Transient expression of Xpn, an XLMR protein related to neurite extension, during brain development and participation in neurite outgrowth.

KIAA2022 has been implicated as a gene responsible for expressing X-linked mental retardation (XLMR) proteins in humans. However, the functional role of KIAA2022 in the human brain remains unclear. Here, we revealed that depletion of Kiaa2022 inhibits neurite outgrowth of PC12 cells, indicating that the gene participates in neurite extension. Thus, we termed Kiaa2022 as an XLMR protein related to neurite extension (Xpn). Using the mouse brain as a model and ontogenetic analysis of Xpn by real-time PCR, we clearly demonstrated that Xpn is expressed transiently during the late embryonic and perinatal stages. In situ hybridization histochemistry further revealed that Xpn-expressing neurons could be categorized ontogenetically into three types. The first type showed transient expression of Xpn during development. The second type maximally expressed Xpn during the late embryonic or perinatal stage. Thereafter, Xpn expression in this type of neuron decreased gradually throughout development. Nevertheless, a significant level of Xpn expression was detected even into adulthood. The third type of neurons initiated expression of Xpn during the embryonic stage, and continued to express the gene throughout the remaining developmental stages. Subsequent immunohistochemical analysis revealed that Xpn was localized to the nucleus and cytoplasm throughout brain development. Our findings indicate that Xpn may participate in neural circuit formation during developmental stages via nuclear and cytoplasmic Xpn. Moreover, disturbances of this neuronal circuit formation may play a role in the pathogenesis of mental retardation.

Possible involvement of CD14+ CD16+ monocyte lineage cells in the epidermal damage of Stevens-Johnson syndrome and toxic epidermal necrolysis.

BACKGROUND: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are characterized by keratinocyte apoptosis and necrosis, resulting in epidermal detachment. Although monocytes abundantly infiltrate the epidermis in SJS/TEN skin lesions, the properties and functions of these cells have not been fully examined. OBJECTIVES: To determine the properties of monocytes infiltrating into the epidermis in SJS/TEN. METHODS: Immunostaining of skin sections was performed to examine the membrane markers of monocytes infiltrating into skin lesions. RESULTS: Immunostaining of cryosections from 11 SJS/TEN skin lesions revealed numerous CD14+ monocytes located along the dermoepidermal junction and throughout the epidermis. The cells coexpressed CD16, CD11c and HLA-DR. CD14+ CD16+ cells were identified in very early lesions without epidermal damage, suggesting that their infiltration is a cause, rather than a result, of epidermal damage. Moreover, these cells expressed CD80, CD86 and CD137 ligand, indicative of their ability to facilitate the proliferation and cytotoxicity of CD8+ T cells. CD16+ cells infiltrating the epidermis and detected at the dermoepidermal junction were immunostained and counted in paraffin-embedded skin sections obtained from 47 patients with drug rash manifested as TEN, SJS, maculopapular-type rash or erythema multiform-type rash. The number of CD16+ monocytes infiltrating the epidermis increased significantly, depending on the grade of epidermal damage. CONCLUSIONS: These findings suggest that the appearance of CD14+ CD16+ cells of monocyte lineage plays an important role in the epidermal damage associated with SJS/TEN, most probably by enhancing the cytotoxicity of CD8+ T cells.

Id1, Id2 and Id3 are induced in rat melanotrophs of the pituitary gland by dopamine suppression under continuous stress.

In rats under continuous stress (CS) there is decreased hypothalamic dopaminergic innervation to the intermediate lobe (IL) of the pituitary gland, which causes hyperactivation and subsequent degeneration of melanotrophs in the IL. In this study, we investigated the molecular basis for the changes that occur in melanotrophs during CS. Using microarray analysis, we identified several genes differentially expressed in the IL under CS conditions. Among the genes up-regulated under CS conditions, we focused on the inhibitor of DNA binding/differentiation (Id) family of dominant negative basic helix-loop-helix (bHLH) transcription factors. RT-PCR, Western blotting and in situ hybridization confirmed the significant inductions of Id1, Id2 and Id3 in the IL of CS rats. Administration of the dopamine D2 receptor agonist bromocriptine prevented the inductions of Id1-3 in the IL of CS rats, whereas application of the dopamine D2 antagonist sulpiride induced significant expressions of Id1-3 in the IL of normal rats. Moreover, an in vitro study using primary cultured melanotrophs demonstrated a direct effect on Id1-3 inductions by dopamine suppression. These results suggest that the decreased dopamine levels in the IL during CS induce Id1-3 expressions in melanotrophs. Because Id family members inhibit various bHLH transcription factors, it is conceivable that the induced Id1-3 would cooperatively modulate gene expressions in melanotrophs under CS conditions to induce hormone secretion.

Molecular mechanism of kallikrein-related peptidase 8/neuropsin-induced hyperkeratosis in inflamed skin.

BACKGROUND: Hyperkeratosis and acanthosis occur in inflamed skin. Proliferation and differentiation of keratinocytes are important processes during epidermal repair after inflammation. Neuropsin and its human homologue kallikrein-related peptidase 8 (KLK8) have been reported to be involved in epidermal proliferation and differentiation, but the involved molecular mechanisms are obscure. OBJECTIVES: To explore the molecular mechanism of KLK8/neuropsin-induced hyperkeratosis and acanthosis in inflamed skin. METHODS: The molecular mechanism involved in KLK8/neuropsin-induced hyperkeratosis and acanthosis in inflamed skin was investigated both in vivo and in vitro using neuropsin knockout mice and KLK8 knockdown human keratinocytes. Neuropsin-related genes were identified by differential gene display. The localization and functional relationship of the molecules affected downstream of KLK8/neuropsin in normal and inflamed skin were analysed by in situ hybridization and immunohistochemistry. RESULTS: Hyperkeratosis and acanthosis in sodium lauryl sulphate-stimulated skin were markedly inhibited in neuropsin knockout mice. Knockdown of KLK8/neuropsin increased transcription factor activator protein-2α (AP-2α) expression and decreased keratin 10 expression in human keratinocytes and mouse skin, respectively. AP-2α has been reported to inhibit epidermal proliferation and keratin 10 expression. Distributional analysis showed that KLK8/neuropsin was expressed in the stratum spinosum, AP-2α was expressed in the stratum basale and the lower part of the stratum spinosum, and keratin 10 was expressed throughout the stratum spinosum. CONCLUSIONS: The above findings suggest the following mechanism of events underlying KLK8/neuropsin-induced hyperkeratosis: (i) skin inflammation increases KLK8/neuropsin expression in the stratum spinosum; (ii) the released KLK8/neuropsin inhibits AP-2α expression in the cells of the stratum basale and stratum spinosum; (iii) the decrease in AP-2α results in cell proliferation in the stratum basale and cell differentiation in the stratum spinosum, with an increase in keratin 10 expression.

DISC1 regulates cell-cell adhesion, cell-matrix adhesion and neurite outgrowth.

Disrupted-in-schizophrenia 1 (DISC1) is a promising susceptibility gene for major mental illness. Recent studies have implicated DISC1 in key neurodevelopmental processes, including neurite outgrowth, neuronal migration and proliferation. Here, we report that DISC1 regulates cell-cell and cell-matrix adhesion and neurite outgrowth. DISC1 overexpression increased expression of the adherence junction protein N-cadherin and enhanced cell-cell adhesion. The increased N-cadherin accumulated in the areas of cell-cell contact. DISC1 overexpression also enhanced cell-matrix adhesion by inducing expression of beta1-integrin protein. In the presence of nerve growth factor (NGF), DISC1 overexpression increased beta1-integrin expression at the cell membrane and growth cone. NGF-induced neurite extension was enhanced by DISC1, and anti-beta1-integrin antibody reduced the neurite outgrowth of DISC1-overexpressing cells to the control level. Furthermore, DISC1 also regulated N-cadherin and beta1-integrin expression at the cell membrane in primary neurons. We conclude that DISC1 regulates cell-cell adhesion and cell-matrix adhesion by regulating the expression of adhesion molecules.

The distribution and characterization of endogenous protein arginine N-methyltransferase 8 in mouse CNS.

Protein arginine N-methyltransferase (PRMT) 8 was first discovered from a database search for genes harboring four conserved methyltransferase motifs, which shares more than 80% homology to PRMT1 in amino acid [Lee J, Sayegh J, Daniel J, Clarke S, Bedford MT (2005) PRMT8, a new membrane-bound tissue-specific member of the protein arginine methyltransferase family. J Biol Chem 280:32890-32896]. Interestingly, its tissue distribution is strikingly restricted to mouse CNS. To characterize the function in the CNS neurons, we raised an antiserum against PRMT8 to perform immunohistochemistry (IHC) and Western blot analysis. By IHC, the immunoreactivity of endogenous PRMT8 was broadly distributed in the CNS neurons with markedly intense signals in the cerebellum, hippocampal formation, and cortex, but was not detected in the cerebellar granular layer. In some subset of the neurons, the immunoreactivity was observed in the dendrites and axon bundles. The subcellular localization of the immunoreactivity was dominantly nuclear, arguing against the original report that exogenously expressed PRMT8 localizes to the plasma membrane via the N-terminal myristoylation. A series of the exogenously expressed proteins with different in-frame translation initiation codons was tested for comparison with the endogenous protein in molecular size. The third initiator codon produced the protein that was equivalent in size to the endogenous and showed a similar localizing pattern in PC12 cells. In conclusion, PRMT8 is a neuron-specific nuclear enzyme and the N-terminus does not contain the glycine end for myristoylation target.

Association of human herpesvirus 6 reactivation with the flaring and severity of drug-induced hypersensitivity syndrome.

BACKGROUND: Drug-induced hypersensitivity syndrome (DIHS) is an adverse reaction with clinical signs of fever, rash and internal organ involvement. In the vast majority of patients in Japan, the causative drugs for DIHS are limited to the following eight: carbamazepine, phenytoin, phenobarbital, zonisamide, mexiletine, dapsone, salazosulfapyridine and allopurinol. The association of human herpesvirus (HHV)-6 reactivation with DIHS has been reported by various groups. OBJECTIVES: To confirm the relationship between the flaring and severity of DIHS and HHV-6 reactivation. METHODS: We evaluated 100 patients with drug rash and systemic symptom(s) caused by the drugs associated with DIHS. HHV-6 reactivation was examined by serological antibody assay and quantitative real-time polymerase chain reaction assay of serial serum samples. RESULTS: Anti-HHV-6 IgG titres increased in 62 of 100 patients, 14-28 days after the onset of symptoms. These patients suffered from severe organ involvement and a prolonged course compared with 38 patients showing no reactivation of HHV-6. Significant amounts of HHV-6 DNA were detected in serum samples from 18 of the 62 patients. Flaring of symptoms such as fever and hepatitis was closely related to HHV-6 reactivation in these 18 patients. It should be emphasized that all five patients with fatal outcome and 10 patients with renal failure were in the HHV-6 reactivation group. CONCLUSIONS: A combination of immunological reaction to a drug and HHV-6 reactivation results in the severe course of DIHS. The demonstration of HHV-6 reactivation is a useful marker of diagnosis as well as prognosis in DIHS.

A novel DISC1-interacting partner DISC1-Binding Zinc-finger protein: implication in the modulation of DISC1-dependent neurite outgrowth.

Disrupted-in-schizophrenia 1 (DISC1) is a gene disrupted by a (1;11) (q42.1;q14.3) translocation that segregates with major psychiatric disorders in a Scottish family. To investigate how DISC1 confers susceptibility to psychiatric disorders, we previously identified fasciculation and elongation protein zeta-1 and Kendrin as DISC1-interacting molecules in a yeast two-hybrid screen of a human brain complementary DNA library. Here, we have further identified a novel DISC1-interacting protein, termed DISC1-Binding Zinc-finger protein (DBZ), which has a predicted C(2)H(2)-type zinc-finger motif and coiled-coil domains. DBZ was co-immunoprecipitated with DISC1 in lysates of PC12 cells and rat brain tissue. The domain of DISC1 interacting with DBZ was close to the translocation breakpoint in the DISC1 gene. DBZ messenger RNA (mRNA) was expressed in human brains, but not in peripheral tissues. In situ hybridization revealed high expression of DBZ mRNA in the hippocampus, olfactory tubercle, cerebral cortex and striatum in rats. Because this pattern of localization was similar to that of the pituitary adenylate cyclase (PAC(1)) receptor for pituitary adenylate cyclase-activating polypeptide (PACAP), which has recently been implicated in neuropsychological functions, we examined whether DISC1/DBZ interaction was involved in the PACAP signaling pathway. PACAP upregulated DISC1 expression and markedly reduced the association between DISC1 and DBZ in PC12 cells. A DISC1-binding domain of DBZ reduced the neurite length in PC12 cells after PACAP stimulation and in primary cultured hippocampal neurons. The present results provide some new molecular insights into the mechanisms of neuronal development and neuropsychiatric disorders.

Reactivation of human herpesvirus (HHV) family members other than HHV-6 in drug-induced hypersensitivity syndrome.

BACKGROUND: Drug-induced hypersensitivity syndrome (DIHS) is characterized by a severe multiorgan hypersensitivity reaction that usually appears after a 3-6-week exposure to certain drugs, including anticonvulsants. There are some reports showing that serum IgG levels often decrease at the early stage of DIHS. Reactivation of human herpesvirus (HHV)-6 has been reported in patients with DIHS, and some other DIHS patients showed reactivation of cytomegalovirus (CMV) or Epstein-Barr virus (EBV). OBJECTIVES: To determine whether reactivation of HHV-6, HHV-7, CMV and/or EBV occurs in patients with DIHS. METHODS: Titres of IgG and IgM antibodies to HHV-6 and HHV-7 were determined using an indirect immunofluorescence antibody assay on admission and at various times after admission. Anti-CMV IgG and IgM antibody titres and anti-EBV capsid antigen IgG, IgA, IgM, and EBV nuclear antigen and EBV early antigen IgG titres were determined by enzyme immunoassay. Polymerase chain reaction (PCR) procedures for HHV-6, HHV-7, CMV and EBV DNAs were performed using serum samples. IgG antibody titres to HHV-6, HHV-7, CMV and EBV were increased after the onset in seven, six, seven and two of seven patients, respectively. IgG antibody titres to HHV-6 and HHV-7 were elevated simultaneously 21-38 days after the onset. RESULTS: IgG antibody titres to CMV and EBV were elevated 10-21 days after the elevation of HHV-6 and HHV-7 antibody titres. PCR showed that HHV-6, HHV-7, CMV and EBV DNAs became positive in six, five, seven and two of seven patients, respectively. HHV-6 and HHV-7 DNAs were detected 21-35 days after the onset, and CMV DNA was detected 10-21 days after detection of HHV-6 and HHV-7 DNAs. CONCLUSION: The present study suggests that in addition to HHV-6 reactivation, reactivation of HHV-7, CMV and/or EBV may also occur following drug eruption in some patients with DIHS.

Immunohistochemical and western analyses of protein arginine N-methyltransferase 3 in the mouse brain.

The distribution of protein arginine N-methyltransferase 3 (PRMT3) was investigated in the mouse brain using indirect immunofluorescence. PRMT3 was observed to be localized in the cell bodies and dendrites of neurons but not in the axons and glial cells, indicating that PRMT3 is involved in neuronal function. The distribution of the immunoreactive neurons in the brain was uneven, indicating that PRMT3 plays a role in specific neuronal systems such as the motor and limbic systems, as well as functions related to the cerebellum. The present ontogenetic analysis of PRMT1 and PRMT3 using Western blot methodology clearly revealed that PRMT3 develops during the perinatal stage and its expression is maintained even in adulthood. PRMT1, on the other hand, is expressed transiently during the early embryonic stage. These findings indicate that PRMT3 is related with neuronal function in both young and adult brains, while PRMT1 has roles in the immature brain, such as the formation of neural circuits.

Cytoplasmic p21(Cip1/WAF1) enhances axonal regeneration and functional recovery after spinal cord injury in rats.

p21(Cip1/WAF1), known as a cell-cycle inhibitory protein, facilitates neurite outgrowth from neurons when present in the cytoplasm. The molecular mechanism of this action is that p21(Cip1/WAF1) forms a complex with Rho-kinase and inhibits its activity. As myelin-derived inhibitors of axonal outgrowth act on neurons by activating Rho, that is responsible for the lack of spontaneous regeneration of the injured central nervous system (CNS), Rho-kinase may be a good molecular target against injuries in the CNS. In this study, we delivered TAT-fusion protein of cytoplasmic p21(Cip1/WAF1) locally after dorsal hemisection of the thoracic spinal cord in rats. The treatment significantly stimulated axonal regeneration and recovery of hindlimb function, and inhibited the cavity formation in the spinal cord after the injury. Cytoplasmic p21(Cip1/WAF1) may provide a potential therapeutic agent that produces functional regeneration following CNS injuries.

GRP94 reduces cell death in SH-SY5Y cells perturbated calcium homeostasis.

The endoplasmic reticulum (ER) resident-94 kDa glucose-regulated protein (GRP94), plays a pivotal role in cell death due to ER stress. In our study expression of GRP94 was increased in human neuroblastoma SH-SY5Y cells due to exposure to calcium ionophore A23187. A23187-mediated cell death was associated with activation of the major cysteine proteases, caspase-3 and calpain. Pretreatment with adenovirus-mediated antisense GRP94 (AdGRP94AS) reduced viability of SH-SY5Y cells subjected to A23187 treatment compared with wild type cells or cells with adenovirus-mediated overexpression of GRP94 (AdGRP94S). These results indicated that suppression of GRP94 is associated with accelerated cell death. Moreover, expression of GRP94 suppressed A23187-induced cell death and stabilized calcium homeostasis.

Disrupted-In-Schizophrenia 1, a candidate gene for schizophrenia, participates in neurite outgrowth.

Disrupted-In-Schizophrenia 1 (DISC1) was identified as a novel gene disrupted by a (1;11)(q42.1;q14.3) translocation that segregated with schizophrenia in a Scottish family. Predicted DISC1 product has no significant homology to other known proteins. Here, we demonstrated the existence of DISC1 protein and identified fasciculation and elongation protein zeta-1 (FEZ1) as an interacting partner of DISC1 by a yeast two-hybrid study. FEZ1 and its nematode homolog are reported to represent a new protein family involved in axonal outgrowth and fasciculation. In cultured hippocampal neurons, DISC1 and FEZ1 colocalized in growth cones. Interactions of these proteins were associated with F-actin. In the course of neuronal differentiation of PC12 cells, upregulation of DISC1/FEZ1 interaction was observed as along with enhanced extension of neurites by overexpression of DISC1. The present study shows that DISC1 participates in neurite outgrowth through its interaction with FEZ1. Recent studies have provided reliable evidence that schizophrenia is a neurodevelopmental disorder. As there is a high level of DISC1 expression in developing rat brain, dysfunction of DISC1 may confer susceptibility to psychiatric illnesses through abnormal development of the nervous system.