Tatsuya Sato

本研究ではアマモを用いた水槽実験による溶存無機炭素の変化のモデル解析とアマモの成分分析の結果から，アマモの季節的な光合成活性の違いが溶存無機炭素の吸収・放出特性に及ぼす影響を明らかにした．アマモによる溶存無機炭素に関する最大光合成速度の最適値は実験の時期によって異なることが明らかになった．モデルによる推定値とアマモのクロロフィルa含有率の結果から，アマモの生長段階の違いが光合成活性や最大光合成速度に影響したことが示唆された．アマモの詳細な諸元の測定値に基づいて得られた結果をモデルに適用し，溶存無機炭素の鉛直プロファイルの特性とアマモの分岐の構造との関係を明らかにした．

Following publication of the original article [1], we noticed a number of errors.

The bed nucleus of the stria terminalis (BNST) contains the highest density of corticotropin-releasing factor (CRF)-producing neurons in the brain. CRF-immunoreactive neurons show a female-biased sexual dimorphism in the dorsolateral BNST in the rat. Since CRF neurons cannot be immunostained clearly with available CRF antibodies in the mouse, we used a mouse line, in which modified yellow fluorescent protein (Venus) was inserted to the CRF gene, and the Neo cassette was removed, to examine the morphological characteristics of CRF neurons in the dorsolateral BNST. Developmental changes of CRF neurons were examined from postnatal stages to adulthood. Gonadectomy (GDX) was carried out in adult male and female mice to examine the effects of sex steroids on the number of CRF neurons in the dorsolateral BNST. The number of Venus-expressing neurons, stained by immunofluorescence, was compared between male and female mice over the course of development. GDX was carried out in adult mice. Immunohistochemistry, in combination with Nissl staining, was carried out, and the effects of sex or gonadal steroids were examined by estimating the number of Venus-expressing neurons, as well as the total number of neurons or glial cells, in each BNST subnucleus, using a stereological method. Most Venus-expressing neurons co-expressed Crf mRNA in the dorsolateral BNST. They constitute a group of neurons without calbindin immunoreactivity, which makes a contrast to the principal nucleus of the BNST that is characterized by calbindin immunostaining. In the dorsolateral BNST, the number of Venus-expressing neurons increased across developmental stages until adulthood. Sexual difference in the number of Venus-expressing neurons was not evident by postnatal day 5. In adulthood, however, there was a significant female predominance in the number of Venus expressing neurons in two subnuclei of the dorsolateral BNST, i.e., the oval nucleus of the BNST (ovBNST) and the anterolateral BNST (alBNST). The number of Venus-expressing neurons was smaller significantly in ovariectomized females compared with proestrous females in either ovBNST or alBNST, and greater significantly in orchiectomized males compared with gonadally intact males in ovBNST. The total number of neurons was also greater significantly in females than in males in ovBNST and alBNST, but it was not affected by GDX. Venus-expressing CRF neurons showed female-biased sexual dimorphism in ovBNST and alBNST of the mouse. Expression of Venus in these subnuclei was controlled by gonadal steroids.

Glucocorticoids (GCs) are essential for stress adaptation, acting centrally and in the periphery. Corticotropin-releasing factor (CRF), a major regulator of adrenal GC synthesis, is produced in the paraventricular nucleus of the hypothalamus (PVH), which contains multiple neuroendocrine and preautonomic neurons. GCs may be involved in diverse regulatory mechanisms in the PVH, but the target genes of GCs are largely unexplored except for the CRF gene (Crh), a well-known target for GC negative feedback. Using a genome-wide RNA-sequencing analysis, we identified transcripts that changed in response to either high-dose corticosterone (Cort) exposure for 12 days (12-day high Cort), corticoid deprivation for 7 days (7-day ADX), or acute Cort administration. Among others, canonical GC target genes were upregulated prominently by 12-day high Cort. Crh was upregulated or downregulated most prominently by either 7-day ADX or 12-day high Cort, emphasizing the recognized feedback effects of GC on the hypothalamic-pituitary-adrenal (HPA) axis. Concomitant changes in vasopressin and apelin receptor gene expression are likely to contribute to HPA repression. In keeping with the pleotropic cellular actions of GCs, 7-day ADX downregulated numerous genes of a broad functional spectrum. The transcriptome response signature differed markedly between acute Cort injection and 12-day high Cort. Remarkably, six immediate early genes were upregulated 1 hour after Cort injection, which was confirmed by quantitative reverse transcription PCR and semiquantitative in situ hybridization. This study may provide a useful database for studying the regulatory mechanisms of GC-dependent gene expression and repression in the PVH.

The anterior part of the embryonic telencephalon gives rise to several brain regions that are important for animal behavior, including the frontal cortex (FC) and the olfactory bulb. The FC plays an important role in decision‐making behaviors, such as social and cognitive behavior, and the olfactory bulb is involved in olfaction. Here, we show the organizing activity of fibroblast growth factor 8 (Fgf8) in the regionalization of the anterior telencephalon, specifically the FC and the olfactory bulb. Misexpression of Fgf8 in the most anterior part of the mouse telencephalon at embryonic day 11.5 (E11.5) by ex utero electroporation resulted in a lateral shift of dorsal FC subdivision markers and a lateral expansion of the dorsomedial part of the FC, the future anterior cingulate and prelimbic cortex. Fgf8‐transfected brains had lacked ventral FC, including the future orbital cortex, which was replaced by the expanded olfactory bulb. The olfactory region occupied a larger area of the FC when transfection efficiency of Fgf8 was higher. These results suggest that Fgf8 regulates the proportions of the FC and olfactory bulb in the anterior telencephalon and has a medializing effect on the formation of FC subdivisions.

PPM1L, a member of the metal-dependent protein phosphatase (PPM) family, is involved in regulating the stress-activated protein kinase pathway and ceramide trafficking. However, the physiological function of PPM1L in the brain is unclear. In this study, we generated and analyzed ppm1l-deficient mice in order to investigate PPM1L functions in the brain. Our results indicate that ppm1l is highly expressed in the central nervous system during mouse development and that ppm1l^Δ/Δ mice display impaired motor performance and morphological abnormalities in the forebrain. Electron microscopic and immunohistochemical analyses suggest that these abnormalities are due to impaired axonal tract formation. Our novel findings suggest an important role for PPM1L in brain development.

In this paper, we review how midbrain and hindbrain are specified. Otx2 and Gbx2 are expressed from the early phase of development, and their expression abuts at the midbrain hindbrain boundary (MHB), where Fgf8 expression is induced, and functions as an organizing molecule for the midbrain and hindbrain. Fgf8 induces En1 and Pax2 expression at the region where Otx2 is expressed to specify midbrain. Fgf8 activates Ras‐ERK pathway to specify hindbrain. Downstream of ERK, Pea3 specifies isthmus (rhombomere 0, r0), and Irx2 may specify r1, where the cerebellum is formed.

It has been shown that strong Fgf8 signal activates Ras‐ERK signaling pathway to determine metencephalon, which consists of rhombomere 1 (r1), where the cerebellum differentiates, and isthmus (r0). The present study was undertaken to check if Ets type transcription factor Pea3 functions downstream of Ras‐ERK signaling to determine metencephalon. Pea3 misexpression resulted in repression of Otx2 expression in the mesencephalon, induction of Gbx2 and Fgf8 expression in the mesencephalon, and differentiation of the trochlear neurons in the posterior mesencephalon. Fate change of the tectum to the cerebellum did not occur. Repression of Pea3 function by misexpressing the chimeric molecule of Engrailed repressor domain EH1 and Pea3 (eh1‐Pea3) resulted in induction of Otx2 expression in the metencephalon, repression of Gbx2 and Fgf8 expression in the metencephalon, and differentiation of the oculomotor neurons in the isthmus. It was concluded that Pea3 plays a pivotal role in determination of the isthmus (r0) property downstream of Fgf8‐Ras‐ERK signaling.

We generated knockout (KO) mice of Nepro, which has been shown to be necessary to maintain neural progenitor cells downstream of Notch in the mouse developing neocortex by using knockdown experiments, to explore its function in embryogenesis. Nepro KO embryos were morphologically indistinguishable from wild type (WT) embryos until the morula stage but failed in blastocyst formation, and many cells of the KO embryos resulted in apoptosis. We found that Nepro was localized in the nucleolus at the blastocyst stage. The number of nucleolus precursor bodies (NPBs) and nucleoli per nucleus was significantly higher in Nepro KO embryos compared with WT embryos later than the 2‐cell stage. Furthermore, at the morula stage, whereas 18S rRNA and ribosomal protein S6 (rpS6), which are components of the ribosome, were distributed to the cytoplasm in WT embryos, they were mainly localized in the nucleoli in Nepro KO embryos. In addition, in Nepro KO embryos, the amount of the mitochondria‐associated p53 protein increased, and Cytochrome c was distributed in the cytoplasm. These findings indicate that Nepro is a nucleolus‐associated protein, and its loss leads to the apoptosis before blastocyst formation in mice.