Publisher Correction: Developmental stage-specific distribution and phosphorylation of Mblk-1, a transcription factor involved in ecdysteroid-signaling in the honey bee brain.

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Developmental stage-specific distribution and phosphorylation of Mblk-1, a transcription factor involved in ecdysteroid-signaling in the honey bee brain.

In the honey bee, the mushroom bodies (MBs), a higher-order center in insect brain, comprise interneurons termed Kenyon cells (KCs). We previously reported that Mblk-1, which encodes a transcription factor involved in ecdysteroid-signaling, is expressed preferentially in the large-type KCs (lKCs) in the pupal and adult worker brain and that phosphorylation by the Ras/MAPK pathway enhances the transcriptional activity of Mblk-1 in vitro. In the present study, we performed immunoblotting and immunofluorescence studies using affinity-purified anti-Mblk-1 and anti-phosphorylated Mblk-1 antibodies to analyze the distribution and phosphorylation of Mblk-1 in the brains of pupal and adult workers. Mblk-1 was preferentially expressed in the lKCs in both pupal and adult worker brains. In contrast, some Mblk-1 was phosphorylated almost exclusively in the pupal stages, and phosphorylated Mblk-1 was preferentially expressed in the MB neuroblasts and lKCs in pupal brains. Immunofluorescence studies revealed that both Mblk-1 and phosphorylated Mblk-1 are located in both the cytoplasm and nuclei of the lKC somata in the pupal and adult worker brains. These findings suggest that Mblk-1 plays a role in the lKCs in both pupal and adult stages and that phosphorylated Mblk-1 has pupal stage-specific functions in the MB neuroblasts and lKCs in the honey bee brain.

Pancreatic ß-cells are generated by neogenesis from non-ß-cells after birth.

The mass of pancreatic ß-cells is maintained throughout lifetime to control blood glucose levels. Although the major mechanism of the maintenance of ß-cell mass after birth is thought to be selfreplication of pre-existing ß-cells, it is possible that pancreatic ß-cells are also generated from non-ß-cells. Here, we address this issue by using the inducible Cre/loxP system to trace ß-cells. We generated Ins2-CreERT2/R26R-YFP double knock-in mice, in which pancreatic ß-cells can be labeled specifically and permanently upon injection of the synthetic estrogen analog tamoxifien, and then traced the ß-cells by pulse and chase experiment in several different conditions. When ß-cells were labeled in adults under physiological and untreated conditions, the frequency of the labeling (labeling index) was not altered significantly throughout the 12-month experimental period. In addition, the labeling index was not changed after ablation of ß-cells by streptozotocin treatment. However, when tamoxifen was injected to pregnant mothers just before they gave birth, the labeling index in the neonates was decreased significantly around weaning, suggesting that ß-cells are generated from non-ß-cells. These results indicate that various mechanisms are involved in the maintenance of ß-cells after birth, and that the present system using knock-in mice is useful for investigation of ß-cell fate.

Characterization of the column and autocellular junctions that define the vasculature of gill lamellae.

Novel adhesion junctions have been characterized that are formed at the interface between pillar cells and collagen columns, both of which are essential constituents of the gill lamellae in fish. We termed these junctions the "column junction" and "autocellular junction" and determined their molecular compositions by immunofluorescence microscopy using pufferfish. We visualized collagen columns by concanavalin A staining and found that the components of integrin-mediated cell-matrix adhesion, such as talin, vinculin, paxillin, and fibronectin, were concentrated on plasma membranes surrounding collagen columns (column membranes). This connection is analogous to the focal adhesion of cultured mammalian cells, dense plaque of smooth muscle cells, and myotendinous junction of skeletal muscle cells. We named this connection the "column junction." In the cytoplasm near the column, actin fibers, actinin, and a phosphorylated myosin light chain of 20 kDa are densely located, suggesting the contractile nature of pillar cells. The membrane infoldings surrounding the collagen columns were found to be connected by the autocellular junction, whose components are highly tyrosine-phosphorylated and contain the tight junction protein ZO-1. This study represents the first molecular characterization and fluorescence visualization of the column and autocellular junctions involved in both maintaining structural integrity and the hemodynamics of the branchial lamellae.