Morphometric study of the lumbar vertebrae in dried anatomical collections

Background

The objective of this anatomical study was to perform the morphometry of dried lumbar vertebrae in human cadavers.

Methods

This study utilized 200 adult human cadaveric dried lumbar vertebrae. The digital Vernier calipers was used to perform the measurements. The height, antero-posterior length, transverse length of the body of the vertebrae, interpedicular distance at the lateral ends, lamina length, height and thickness, superior and inferior articular facet height and width, mid sagittal and transverse diameter of vertebral foramen, height, width and thickness of the pars inter-articularis were measured.

Results

The vertebral body's anteroposterior length was more at the lower border than at the superior border ( p < 0.01). The length of lamina was higher over the right in comparison to the left (p < 0.001). The height of lamina, width of inferior articular facet, diameter of lateral recess and thickness of pars inter-articularis were greater for the left sided specimens ( p < 0.01). The statistical significance was not observed for the comparison of the remaining parameters ( p > 0.05).

Conclusion

This anatomical study offered several dimensions of lumbar vertebrae, which are essential in the surgical practice. The implants at the lumbar vertebrae need to be manufactured based on the anatomical dimensions of that particular sample population.

Incorporating mutational heterogeneity to identify genes that are enriched for synonymous mutations in cancer

BACKGROUND

Synonymous mutations, which change the DNA sequence but not the encoded protein sequence, can affect protein structure and function, mRNA maturation, and mRNA half-lives. The possibility that synonymous mutations might be enriched in cancer has been explored in several recent studies. However, none of these studies control for all three types of mutational heterogeneity (patient, histology, and gene) that are known to affect the accurate identification of non-synonymous cancer-associated genes. Our goal is to adopt the current standard for non-synonymous mutations in an investigation of synonymous mutations.

RESULTS

Here, we create an algorithm, MutSigCVsyn, an adaptation of MutSigCV, to identify cancer-associated genes that are enriched for synonymous mutations based on a non-coding background model that takes into account the mutational heterogeneity across these levels. Using MutSigCVsyn, we first analyzed 2572 cancer whole-genome samples from the Pan-cancer Analysis of Whole Genomes (PCAWG) to identify non-synonymous cancer drivers as a quality control. Indicative of the algorithm accuracy we find that 58.6% of these candidate genes were also found in Cancer Census Gene (CGC) list, and 66.2% were found within the PCAWG cancer driver list. We then applied it to identify 30 putative cancer-associated genes that are enriched for synonymous mutations within the same samples. One of the promising gene candidates is the B cell lymphoma 2 (BCL-2) gene. BCL-2 regulates apoptosis by antagonizing the action of proapoptotic BCL-2 family member proteins. The synonymous mutations in BCL2 are enriched in its anti-apoptotic domain and likely play a role in cancer cell proliferation.

CONCLUSION

Our study introduces MutSigCVsyn, an algorithm that accounts for mutational heterogeneity at patient, histology, and gene levels, to identify cancer-associated genes that are enriched for synonymous mutations using whole genome sequencing data. We identified 30 putative candidate genes that will benefit from future experimental studies on the role of synonymous mutations in cancer biology.

How soluble misfolded proteins bypass chaperones at the molecular level

Subpopulations of soluble, misfolded proteins can bypass chaperones within cells. The extent of this phenomenon and how it happens at the molecular level are unknown. Through a meta-analysis of the experimental literature we find that in all quantitative protein refolding studies there is always a subpopulation of soluble but misfolded protein that does not fold in the presence of one or more chaperones, and can take days or longer to do so. Thus, some misfolded subpopulations commonly bypass chaperones. Using multi-scale simulation models we observe that the misfolded structures that bypass various chaperones can do so because their structures are highly native like, leading to a situation where chaperones do not distinguish between the folded and near-native-misfolded states. More broadly, these results provide a mechanism by which long-time scale changes in protein structure and function can persist in cells because some misfolded states can bypass components of the proteostasis machinery.

Functional genomic analysis of adult and pediatric brain tumor isolates

Background

Adult and pediatric tumors display stark differences in their mutation spectra and chromosome alterations. Here, we attempted to identify common and unique gene dependencies and their associated biomarkers among adult and pediatric tumor isolates using functional genetic lethal screens and computational modeling.

Methods

We performed CRISRP-Cas9 lethality screens in two adult glioblastoma (GBM) tumor isolates and five pediatric brain tumor isolates representing atypical teratoid rhabdoid tumors (ATRT), diffuse intrinsic pontine glioma, GBM, and medulloblastoma. We then integrated the screen results with machine learning-based gene-dependency models generated from data from >900 cancer cell lines.

Results

We found that >50% of candidate dependencies of 280 identified were shared between adult GBM tumors and individual pediatric tumor isolates. 68% of screen hits were found as nodes in our network models, along with shared and tumor-specific predictors of gene dependencies. We investigated network predictors associated with ADAR, EFR3A, FGFR1 (pediatric-specific), and SMARCC2 (ATRT-specific) gene dependency among our tumor isolates.

Conclusions

The results suggest that, despite harboring disparate genomic signatures, adult and pediatric tumor isolates share a preponderance of genetic dependences. Further, combining data from primary brain tumor lethality screens with large cancer cell line datasets produced valuable insights into biomarkers of gene dependency, even for rare cancers.

Importance of the Study

Our results demonstrate that large cancer cell lines data sets can be computationally mined to identify known and novel gene dependency relationships in adult and pediatric human brain tumor isolates. Gene dependency networks and lethality screen results represent a key resource for neuro-oncology and cancer research communities. We also highlight some of the challenges and limitations of this approach.

Efficacy and dose-response relationship of oral treprostinil in PAH patients on monotherapy or dual background therapy

Background

FREEDOM-C and FREEDOM-C2 were randomized, placebo-controlled, double-blinded international, multicenter studies investigating the use of oral treprostinil (TRE) in subjects on mono or dual background pulmonary arterial hypertension (PAH) therapies. Both had a primary endpoint of change in 6-minute walk distance (6MWD) at Week 16 vs baseline. Previous post-hoc analyses combining mono and dual therapy subjects (PDE-5i and/or ERA) from these studies revealed a TRE dose-dependent increase in 6MWD. (1. White & Rao, 2016)

Purpose

This post-hoc analysis was performed to determine if subjects from FREEDOM-C and FREEDOM-C2 derive improvements in 6MWD with increasing doses of TRE when stratified by mono or dual background therapy and to determine if PAH background therapies (mono or dual) impacted 6MWD.

Methods

All active subjects (n=331) from FREEDOM-C and FREEDOM-C2 were grouped into TRE dose tertiles (low-dose: ≤2 mg BID, mid-dose: &gt;2 mg to ≤3.5 mg BID, and high-dose: &gt;3.5 mg BID). Placebo subjects (n=329) were in a separate 0 mg dose group. No data imputation was implemented.

Comparisons of 6MWD change at Weeks 4, 8, 12, and 16 between mono and dual therapy subgroups at any dose group were performed using a two-sample t-test or nonparametric Wilcoxon rank-sum test. The nonparametric Kruskal-Wallis test was conducted with subsequent pairwise comparisons of 6MWD change at Week 16 between the four dose groups through Dunn's approach. Additionally, the Jonckheere-Terpstra test was used to assess the linear trend for 6MWD improvement with higher doses of TRE.

Results

Baseline characteristics of the combined intention to treat (ITT) population and summary of 6MWD for subjects with both baseline and Week 16 data are in Table 1. 6MWD change improved steadily to Week 16 in subjects at higher TRE doses, regardless of the number of PAH background therapies (Figure 1). No statistical differences were found between mono and dual therapy at any time point or for any dose group. At Week 16, there was a significant difference in 6MWD change between the placebo group and high dose group within both mono and dual background therapy subjects. The difference between the low- and high-dose groups was significant for subjects on dual background therapy. There was a significant positive linear trend for TRE doses in 6MWD improvement at Week 16 for both monotherapy subjects (one-sided p-value = 0.0002) and dual therapy subjects (one-sided p-value = 0.0242).

Conclusions

6MWD improved in PAH patients regardless of their background therapy (monotherapy or dual background) and derive greater 6MWD improvements with higher doses of TRE. The observed dose-dependent 6MWD increase supports the use of TRE in sequential combination with background therapies (mono or dual).

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): United Therapeutics Corporation

Novel MSH6 mutation predicted metastasis in eyelid and periocular squamous cell carcinoma

BACKGROUND

Our previous research revealed the relative local aggressiveness of eyelid and periocular squamous cell carcinoma (EPSCC), but its distinct genetic characteristics involved remain unknown.

OBJECTIVES

We conducted this study based on next-generation sequencing to identify the genetic distinctiveness of EPSCC and damaging mutations for possible etiology and poor prognosis.

METHODS

We performed sequencing using a 556-gene panel (smartonco) in 48 EPSCCs. Cox hazards model was applied to explore mutated genes that increase risk of metastasis and death. Pathogenesis of the mutations was predicted by sequence alignment algorithms.

RESULTS

The most commonly mutated genes were KMT2C (N=17, 35%), LRP1B (N=14, 29%), KMT2D (N=12, 25%), PTCH1(N=10, 21%) and TP53(N=10, 21%). DNA mismatch repair (MMR) genes (42%) like MSH6(19%) and MLH3(12%) were among the most frequently mutated genes. Cell cycle regulators including TP53(21%) and CDKN2A (10%) were less frequently mutated than in other squamous cell carcinomas (SCCs). Ultra violet exposure, MMR deficiency and aging were the main etiology. Of note, KMT2C has a deleterious mutation hotspot. Patients burdened with MSH6 mutation has a higher risk of overall metastasis (P=0.045, HR=5.165) and nodal metastasis (P=0.022, HR=14.038). Moreover, a hotspot mutation MSH6^E52A brought an even higher risk of nodal metastasis (P=0.011, HR=18.745).

CONCLUSIONS

EPSCCs displayed a unique mutation profile from cutaneous SCCs and mucosal SCCs. We have identified novel damaging mutations in epigenetic regulators like KMT2C boosted early onset of EPSCCs in addition to UVR, aging or MMR deficiency. And malfunction of MMR genes worsened prognosis.

POS1002 DIAGNOSTIC DELAY AND ITS ASSOCIATED FACTORS IN CHINESE AXIAL SPONDYLOARTHRITIS: A RETROSPECTIVE STUDY

Background

Few data on the prolonged diagnosis and its associated factors in Chinese axial spondyloarthritis (axSpA) is available.

Objectives

To delineate the landscape of diagnostic delay in Chinese axSpA, investigate its associated factors and explore its potential impact on medication modalities.

Methods

A total of 1,295 patients fulfilling the ASAS classification criteria were obtained. Demographic and clinical data were collected through predesigned questionnaires and available medical records. Logistic regression analyses in univariate and multivariable model were performed, using the median of diagnostic delay as cut-off point for group classification. Differences between early and late diagnosed group were subsequently compared by the Pearson chi-square test or Mann-Whitney U test.

Results

The median (IQR) diagnostic delay in Chinese axSpA was 3.0 (1.0~7.0) years and 24.8% of them reported a history of misdiagnosis. Older age at onset (OR=0.97, P<0.001) and higher education attainment (P=0.001) were correlated with early diagnosis of axSpA, whereas coming from less developed areas (P=0.002), a history of peripheral arthritis at the time of diagnosis (OR=1.58, P=0.002) and history of misdiagnosis (OR=1.98, P<0.001) increased the risk of diagnostic delay. Medication modalities were similar between two groups, but the proportion with no medication ever and percentage without regular medication in recent 3 months were higher in the late diagnosed group than early group (26.5% vs. 20.7%, P=0.02; 34.7% vs. 28.6%, P=0.02).

Conclusion

Our findings depicted a detailed spectrum of diagnostic delay in Chinese axSpA, verified five associated factors and pinpointed a remarkable treatment delay even after diagnosis, especially in late diagnosis group.

References

[1]Masson Behar V, Dougados M, Etcheto A, Kreis S, Fabre S, Hudry C, et al. Diagnostic delay in axial spondyloarthritis: A cross-sectional study of 432 patients. Joint bone spine. 2017;84(4):467-71.

Figure 1.

Cumulative distribution of age at onset and age at diagnosis in Chinese axSpA

(A) the entire group. (B) stratified by early and late diagnosed group. (C) stratified by education level (college, middle school, secondary school). (D) stratified by history of peripheral arthritis when diagnosed. (E) stratified by history of misdiagnoses when diagnosed. (F) stratified by native place, as statistical significance was found between eastern coastal and western China, only these two groups were presented.

Disclosure of Interests

None declared

Genomic and experimental evidence that ALKATI does not predict single agent sensitivity to ALK inhibitors

Genomic data can facilitate personalized treatment decisions by enabling therapeutic hypotheses in individual patients. Mutual exclusivity has been an empirically useful signal for identifying activating mutations that respond to single agent targeted therapies. However, a low mutation frequency can underpower this signal for rare variants. We develop a resampling based method for the direct pairwise comparison of conditional selection between sets of gene pairs. We apply this method to a transcript variant of anaplastic lymphoma kinase (ALK) in melanoma, termed ALK^ATI that was suggested to predict sensitivity to ALK inhibitors and we find that it is not mutually exclusive with key melanoma oncogenes. Furthermore, we find that ALK^ATI is not likely to be sufficient for cellular transformation or growth, and it does not predict single agent therapeutic dependency. Our work strongly disfavors the role of ALK^ATI as a targetable oncogenic driver that might be sensitive to single agent ALK treatment.

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A method to test rare genomic findings for their relative conditional selection

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ALK^ATI is not as mutually exclusive with BRAF or NRAS as they are with each other

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ALK^ATI is not likely to be sufficient for cellular transformation or growth in vitro

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Expressing activated oncogenic ALK in BRAF_V600E melanoma cells is cytotoxic

[Clinical efficacy and pregnancy outcomes of fertility-preserving re-treatment after recurrence of the patient with atypical endometrial hyperplasia and early stage endometrial carcinoma]

Objective: To analyze the clinical efficacy and pregnancy outcomes of fertility- preserving re-treatment in patients with recurrent atypical endometrial hyperplasia (AEH) and early stage endometrial carcinoma (EEC) after achieved complete remission (CR) of primary fertility-preserving therapy. Methods: There were 104 cases of AEH and EEC collected from 9 hospitals in the multi-center research network platform of fertility-preserving therapy of endometrial carcinoma in China from January 2005 to May 2019. Thirth-one cases of them relapsed from four hospitals mentioned above,who achieved CR after primary fertility-preserving therapy,was analyzed retrospectively. Of the 31 cases, 27 cases chose fertility-preserving re-treatment. The demographic characteristics, re-treatment effect, clinical factors and pregnancy outcomes were observed. Results: (1) There were 16 AEH cases and 11 ECC cases among 27 recurrent patients who chose fertility-preserving therapy again. After re-treatment, CR was found in 13 out of 16 cases of AEH and 9 out of 11 cases of EEC. The overall CR rate was 81% (22/27). (2) After CR of recurrence, 5 cases (23%, 5/22) of re-recurrence were found after with a median time of 33 months (range 21-80 months). There were 4 cases underwent comprehensive surgical staging, and 1 patient chose the third round of fertility preservation therapy with fully informed consent, and CR was reached after 15 months. (3) There were 16 cases with pregnancy intention, with a total of 12 pregnancies, including 5 cases were natural pregnancy and 7 cases were assisted reproductive technology pregnancy. There were 5 live births. The follow-up time was up to May 2019, and the median follow-up time was 73 months (range 0-123 months). All 27 patients had disease free survival. Conclusions: Recurrent patients with AEH and EEC after achieving successful fertility-preserving therapy could choose fertility-preserving therapy again with comprehensive assessment and fully informed consent. After re-treatment, there is a certain tumor CR rate and pregnancy rate, while the close follow-up is required during treatment.

Quality of life of a migrant population with tuberculosis in West China

OBJECTIVE

To describe the quality of life (QOL) of the migrant population with pulmonary tuberculosis (PTB) in West China, and identify factors associated with QOL.

METHODS

A pilot investigation was conducted among 103 migrant individuals with PTB in Nanchong Region, Sichuan Province, China. The QOL and social support of the patients were investigated using a short version of the World Health Organization Quality of Life questionnaire and the Social Support Rating Scale, respectively.

RESULTS

The mean scores of the QOL of the migrant population were respectively 12.1, 12.9 and 11.7 for the physical, psychological and environmental domains; these were significantly lower than those of the general Chinese population. Non-parametric tests detected the significant effects of the following: 1) educational levels on all domains, including social relationship; 2) age on all domains, except psychological; 3) personal income on the physical and environmental domains; and 4) subjective support on all domains, except psychological. Multivariate logistic regression analyses confirmed that educational levels and subjective support were significantly associated with the global health status of the migrant population.

CONCLUSIONS

The QOL of patients with TB among the migrant population in West China was poor; education and subjective support were important influential factors.

Effects of Pregnancy on the Solubility of Halogenated Volatile Anaesthetics in Rat Blood and Tissues

This study was designed to evaluate the effects of pregnancy on the solubility of halogenated volatile anaesthetics in rat blood and tissues. Tissue samples from 10 pregnant and 10 non-pregnant adult female Sprague Dawley rats, including the heart, liver, kidney and brain, were obtained and made into respective homogenates. Blood/gas and tissue/gas partition coefficients for halothane, sevoflurane and isoflurane were determined by the method of two-stage headspace equilibration by gas chromatography with each of the homogenates. Values were analysed by t-test or one-way analysis of variance. The solubility within blood and brain for halothane in the pregnant group (2.90 ± 0.44, 5.55 ± 0.73) was significantly lower than that of the non-pregnant group (3.42±0.23, 6.33±0.64; P <0.05). However, there were no significant differences between the two groups for liver, kidney or heart solubility. For sevoflurane and isoflurane, there were no significant differences in solubility between the two groups. In conclusion, pregnancy decreased the solubility of halothane within the blood and brain, whereas the solubility of halothane in other tissues including the liver, kidney and heart showed no significant alteration. Pregnancy did not affect the solubility of sevoflurane or isoflurane within blood or the other tissues studied.

A comparison of the effect of total intravenous anaesthesia with propofol and remifentanil and inhalational anaesthesia with isoflurane on the release of pro- and anti-inflammatory cytokines in patients undergoing open cholecystectomy

The aim of the study was to investigate the effects of two anaesthetic techniques (total intravenous technique vs. inhalational technique) on changes in pro- and anti-inflammatory cytokine levels during open cholecystectomy. Forty ASA PS I-II patients undergoing open cholecystectomy were randomly assigned to two groups. Group R received total intravenous anaesthesia with propofol and remifentanil and group F received balanced inhalational anaesthesia with isoflurane. The plasma levels of tumour necrosis factor-alpha (TNF-alpha), interleukin IL-6 and interleukin IL-10 were measured during and after surgery. The pro-inflammatory cytokine levels (TNF-alpha and IL-6) and the anti-inflammatory cytokine (IL-10) showed a significant increase in their concentrations compared with pre-induction levels in both groups (P < 0.05). By the end of anaesthesia and surgery, TNF-alpha and IL-6 were significantly lower in group R than in group F (P < 0.05). At the end of anaesthesia and 12 hours postoperatively, IL-10 levels in group R were higher than in group F (P < 0.05). These findings suggest that total intravenous anaesthesia using propofol and remifentanil suppresses the inflammatory response caused by surgery to a greater extent than a balanced inhalation technique using isoflurane.

Inhibition of medulloblastoma cell invasion by Slit

Invasion of brain tumor cells has made primary malignant brain neoplasms among the most recalcitrant to therapeutic strategies. We tested whether the secreted protein Slit2, which guides the projection of axons and developing neurons, could modulate brain tumor cell invasion. Slit2 inhibited the invasion of medulloblastoma cells in a variety of in vitro models. The effect of Slit2 was inhibited by the Robo ectodomain. Time-lapse videomicroscopy indicated that Slit2 reduced medulloblastoma invasion rate without affecting cell direction or proliferation. Both medulloblastoma and glioma tumors express Robo1 and Slit2, but only medulloblastoma invasion is inhibited by recombinant Slit2 protein. Downregulation of activated Cdc42 may contribute to this differential response. Our findings reinforce the concept that neurodevelopmental cues such as Slit2 may provide insights into brain tumor invasion.

Signal transduction in neuronal migration: roles of GTPase activating proteins and the small GTPase Cdc42 in the Slit-Robo pathway

The Slit protein guides neuronal and leukocyte migration through the transmembrane receptor Roundabout (Robo). We report here that the intracellular domain of Robo interacts with a novel family of Rho GTPase activating proteins (GAPs). Two of the Slit-Robo GAPs (srGAPs) are expressed in regions responsive to Slit. Slit increased srGAP1-Robo1 interaction and inactivated Cdc42. A dominant negative srGAP1 blocked Slit inactivation of Cdc42 and Slit repulsion of migratory cells from the anterior subventricular zone (SVZa) of the forebrain. A constitutively active Cdc42 blocked the repulsive effect of Slit. These results have demonstrated important roles for GAPs and Cdc42 in neuronal migration. We propose a signal transduction pathway from the extracellular guidance cue to intracellular actin polymerization.

Neuronal migration and the evolution of the human brain

A new study demonstrating a pathway for neuronal migration in humans, but not in monkeys, suggests that migration has a key role in the evolution of the brain, as well as its development.

Role of PI3-kinase in isoproterenol and IGF-1 induced ecNOS activity

Phosphatidylinositol 3-kinase (PI3-K) has been shown to mediate insulin and insulin-like growth factor-1 (IGF-1)-induced nitric oxide (NO) generation and, thus, vascular tone. A role for PI3-K in G-protein-coupled receptor signal transduction has been reported. As beta (beta2)-adrenergic vascular actions are partly dependent on NO, we have investigated the role of PI3-K in isoproterenol (Iso) and IGF-1 induced endothelial NO synthase (ecNOS) activity in rat aortic endothelial cells (RAEC). Cell lysates of RAEC, exposed to Iso (10 micromol/L) for 5 min and 6 h, and to IGF-1 (100 nM) for 10 min and 6 h, or pretreated with PI3-K inhibitor Wortmannin (WT), were used for measuring PI3-K activity, p85kDa regulatory protein, and citrulline production. Results show that Iso and IGF-1 increased a p85 subunit and citrulline production, and also enhanced 32P incorporation into PIP3. Pretreatment with WT inhibited Iso-stimulated ecNOS, as well as, PI3-K activity. Iso enhanced association of ecNOS with the triton X-100-insoluble fraction of RAEC. These data indicate that the endothelial cell PI3-K pathway mediates, in part, the release of NO and subsequent vasorelaxation in response to this beta-agonist, as well as, IGF-1.

The neuronal repellent Slit inhibits leukocyte chemotaxis induced by chemotactic factors

Migration is a basic feature of many cell types in a wide range of species. Since the 1800s, cell migration has been proposed to occur in the nervous and immune systems, and distinct molecular cues for mammalian neurons and leukocytes have been identified. Here we report that Slit, a secreted protein previously known for its role of repulsion in axon guidance and neuronal migration, can also inhibit leukocyte chemotaxis induced by chemotactic factors. Slit inhibition of the chemokine-induced chemotaxis can be reconstituted by the co-expression of a chemokine receptor containing seven transmembrane domains and Roundabout (Robo), a Slit receptor containing a single transmembrane domain. Thus, there is a functional interaction between single and seven transmembrane receptors. Our results reveal the activity of a neuronal guidance cue in regulating leukocyte migration and indicate that there may be a general conservation of guidance mechanisms underlying metazoan cell migration. In addition, we have uncovered an inhibitor of leukocyte chemotaxis, and propose a new therapeutic approach to treat diseases involving leukocyte migration and chemotactic factors.

Short-range guidance of olfactory bulb axons is independent of repulsive factor slit

During development, mitral cells, the major output neurons of the olfactory bulb, project their axons caudolaterally into the telencephalon and form the lateral olfactory tract (LOT). Two types of guidance cues have been suggested for this projection. First, a long-range factor Slit, which is secreted from the septum, repels mitral cell axons into a caudolateral direction. Second, the pathway of mitral cell axons contains a subset of neurons designated as lot cells, which guide the axons through short-range interactions. It is not clear how these two guidance cues relate to each other and how they share the physiological roles. Here we examined the behavior of mitral cell axons in organotypic culture on ectopic application of Slit and inhibition of endogenous Slit signaling. The results suggested that the short-range guidance cue in the LOT pathway functions independently from Slit. Furthermore, our results showed that removal of the septum and inhibition of Slit signaling did not affect the projection of mitral cell axons. Although the septum and exogenous Slit can repel olfactory bulb axons, our results cast doubts on the physiological relevance of the septum and endogenous Slit in guiding the projection of mitral cell axons.

The N-terminal leucine-rich regions in Slit are sufficient to repel olfactory bulb axons and subventricular zone neurons

The Slit proteins are a new family of secreted guidance cues involved in axon guidance and neuronal migration. Each mammalian Slit protein contains >1400 amino acid residues, with four leucine-rich regions (LRRs), nine epidermal growth factor repeats, a laminin G domain, and a C-terminal cysteine-rich domain. A receptor for Slit is the transmembrane protein Roundabout (Robo), whose extracellular part contains five Ig domains and three fibronectin type III repeats. We report here that the LRRs in Slit are sufficient for binding to the Ig domains of Robo. Mutant forms of Slit containing only the LRRs function as chemorepellents for axons projecting from the olfactory bulb both in vitro and in the telencephalon. The LRRs can repel neurons migrating from the anterior subventricular zone (SVZa) to the olfactory bulb in brain slices isolated from neonatal rodents. However, the LRRs do not show repulsive effects on the SVZa neurons migrating in collagen gels. Our results indicate that the same LRRs are sufficient for guiding both axon projection and neuronal migration and suggest that the other regions in the Slit proteins may be involved in regulating the diffusion and distribution of the Slit proteins. The fact that the same domains are involved in guiding axon projection and neuronal migration further strengthens the idea of a conserved guidance mechanism for these important processes.

Effects of intrahippocampal aniracetam treatment on Y-maze avoidance learning performance and behavioral long-term potentiation in dentate gyrus in rat

Effects of intrahippocampal treatment of aniracetam, a selective agonist for DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproionic acid (AMPA) receptors, on Y-maze avoidance learning task and behavioral long-term potentiation (LTP) in perforant path-dentate gyrus were studied in freely moving rats by using in vivo electrophysiology combined with behavioral tests. The results were as follows: (1) intrahippocampal treatment of aniracetam reversibly enhanced basal synaptic transmission in perforant path to dentate gyrus in a dosage dependent manner; (2) aniracetam produced improvement in Y-maze learning performance when administration occurred 5 min prior to maze learning; (3) aniracetam administration significantly facilitated behavioral LTP in dentate gyrus, while the maximal amplitude of LTP has no significant difference when compared to saline group. The present results indicate that hippocampal AMPA receptors are involved in learning and memory.

Duplications and defects in the CYP2A6 gene: identification, genotyping, and in vivo effects on smoking

In humans, 80% of nicotine is metabolized to the inactive metabolite cotinine by the enzyme CYP2A6, which can also activate tobacco smoke procarcinogens (e.g., 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone). Previously, we demonstrated that individuals who are nicotine-dependent and have defective CYP2A6 alleles (*2, *3) smoked fewer cigarettes; however, we recognize that the genotyping method used for the CYP2A6*3 allele gave a high false-positive rate. In the current study we used improved genotyping methods to examine the effects of the defective CYP2A6*2 and CYP2A6*4 alleles on smoking behavior. We found that those with the defective alleles (N = 14) smoked fewer cigarettes per day than those homozygous (N = 277) for wild-type alleles (19 versus 28 cigarettes per day, P <.001). In addition, we identified a duplicated form of the CYP2A6 gene, corresponding to the gene deletion CYP2A6*4 allele, developed a genotyping assay, assessed the gene copy number, and examined its prevalence in Caucasian smokers (N = 296). We observed an ascending rank order for plasma cotinine and breath carbon monoxide levels (an index of smoke inhalation) in individuals with null (CYP2A6*2 and CYP2A6*4) alleles (N = 14), those homozygous for wild-type (CYP2A6*1/*1) alleles (N = 277), and those with our newly identified CYP2A6 gene duplication (N = 5). The phenotype, as determined by plasma nicotine/cotinine ratios, had a descending rank order for these three genotype groups that did not reach significance. Although further characterization is required for the duplication gene variant, these results extend our previous findings and suggest a substantial influence of CYP2A6 genotype and phenotype on smoking behavior.

[The molecular mechanism of neuronal migration]

A large amount of work since the late 1800 have shown that, during embryonic and postnatal development, the majority, if not all, neurons in mammalian nervous system have to migrate a certain distance to reach their final destination. An interesting question is how neurons are guided for their migration. We are interested in the molecular mechanisms underlying neuronal migration and our work published in 1999 indicates that there are diffusible molecules in the brain which can guide the direction of migrating neurons; specifically, a secreted protein called Slit is repulsive to neurons and its concentration gradient guides neuronal migration.

Regional and cellular distribution of CYP2D subfamily members in rat brain

1. Human CYP2D6 is present in brain, metabolizes many drugs and has been implicated in Parkinson's and Alzheimer's diseases and some cancers. It is still unclear which of the six known rat CYP2D subfamily members is/are homologous to human CYP2D6. 2. In this study, RT-PCR, Southern and Western blotting and immunohistochemical techniques were used to study the distribution of CYP2D subfamily member mRNA and proteins across 10 rat brain regions. CYP2D subfamily mRNA and protein levels were correlated with brain dextromethorphan O-demethylation (DOD), a measure of human CYP2D6 and rat CYP2D1 activities. 3. The data showed a strong relationship between CYP2D1 and CYP2D1-18 with brain DOD activity. In addition, it was shown that CYP2D proteins are present in brain mitochondrial as well as microsomal membranes. CYP2D subfamily member mRNA and proteins varied across brain regions and were highly concentrated in specific cell types. 4. These data strongly suggest that CYP2D1 and not CYP2D5 mediates DOD activity in rat brain, and may be the rat homologue of human CYP2D6. The highly localized nature of CYP2D indicates that in specific neurones enzyme levels may approach hepatic levels and, hence, contribute to local alterations in brain drug metabolism.

brakeless is required for photoreceptor growth-cone targeting in Drosophila

The R1-R6 subclass of photoreceptor neurons (R cells) in the Drosophila compound eye form specific connections with targets in the optic ganglia. In this paper, we report the identification of a gene, brakeless (bks), that is essential for R1-R6 growth cone targeting. In brakeless mutants, R1-R6 growth cones frequently fail to terminate migration in their normal target, the lamina, and instead project through it and terminate in the second optic ganglion, the medulla. Genetic mosaic analysis and transgene rescue experiments indicate that bks functions in R cells and not within the lamina target region. bks encodes a nuclear protein. We propose that it participates in a gene expression pathway regulating one or more growth cone components controlling R1-R6 targeting.

Embryonic expression and extracellular secretion of Xenopus slit

The slit genes have recently been found to encode proteins with a conserved chemorepulsive activity for axons in invertebrates and vertebrates. We have determined the expression pattern of a slit gene in Xenopus embryos. In the neural tube, slit is expressed at the ventral and dorsal midlines, and the motor neurons. slit is also expressed in a changing pattern in the retina. The full-length Xenopus Slit protein is secreted extracellularly, whereas its receptor Roundabout can not be secreted. Using a myc-tagged secreted Slit protein, we confirmed the binding of Slit to Roundabout expressed on the cell surface. These results confirm Slit-Roundabout interactions and the biochemical properties of Slit and Roundabout proteins, and further support the idea that Slit may guide axon projections in multiple regions of the embryo.

The SH2/SH3 adaptor protein dock interacts with the Ste20-like kinase misshapen in controlling growth cone motility

Recent studies suggest that the SH2/SH3 adaptor Dock/Nck transduces tyrosine phosphorylation signals to the actin cytoskeleton in regulating growth cone motility. The signaling cascade linking the action of Dock/Nck to the reorganization of cytoskeleton is poorly understood. We now demonstrate that Dock interacts with the Ste20-like kinase Misshapen (Msn) in the Drosophila photoreceptor (R cell) growth cones. Loss of msn causes a failure of growth cones to stop at the target, a phenotype similar to loss of dock, whereas overexpression of msn induces pretarget growth cone termination. Physical and genetic interactions between Msn and Dock indicate a role for Msn in the Dock signaling pathway. We propose that Msn functions as a key controller of growth cone cytoskeleton in response to Dock-mediated signals.