Flexible search for single-axon morphology during neuronal spontaneous polarization

Polarization, a disruption of symmetry in cellular morphology, occurs spontaneously, even in symmetrical extracellular conditions. This process is regulated by intracellular chemical reactions and the active transport of proteins and it is accompanied by cellular morphological changes. To elucidate the general principles underlying polarization, we focused on developing neurons. Neuronal polarity is stably established; a neuron initially has several neurites of similar length, but only one elongates and is selected to develop into an axon. Polarization is flexibly controlled; when multiple neurites are selected, the selection is eventually reduced to yield a single axon. What is the system by which morphological information is decoded differently based on the presence of a single or multiple axons? How are stability and flexibility achieved? To answer these questions, we constructed a biophysical model with the active transport of proteins that regulate neurite growth. Our mathematical analysis and computer simulation revealed that, as neurites elongate, transported factors accumulate in the growth cone but are degraded during retrograde diffusion to the soma. Such a system effectively works as local activation-global inhibition mechanism, resulting in both stability and flexibility. Our model shows good accordance with a number of experimental observations.     

Superoxide dismutase (SOD) as a potential inhibitory mediator of inflammation via neutrophil apoptosis

Superoxide dismutase (SOD) is supposed to be an effective agent for neutrophil-mediated inflammation in the area of critical medicine. We investigated the involvement of SOD in the regulation of neutrophil apoptosis. Exogenously added SOD effectively induced neutrophil apoptosis, and the fluorescence patterns determined using annexin-V and the 7-AAD were similar to those seen in Fas-mediated neutrophil apoptosis. Neutrophils are short-lived leukocytes that need to be removed safely by apoptosis. The clearance of apoptotic neutrophils from sites of inflammation is a crucial determinant of the resolution of inflammation. Catalase inhibited the neutrophil apoptosis and caspase-3 activation. Spontaneous apoptosis, hydrogen peroxide and anti-Fas antibody-induced apoptosis of neutrophils were accelerated in Down's syndrome patients, in whom the SOD gene is overexpressed. Hydrogen peroxide was thought to be a possible major mediator of ROS-induced neutrophil apoptosis in caspase-dependent manner. Neutrophil apoptosis represents a crucial step in the mechanism governing the resolution of inflammation and has been suggested as a possible target for the control of neutrophil-mediated tissue injury. SOD may be a potential inhibitory mediator of neutrophil-mediated inflammation.     

Key regulators in neuronal polarity

Neurons are highly polarized cells, most of which develop a single axon and several dendrites. These two compartments acquire specific characteristics that enable neurons to transmit intercellular signals from several dendrites to an axon. A wealth of recent studies has shown that PI 3-kinase, Rho family GTPases, the Par complex, and cytoskeleton-related proteins participate in the initial events of neuronal polarization. Here, we review the role of polarity-regulating molecules and the potential mechanisms underlying the specification of an axon and dendrites.     

Sericin enhances attachment of cultured human skin fibroblasts

Human skin fibroblasts were cultured on sericin prepared from cocoon shells. The living cell number after 72 h was enhanced to 250% of the no-sericin control. The increase was due to the acceleration of the initial attachment of the cells. It was found that sericin M, the main component of about 400 kDa, and its serine-rich repetitive domain were the active principles.     

Transgenic rats overexpressing the human MrgX3 gene show cataracts and an abnormal skin phenotype

The human MrgX3 gene, belonging to the mrgs/SNSRs (mas related genes/sensory neuron specific receptors) family, was overexpressed in transgenic rats using the actin promoter. Two animal lines showed cataracts with liquification/degeneration and swelling of the lens fiber cells. The transient epidermal desquamation was observed in line with higher gene expression. Histopathology of the transgenic rats showed acanthosis and focal parakeratosis. In the epidermis, there was an increase in cellular keratin 14, keratin 10, and loricrin, as well as PGP 9.5 in innervating nerve fibers. These phenotypes accompanied an increase in the number of proliferating cells. These results suggest that overexpression of the human MrgX3 gene causes a disturbance of the normal cell-differentiation process.     

Kinetochore capture and bi-orientation on the mitotic spindle

Kinetochores are large protein complexes that are formed on chromosome regions known as centromeres. For high-fidelity chromosome segregation, kinetochores must be correctly captured on the mitotic spindle before anaphase onset. During prometaphase, kinetochores are initially captured by a single microtubule that extends from a spindle pole and are then transported poleward along the microtubule. Subsequently, microtubules that extend from the other spindle pole also interact with kinetochores and, eventually, each sister kinetochore attaches to microtubules that extend from opposite poles - this is known as bi-orientation. Here we discuss the molecular mechanisms of these processes, by focusing on budding yeast and drawing comparisons with other organisms.     

Role of Rho-kinase in regulation of insulin action and glucose homeostasis

Accumulating evidence indicates an important role for serine phosphorylation of IRS-1 in the regulation of insulin action. Recent studies suggest that Rho-kinase (ROK) is a mediator of insulin signaling, via interaction with IRS-1. Here we show that insulin stimulation of glucose transport is impaired when ROK is chemically or biologically inhibited in cultured adipocytes and myotubes and in isolated soleus muscle ex vivo. Inactivation of ROK also reduces insulin-stimulated IRS-1 tyrosine phosphorylation and PI3K activity. Moreover, inhibition of ROK activity in mice causes insulin resistance by reducing insulin-stimulated glucose uptake in skeletal muscle in vivo. Mass spectrometry analysis identifies IRS-1 Ser632/635 as substrates of ROK in vitro, and mutation of these sites inhibits insulin signaling. These results strongly suggest that ROK regulates insulin-stimulated glucose transport in vitro and in vivo. Thus, ROK is an important regulator of insulin signaling and glucose metabolism.     

CD24 is expressed specifically in the nucleus pulposus of intervertebral discs

Intervertebral disc (IVD) consists of a soft gelatinous material in its center, the nucleus pulposus (NP), bounded peripherally by fibrocartilage, annulus fibrosus (AF). Despite the number of patients with IVD degeneration, gene expression analysis has not been undertaken in NP and therefore little is known about the molecular markers expressed in NP. Here, we undertook a microarray screen in NP with the other nine tissues to identify the specific cell surface markers for NP. Five membrane associating molecules out of 10,490 genes were identified as highly expressing genes in NP compared with the other tissues. Among them, we identified CD24, a glycosylphosphatidylinositol (GPI) anchor protein as a cell surface marker for NP. CD24 expression was also detected in the herniated NP and chordoma, a malignant primary tumor derived from notochordal cells, while it was absent in chondrosarcoma. Therefore, CD24 is a molecular marker for NP as well as the diseases of IVD.     

Pnlip encoding pancreatic lipase is possible candidate for obesity QTL in the OLETF rat

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat exhibits polygenic obesity, and one of quantitative trait loci (QTLs) responsible for a susceptibility to obesity in the OLETF, Nidd6/of, has been mapped to the approximately 10-cM genomic region between D1Rat166 and D1Rat90 on chromosome 1 in (OLETF x normal) F2 intercross. In this study, we have attempted to identify the causal gene for the Nidd6/of QTL. A Nidd6/of congenic strain, constructed by introgressing the OLETF allele on the mapped Nidd6/of region in the normal F344 rat strain, confirmed the existence of the Nidd6/of as obesity QTL. The Nidd6/of region was refined to a approximately 2.3-cM genomic region between D1Rat225 and D1Rat90, using informative recombinants selected from (Nidd6/of congenic x F344) F1 x Nidd6/of congenic backcross progenies. Among 46 genes located within the approximately 2.3-cM region, pancreatic lipase gene, Pnlip, was regarded as the most prominent and physiologically relevant positional candidate for the Nidd6/of QTL. We found that Pnlip possesses an OLETF allele-specific increase of mRNA levels in the pancreas, and that the OLETF allele is longer in variable number of tandem repeat (VNTR) within the 5'-flanking region than normal alleles. We further showed that the Nidd6/of QTL completely cosegregates with Pnlip VNTR in the informative recombinants from (Nidd6/of congenic x F344) F1 x Nidd6/of congenic backcross progenies. These results suggest that Pnlip is possible candidate for the Nidd6/of QTL.     

Fate of GFP-expressing Escherichia coli in the midgut and response to ingestion in a tick, Ornithodoros moubata (Acari: Argasidae)

Ticks are well-known vectors of various pathogens but migration of the pathogens in the tick midgut is not fully understood. In the present study, the fate of microbes in the midgut of Ornithodoros moubata was observed using green fluorescent protein (GFP)-expressing Escherichia coli. Fluctuations in the percentage of hemocytes in the hemolymph (Hc) and expression of an antimicrobial peptide, defensin, in the midgut was also investigated. Most E. coli gradually disappeared in the midgut after ingestion fluctuations in Hc coincided with the changes. Expression of defensin was also confirmed and slightly up-regulated after E. coli ingestion. Moreover, it was demonstrated that E. coli can not pass through the tick midgut epithelium after ingestion by the hemolymph cultures. It is known that various pathogens and host immunoglobulins ingested with a blood meal can enter into the hemocoel, which suggests the presence of unique and complex passage mechanisms for each molecule and organism. The results obtained here help to clarify that digestion enzymes is an important function of the tick midgut to protect against invading molecules and organisms.