In the urodele amphibian Pleurodeles waltl, sex differentiation is genetically controlled, that is, ZZ male vs ZW female, but may be influenced by temperature, which induces a female-to-male sex ...reversal. We investigated whether steroidogenic factor 1 (SF-1) could be involved in Pleurodeles sex differentiation or in temperature-dependent sex reversal by cloning a Pleurodeles SF-1 cDNA and examining its developmental expression. The 468-amino-acid deduced protein is highly conserved in comparison with other species. In ZZ and ZW control larvae, SF-1 mRNA is detected at the first stage of the thermosensitive period (TSP) in the gonad-mesonephros-interrenal complex (GMI). By the end of TSP at stage 55, SF-1 is expressed in the gonad (Gd) and in the mesonephros-interrenal (MI) both in ZZ and ZW larvae. During this stage, a transient, ZW-specific increase of SF-1 transcription occurs not only in Gd but also in MI, this increase starting earlier in Gd than in MI. Therefore, in P. waltl, an SF-1 upregulation occurs after the onset of the ovarian-specific increase of aromatase mRNA expression. At the end of metamorphosis, the SF-1 transcription level in Gd and MI is nearly the same in both ZZ and ZW larvae. Besides, after long-term heat treatment leading to sex reversal, SF-1 mRNA upregulation is not observed in ZW larvae, in either Gd or MI. However, SF-1 expression is not decreased after a 48-h heat shock applied at the end of the TSP, suggesting that temperature has no inhibitory effect by itself in long-term heat treatment. Estradiol benzoate treatments show that, at the end of the TSP, SF-1 gene transcription could be controlled by the estrogen level. This is in accordance with the female-enriched SF-1 expression and the decreased SF-1 expression following long-term, sex-reversing heat treatment, which is known to decrease aromatase expression and activity. Thus, it is unlikely that SF-1 is directly involved in Pleurodeles temperature-dependent sex reversal.
In Alzheimer’s disease, neurofibrillary degeneration results from the aggregation of abnormally phosphorylated Tau proteins into paired helical filaments. These Tau variants displayed specific ...epitopes that are immunoreactive with anti-phospho-Tau antibodies such as AT100. As shown in in vitro experiments, glycogen synthase kinase 3 β (GSK3β) and protein kinase A (PKA) may be key kinases in these phosphorylation events. In the present study, Tau was microinjected into
Xenopus oocytes. Surprisingly, in this system, AT100 was generated without any GSK3β and PKA contribution during the progesterone or insulin-induced maturation process. Our results demonstrate that a non-modified physiological process in a cell model can generate the most specific Alzheimer epitope of Tau pathology.
Fully-grown G2-arrested Xenopus oocytes resume meiosis upon hormonal stimulation. Resumption of meiosis is characterized by germinal vesicle breakdown, chromosome condensation, and organization of a ...bipolar spindle. These cytological events are accompanied by activation of MPF and the p39(Mos)-MEK1-Xp42(Mpk1)-p90(Rsk) pathways. The latter cascade is activated upon p39(Mos) accumulation. Using U0126, a MEK1 inhibitor, and p39(Mos) antisense morpholino and phosphorothioate oligonucleotides, we have investigated the role of the members of the p39(Mos)-MEK1-Xp42(Mpk1)-p90(Rsk) in spindle morphogenesis. First, we have observed at a molecular level that prevention of p39(Mos) accumulation always led to MEK1 phosphorylation defects, even when meiosis was stimulated through the insulin Ras-dependent pathway. Moreover, we have observed that Raf1 phosphorylation that occurs during meiosis resumption was dependent upon the activity of MEK1 or Xp42(Mpk1) but not p90(Rsk). Second, inhibition of either p39(Mos) accumulation or MEK1 inhibition led to the formation of a cytoplasmic aster-like structure that was associated with condensed chromosomes. Spindle morphogenesis rescue experiments using constitutively active Rsk and purified murine Mos protein suggested that p39(Mos) or p90(Rsk) alone failed to promote meiotic spindle organization. Our results indicate that activation of the p39(Mos)-MEK1-Xp42(Mpk1)-p90(Rsk) pathway is required for bipolar organization of the meiotic spindle at the cortex.
We have previously shown that abnormal Tau species are produced during the neurofibrillary degeneration of the Alzheimer type. These abnormal Tau proteins consist of a characteristic triplet named ...Tau 55, Tau 64 and Tau 69 which are constantly found in Alzheimer's disease (AD) and Downs syndrome brain regions with tangles. To determine if abnormal Tau species are also produced in other neurodegenerative conditions where intraneuronal filamentous Tau aggregates are observed, we have undertaken an immuno-blot study of brain homogenates from patients with progressive supranuclear palsy (PSP), a neurological disorder characterized by the presence of tangles in subcortical and cortical brain areas. We show here that abnormal Tau species are produced in PSP but that they are different from those in AD. Indeed, although Tau 64 and 69 were present in PSP brain homogenates, possibly as the result of an abnormal phosphorylation as in AD, they were detected in smaller amounts (three times lower) than in AD. In addition Tau 55 was undetected by the immunological tools, such as the absorbed anti-PHF antisera, which specifically label the abnormal Tau proteins. Also the two-dimensional analysis revealed different isoelectric properties. Our results suggest that the production of abnormal Tau species is a very important event during all types of neurofibrillary degeneration. The differences in the pathological Tau-variant profile that were observed between PSP and AD possibly reflect different etiopathogenetic pathways and might explain the formation of different types of filamentous Tau aggregates.
Six different brain areas from 6 patients with Down's syndrome (DS) of different ages were studied in respect of their Tau protein content using the western-blot technique. They were also studied ...histologically using a Palmgren (silver staining) method in order to reveal the presence of NFT and SP. The results of these studies show that Tau 64 and 69, two pathological Tau variants recently described in the brains of patients with Alzheimer's disease (AD), are also present in the brains of patients with DS. Alkaline phosphatase treatment demonstrates that their heavy molecular weight is due, as in AD, to an abnormal phosphorylation of Tau proteins. The results of this study show that the detection of Tau 64 and 69 in the brain of these patients is correlated with the presence of neurofibrillary tangles (NFT) and senile plaques (SP). These findings confirm that DS can act as a model for the study of the pathological events that occur in AD. Moreover, they suggest that the abnormal phosphorylation of Tau proteins, enhancing a shift of their electrophoretic mobility, might be an important step among the sequence of events that characterize neurofibrillary degeneration.
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