CSF hypocretin levels in Guillain-Barre syndrome and other inflammatory neuropathies

CSF hypocretin-1 was measured in 28 Guillain-Barré syndrome (GBS), 12 Miller-Fisher syndrome, 12 chronic inflammatory demyelinating polyneuropathy (CIDP), and 48 control subjects. Seven GBS subjects had undetectably low hypocretin-1 levels (<100 pg/mL). Hypocretin-1 levels were moderately reduced in an additional 11 GBS, 5 Miller-Fisher syndrome, and 1 CIDP subject. Low levels in GBS occurred early in the disease and were associated with upper CNS level abnormalities.

Gradient liquid chromatography of leucine-enkephalin peptide and its metabolites with electrochemical detection using highly boron-doped diamond electrode

Boron-doped diamond thin film (BDD) electrodes have been used to study the oxidation reactions and to detect leucine-enkephalinamide (LEA) and its metabolites, tyrosine (T), tyrosyl-alanine (TA), tyrosyl-alanine-glycine (TAG) and leucine-enkephalin (LE) using cyclic voltammetry (CV), flow-injection analysis (FIA), and gradient liquid chromatography (LC) with amperometric detection. At diamond electrodes, well-defined and highly reproducible cyclic voltammograms were obtained with signal-to-background (S/B) ratios 5-10 times higher than those observed for glassy carbon (GC) electrodes. The analytical peaks of LC for LEA and its metabolites were well resolved. No deactivation of BDD electrodes was found after several experiments with standard as well as plasma samples, indicating high stability of the electrode. Calibration curves were linear over a wide range from 0.06 to 30 microM with regression coefficients of 0.999 for all compounds. The limits of detection obtained based on a signal-to-noise ratio of 3:1 were 3, 2.2, 2.7, 20 and 11 nM for T, TA, TAG, LE and LEA, respectively. These values were at least one order lower than those obtained at GC electrodes, which has given limits of detection of 22.88, 20.64, 89.57, 116.04 and 75.67 for T, TA, TAG, LE and LEA, respectively. Application of this method to real samples was demonstrated and validated using rabbit serum samples. This work shows the promising use of conducting diamond as an amperometric detector in gradient LC, especially for the analysis of enkephalinamide and its metabolites.

Association between serotonin 4 receptor gene polymorphisms and bipolar disorder in Japanese case-control samples and the NIMH Genetics Initiative Bipolar Pedigrees

Possible irregularities in serotonergic neurotransmission have been suggested as causes of a variety of neuropsychiatric diseases. We performed mutation and association analyses of the HTR4 gene, on 5q32, encoding the serotonin 4 receptor in mood disorders and schizophrenia. Mutation analysis was performed on the HTR4 exons and exon/intron boundaries in 48 Japanese patients with mood disorders and 48 patients with schizophrenia. Eight polymorphisms and four rare variants were identified. Of these, four polymorphisms at or in close proximity to exon d, g.83097C/T (HTR4-SVR (splice variant region) SNP1), g.83159G/A (HTR4-SVRSNP2), g.83164 (T)9-10 (HTR4-SVRSNP3), and g.83198A/G (HTR4-SVRSNP4), showed significant association with bipolar disorder with odds ratios of 1.5 to 2. These polymorphisms were in linkage disequilibrium, and only three common haplotypes were observed. One of the haplotypes showed significant association with bipolar disorder (P = 0.002). The genotypic and haplotypic associations with bipolar disorder were confirmed by transmission disequilibrium test in the NIMH Genetics Initiative Bipolar Pedigrees with ratios of transmitted to not transmitted alleles of 1.5 to 2.0 (P = 0.01). The same haplotype that showed association with bipolar disorder was suggested to be associated with schizophrenia in the case-control analysis (P = 0.003) but was not confirmed when Japanese schizophrenia families were tested. The polymorphisms associated with mood disorder were located within the region that encodes the divergent C-terminal tails of the 5-HT(4) receptor. These findings suggest that genomic variations in the HTR4 gene may confer susceptibility to mood disorder.

Membrane potential and bicarbonate secretion in isolated interlobular ducts from guinea-pig pancreas

The interlobular duct cells of the guinea-pig pancreas secrete HCO(3)(-) across their luminal membrane into a HCO(3)(-)-rich (125 mM) luminal fluid against a sixfold concentration gradient. Since HCO(3)(-) transport cannot be achieved by luminal Cl-/HCO(3)(-) exchange under these conditions, we have investigated the possibility that it is mediated by an anion conductance. To determine whether the electrochemical potential gradient across the luminal membrane would favor HCO(3)(-) efflux, we have measured the intracellular potential (V(m)) in microperfused, interlobular duct segments under various physiological conditions. When the lumen was perfused with a 124 mM Cl- -25 mM HCO(3)(-) solution, a condition similar to the basal state, the resting potential was approximately -60 mV. Stimulation with dbcAMP or secretin caused a transient hyperpolarization (approximately 5 mV) due to activation of electrogenic Na+-HCO(3)(-) cotransport at the basolateral membrane. This was followed by depolarization to a steady-state value of approximately -50 mV as a result of anion efflux across the luminal membrane. Raising the luminal HCO(3)(-) concentration to 125 mM caused a hyperpolarization (approximately 10 mV) in both stimulated and unstimulated ducts. These results can be explained by a model in which the depolarizing effect of Cl- efflux across the luminal membrane is minimized by the depletion of intracellular Cl- and offset by the hyperpolarizing effects of Na+-HCO(3)(-) cotransport at the basolateral membrane. The net effect is a luminally directed electrochemical potential gradient for HCO(3)(-) that is sustained during maximal stimulation. Our calculations indicate that the electrodiffusive efflux of HCO(3)(-) to the lumen via CFTR, driven by this gradient, would be sufficient to fully account for the observed secretory flux of HCO(3)(-).

Increase of transcriptional levels of egr-1 and nur77 genes due to both nicotine treatment and withdrawal in pheochromocytoma cells

The influence of nicotine on the expression of egr-1 and nur77 genes by nicotine treatment and withdrawal was assessed using PC12 cells. Nicotine treatment significantly increased the amount of mRNA for egr-1 and nur77 genes at 0.5 h post-nicotine treatment in the PC12 cells. In addition, nicotine withdrawal also elevated transcriptional levels of egr-1 and nur77 genes in Northern blot analyses. Nicotine treatment (200 microM) was also found to significantly increase expressional levels of Egr-1 and Nur77 proteins at 0.5 h post-nicotine treatment. In contrast, Egr-1 and Nur77 protein levels were dramatically decreased by nicotine withdrawal. These results suggest that expressional levels of Egr-1 and Nur77 proteins in neural cells may affect the transcriptional activity of late-response genes after nicotine withdrawal.

Impaired blood rheology by remnant-like lipoprotein particles: studies in patients with fatty liver disease

Fatty liver disease (FLD) characterised by a high plasma levels of lipoproteins and remnant-like lipoproteins (RLP) is a risk factor for impaired microvascular blood flow, endothelial cell dysfunction and atherosclerosis. Using an immunoseparation technique with a gel mixture containing human monoclonal antibodies to apo A-I and apo B-100, we separated and measured RLP cholesterol (RLP-C) levels which reflect RLP in patients with FLD (n=20). Whole blood transit time (TT) was determined by a microchannel method (MC-FAN) which allows blood flow to be viewed via a microscope connected to an image display unit. RLP-C levels were higher (P<0.01) in FLD, 15.6 +/- 1.0 mg/dl compared with 4.8 +/- 0.5 mg/dl for controls (n=20). Similarly, TT was longer (P<0.01) in FLD, 284.5 +/- 26.1 sec/100 microl compared with 82.8 +/- 1.0 sec/100 microl for controls. Since the liver is a major site for RLP formation and degradation, it is affected to a greater extent in patients with FLD. It is likely that high levels of RLP can impair microvascular perfusion in the liver tissue and contribute to the development and progression of FLD.

Chloride transport in microperfused interlobular ducts isolated from guinea-pig pancreas

Isolated interlobular ducts from the guinea-pig pancreas secrete a HCO3--rich fluid in response to secretin. To determine the role of Cl- transporters in this process, intracellular Cl- concentration ([Cl-]i) was measured in ducts loaded with the Cl--sensitive fluoroprobe, 6-methoxy-N-ethylquinolinium chloride (MEQ). [Cl-]i decreased when the luminal Cl- concentration was reduced. This effect was stimulated by forskolin, was not dependent on HCO3- and was not inhibited by application of the anion channel/transporter inhibitor H2DIDS to the luminal membrane. It is therefore attributed to a cAMP-stimulated Cl- conductance, probably the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel. [Cl-]i also decreased when the basolateral Cl- concentration was reduced. This effect was not stimulated by forskolin, was largely dependent on HCO3- and was inhibited by basolateral H2DIDS. It is therefore mediated mainly by Cl-/HCO3- exchange. With high Cl- and low HCO3- concentrations in the lumen, steady-state [Cl-]i was 25-35 mM in unstimulated cells. Stimulation with forskolin caused [Cl-]i to increase by approximately 4 mM due to activation of the luminal anion exchanger. With low Cl- and high HCO3- concentrations in the lumen to simulate physiological conditions, steady-state [Cl-]i was 10-15 mM in unstimulated cells. Upon stimulation with forskolin, [Cl-]i fell to approximately 7 mM due to increased Cl- efflux via the luminal conductance. We conclude that, during stimulation under physiological conditions, [Cl-]i decreases to very low levels in guinea-pig pancreatic duct cells, largely as a result of the limited capacity of the basolateral transporters for Cl- uptake. The resulting lack of competition from intracellular Cl- may therefore favour HCO3- secretion via anion conductances in the luminal membrane, possibly CFTR.

Association analysis of the pituitary adenyl cyclase activating peptide gene (PACAP) on chromosome 18p11 with schizophrenia and bipolar disorders

In neurons, pituitary adenyl cyclase activating peptide (PACAP) stimulates signaling cascades, involving cAMP and calcium. PACAP appears to play a role in up-regulation of tyrosine hydroxylase and dopamine beta-hydroxylase via protein kinase C and/or protein kinase A. Furthermore, the PACAP gene (ADCYAP1) is located in chromosome 18p11, where linkage of bipolar disorders and schizophrenia has been reported. In this study, we scanned the coding region of the PACAP gene for mutations in 24 Japanese patients with schizophrenia and 24 Japanese patients with bipolar disorders. No variant in the coding region was found. One polymorphism, INV3-37A/T, in the third intron was detected. Case-control comparisons revealed no significant association between this polymorphism and schizophrenia or bipolar disorders. This study did not provide evidence for the contribution of the PACAP gene to the etiology of schizophrenia or bipolar disorders in the Japanese population.

Isoform-specific effects of apolipoprotein E on atherogenesis: gene transduction studies in mice

BACKGROUND

We recently used a bone marrow-based gene therapy approach to show that small amounts of retrovirus-derived human apolipoprotein E3 (apoE3) produced by macrophages are protective against early atherosclerosis in apoE-deficient mice.

METHODS AND RESULTS

In the present study, we evaluated whether the effect produced by macrophage-derived apoE3 is related to its ability to bind cellular membranes. To this end, we used apoE2 and apoEcys142, dysfunctional human variants with reduced binding to the LDL receptor or to heparan sulfate proteoglycans, respectively. ApoE-deficient mice, 5 weeks of age, received transplants of apoE(-/-) bone marrow cells transduced with either parental retrovirus or apoE3, apoE2, or apoEcys142 retroviral vectors. Human apoE was detected by ELISA in the serum of apoE3, apoE2, and apoEcys142 mice as early as 4 weeks after bone marrow transplantation, and at 8 weeks, plasma apoE levels were 55.5+/-20.3, 50.5+/-8.7, and 15.3+/-7.3 microgram/dL, respectively. In all groups, cholesterol levels increased with age but were not affected by apoE expression. As previously demonstrated, the lesion area in male apoE3 mice (3808+/-2224 micrometer(2)/section) was 40% smaller than that in control mice (6503+/-3475 micrometer(2)/section). In apoE2 mice, however, the lesion area was similar to that of controls (5991+/-2771 micrometer(2)/section), and apoEcys142 mice showed an unexpected and significant increase in lesion size (10 320+/-6128 micrometer(2)/section). Thus, transplantation with marrow transfected with receptor binding-defective apoE variants did not replicate the antiatherogenic effect of apoE3.

CONCLUSIONS

These data provide in vivo evidence suggesting that macrophage-derived apoE delays development of atherosclerosis through a receptor-dependent pathway.

[A new development in interventional radiology for hepatocellular carcinoma]

In Japan, interventional radiology (IVR) treatments such as transcatheter arterial embolization (TAE), percutaneous ethanol injection therapy (PEIT), and intraarterial infusion chemotherapy play an important role in the treatment of hepatocellular carcinoma because of the associated cirrhosis (impairment of liver function) and occasional multicentricity. With progress in catheters, embolic materials, and imaging equipment such as the so-called "IVR-CT", superselective TAE and precise evaluation of tumor lesions has become feasible. However, the impact of TAE on survival in patients with hepatocellular carcinoma remains to be determined because no survival benefit was seen in four of five randomized controlled trials (RCTs) in Europe and Eastern countries, in which TAE was compared with no treatment (3 trials), i.v. 5-fluorouracil (1 trial), or tamoxifen (1 trial). To resolve questions arising from these results, a fair number of trials, particularly RCTs are needed in Japan.

Increased cholesterol efflux in apolipoprotein AI (ApoAI)-producing macrophages as a mechanism for reduced atherosclerosis in ApoAI((-/-)) mice

The concentration of apolipoprotein (apo) AI in the artery wall is thought to enhance cellular cholesterol efflux and protect against atherosclerosis. It has been shown that although macrophages do not make apoAI, they respond to it by increased cholesterol efflux. We hypothesized that macrophage production of apoAI would increase cholesterol efflux and reduce atherogenesis. In this study, we produced mice expressing human apoAI under the control of the macrophage-specific scavenger receptor-A promoter (mphi-AI). Human apoAI was detectable in the serum HDL fraction of mphi-AI transgenic mice at concentrations too low to affect serum cholesterol or HDL levels. Immunoblotting showed the presence of human apoAI in transgenic macrophage culture supernatants, mostly as lipoprotein-free protein, with a small component associated with HDL-like particles. Atherosclerosis studies using apoAI((-/-)) mice transplanted with mphi-AI bone marrow showed that in the absence of macrophage-derived apoE, local expression of apoAI reduced diet-induced lesions in the proximal aorta. Additionally, mphi-AI macrophages showed a 40% increase in cholesterol efflux compared with control macrophages. These data support the hypothesis that apoAI production by macrophages in the artery wall is protective against atherosclerosis. This protection is likely mediated by increased cholesterol efflux and decreased foam cell formation in vivo.

Retrovirus-mediated expression of apolipoprotein A-I in the macrophage protects against atherosclerosis in vivo

We have previously reported that the lack of apolipoprotein (apo) E expression by macrophages promotes foam cell formation in vivo. Because transgenic mice overexpressing human apoA-I from the liver (h-apoA-I TgN) are protected from the atherogenesis induced by apoE deficiency, we hypothesized that the presence of apoA-I in the vessel wall could reduce the negative effect of apoE deficiency on lesion growth. To address this issue, we used both retroviral transduction and transgenic approaches to produce in vivo systems where apoA-I is expressed from macrophages. In the retroviral transduction study, apoA-I-deficient (apoA-I(-/-)) mice reconstituted with apoE-deficient (apoE(-/-)) bone marrow cells that were infected with a retroviral vector expressing human apoA-I (MFG-HAI) had 95% lower atherosclerotic lesion area than that of recipients of apoE(-/-) bone marrow cells infected with the parental virus (MFG). To determine whether the protective effect of locally produced apoA-I was due to the lack of systemic apoA-I, we conducted a different experiment using h-apoA-I TgN mice as recipients of apoE(-/-) bone marrow with or without human apoA-I (driven by a macrophage-specific transgene defined as mphi-AI). Aortic lesion area in apoE(-/-)/mphi-AI --> h-apoA-I TgN mice was decreased by 85% compared with apoE(-/-) --> h-apoA-I TgN mice. These data demonstrate that expression of apoA-I from macrophages protects against atherogenesis without affecting plasma apoA-I and high density lipoprotein cholesterol levels.

5-hydroxytryptamine strongly inhibits fluid secretion in guinea pig pancreatic duct cells

We studied the distribution of 5-hydroxytryptamine- (5-HT-) containing cells in the guinea pig pancreas and examined the effects of 5-HT on fluid secretion by interlobular pancreatic ducts. The 5-HT-immunoreactive cells with morphological characteristics of enterochromaffin (EC) cells were scattered throughout the duct system and were enriched in islets of Langerhans. The fluid secretory rate in the isolated interlobular ducts was measured by videomicroscopy. Basolateral applications of 5-HT strongly but reversibly reduced HCO(3)-dependent, as well as secretin- and acetylcholine- (ACh-) stimulated, fluid secretion, whereas 5-HT applied into the lumen had no such effects. Secretin-stimulated fluid secretion could be inhibited by a 5-HT(3) receptor agonist, but not by agonists of the 5-HT(1), 5-HT(2), or 5-HT(4) receptors. Under the stimulation with secretin, 5-HT decreased the intracellular pH (pH(i)) and reduced the rate of pH(i) recovery after acid loading with NH(4)(+), suggesting that 5-HT inhibits the intracellular accumulation of HCO3(-). The elevation of intraductal pressure in vivo reduced secretin-stimulated fluid secretion, an effect that could be attenuated by a 5-HT(3) receptor antagonist. Thus, 5-HT, acting through basolateral 5-HT(3) receptors, strongly inhibits spontaneous, secretin-, and ACh-stimulated fluid secretion by guinea pig pancreatic ducts. 5-HT released from pancreatic ductal EC cells on elevation of the intraductal pressure may regulate fluid secretion of neighboring duct cells in a paracrine fashion.

Identification of AF17 as a downstream gene of the beta-catenin/T-cell factor pathway and its involvement in colorectal carcinogenesis

To elucidate the molecular mechanism of colorectal carcinogenesis, we have been attempting to isolate genes involved in the beta-catenin/T-cell factor pathway. In the experiments reported here, analysis by cDNA microarray indicated that AF17, a fusion partner of the MLL gene in acute leukemias with t(11;17)(q23;q21), was transactivated according to accumulation of beta-catenin. Expression of AF17 was significantly enhanced in 8 of the 12 colorectal cancer tissues examined. Introduction of a plasmid designed to express AF17 stimulated growth of NIH3T3 cells, and fluorescence-activated cell sorter analysis indicated that the AF17 regulation of cell-cycle progression was occurring mainly at the G(2)-M transition. Our results suggest that the AF17 gene product is likely to be involved in the beta-catenin-T-cell factor/lymphoid enhancer factor signaling pathway and to function as a growth-promoting, oncogenic protein. These findings should aid development of new strategies for diagnosis, treatment, and prevention of colon cancers and acute leukemias by clarifying the pathogenesis of these conditions.

Identification of AXUD1, a novel human gene induced by AXIN1 and its reduced expression in human carcinomas of the lung, liver, colon and kidney

Axin, an important regulator of beta-catenin, is frequently mutated in human hepatocellular carcinomas (HCCs), and transduction of the wild-type Axin gene (AXIN1) induces apoptosis in HCC cells as well as in colon cancer cells. To investigate the detailed biological function of Axin, we searched on a cDNA microarray for genes whose expression was altered by transfer of wild-type AXIN1 into colon-cancer cell line LoVo. Among the genes showing altered expression, we focused on one, termed AXUD1 (AXIN1 up-regulated), that revealed enhanced expression in response to exogenously expressed AXIN1 but not to LacZ, a control gene. The AXUD1 gene consists of five exons and encodes a transcript with an open reading frame of 1767 bp. A 3.2-kb transcript of AXUD1 was expressed in all human tissues examined, most abundantly in lung, placenta, skeletal muscle, pancreas and leukocyte. By radiation-hybrid mapping we assigned its chromosomal location at 3p22, a region where frequent loss of heterozygosity has been reported in lung, renal, prostate, breast and cervical cancers. AXUD1 was frequently down-regulated in lung, kidney, liver and colon cancers compared with their corresponding normal tissues, suggesting that AXUD1 may have a tumor-suppressor function in those organs.

Age-dependent and tissue-specific CAG repeat instability occurs in mouse knock-in for a mutant Huntington's disease gene

Huntington's disease (HD) is a neurodegenerative disorder characterized by the expansion of CAG repeats in exon 1 of the HD gene. To clarify the instability of expanded CAG repeats in HD patients, an HD model mouse has been generated by gene replacement with human exon 1 of the HD gene with expansion to 77 CAG repeats. Chimeric proteins composed of human mutated exon 1 and mouse huntingtin are expressed ubiquitously in brain and peripheral tissues. One or two CAG repeat expansion was found in litters from paternal transmission, whereas contraction of CAG repeat in litters was observed through maternal transmission. Elderly mice show greater CAG repeat instability than younger mice, and a unique case was observed of an expanded 97 CAG repeat mouse. Somatic CAG repeat instability is particularly pronounced in the liver, kidney, stomach, and brain but not in the cerebellum of 100-week-old mice. The same results of expanded CAG repeat instability as observed in this HD model mouse were confirmed in the human brain of HD patients. Glial fibrillary acidic protein (GFAP)-positive cells have been found to be increased in the substantia nigra (SN), globus pallidus (GP), and striatum (St) in the brains of 40-week-old affected mice, although without neuronal cell death. The CAG repeat instability and increase in GFAP-positive cells in this mouse model appear to mirror the abnormalities in HD patients. The HD model mouse may therefore have advantages for investigations of molecular mechanisms underlying instability of CAG repeats.

Cellular localization of group IIA phospholipase A2 in rats

It has been known that group II phospholipase A2 (PLA2) mRNA and protein are present in the homogenates of the spleen, lung, liver, and kidney in normal rats, but the cellular origin of this enzyme has not been yet identified. At present, five subtypes of group II PLA2 have been identified in mammals. Antibodies or mRNA probes previously used for detecting group II PLA2 need to be evaluated to identify the subtypes of group II PLA2. In this study we tried to identify group IIA PLA2-producing cells in normal rat tissues by in situ hybridization (ISH) using an almost full-length RNA probe for rat group IIA enzyme. Group IIA PLA2 mRNA was detected in megakaryocytes in the spleen and Paneth cells in the intestine by ISH. These cells were also immunopositive for an antibody raised against group IIA PLA(2) isolated from rat platelets. Group IIA PLA2 mRNA-positive cells were not detected in lung, liver, kidney, and pancreas. Under normal conditions, group IIA PLA2-producing cells are splenic megakaryocytes and intestinal Paneth cells in rats.

Pancreatic ductal bicarbonate secretion: past, present and future

The pancreatic duct epithelium in the guinea-pig and many other species secretes HCO(3)(-) at concentrations approaching 150 mM. This cannot be explained by conventional models based upon HCO(3)(-) secretion via an anion exchanger at the luminal membrane because: 1) under these conditions, the Cl(-) and HCO(3)(-) concentration gradients would favour HCO(3)(-) reabsorption rather than secretion, and 2) the luminal anion exchanger appears to be inhibited by luminal HCO(3)(-) concentrations of 125 mM or more. There may, however, be a sufficiently large electrochemical gradient to drive HCO(3)(-) secretion across the luminal membrane via an anion conductance. In contrast to earlier studies on rat ducts, the membrane potential E(m) in guinea-pig duct cells does not depolarise appreciably upon stimulation with secretagogues but remains constant at about -60 mV. Consequently, even with 125 mM or more HCO(3)(-) in the lumen and an estimated 20 mM in the cytoplasm, the electrochemical gradient for HCO(3)(-) will still favour secretion to the lumen. Under the same conditions, the intracellular Cl(-) concentration drops to very low levels (approximately 7 mM) presumably because, although Cl(-) may leave freely through the cystic fibrosis transmembrane conductance regulator (CFTR) channels in the luminal membrane, there is no major pathway for Cl(-) uptake across the basolateral membrane. Consequently a HCO(3)(-)-rich secretion may arise as a result of the lack of competition from intracellular Cl(-) for efflux via the anion conductances at the luminal membrane. Whether CFTR, or another anion conductance, provides such a pathway for HCO(3)(-) remains to be seen.

Isolation of a novel human gene, ARHGAP9, encoding a rho-GTPase activating protein

Members of the Rho family of small guanosine triphosphatases (Rho-GTPases) have emerged as key coordinators of signaling pathways leading to remodeling of the actin cytoskeleton, a process that plays a critical role in cell adhesion and migration. However, the precise regulatory mechanisms remain to be elucidated. Here we report isolation of a novel human gene, ARHGAP9, which encodes a protein containing a Rho-GTPase activating protein (Rho-GAP) domain, a src-homology 3 (SH3) domain, a pleckstrin homology (PH) region, and a WW domain. In vitro, the recombinant protein revealed substantial GAP activity toward Cdc42Hs and Rac1, and less toward RhoA. The transcript was predominantly expressed in peripheral blood leukocytes, spleen, and thymus. Exogenous expression of the entire coding region of ARHGAP9 into human leukemia KG-1 cells repressed adhesion of the cells to fibronectin and collagen IV. Our results indicate that ARHGAP9 is involved in regulating adhesion of hematopoietic cells to extracellular matrix.