intranuclear lamin foci with RNA splicing factors. J. Cell
Sci. 112,
4651-4661.
Kasinathan, P., Knott, J. G., Moreira, P. N., Burnside, A. S.,
Jerry, D. J. and Robl, J. M. (2001a). Effect of fibroblast
donor cell age and cell cycle on development of bovine nuclear transfer
embryos in vitro. Biol. Reprod.
64,
1487-1493.
Kasinathan, P., Knott, J. G., Wang, Z., Jerry, D. J. and Robl, J. M. (2001b). Production of calves from G1 fibroblasts. Nat. Biotechnol. 19, 1176-1178.[CrossRef][Medline]
Lanza, R. P., Cibelli, J. B., Faber, D., Sweeney, R. W.,
Henderson, B., Nevala, W., West, M. D. and Wettstein, P. J.
(2001). Cloned cattle can be healthy and normal.
Science 294,
1893-1894.
Martins, S. B., Eide, T., Steen, R. L., Jahnsen, T.,
Skålhegg, B. S. and Collas, P. (2000). HA95 is a
protein of the chromatin and nuclear matrix regulating nuclear envelope
dynamics. J. Cell Sci.
113,
3703-3713.
Moir, R. D., Spann, T. P., Herrmann, H. and Goldman, R. D.
(2000). Disruption of nuclear lamin organization blocks the
elongation phase of DNA replication. J. Cell Biol.
149,
1179-1192.
Oback, B. and Wells, D. (2002). Donor cells for nuclear cloning: many are called, but few are chosen. Cloning Stem Cells 4, 147-168.[CrossRef][Medline]
Prather, R. S., Kubiak, J., Maul, G. G., First, N. L. and Schatten, G. (1991). The expression of nuclear lamin A and C epitopes is regulated by the developmental stage of the cytoplasm in mouse oocytes or embryos. J. Exp. Zool. 257, 110-114.[Medline]
Smith, F. D. and Scott, J. D. (2002). Signaling complexes: junctions on the intracellular information super highway. Curr. Biol. 12, R32-R40.[CrossRef][Medline]
Spann, T. P., Moir, R. D., Goldman, A. E., Stick, R. and
Goldman, R. D. (1997). Disruption of nuclear lamin
organization alters the distribution of replication factors and inhibits DNA
synthesis. J. Cell Biol.
136,
1201-1212.
Steen, R. L. and Collas, P. (2001).
Mistargeting of B-type lamins at the end of mitosis: implications on cell
survival and regulation of lamins A/C expression. J. Cell
Biol. 153,
621-626.
Stice, S. L. and Robl, J. M. (1988). Nuclear reprogramming in nuclear transplant rabbit embryos. Biol. Reprod. 39, 657-664.[Abstract]
Stierlé, S., Couprie, J., Östlund, C., Krimm, I., Zinn-Justin, S., Hossenlopp, P., Worman, H. J., Courvalin, J.-C. and Duband-Goulet, I. The carboxyl-terminal region common to lamins A and C contains a DNA binding domain. Biochemistry 42, 4819-4828.
Sullivan, T., Escalante-Alcalde, D., Bhatt, H., Anver, M., Bhat,
N., Nagashima, K., Stewart, C. L. and Burke, B. (1999). Loss
of A-type lamin expression compromises nuclear envelope integrity leading to
muscular dystrophy. J. Cell Biol.
147,
913-920.
Tasken, K. A., Collas, P., Kemmner, W. A., Witczak, O., Conti,
M. and Tasken, K. (2001). Phosphodiesterase 4D and protein
kinase a type II constitute a signaling unit in the centrosomal area.
J. Biol. Chem. 276,
21999-22002.
Vigouroux, C. and Bonne, G. (2002). One gene, two proteins, five diseases. In Dynamics of the Nuclear Envelope in Embryos and Somatic Cells (ed. P. Collas), pp 153-172. Georgetown, TX: Landes Bioscience.
Wakayama, T., Perry, A. C., Zuccotti, M., Johnson, K. R. and Yanagimachi, R. (1998a). Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei. Nature 394, 369-374.[CrossRef][Medline]
Wakayama, T., Whittingham, D. G. and Yanagimachi, R. (1998b). Production of normal offspring from mouse oocytes injected with spermatozoa cryopreserved with or without cryoprotection. J. Reprod. Fertil. 112, 11-17.[Abstract]
Wakayama, T., Rodriguez, I., Perry, A. C., Yanagimachi, R. and
Mombaerts, P. (1999). Mice cloned from embryonic stem cells.
Proc. Natl. Acad. Sci. USA
96,
14984-14989.
Zeng, C. (2000). NuMA: a nuclear protein involved in mitotic centrosome function. Microsc. Res. Tech. 49, 467-477.[CrossRef][Medline]
Related articles in JCS: