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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

During spermatogenesis, mRNA localization and translation are believed to be regulated in a stage-specific manner. We report here that the Protamine2 (Prm2) mRNA transits through chromatoid bodies of round spermatids and localizes to cytosol of elongating spermatids for translation. The transacting factor CBF-A, also termed Hnrnpab, contributes to temporal regulation of Prm2 translation. We found that CBF-A co-localizes with the Prm2 mRNA during spermatogenesis, directly binding to the A2RE/RTS element in the 3' UTR. Although both p37 and p42 CBF-A isoforms interacted with RTS, they associated with translationally repressed and de-repressed Prm2 mRNA, respectively. Only p42 was found to interact with the 5' cap complex, and to co-sediment with the Prm2 mRNA in polysomes. In CBF-A knockout mice, expression of protamine 2 (PRM2) was reduced and the Prm2 mRNA was prematurely translated in a subset of elongating spermatids. Moreover, a high percentage of sperm from the CBF-A knockout mouse showed abnormal DNA morphology. We suggest that CBF-A plays an important role in spermatogenesis by regulating stage-specific translation of testicular mRNAs.

DOI： 10.1371/journal.pgen.1003858

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC CELL BIOLOGY  

In neurons certain mRNA transcripts are transported to synapses through mechanisms that are not fully understood. Here we report that the heterogeneous nuclear ribonucleoprotein CBF-A (CArG Box binding Factor A) facilitates dendritic transport and localization of activity-regulated cytoskeleton-associated protein (Arc), brain-derived neurotrophic factor (BDNF), and calmodulin-dependent protein kinase II (CaMKII alpha) mRNAs. We discovered that, in the adult mouse brain, CBF-A has a broad distribution. In the nucleus, CBF-A was found at active transcription sites and interchromosomal spaces and close to nuclear pores. In the cytoplasm, CBF-A localized to dendrites as well as pre- and postsynaptic sites. CBF-A was found in synaptosomal fractions, associated with Arc, BDNF, and CaMKII alpha mRNAs. Electrophoretic mobility shift assays demonstrated a direct interaction mediated via their hnRNP A2 response element (A2RE)/RNA trafficking sequence (RTS) elements located in the 3' untranslated regions. In situ hybridization and microscopy on live hippocampal neurons showed that CBF-A is in dynamic granules containing Arc, BDNF, and CaMKII alpha mRNAs. N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) postsynaptic receptor stimulation led to CBF-A accumulation in dendrites; increased Arc, BDNF, and CaMKII alpha mRNA levels; and increased amounts of transcripts coprecipitating with CBF-A. Finally, CBF-A gene knockdown led to decreased mRNA levels. We propose that CBF-A cotranscriptionally binds RTSs in Arc, BDNF, and CaMKII alpha mRNAs and follows the transcripts from genes to dendrites, promoting activity-dependent nuclear sorting of transport-competent mRNAs.

DOI： 10.1091/mbc.E10-11-0904

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記述言語：英語   出版者・発行元：LANDES BIOSCIENCE  

Upon nuclear export, RNP particles are either localized to polysomes or further assembled into larger RNA granules which are transported to the cellular periphery for localized translation. These mechanisms are important for asymmetric mRNA and protein distribution and have profound impact on cellular physiology. mRNA transport and localization requires cis-acting elements and cellular transacting factors. hnRNP A2 functions as transacting factor for MBP mRNA transport in myelin-producing oligodendrocytes processes through a mechanism of direct RTS recognition. Here we examine the molecular mechanisms which regulate MBP mRNA transport in mouse oligodendrocytes in view of the recent discovery of CBF-A as novel transacting factor. CBF-A is highly conserved and in humans it is referred to as hnRNP A/B. Since actin has a key role in mRNA biogenesis and it is associated with both CBF-A and hnRNP A2 in pre-mRNP/mRNP complexes, we discuss integrative models underscoring the importance of actin-associated hnRNPs in mRNA biogenesis control at the post-transcriptional level.

DOI： 10.4161/rna.6.2.8195

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Although nasal mucus is thought to play important roles in the mammalian olfactory system, the mechanisms of secretion of it and its physiological roles are poorly understood. Here we show that type 2 and type 3 IP3 receptors (IP3R2 and IP3R3) play critical roles in olfactory mucus secretion. Histological studies showed that IP3R2 and IP3R3 are predominantly expressed in two types of nasal glands, the anterior glands of the nasal septum and the lateral nasal glands (LNG), which contain mucosal proteins secreted to the main olfactory epithelium. We therefore examined LNG acinar cells, and found that acetylcholine-mediated calcium responses and fluid- and protein- secretion in the acinar cells were markedly decreased in IP3R2-R3 double-knockout (KO) mice. We also found nasal inflammation and a decrease in olfactory capacity in IP3R2-R3 KO mice. Despite intact signal transduction in the olfactory epithelium, IP3R2-R3 KO mice exhibited elevated threshold sensitivity to odorants on in vivo imaging of olfactory glomerular responses and behavioral tests. Our findings suggest that IP3R2 and IP3R3 mediate nasal mucus secretion, which is important for the maintenance of nasal tissue as well as the perception of odors.

DOI： 10.1111/j.1460-9568.2008.06240.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL PUBLISHING  

A subset of olfactory receptors (ORs) is expressed in mammalian male germ cells. Recent studies on human and mouse sperm have suggested that calcium signaling via a testicular OR regulates sperm flagellar motility. However, it remains to be determined at what stages testicular ORs are expressed during spermatogenesis and whether each germ cell expresses one or multiple ORs. Here we examined the developmental expression profiles of several mouse testicular OR genes using an in situ hybridization technique at the cellular level. We found that OR transcripts in the spermatogenic cells are expressed in three developmental stages: late pachyten spermatocytes, early round spermatids, or late round spermatids. The OR mRNAs were condensed in a single dot-like structure within the nuclei of a subpopulation of spermatogenic cells. Double-fluorescent in situ hybridization revealed that some cells contained two dot-like signals derived from transcripts of two different ORs, suggesting that single spermatogenic cells could express more than one OR. One cell-multiple OR gene expression combined with variability in expression appears to result in heterogeneity in the repertoire of ORs expressed by individual spermatogenic cells. Although the functional consequence of heterogeneous OR expression awaits development of a methodology for characterizing OR proteins, our observations give insights into OR gene expression as well as OR function(s) in spermatogenic cells.

DOI： 10.1111/j.1365-2443.2005.00915.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：COMPANY OF BIOLOGISTS LTD  

Although a subset of the olfactory receptor (OR) gene family is expressed in testis, neither their developmental profile nor their physiological functions have been fully characterized. Here, we show that MOR23 (a mouse OR expressed in the olfactory epithelium and testis) functions as a chemosensing receptor in mouse germ cells. In situ hybridization showed that MOR23 was expressed in round spermatids during stages VI-BIII of spermatogenesis. Lyral, a cognate ligand of MOR23, caused an increase in intracellular Ca2+ in a fraction of spermatogenic cells and spermatozoa. We also generated transgenic mice that express high levels of MOR23 in the testis and examined the response of their germ cells to lyral. The results provided evidence that lyral-induced Ca2+ increases were indeed mediated by MOR23. In a sperm accumulation assay, spermatozoa migrated towards an increasing gradient of lyral. Tracking and sperm flagellar analyses suggest that Ca2+ increases caused by MOR23 activation lead to modulation of flagellar configuration, resulting in chemotaxis. By contrast, a gradient of a cAMP analog or K8.6 solution, which elicit Ca2+ influx in spermatozoa, did not cause sperm accumulation, indicating that chemosensing and regulation of sperm motility was due to an OR-mediated local Ca2+ increase. The present studies indicate that mouse testicular ORs might play a role in chemoreception during sperm-egg communication and thereby regulate fertilization.

DOI： 10.1242/jcs.01507

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記述言語：日本語   出版者・発行元：JAPANESE BIOCHEMICAL SOC  

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