Neurogenesis in the adult hippocampal dentate gyrus is promoted by transient forebrain ischemia. The mechanism responsible for this ischemia-induced neurogenesis, however, remains to be determined. ...It has been suggested that there may be a close relationship between neurogenesis and the expression of vascular endothelial growth factor, an angiogenic factor. The purpose of the present study was to examine the relationship between vascular endothelial growth factor and cell proliferation in the dentate gyrus after transient forebrain ischemia. The mRNA expression of vascular endothelial growth factor was increased in the dentate gyrus on day 1 after ischemia. Immunohistochemical analysis on day 9 after ischemia, when a significant increase in cell proliferation was seen, showed that the cerebral vessel space in the subgranular zone of the dentate gyrus had not been affected by the ischemia. Neither were the vascular densities on days 1 and 3 after ischemia altered compared with those of non-operated naïve control rats. Furthermore, the distance from the center of the proliferative cells to the nearest cerebral vessel of ischemic rats was comparable to that of the sham-operated rats. We demonstrated that transient forebrain ischemia-induced cell proliferation and differentiation to mature neurons in the hippocampal dentate gyrus was attenuated by the i.c.v. administration of a vascular endothelial growth factor receptor tyrosine kinase inhibitor. These results suggest that vascular endothelial growth factor receptor at the early period of reperfusion may contribute to neurogenesis rather than to angiogenesis in the hippocampal dentate gyrus.
Loss- or gain-of-function mutations in ATP-sensitive potassium channel (K-ATP)-encoding genes, KCNJ8 and ABCC9, cause human central nervous system disorders with unknown pathogenesis. Here, using ...mice, zebrafish, and cell culture models, we investigated cellular and molecular causes of brain dysfunctions derived from altered K-ATP channel function. We show that genetic/chemical inhibition or activation of KCNJ8/ABCC9-containing K-ATP channel function leads to brain-selective suppression or promotion of arterial/arteriolar vascular smooth muscle cell (VSMC) differentiation, respectively. We further show that brain VSMCs develop from KCNJ8/ABCC9-containing K-ATP channel-expressing mural cell progenitor and that K-ATP channel cell autonomously regulates VSMC differentiation through modulation of intracellular Ca2+ oscillation via voltage-dependent calcium channels. Consistent with defective VSMC development, Kcnj8 knockout mice showed deficiency in vasoconstrictive capacity and neuronal-evoked vasodilation leading to local hyperemia. Our results demonstrate a role for KCNJ8/ABCC9-containing K-ATP channels in the differentiation of brain VSMC, which in turn is necessary for fine-tuning of cerebral blood flow.
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•Pericyte-enriched K-ATP channel cell autonomously promotes arterial VSMC development•K-ATP channel controls VSMC differentiation by modulating Ca2+ oscillation via VDCC•K-ATP channel dysfunction leads to defective VSMC differentiation•VSMC defects evoked by K-ATP channel dysfunction leads to neurovascular uncoupling
Ando et al. show that an ATP-sensitive potassium (K-ATP) channel composed of Kir6.1 (KCNJ8) and Sur2B (ABCC9) is essential for brain functional hyperemic responses and that this reflects a critical and brain-specific role of K-ATP channels during vascular smooth muscle cell (VSMC) differentiation from mural cell progenitors.
A plant modulates its developmental processes in response to light by several informational photoreceptors such as phytochrome. Phytochrome is a dimeric chromoprotein which regulates various aspects ...of plant development from seed germination to flowering. Upon absorption of red light, phytochrome translocates from the cytoplasm to the nucleus, and regulates gene expression through interaction with transcription factors such as PIF3 (refs 5-7). The phytochrome polypeptide has two domains: the amino-terminal photosensory domain with a chromophore and the carboxy-terminal domain which contains signalling motifs such as a kinase domain. The latter is widely believed to transduce the signal to downstream components. Here we show that the C-terminal domain of Arabidopsis phytochrome B (phyB), which is known as the most important member of the phytochrome family, is not directly involved in signal transduction. The N-terminal domain isolated from phyB, when dimerized and localized in the nucleus, triggered full phyB responses with much higher photosensitivity than the full-length phyB. These findings indicate that the C-terminal domain attenuates the activity of phyB rather than positively transducing the signal.
We report new palaeointensity results concerning the Auckland geomagnetic excursions using the double heating technique of the Shaw method with low temperature demagnetisation (LTD-DHT Shaw method). ...The excursional palaeodirections recorded in six volcanoes of the Auckland volcanic field, New Zealand, have been classified into three groups: north-down (ND), west-up (WU) and south-up (SU) directions. In the present study, five to six consistent palaeointensities have been obtained from each of five volcanoes recording the Auckland geomagnetic excursions. The Wiri (27
ka), Crater Hill and Puketutu volcanoes (ND group) yielded mean palaeointensities of 10.6
±
1.2 (1
σ), 11.8
±
2.8 and 11.1
±
0.4
μT, respectively. The Hampton Park volcano (55
ka; WU group) gave 9.5
±
1.2
μT while the McLennan Hills volcano (SU group) gave 2.5
±
0.5
μT. It is notable that consistent palaeointensities have been obtained from the three different volcanoes which have almost the same palaeodirections (ND group), possibly supporting the reliability of the palaeointensity data. These five palaeointensities for the Auckland geomagnetic excursions correspond to virtual dipole moments (VDMs) of 0.6–2.1
×
10
22
A
m
2, whereas three mean palaeointensities obtained from the Auckland volcanoes having non-excursional palaeodirections are 13.1–40.0
μT giving stronger VDMs of 2.1–6.9
×
10
22
A
m
2. These results suggest that the dipole component of the geomagnetic field reduced to about 2
×
10
22
A
m
2 or less during the Auckland geomagnetic excursions.
The double heating technique of the Shaw method with low-temperature demagnetisation (LTD-DHT Shaw method) for determination of geomagnetic palaeointensity is applied to samples exhibiting ...high-temperature oxidation states from the Kilauea 1970 lava, Hawaii Island. Results are obtained for 11 of the 12 specimens prepared from five block samples, yielding an average palaeointensity of 38.2
±
2.8
μT (
N
=
11, ±1
σ). This value is consistent with the expected value determined from DGRF 1970 (35.8
μT), and does not appear to be significantly dependent on the high-temperature oxidation state. Coe's version of the Thellier method was also applied to nine specimens prepared from the same block samples, and successful results were obtained for seven specimens, giving an average palaeointensity of 43.2
±
8.4
μT (
N
=
7). Although this average is statistically consistent with the expected value, the results include erroneously high palaeointensities (52.1 and 55.4
μT) for specimens from one block sample of intermediate high-temperature oxidation state. The present results therefore reinforce the broader applicability of the LTD-DHT Shaw method for samples with high-temperature oxidation states compared with Coe's version of the Thellier method. It is also shown that the samples yielding overestimated Thellier palaeointensities tend to fall close to the mixing line between single-domain (and/or pseudo-single-domain) and multidomain components on the Day plot. This relationship may be useful as a pre-selection technique for application of the Thellier method.
Chloroplast development requires the coordinated expression of nuclear and chloroplastic genes. A hypothesized signal from the chloroplast couples the transcription of certain nuclear genes encoding ...photosynthetic proteins with chloroplast function. We have previously described an Arabidopsis thaliana mutant, gun1, which has a defect in the signal transduction pathway coupling such nuclear and plastidic gene-expression. Here we show that gum seedlings are also defective in establishing photoautotrophic growth. gun1 seedlings develop normally in the dark, but, based on morphological criteria and the kinetics of chlorophyll accumulation, photosynthetic mRNA accumulation, and the differentiation of etioplasts to chloroplasts, are retarded in their ability to de-etiolate. Therefore, we propose that the GUN1 gene plays an important role in the transition from heterotrophic to photoautotrophic growth, suggesting an important physiological role for the plastic-nucleus signaling pathway during biogenesis
Mural cells (MCs) are essential for blood vessel stability and function; however, the mechanisms that regulate MC development remain incompletely understood, in particular those involved in MC ...specification. Here, we investigated the first steps of MC formation in zebrafish using transgenic reporters. Using
and
reporters, we show that the onset of expression of
, a pericyte marker in adult mice and zebrafish, occurs almost coincidentally with an increment in
expression in peri-arterial mesenchymal cells, suggesting that these transcriptional changes mark the specification of MC lineage cells from naïve
mesenchymal cells. The emergence of peri-arterial
MCs required Notch signaling. We found that
-positive cells express
in addition to
, and although depletion of
or
failed to block MC emergence, embryos depleted of both
and
lost mesoderm- as well as neural crest-derived
MCs. Using reporters that read out Notch signaling and Notch2 receptor cleavage, we show that Notch activation in the mesenchyme precedes specification into
MCs. Taken together, these results show that Notch signaling is necessary for peri-arterial MC specification.
Platelet derived growth factor beta and its receptor, Pdgfrb, play essential roles in the development of vascular mural cells, including pericytes and vascular smooth muscle cells. To determine if ...this role was conserved in zebrafish, we analyzed pdgfb and pdgfrb mutant lines. Similar to mouse, pdgfb and pdgfrb mutant zebrafish lack brain pericytes and exhibit anatomically selective loss of vascular smooth muscle coverage. Despite these defects, pdgfrb mutant zebrafish did not otherwise exhibit circulatory defects at larval stages. However, beginning at juvenile stages, we observed severe cranial hemorrhage and vessel dilation associated with loss of pericytes and vascular smooth muscle cells in pdgfrb mutants. Similar to mouse, pdgfrb mutant zebrafish also displayed structural defects in the glomerulus, but normal development of hepatic stellate cells. We also noted defective mural cell investment on coronary vessels with concomitant defects in their development. Together, our studies support a conserved requirement for Pdgfrb signaling in mural cells. In addition, these zebrafish mutants provide an important model for definitive investigation of mural cells during early embryonic stages without confounding secondary effects from circulatory defects.
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DOCK180 was originally identified as one of two major proteins bound to the Crk oncogene product and became an archetype of the CDM family of proteins, including Ced-5 of Caenorhabditis elegans and ...Mbc of Drosophila melanogaster. Further study has suggested that DOCK180 is involved in the activation of Rac by the CrkII-p130(Cas) complex. With the use of deletion mutants of DOCK180, we found that the C-terminal region containing a cluster of basic amino acids was required for binding to and activation of Rac. This region showed high amino-acid sequence similarity to the consensus sequence of the phosphoinositide-binding site; this led us to examine whether this basic region binds to phosphoinositides. For this purpose we used PtdIns(3,4,5)P(3)-APB beads, as reported previously Shirai, Tanaka, Terada, Sawada, Shirai, Hashimoto, Nagata, Iwamatsu, Okawa, Li et al. (1998) Biochim. Biophys. Acta 1402, 292-302. By using various competitors, we demonstrated the specific binding of DOCK180 to PtdIns(3,4,5)P(3). The expression of active phosphoinositide 3-kinase (PI-3K) did not enhance a DOCK180-induced increase in GTP-Rac; however, the expression of PI-3K translocated DOCK180 to the plasma membrane. Thus DOCK180 contained a phosphoinositide-binding domain, as did the other guanine nucleotide exchange factors with a Dbl homology domain, and was translocated to the plasma membrane on the activation of PI-3K.
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