Turn-on mode fluorescent diarylethene containing neopentyl substituents that undergoes all-visible-light switching.

This paper presents a strategy for improving the all-visible-light switching response of turn-on mode fluorescent diarylethene derivatives. Introduction of neopentyl or isobutyl substituents at the reactive carbons (2- and 2'-positions) of an oxidized bis(benzothienyl)perfluorocyclopentene derivative, which undergoes both cyclization and cycloreversion reactions upon irradiation with visible light, was effective in increasing the cycloreversion quantum yield by one or two orders of magnitude in comparison with the yield of an ethyl-substituted derivative. Any significant influence on the cyclization and fluorescence quantum yields was not observed by the introduction of neopentyl or isobutyl substituents.

Matcha and Its Components Control Angiogenic Potential.

The brain needs the appropriate capillary networks to maintain normal brain function. Since previous studies showed age-related decrease in the cortical capillaries, it is suggested that protection against capillary aging is critical for maintaining brain function. Epidemiological studies have indicated that brain functions were protected from age-related decline by the long-term consumption of matcha. However, whether matcha has protective effects on capillary aging has not been studied yet. In this study, we utilized Flt1-DsR mice that expressed a red fluorescent protein in vascular endothelial cells to visualize cortical capillaries clearly. We found that cortical capillary density decreased in aging Flt1-DsR mice. Our results of the aortic ring assay and tube formation assay revealed that matcha and its components vitamin K1 and lutein, which are abundant in matcha powder, enhanced the angiogenic potential. Moreover, we evaluated the effect of long-term ingestion of matcha on mouse cortical capillary aging by using imaging experiments. The capillary density of the Flt1-DsR mice, which were fed matcha-containing food, indicated the protective effects of matcha ingestion on capillary aging in a limited cortical layer. These results suggest that biological regulation of matcha and its components affect the angiogenic potential, which is related to the prevention of capillary aging.

Turn-on mode fluorescent diarylethenes: effect of electron-donating and electron-withdrawing substituents on photoswitching performance†.

Diarylethene derivatives having benzothiophene S,S-dioxide groups undergo turn-on mode fluorescence photoswitching. For the practical application to super-resolution fluorescence microscopy, photoswitchable fluorescent molecules are desired to be resistant against photodegradation. Here we synthesized turn-on mode fluorescent diarylethenes having electron-withdrawing (trifluoromethyl or nitro) or electron-donating (methyl, methoxy, or dimethylamino) substituents on phenyl rings at 6- and 6'-positions of the benzothiophene S,S-dioxide groups and examined the effect of the substituents on the photoswitchiing performance. The derivatives having electron-donating substituents showed significant bathochromic shifts of the absorption and fluorescence spectra. The cycloreversion quantum yield was increased by introducing electron-withdrawing substituents, while it was decreased by the electron-donating ones. Introduction of electron-donating substituents was found to remarkably improve the fatigue resistance of the fluorescent diarylethene under continuous ultraviolet (UV) irradiation. Such highly fatigue-resistant fluorescent diarylethenes are useful for super-resolution fluorescence imaging or single-molecule fluorescence tracking.

Spatiotemporally Dependent Vascularization Is Differently Utilized among Neural Progenitor Subtypes during Neocortical Development.

To facilitate efficient oxygen and nutrient delivery, blood vessels in the brain form three-dimensional patterns. However, little is known about how blood vessels develop stereographically in the neocortex and how they control the expansion and differentiation of neural progenitors during neocortical development. We show that highly vascularized and avascular regions are strictly controlled in a spatially and temporally restricted manner and are associated with distinct cell populations. Dividing basal progenitors and oligodendrocyte precursors preferentially contact honeycomb vessels, but dividing apical progenitors are localized in avascular regions without Flt1-positive endothelial cells but directly contact with sprouting neovascular tip cells. Therefore, not all blood vessels are associated equally with neural progenitors. Furthermore, a disruption of normal vascular patterning can induce abnormalities in neural development, whereas the impaired features of neural progenitors influenced angiogenesis patterning. These results indicate that close association between the nervous and vascular systems is essential for neocortex assembly.

Thermally reversible photochromism of dipyrrolylethenes.

Although diarylethene derivatives are considered to undergo thermally irreversible photochromic reactions, this is not always the case. Here, we report on thermally reversible photochromic diarylethenes having pyrrole-2-carbonitrile aryl groups. The thermal stability of the coloured closed-ring isomer of 1,2-bis(2-alkyl-5-cyano-1-methyl-3-pyrrolyl)perfluorocyclopentene was found to depend on alkyl substituents at the 2- and 2'-positions. The closed-ring isomer of the ethyl-substituted derivative thermally returned back to the open-ring isomer much faster than that of the methyl-substituted derivative. The difference in the thermal stability was well explained by the ground state energy difference between open- and closed-ring isomers. Excellent fatigue resistance and appropriate thermal fading rates were observed for the derivative having cyano substituents at the 5- and 5'-positions and methyl substituents at the 2-, 2'-, 4- and 4'-positions. The UV-irradiated colouration and thermal decolouration cycle can be repeated more than 103 times.

A Prdm8 target gene Ebf3 regulates multipolar-to-bipolar transition in migrating neocortical cells.

Precise control of neuronal migration is essential for the development of the neocortex. However, the molecular mechanisms underlying neuronal migration remain largely unknown. Here we identified helix-loop-helix transcription factor Ebf3 as a Prdm8 target gene, and found that Ebf3 is a key regulator of neuronal migration via multipolar-to-bipolar transition. Ebf3 knockdown cells exhibited severe defects in the formation of leading processes and an inhibited shift to the locomotion mode. Moreover, we found that Ebf3 knockdown represses NeuroD1 transcription, and NeuroD1 overexpression partially rescued migration defects in Ebf3 knockdown cells. Our findings highlight the critical role of Ebf3 in multipolar-to-bipolar transition via positive feedback regulation of NeuroD1 in the developing neocortex.

Prdm16 is crucial for progression of the multipolar phase during neural differentiation of the developing neocortex.

The precise control of neuronal migration and morphological changes during differentiation is essential for neocortical development. We hypothesized that the transition of progenitors through progressive stages of differentiation involves dynamic changes in levels of mitochondrial reactive oxygen species (mtROS), depending on cell requirements. We found that progenitors had higher levels of mtROS, but that these levels were significantly decreased with differentiation. The Prdm16 gene was identified as a candidate modulator of mtROS using microarray analysis, and was specifically expressed by progenitors in the ventricular zone. However, Prdm16 expression declined during the transition into NeuroD1-positive multipolar cells. Subsequently, repression of Prdm16 expression by NeuroD1 on the periphery of ventricular zone was crucial for appropriate progression of the multipolar phase and was required for normal cellular development. Furthermore, time-lapse imaging experiments revealed abnormal migration and morphological changes in Prdm16-overexpressing and -knockdown cells. Reporter assays and mtROS determinations demonstrated that PGC1α is a major downstream effector of Prdm16 and NeuroD1, and is required for regulation of the multipolar phase and characteristic modes of migration. Taken together, these data suggest that Prdm16 plays an important role in dynamic cellular redox changes in developing neocortex during neural differentiation.

Deletion of Prdm8 impairs development of upper-layer neocortical neurons.

Upper-layer (UL) neocortical neurons are the most prominent distinguishing features of the mammalian neocortex compared with those of the avian dorsal cortex and are vastly expanded in primates. However, little is known about the identities of the genes that control the specification of UL neurons. Here, we found that Prdm8, a member of the PR (PRDI-BF1 and RIZ homology) domain protein family, was specifically expressed in the postnatal UL neocortex, particular those in late-born RORß-positive layer IV neurons. We generated homozygous Prdm8 knockout (Prdm8 KO) mice and found that the deletion of Prdm8 causes growth retardation and a reduced brain weight, although the brain weight-to-body weight ratio is unchanged at postnatal day 8 (P8). Immunohistochemistry showed that the relative UL thickness, but not the thickness of the deep layer (DL), was significantly reduced in Prdm8 KO mice compared with wild-type (WT) mice. In addition, we found that a number of late-born Brn2-positive UL neurons were significantly decreased in Prdm8 KO mice. To identify genes regulated by Prdm8 during neocortical development, we compared expression profiling analysis in Prdm8 KO and WT mice, and identified some candidate genes. These results suggest that the proper expression of Prdm8 is required for the normal development and construction of UL neurons in the mammalian neocortex.