p600 Plays Essential Roles in Fetal Development

p600 is a multifunctional protein implicated in cytoskeletal organization, integrin-mediated survival signaling, calcium-calmodulin signaling and the N-end rule pathway of ubiquitin-proteasome-mediated proteolysis. While push, the Drosophila counterpart of p600, is dispensable for development up to adult stage, the role of p600 has not been studied during mouse development. Here we generated p600 knockout mice to investigate the in vivo functions of p600. Interestingly, we found that homozygous deletion of p600 results in lethality between embryonic days 11.5 and 13.5 with severe defects in both embryo and placenta. Since p600 is required for placental development, we performed conditional disruption of p600, which deletes selectively p600 in the embryo but not in the placenta. The conditional mutant embryos survive longer than knockout embryos but ultimately die before embryonic day 14.5. The mutant embryos display severe cardiac problems characterized by ventricular septal defects and thin ventricular walls. These anomalies are associated with reduced activation of FAK and decreased expression of MEF2, which is regulated by FAK and plays a crucial role in cardiac development. Moreover, we observed pleiotropic defects in the liver and brain. In sum, our study sheds light on the essential roles of p600 in fetal development.

Current-induced magnetic domain wall motion below intrinsic threshold triggered by Walker breakdown

Controlling the position of a magnetic domain wall with electric current may allow for new types of non-volatile memory and logic devices. To be practical, however, the threshold current density necessary for domain wall motion must be reduced below present values. Intrinsic pinning due to magnetic anisotropy, as recently observed in perpendicularly magnetized Co/Ni nanowires, has been shown to give rise to an intrinsic current threshold J(th)(0). Here, we show that domain wall motion can be induced at current densities 40% below J(th)(0) when an external magnetic field of the order of the domain wall pinning field is applied. We observe that the velocity of the domain wall motion is the vector sum of current- and field-induced velocities, and that the domain wall can be driven against the direction of a magnetic field as large as 2,000 Oe, even at currents below J(th)(0). We show that this counterintuitive phenomenon is triggered by Walker breakdown, and that the additive velocities provide a unique way of simultaneously determining the spin polarization of current and the Gilbert damping constant.

Feasibility of cytological diagnosis of sarcoidosis with endobronchial US-guided transbronchial aspiration

BACKGROUND

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has a high diagnostic value in sarcoidosis if the obtained histological specimen is indicative of a non-caseating epithelioid-cell granuloma. However, EBUS-TBNA in sacoidosis sometimes affords solely cytological specimens.

OBJECTIVE

To investigate the relevance of EBUS-TBNA cytology specimens in diagnosing sarcoidosis.

DESIGN

The study population comprised 72 patients with sarcoidosis and 116 patients who had thoracic malignancies and intrathoracic lymphadenopathy but were eventually proven to be metastasis-free (controls). The EBUS-TBNA samples obtained for these subjects were blindly evaluated for the presence of epithelioid cell clusters by 2 independent cytoscreeners and a pathologist.

RESULTS

Interobserver variability in the specimen grading was minimal. The sensitivity and specificity were 65.3% and 94.0%, respectively. The sensitivity was high, at 87.5%, for the combined cytological and histological examinations. Of 7 controls whose cytological specimens showed epithelioid cell clusters, 3 were also deemed positive for sarcoidosis on histological examination, which indicated that they had sarcoid reaction to cancer.

CONCLUSIONS

Cytological evaluation of the EBUS-TBNA specimens had higher sensitivity than histological evaluation alone for intrathoracic lymphadenopathy due to sarcoidosis. It should be recognized, however, that up to 6% of patients with thoracic malignancy may have sarcoid reaction in non-metastatic lymph nodes.

DNA ends alter the molecular composition and localization of Ku multicomponent complexes

The Ku heterodimer plays an essential role in non-homologous end-joining and other cellular processes including transcription, telomere maintenance and apoptosis. While the function of Ku is regulated through its association with other proteins and nucleic acids, the specific composition of these macromolecular complexes and their dynamic response to endogenous and exogenous cellular stimuli are not well understood. Here we use quantitative proteomics to define the composition of Ku multicomponent complexes and demonstrate that they are dramatically altered in response to UV radiation. Subsequent biochemical assays revealed that the presence of DNA ends leads to the substitution of RNA-binding proteins with DNA and chromatin associated factors to create a macromolecular complex poised for DNA repair. We observed that dynamic remodeling of the Ku complex coincided with exit of Ku and other DNA repair proteins from the nucleolus. Microinjection of sheared DNA into live cells as a mimetic for double strand breaks confirmed these findings in vivo.

Differential expression of Toll-like receptor 4 and human monocyte subsets in acute myocardial infarction

OBJECTIVE

To investigate the involvement of Toll-like receptor 4 (TLR4) expression on two monocyte subsets in the pathologic processes related to acute coronary syndrome. How monocytes, which have recently been shown to comprise two distinct subsets, mediate the process of coronary plaque rupture remains to be fully elucidated. Recent studies have shown that TLR4 is involved in monocyte activation of patients with accelerated forms of atherosclerosis.

METHODS

We enrolled 65 patients with acute myocardial infarction (AMI, n=22), unstable angina pectoris (UAP, n=16), and stable angina pectoris (SAP, n=27) who underwent coronary angiography and 15 healthy controls. The expression of TLR4 on two monocyte subsets (CD14(+)CD16(-) and CD14(+)CD16(+)) was measured by flow cytometry.

RESULTS

In patients with AMI, TLR4 was more expressed on circulating CD14(+)CD16(+) monocytes than on CD14(+)CD16(-) monocytes (p<0.001). The expression levels of TLR4 on CD14(+)CD16(+) monocytes were significantly elevated in patients with AMI compared with other 3 groups. TLR4 expression levels on CD14(+)CD16(+) monocytes were significantly elevated at the culprit site compared with the systemic level (p=0.044). The up-regulation of TLR4 on admission was remarkably decreased 12 days after AMI (p<0.001). In addition, plasma levels of tumor necrosis factor-α were positively correlated with TLR4 expression levels on monocytes in patients with AMI (r=0.47, p=0.027).

CONCLUSION

TLR overexpression on CD14(+)CD16(+) monocytes in AMI, as demonstrated both in the circulation and at the coronary culprit site, might be associated with the pathogenesis of AMI.

Observation of the intrinsic pinning of a magnetic domain wall in a ferromagnetic nanowire

The spin transfer torque is essential for electrical magnetization switching. When a magnetic domain wall is driven by an electric current through an adiabatic spin torque, the theory predicts a threshold current even for a perfect wire without any extrinsic pinning. The experimental confirmation of this 'intrinsic pinning', however, has long been missing. Here, we give evidence that this intrinsic pinning determines the threshold, and thus that the adiabatic spin torque dominates the domain wall motion in a perpendicularly magnetized Co/Ni nanowire. The intrinsic nature manifests itself both in the field-independent threshold current and in the presence of its minimum on tuning the wire width. The demonstrated domain wall motion purely due to the adiabatic spin torque will serve to achieve robust operation and low energy consumption in spintronic devices.

[A case of giant heterotopic Brunner's gland adenoma prolapsing into the duodenum]

A 81-year-old woman admitted with general fatigue was found to have a giant polyp in the gastric antrum by endoscopy. The polyp prolapsed into the duodenum through the pylorus. Angiographic examination of the abdomen revealed the polyp to be about 90×35 mm in size. Laparotomy was performed. It was finally diagnosed as heterotopic Brunner's gland adenoma which had a stalk on the antrum of the stomach. Heterotopic Brunner's gland adenoma is rare. Only 3 cases including the present case have been reported in Japan.

Tissue plasminogen activator and plasminogen are critical for osmotic homeostasis by regulating vasopressin secretion

Systemic osmotic homeostasis is regulated mainly by neuroendocrine system of arginine-vasopressin (AVP) in mammalians. In the present study, we demonstrated that the immunoreactivity of tissue plasminogen activator (tPA) was observed specifically at neurosecretory granules of AVP-positive magnocellular terminals and that of plasminogen was seen at astrocytes in the neurohypophysis (NH). Both tPA and plasminogen knockout (KO) mice revealed higher plasma osmolarity upon water deprivation, a chronic osmotic stimulation, as compared with their wild-type (WT) animals, indicating abnormal osmotic control in these KO mice. tPA KO mice but not plasminogen ones revealed lower ability in secreting AVP into the blood circulation upon an acute osmotic stimulation. Both tPA and plasminogen KO animals showed lower ability in secreting AVP into the blood circulation upon a chronic osmotic stimulation. The recombinant tPA was able to promote the release of AVP from isolated NH. Chronic osmotic stimulation decreased the laminin expression level of neurohypophysial microvessel in WT mice but not in plasminogen KO ones. We suggest that AVP secretion is critically regulated by tPA-dependent facilitation of AVP release from terminals and plasminogen-dependent increase of AVP permeability across microvessels possibly via laminin degradation.

HJURP is a cell-cycle-dependent maintenance and deposition factor of CENP-A at centromeres

The histone H3 variant CenH3, called CENP-A in humans, is central in centromeric chromatin to ensure proper chromosome segregation. In the absence of an underlying DNA sequence, it is still unclear how CENP-A deposition at centromeres is determined. Here, we purified non-nucleosomal CENP-A complexes to identify direct CENP-A partners involved in such a mechanism and identified HJURP. HJURP was not detected in H3.1- or H3.3-containing complexes, indicating its specificity for CENP-A. HJURP centromeric localization is cell cycle regulated, and its transient appearance at the centromere coincides precisely with the proposed time window for new CENP-A deposition. Furthermore, HJURP downregulation leads to a major reduction in CENP-A at centromeres and impairs deposition of newly synthesized CENP-A, causing mitotic defects. We conclude that HJURP is a key factor for CENP-A deposition and maintenance at centromeres.

Why the carrot is more effective than the stick: different dynamics of punishment memory and reward memory and its possible biological basis

One of the most extensively debated topics in educational psychology is whether punishment or reward is more effective for producing short-term and long-term behavioral changes, and it has been proposed that the effect of punishment is less durable than the effect of reward. However, no conclusive evidence to support this proposal has been obtained in any animals. We recently found that punishment memory decayed much faster than reward memory in olfactory learning and visual pattern learning in crickets. We also found that neurotransmitters conveying punishment and reward signals differ in crickets: dopaminergic and octopaminergic neurons play critical roles in conveying punishment and reward signals, respectively. In this study, we investigated whether these features are general features of cricket learning or are specific to olfactory and visual pattern learning. We found that crickets have the capability of color learning and that their color learning has the same features. Based on our findings in crickets and those reported in other species of insects, we conclude that these two features are conserved in many forms of insect learning. In mammals, aminergic neurons are known to convey reward and punishment signals in learning of a variety of sensory stimuli. We propose that the faster decay of punishment memory than reward memory observed in insects and humans reflects different cellular and biochemical processes after activation of receptors for amines conveying punishment and reward signals. The possible adaptive significance of relatively limited durability of punishment memory is proposed.

Structural basis of UV DNA-damage recognition by the DDB1-DDB2 complex

Ultraviolet (UV) light-induced pyrimidine photodimers are repaired by the nucleotide excision repair pathway. Photolesions have biophysical parameters closely resembling undamaged DNA, impeding discovery through damage surveillance proteins. The DDB1-DDB2 complex serves in the initial detection of UV lesions in vivo. Here we present the structures of the DDB1-DDB2 complex alone and bound to DNA containing either a 6-4 pyrimidine-pyrimidone photodimer (6-4PP) lesion or an abasic site. The structure shows that the lesion is held exclusively by the WD40 domain of DDB2. A DDB2 hairpin inserts into the minor groove, extrudes the photodimer into a binding pocket, and kinks the duplex by approximately 40 degrees. The tightly localized probing of the photolesions, combined with proofreading in the photodimer pocket, enables DDB2 to detect lesions refractory to detection by other damage surveillance proteins. The structure provides insights into damage recognition in chromatin and suggests a mechanism by which the DDB1-associated CUL4 ubiquitin ligase targets proteins surrounding the site of damage.

Detection of human papillomavirus type 56 in Bowen's disease involving the nail matrix

BACKGROUND

As Bowen's disease of the nail apparatus is quite rare, there have been only a few reports on the prevalence of human papillomavirus (HPV) infection in this condition.

OBJECTIVES

The purpose of this study was to clarify the association of HPV with this disease involving the nail apparatus.

METHODS

Five patients with Bowen's disease of the nail apparatus were investigated clinically, virologically and histologically. Total DNAs extracted from excised skin lesions were analysed using polymerase chain reaction (PCR) for the presence of HPV DNA and the amplified products were subjected to DNA sequence analyses. Histological localization of HPV DNA was examined by in situ hybridization.

RESULTS

In three of five patients, HPV was detected by PCR amplification, and subsequent sequence analyses of the PCR products showed the sequences of HPV type 56. A common clinical feature of the three HPV-positive patients was longitudinal melanonychia. In contrast, the two HPV-negative patients presented with a convex nail deformity and a periungual ulcerative lesion. In two of three positive cases, there was a silent point mutation in the L1 gene of each HPV. In the remaining one case, the nucleotide sequence was consistent with the consensus sequence of HPV 56. Sequence analyses of the E6 gene revealed the infection of different variants of HPV 56 among the three cases. The viral genomes were located in keratinocyte nuclei upon in situ hybridization.

CONCLUSIONS

HPV 56 may be involved in the carcinogenesis of Bowen's disease affecting the nail matrix with longitudinal pigmentation.

Nonhepatocytic malignant mixed tumor of the liver in adults: report of a long surviving case

A primary nonhepatocytic malignant mixed tumor in the liver contains both epithelial and mesenchymal components, and the incidence in adults is extremely rare. A 45-year-old female was admitted because of abdominal fullness. Abdominal imaging studies revealed a huge cystic tumor with a mural nodule in the right lobe. A right trisegmentectomy and an invaded partial diaphragm resection were performed. Diagnosis was established after surgery. The patient is still alive 11 years after surgery, and to our knowledge is the longest surviving patient with a primary nonhepatocytic malignant mixed primary tumor of the liver.

Isolation of XAB2 complex involved in pre-mRNA splicing, transcription, and transcription-coupled repair

Nucleotide excision repair is a versatile repair pathway that counteracts the deleterious effects of various DNA lesions. In nucleotide excision repair, there is a transcription-coupled repair (TCR) pathway that focuses on DNA damage that blocks RNA polymerase IIo in transcription elongation. XAB2 (XPA-binding protein 2), containing tetratricopeptide repeats, has been isolated by virtue of its ability to interact with xeroderma pigmentosum group A protein (XPA). Moreover, XAB2 has been shown to interact with Cockayne syndrome group A and B proteins (CSA and CSB) and RNA polymerase II, as well as XPA, and is involved in TCR and transcription. Here we purified XAB2 as a multimeric protein complex consisting of hAquarius, XAB2, hPRP19, CCDC16, hISY1, and PPIE, which are involved in pre-mRNA splicing. Knockdown of XAB2 with small interfering RNA in HeLa cells resulted in a hypersensitivity to killing by UV light and a decreased recovery of RNA synthesis after UV irradiation and regular RNA synthesis. Enhanced interaction of XAB2 with RNA polymerase IIo or XPA was observed in cells treated with DNA-damaging agents, indicating DNA damage-responsive activity of the XAB2 complex. These results indicated that the XAB2 complex is a multifunctional factor involved in pre-mRNA splicing, transcription, and TCR.