The role of maternal VegT in establishing the primary germ layers in Xenopus embryos

VegT is a T-box transcription factor whose mRNA is synthesized during oogenesis and localized in the vegetal hemisphere of the egg and early embryo. We show that maternally expressed VegT controls the pattern of primary germ layer specification in Xenopus embryos. Reduction of the maternal store completely alters the fates of different regions of the blastula so that animal cell fate is changed from epidermis and nervous system to epidermis only, equatorial cell fate is changed from mesoderm to ectoderm, and vegetal cell fate is changed from endoderm to mesoderm and ectoderm. Vegetal cells lose their capacity both to form endoderm and to release mesoderm-inducing signals. These results show that a single maternally expressed gene controls the patterning of the Xenopus blastula.

Maternal beta-catenin establishes a ‘dorsal signal’ in early Xenopus embryos

In previous work, we demonstrated that maternally encoded beta-catenin, the vertebrate homolog of armadillo, is required for formation of dorsal axial structures in early Xenopus embryos (Heasman, J., Crawford, A., Goldstone, K., Garner-Hamrick, P., Gumbiner, B., Kintner, C., Yoshida-Noro, C. and Wylie, C. (1994). Cell 79, 791–803). Here we investigated, firstly, the role(s) of beta-catenin in spatial terms, in different regions of the embryo, by injecting beta-catenin mRNA into individual blastomeres of beta-catenin-depleted embryos at the 32 cell stage. The results indicate that beta-catenin can rescue the dorsal axial structures in a non-cell-autonomous way and without changing the fates of the injected cells. This suggests that cells overexpressing beta-catenin send a ‘dorsal signal’ to other cells. This was confirmed by showing that beta-catenin overexpressing animal caps did not cause wild-type caps to form mesoderm, but did cause isolated beta-catenin-deficient marginal zones to form dorsal mesoderm. Furthermore beta-catenin-deficient vegetal masses treated with overexpressing caps regained their ability to act as Nieuwkoop Centers. Secondly, we studied the temporal activity of beta-catenin. We showed that zygotic transcription of beta-catenin starts after the midblastula transition (MBT), but does not rescue dorsal axial structures. We further demonstrated that the vegetal mass does not release a dorsal signal until after the onset of transcription, at the midblastula stage, suggesting that maternal beta-catenin protein is required at or before this time. Thirdly we investigated where, in relationship to other gene products known to be active in axis formation, beta-catenin is placed. We find that BVg1, bFGF, tBR (the truncated form of BMP2/4R), siamois and noggin activities are all downstream of beta-catenin, as shown by the fact that injection of their mRNAs rescues the effect of depleting maternally encoded beta-catenin. Interference with the action of glycogen synthase kinase (GSK), a vertebrate homolog of the Drosophila gene product, zeste white 3 kinase, does not rescue the effect, suggesting that it is upstream.

Insulin reduces norepinephrine transporter mRNA in vivo in rat locus coeruleus

Acute and chronic in vitro insulin treatment can inhibit the uptake of norepinephrine (NE) by adult rat brain synaptosomes and slices, fetal neuronal cultures, and PC12 cells. In the present study we tested whether chronic in vivo insulin treatment could alter the biosynthetic capacity of rat locus coeruleus neurons for the NE transporter protein (NET). Chronic third ventricular insulin treatment resulted in a suppression of NET mRNA to about one third of the level of vehicle-treated controls. Our finding suggests that insulin may play a regulatory role in the synthesis of this transporter, thereby modulating activity in CNS noradrenergic pathways.

Preferentially localized dynein and perinuclear dynactin associate with nuclear pore complex proteins to mediate genomic union during mammalian fertilization

Fertilization is complete once the parental genomes unite, and requires the migration of the egg nucleus to the sperm nucleus (female and male pronuclei, respectively) on microtubules within the inseminated egg. Neither the molecular mechanism of pronucleus binding to microtubules nor the role of motor proteins in regulating pronuclear motility has been fully characterized, and the failure of zygotic development in some patients suggests that they contribute to human infertility. Based on the minus-end direction of female pronuclear migration, we propose a role for cytoplasmic dynein and dynactin in associating with the pronuclear envelope and mediating genomic union. Our results show that dynein intermediate and heavy chains preferentially concentrate around the female pronucleus, whereas dynactin subunits p150Glued, p50 and p62 localize to the surfaces of both pronuclei. Transfection of antibodies against dynein and dynactin block female pronuclear migration in zygotes. Both parthenogenetic activation in oocytes and microtubule depolymerization in zygotes significantly reduce the localization of dynein to the female pronucleus but do not inhibit the pronuclear association of dynactin. When immunoprecipitated from zygotes, p150Glued associates with nuclear pore complex proteins, as well as the intermediate filament vimentin and dynein. Antibodies against nucleoporins and vimentin inhibit pronuclear apposition when transfected into zygotes. We conclude that preferentially localized dynein and perinuclear dynactin associate with the nuclear pore complex and vimentin and are required to mediate genomic union. These data suggest a model in which dynein accumulates and binds to the female pronucleus on sperm aster microtubules, where it interacts with dynactin, nucleoporins and vimentin.

Involvement of polyamines in selenomethionine induced apoptosis and mitotic alterations in human tumor cells

The efficacy of dietary selenium supplementation is currently being evaluated in intervention trials. However, the biological mechanisms underlying the cancer chemopreventive effects of selenium supplementation have yet to be elucidated. Selenium metabolism and polyamine biosynthesis are linked in their common requirement for S-adenosylmethionine. Selenomethionine was the predominant form of selenium in the dietary supplement, therefore we evaluated the anti-tumorigenic effects of selenomethionine. We found that selenomethionine inhibited tumor growth (both in A549 lung and HT29 colon cancer cells) in a dose-dependent manner. At 24 and 72 h, polyamine content of A549 and HT29 cancer cell lines was decreased at doses that inhibited 50% of normal growth. Selenomethionine treatment induced apoptosis in both cancer cell lines. Exogenous spermine administration, which replenishes intracellular polyamine levels, prevented selenomethionine induced apoptosis. Selenomethionine administration to the cancer cell lines increased the number of cells in metaphase. This cell cycle effect appeared to be reversed with the co-administration of selenomethionine and spermine. These data suggested that at least part of the anti-carcinogenic effects of selenium supplementation might be due to a depletion in polyamine levels. This depletion of polyamines leads to an induction in apoptosis and perturbations in the cell cycle.

Histone lysine trimethylation exhibits a distinct perinuclear distribution in Plzf-expressing spermatogonia

Chromatin structure plays an important role in the regulation of gene expression. Methylation of lysine residues on histone tails is an epigenetic mark that influences chromatin repression when specifically imparted on lysines 9 and 27 of histone H3, and on lysine 20 of H4. Histone lysines can be mono-, di-, and trimethylated, and all three modification states have been identified in different nuclear domains. Correlation of these methylated histone states to different stages of cell differentiation, however, is not extensive. Mammalian spermatogenesis is a developmental process ideal for studying the epigenetic control of differentiation. Maintenance of spermatogonial stem cells requires the transcriptional repressor Plzf, but a role for histone methylation has not been established. Here we show that Plzf-expressing spermatogonia completely lack monomethyl-H3-K27 and monomethyl-H4-K20, and contain very little monomethyl-H3-K9. Dimethylated H3-K27 and H4-K20 are detected as punctate foci in Plzf-positive cells, but dimethyl-H3-K9 is absent. Trimethylated H3-K9 and H4-K20 exhibit a unique perinuclear distribution that coincides with Plzf expression, localizing to punctate foci in more differentiated spermatogonia. Loss of Plzf correlates with increased punctate distribution of trimethylated H3-K9 and H4-K20 at the expense of perinuclear localization. These data signify the possible importance of different histone lysine methylation states in the epigenetic control of spermatogenesis.

Biparental inheritance of gamma-tubulin during human fertilization: molecular reconstitution of functional zygotic centrosomes in inseminated human oocytes and in cell-free extracts nucleated by human sperm

Human sperm centrosome reconstitution and the parental contributions to the zygotic centrosome are examined in mammalian zygotes and after exposure of spermatozoa to Xenopus laevis cell-free extracts. The presence and inheritance of the conserved centrosomal constituents gamma-tubulin, centrin, and MPM-2 (which detects phosphorylated epitopes) are traced, as is the sperm microtubule-nucleating capability on reconstituted centrosomes. gamma-Tubulin is biparentally inherited in humans (maternal >> than paternal): Western blots detect the presence of paternal gamma-tubulin. Recruitment of maternal gamma-tubulin to the sperm centrosome occurs after sperm incorporation in vivo or exposure to cell-free extract, especially after sperm "priming" induced by disulfide bond reduction. Centrin is found in the proximal sperm centrosomal region, demonstrates expected calcium sensitivity, but appears absent from the zygotic centrosome after sperm incorporation or exposure to extracts. Sperm centrosome phosphorylation is detected after exposure of primed sperm to egg extracts as well as during the early stages of sperm incorporation after fertilization. Finally, centrosome reconstitution in cell-free extracts permits sperm aster microtubule assembly in vitro. Collectively, these results support a model of a blended zygotic centrosome composed of maternal constituents attracted to an introduced paternal template after insemination.

T cell profiles in vitiligo

The purpose of our investigation was to quantitatively assess T cell profiles in vitiligo and to correlate any aberrations in these findings with the spectrum of clinical disease. Twenty randomly selected vitiligo patients and sixteen healthy matched control subjects were studied. The immunofluorescence and complement-mediated cytotoxicity assays were used to determine the percentages of total T (OKT3), helper (OKT4), and suppressor (OKT8) cells in the peripheral blood of patients and controls. Both assays gave comparable results. Patients with vitiligo had a statistically significant decrease in helper cells and helper/suppressor ratios in comparison with control subjects (p less than 0.01). In addition, there was a statistically significant decrease in helper cells among patients with a disease duration of less than 1 year (p less than 0.01) and in patients who produced serum autoantibodies (p less than 0.05). These findings tend to suggest that aberrations in cell-mediated immunity may be operative in the pathogenesis of vitiligo.

Multimodal molecular analysis of astroblastoma enables reclassification of most cases into more specific molecular entities

Astroblastoma is a rare and controversial glioma with variable clinical behavior. The diagnosis currently rests on histologic findings of a circumscribed glioma with astroblastomatous pseudorosettes and vascular hyalinization. Immunohistochemical studies have suggested different oncogenic drivers, such as BRAF p.V600E, but very few cases have been studied using genome-wide methodologies. Recent genomic profiling identified a subset of CNS embryonal tumors with astroblastoma-like morphology that harbored MN1 gene fusions, termed "CNS high-grade neuroepithelial tumors with MN1 alteration" (CNS-HGNET-MN1). To further characterize the genetic alterations that drive astroblastomas, we performed targeted next-generation sequencing (NGS) of 500 cancer-associated genes in a series of eight cases. We correlated these findings with break-apart fluorescence in situ hybridization (FISH) analysis of the MN1 locus and genome-wide DNA methylation profiling. Four cases showed MN1 alteration by FISH, including two pediatric cases that lacked other pathogenic alterations, and two adult cases that harbored other cancer-associated gene mutations or copy number alterations (eg, CDKN2A/B homozygous deletion, TP53, ATM and TERT promoter mutations). Three of these cases grouped with the CNS-HGNET-MN1 entity by methylation profiling. Two of four MN1 intact cases by FISH showed genetic features of either anaplastic pleomorphic xanthoastrocytoma (BRAF p.V600E mutation, CDKN2A/B homozygous deletion and TERT promoter mutation) or IDH-wildtype glioblastoma (trisomy 7, monosomy 10, CDK4 amplification and TP53, NRAS and TERT promoter mutations) and these cases had an aggressive clinical course. Two clinically indolent cases remained unclassifiable despite multimodal molecular analysis. We conclude that astroblastoma histology is not specific for any entity including CNS-HGNET-MN1, and that additional genetic characterization should be considered for astroblastomas, as a number of these tumors likely contain a methylation profile or genetic alterations that suggest classification as other tumor entities. Our heterogeneous molecular findings help to explain the clinical unpredictability of astroblastoma.

Adult-onset acid maltase deficiency: a postmortem study

In a postmortem study of a patient with adult-onset acid maltase deficiency (AMD), morphological abnormalities were confined to skeletal muscle and consisted of a vacuolar myopathy. Acid maltase activity, however, was approximately 6% of normal in muscle, liver, and brain, and 3% of normal in heart. Kinetic characteristics, and inhibition by antibodies and Zn++, showed that the residual activity was "authentic" acid maltase. Neutral maltase activity was normal in muscle and liver, but decreased in brain (55% of normal) and heart (19% of normal). Although the relative decrease of acid maltase was similar in different tissues, absolute residual activity was lowest in skeletal muscle: this may explain the selective involvement of this tissue in late-onset AMD.

Randomised controlled trial adapting US school obesity prevention to England

OBJECTIVES

To determine whether a school obesity prevention project developed in the United States can be adapted for use in England.

METHODS

A pilot cluster randomised controlled trial and interviews with teachers were carried out in 19 primary schools in South West England. Participants included 679 children in year 5 (age 9-10). Baseline and follow-up assessments were completed for 323 children (screen viewing) and 472 children (body mass index). Sixteen lessons on healthy eating, physical activity and reducing TV viewing were taught over 5 months by teachers. Main outcome measures were hours of screen activities, body mass index, mode of transport to school and teachers' views of the intervention.

RESULTS

Children from intervention schools spent less time on screen-viewing activities after the intervention but these differences were imprecisely estimated: mean difference in minutes spent on screen viewing at the end of the intervention (intervention schools minus control schools) adjusted for baseline levels and clustering within schools was -11.6 (95% CI -42.7 to 19.4) for a week day and was -15.4 (95% CI -57.5 to 26.8) for a Saturday. There was no difference in mean body mass index or the odds of obesity.

CONCLUSIONS

It is feasible to transfer this US school-based intervention to UK schools, and it may be effective in reducing the time children spend on screen-based activities. The study has provided information for a full-scale trial, which would require 50 schools ( approximately 1250 pupils) to detect effects on screen viewing and body mass index over 2 years of follow-up.

Neural Correlates of Auditory Figure-Ground Segregation Based on Temporal Coherence

To make sense of natural acoustic environments, listeners must parse complex mixtures of sounds that vary in frequency, space, and time. Emerging work suggests that, in addition to the well-studied spectral cues for segregation, sensitivity to temporal coherence-the coincidence of sound elements in and across time-is also critical for the perceptual organization of acoustic scenes. Here, we examine pre-attentive, stimulus-driven neural processes underlying auditory figure-ground segregation using stimuli that capture the challenges of listening in complex scenes where segregation cannot be achieved based on spectral cues alone. Signals ("stochastic figure-ground": SFG) comprised a sequence of brief broadband chords containing random pure tone components that vary from 1 chord to another. Occasional tone repetitions across chords are perceived as "figures" popping out of a stochastic "ground." Magnetoencephalography (MEG) measurement in naïve, distracted, human subjects revealed robust evoked responses, commencing from about 150 ms after figure onset that reflect the emergence of the "figure" from the randomly varying "ground." Neural sources underlying this bottom-up driven figure-ground segregation were localized to planum temporale, and the intraparietal sulcus, demonstrating that this area, outside the "classic" auditory system, is also involved in the early stages of auditory scene analysis."

Randomized controlled multisite trial of injected bulking agents for women with intrinsic sphincter deficiency: mid-urethral injection of Zuidex via the Implacer versus proximal urethral injection of Contigen cystoscopically

OBJECTIVES

To determine whether Zuidex using a non-cystoscopy mid-urethral injection technique produces as good a result (i.e. was not inferior) as Contigen injected endoscopically at the bladder neck in the treatment of urinary stress incontinence secondary to intrinsic sphincter deficiency in adult women.

METHODS

A prospective 2:1 randomized trial of mid-urethral injections of Zuidex-Implacer vs proximal urethral cystoscopic injections of Contigen was performed in 344 women with intrinsic sphincter deficiency at 23 North American sites, and followed up for >1 year from last treatment.

RESULTS

Outcomes at 12 months from last treatment failed to demonstrate that mid-urethral injected Zuidex was equivalent to cystoscopically injected Contigen in primary and secondary outcome variables. The primary outcome, the proportion of women who achieved a 50% reduction in urinary leakage on provocation testing, was achieved in 84% of Contigen-treated women vs 65% of Zuidex-treated women.

CONCLUSIONS

Confounding multiple variables inherent in the study design make a detailed analysis of study outcomes difficult.

Mechanisms of pelvic floor muscle function and the effect on the urethra during a cough

BACKGROUND

Current measurement tools have difficulty identifying the automatic physiologic processes maintaining continence, and many questions still remain about pelvic floor muscle (PFM) function during automatic events.

OBJECTIVE

To perform a feasibility study to characterise the displacement, velocity, and acceleration of the PFM and the urethra during a cough.

DESIGN, SETTING, AND PARTICIPANTS

A volunteer convenience sample of 23 continent women and 9 women with stress urinary incontinence (SUI) from the general community of San Francisco Bay Area was studied.

MEASUREMENTS

Methods included perineal ultrasound imaging, motion tracking of the urogenital structures, and digital vaginal examination. Statistical analysis used one-tailed unpaired student t tests, and Welch's correction was applied when variances were unequal.

RESULTS AND LIMITATIONS

The cough reflex activated the PFM of continent women to compress the urogenital structures towards the pubic symphysis, which was absent in women with SUI. The maximum accelerations that acted on the PFM during a cough were generally more similar than the velocities and displacements. The urethras of women with SUI were exposed to uncontrolled transverse acceleration and were displaced more than twice as far (p=0.0002), with almost twice the velocity (p=0.0015) of the urethras of continent women. Caution regarding the generalisability of this study is warranted due to the small number of women in the SUI group and the significant difference in parity between groups.

CONCLUSIONS

During a cough, normal PFM function produces timely compression of the pelvic floor and additional external support to the urethra, reducing displacement, velocity, and acceleration. In women with SUI, who have weaker urethral attachments, this shortening contraction does not occur; consequently, the urethras of women with SUI move further and faster for a longer duration.

Profilin and actin-related proteins regulate microfilament dynamics during early mammalian embryogenesis

BACKGROUND

Profilins are ubiquitous proteins widely distributed in animals, including humans. They regulate actin polymerization by sequestering actin monomers in association with other actin-related proteins (Arps). Actin remodelling is essential for oocyte maturation, fertilization and embryo development; yet the role of profilins in these events is not well understood. Here we investigate profilin distribution and function during bovine fertilization and early embryogenesis, and we examine profilin localization with respect to the co-distribution of other Arps.

METHODS AND RESULTS

Western blotting, confocal microscopy with immunofluorescence and protein inhibition studies with antibodies were implemented. Profilin distributes inside interphase nuclei, throughout the cytoplasm and near the cell cortex at different stages of bovine oocyte maturation, fertilization and embryo development. Expression is detected through the blastocyst stage, where profilin localizes to the inner cell mass as well as trophectoderm. Profilin co-distributes with actin monomers and Arps vasodilator-stimulated phospho protein, p140mDia, Arp 3 and p80 coilin in pronucleate-stage zygotes. Antiprofilin antibodies inhibit normal embryo development by disrupting microfilaments, but not microtubules, and result in a higher concentration of profilin and p140mDia mislocalized to the cortex.

CONCLUSIONS

These findings demonstrate that profilin regulates actin dynamics both within the cytoplasm and inside the nuclei of developing mammalian embryos and that its function is essential during fertilization to ensure successful development.

A new once-daily formulation of tolterodine provides superior efficacy and is well tolerated in women with overactive bladder

This study evaluated the efficacy and tolerability of new extended-release (ER) tolterodine for the treatment of overactive bladder in women. In this subpopulation analysis of a double-blind multicenter trial, 1235 female patients were randomized to oral therapy with tolterodine ER 4 mg once daily (n=417), tolterodine IR 2 mg twice daily (n=408) or placebo (n=410) for 12 weeks. Both formulations reduced the mean number of urge incontinence episodes per week (both P=0.001 vs placebo); tolterodine ER was more effective than tolterodine IR (P=0.036). Both formulations significantly improved all other micturition chart variables compared to placebo. Dry mouth was the most common adverse event. There were no safety concerns. Toltrodine ER 4 mg once daily is effective and well tolerated in the treatment of women with overactive bladder, and reduces urge incontinence episodes more than the existing IR twice-daily formulation.

Carboplatin, ifosfamide and etoposide with mid-course vincristine and thoracic radiotherapy for 'limited' stage small cell carcinoma of the bronchus

Forty-two patients with small cell lung cancer were treated with a combination of carboplatin, ifosfamide and etoposide. Vincristine was given on day 14 of each course, the courses being repeated every 28 days for a maximum of six. Thoracic radiotherapy was given 4 weeks after the last course of chemotherapy but no prophylactic cranial radiotherapy was administered. Thirty patients had clinically limited state disease, the remaining patients having contralateral neck lymphadenopathy and/or pleural effusions. Elevated enzyme levels (alkaline phosphatase, LDH, ALT, GGT) were noted in 69% of patients. Twenty-four patients (57%) achieved a complete response (CR) when assessed one month after the end of treatment. A further 21% of patients had a partial response (PR). Median duration of CR was 14 months and of PR 8 months. Cerebral metastases were the sole site of relapse in 13% of the CR patients. Myelosuppression was severe with a median nadir of neutropenia of 0.2 x 10(9) cells 1-1. However, 74% of the patient group received all six courses of chemotherapy and only 16 courses (7%) were delayed because of toxicity. There were three deaths associated with treatment-related neutropenia. The median survival of the total group was 14 months, with an actuarial 2 year survival of 37% and a minimum follow-up of 18 months. [A recent analysis, March 1989, demonstrated a 33%, 2 year actual survival.]

Exercise and nutrition interventions in advanced lung cancer: a systematic review

In this systematic review, we sought to evaluate the effect of physical activity or nutrition interventions (or both) in adults with advanced non-small-cell lung cancer (nsclc).

METHODS

A systematic search for relevant clinical trials was conducted in 6 electronic databases, by hand searching, and by contacting key investigators. No limits were placed on study language. Information about recruitment rates, protocol adherence, patient-reported and clinical outcome measures, and study conclusions was extracted. Methodologic quality and risk of bias in each study was assessed using validated tools.

MAIN RESULTS

Six papers detailing five studies involving 203 participants met the inclusion criteria. Two of the studies were single-cohort physical activity studies (54 participants), and three were controlled nutrition studies (149 participants). All were conducted in an outpatient setting. None of the included studies combined physical activity with nutrition interventions.

CONCLUSIONS

Our systematic review suggests that exercise and nutrition interventions are not harmful and may have beneficial effects on unintentional weight loss, physical strength, and functional performance in patients with advanced nsclc. However, the observed improvements must be interpreted with caution, because findings were not consistent across the included studies. Moreover, the included studies were small and at significant risk of bias. More research is required to ascertain the optimal physical activity and nutrition interventions in advanced inoperable nsclc. Specifically, the potential benefits of combining physical activity with nutrition counselling have yet to be adequately explored in this population.

Golgi dynamics during meiosis are distinct from mitosis and are coupled to endoplasmic reticulum dynamics until fertilization

One current theory of the Golgi apparatus views its organization as containing both a matrix fraction of structural proteins and a reservoir of cycling enzymes. During mitosis, the putative matrix protein GM130 is phosphorylated and relocalized to spindle poles. When the secretory pathway is inhibited during interphase, GM130 redistributes to regions adjacent to vesicle export sites on the endoplasmic reticulum (ER). Strikingly, meiotic maturation and fertilization in nonrodent mammalian eggs presents a unique experimental environment for the Golgi apparatus, because secretion is inhibited until after fertilization, and because the centrosome is absent until introduced by the sperm. Here, we test the hypothesis that phosphorylated GM130 associates not with meiotic spindle poles, but with ER clusters in the mature bovine oocyte. At the germinal vesicle stage, phosphorylated GM130 is observed as fragments dispersed throughout the cytoplasm. During meiotic maturation, GM130 reorganizes into punctate foci that associate near the ER-resident protein calreticulin and is notably absent from the meiotic spindle. GM130 colocalizes with Sec23, a marker for ER vesicle export sites, but not with Lens culinaris agglutinin, a marker for cortical granules. Because disruption of vesicle transport has been shown to block meiotic maturation and embryonic cleavage in some species, we also test the hypothesis that fertilization and cytokinesis are inhibited with membrane trafficking disruptor brefeldin A (BFA). Despite Golgi fragmentation after BFA treatment, pronuclei form and unite, and embryos cleave and develop through the eight-cell stage. We conclude that, while the meiotic phosphorylation cycle of GM130 mirrors that of mitosis, absence of a maternal centrosome precludes Golgi association with the meiotic spindle. Fertilization introduces the sperm centrosome that can reorganize Golgi proteins, but neither fertilization nor cytokinesis prior to compaction requires a functional Golgi apparatus.

WAVE1 intranuclear trafficking is essential for genomic and cytoskeletal dynamics during fertilization: cell-cycle-dependent shuttling between M-phase and interphase nuclei

A-kinase-anchoring proteins (AKAP) help regulate the intracellular organization of cyclic AMP-dependent kinase (PKA) and actin within somatic cells. Elevated levels of cAMP also help maintain meiotic arrest in immature oocytes, with AKAPs implicated as critical mediators but poorly understood during this process. Here we test the hypothesis that the AKAP WAVE1 is required during mammalian fertilization, and identify a nuclear localization of WAVE1 that is independent of actin and actin-related proteins (Arp). Immunofluorescence and immunoprecipitation experiments show a redistribution of WAVE1 from the cortex in germinal vesicle (GV) oocytes to cytoplasmic foci in oocytes arrested in second meiosis (Met II). Following sperm entry, WAVE1 relocalizes to the developing male and female pronuclei. Association of WAVE1 with a regulatory subunit of PKA is detected in both Met II oocytes and pronucleate zygotes, but interaction with Arp 2/3 is observed only in Met II oocytes. WAVE1 redistributes to the cytoplasm upon nuclear envelope breakdown at mitosis, and concentrates at the cleavage furrow during embryonic cell division. Blocking nuclear pore formation with microinjected wheat germ agglutinin does not inhibit the nuclear localization of WAVE1, suggesting that this event precedes nuclear envelope formation. Neither depolymerization nor stabilization of actin affects WAVE1 distribution. Microtubule stabilization with Taxol, however, redistributes WAVE1 to the centrosome, and anti-WAVE1 antibodies prevent both the nuclear distribution of WAVE1 and the migration and apposition of pronuclei. These findings show that WAVE1 sequestration to the nucleus is required during fertilization, and is an actin-independent event that relies on dynamic microtubules but not nuclear pores.