Constitutive role of GADD34 and CReP in cancellation of phospho-eIF2α-dependent translational attenuation and insulin biosynthesis in pancreatic ß cells.

Insulin biosynthesis has been well characterized with respect to transcriptional and post-translational regulation. However, the relationship between translational regulation of insulin and protein quality control in the endoplasmic reticulum (ER) remains to be clarified. Here we carried out forced expression of insulin in non-insulin-producing cells and compared activation level of ER stress-responsive molecules between insulin-producing cells and non-insulin-producing cells under normal culture condition or ER stress condition. Forced expression of insulin in non-insulin-producing cells caused severe ER stress with striking translational attenuation through phosphorylation of eIF2α by activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK), resulting in inhibition of insulin production at the protein level. We also found that GADD34 and CReP are highly expressed in the cells that endogenously produce insulin and that eIF2α shows constitutively low phosphorylation level in these cells although PERK is constitutively activated under both normal culture conditions and physiological conditions in the same cells. Inhibition of eIF2α phosphatase further decreased insulin level in pancreatic ß cells. These findings suggest that eIF2α phosphorylation level is kept low by GADD34- and/or CReP-regulated phosphatases in pancreatic ß cells and that cancellation of phospho-eIF2α-dependent translational inhibition by the molecular mechanism contributes to mass production of insulin in pancreatic ß cells.

Distinct subdivisions of subcortical U-fiber regions in the gyrencephalic ferret brain.

The human cerebrum contains a large amount of cortico-cortical association fibers. Among them, U-fibers are short-range association fibers located in white matter immediately deep to gray matter. Although U-fibers are thought to be crucial for higher cognitive functions, the organization within U-fiber regions are still unclear. Here we investigated the properties of U-fiber regions in the ferret cerebrum using neurochemical, neuronal tracing, immunohistochemical and electron microscopic techniques. We found that U-fiber regions can be subdivided into two regions, which we named outer and inner U-fiber regions. We further uncovered that outer U-fiber regions have smaller-diameter axons with thinner myelin compared with inner U-fiber regions. These findings may indicate functional complexity within U-fiber regions in the cerebrum.

The origin and development of subcortical U-fibers in gyrencephalic ferrets.

In the white matter of the human cerebrum, the majority of cortico-cortical fibers are of short range, connecting neighboring cortical areas. U-fibers represent connections between neighboring areas and are located in the white matter immediately deep to the cerebral cortex. Using gyrencephalic carnivore ferrets, here we investigated the neurochemical, anatomical and developmental features of U-fibers. We demonstrate that U-fibers were derived from neighboring cortical areas in ferrets. U-fiber regions in ferrets were intensely stained with Gallyas myelin staining and Turnbull blue iron staining. We further found that U-fibers were derived from neurons in both upper and lower layers in neighboring areas of the cerebral cortex and that U-fibers were formed later than axons in the deep white matter during development. Our findings shed light on the fundamental features of U-fibers in the gyrencephalic cerebral cortex. Because genetic manipulation techniques for ferrets are now available, ferrets should be an important option for investigating the development, functions and pathophysiological changes of U-fibers.

Transgenic mouse model for imaging of interleukin-1ß-related inflammation in vivo.

Inflammation is a biological response associated with symptoms of various diseases, and its study is important in gaining an understanding of the pathological conditions of such diseases and in making strategic plans for promoting healing. It is therefore essential to develop technologies for the detection of inflammatory conditions. Interleukin-1ß (IL-1ß) is a proinflammatory cytokine produced and secreted mainly by monocytes and macrophages in response to inflammatory stimulation. The activation of IL-1ß is regulated through transcriptional induction by the promoter and post-translational processing by the inflammasome. Here we have developed a reporter gene to monitor the activation status of IL-1ß by using a dual regulation system and, by using the reporter gene, we have established a mouse model that permits low-invasive visualization of the inflammatory status. Previous reporter systems dependent on the transcription or processing of IL-1ß show problems in terms of background noise or signal specificity. Our reporter system overcomes these weaknesses by combining advantages from regulation by a promoter and processing of IL-1ß. Our mouse model detected specific physiological inflammation in the liver and pancreas caused by hepatitis or pancreatitis models, respectively. Our reporter gene and mouse model are therefore expected to become useful bioresources for future medical science.