Identification of Novel HIV-1 Latency-Reversing Agents from a Library of Marine Natural Products

Natural products originating from marine and plant materials are a rich source of chemical diversity and unique antimicrobials. Using an established in vitro model of HIV-1 latency, we screened 257 pure compounds from a marine natural product library and identified 4 (psammaplin A, aplysiatoxin, debromoaplysiatoxin, and previously-described alotaketal C) that induced expression of latent HIV-1 provirus in both cell line and primary cell models. Notably, aplysiatoxin induced similar levels of HIV-1 expression as prostratin but at up to 900-fold lower concentrations and without substantial effects on cell viability. Psammaplin A enhanced HIV-1 expression synergistically when treated in combination with the protein kinase C (PKC) activator prostratin, but not the histone deacetylase inhibitor (HDACi) panobinostat, suggesting that psammaplin A functions as a latency-reversing agent (LRA) of the HDACi class. Conversely, aplysiatoxin and debromoaplysiatoxin synergized with panobinostat but not prostratin, suggesting that they function as PKC activators. Our study identifies new compounds from previously untested marine natural products and adds to the repertoire of LRAs that can inform therapeutic “shock-and-kill”-based strategies to eliminate latent HIV-infected reservoirs.

Inhibition of NF-κB-dependent HIV-1 replication by the marine natural product bengamide A

HIV-1 inhibitors that act by mechanisms distinct from existing antiretrovirals can provide novel insights into viral replication and potentially inform development of new therapeutics. Using a multi-cycle HIV-1 replication assay, we screened 252 pure compounds derived from marine invertebrates and microorganisms and identified 6 (actinomycin Z₂, bastadin 6, bengamide A, haliclonacyclamine A + B, keramamine C, neopetrosiamide B) that inhibited HIV-1 with 50% effective concentrations (EC₅₀s) of 3.8 μM or less. The most potent inhibitor, bengamide A, blocked HIV-1 in a T cell line with an EC₅₀ of 0.015 μM and in peripheral blood mononuclear cells with an EC₅₀ of 0.032 μM. Bengamide A was previously described to inhibit NF-κB signaling. Consistent with this mechanism, bengamide A suppressed reporter expression from an NF-κB-driven minimal promoter and an HIV-1 long terminal repeat (LTR) with conserved NF-κB response elements, but lacked activity against an LTR construct with mutation of these elements. In single-cycle HIV-1 infection assays, bengamide A also suppressed viral protein expression when viruses encoded an intact LTR but exhibited minimal activity against those with mutated NF-κB elements. Finally, bengamide A did not inhibit viral DNA accumulation, indicating that it likely acts downstream of this step in HIV-1 replication. Our study identifies multiple new antiviral compounds including an unusually potent inhibitor of HIV-1 gene expression.

The Croton megalobotrys Müll Arg. traditional medicine in HIV/AIDS management: Documentation of patient use, in vitro activation of latent HIV-1 provirus, and isolation of active phorbol esters

ETHNOPHARMACOLOGICAL RELEVANCE

Current HIV therapies do not act on latent cellular HIV reservoirs; hence they are not curative. While experimental latency reversal agents (LRAs) can promote HIV expression in these cells, thereby exposing them to immune recognition, existing LRAs exhibit limited clinical efficacy and high toxicity. We previously described a traditional 3-step medicinal plant regimen used for HIV/AIDS management in Northern Botswana that inhibits HIV replication in vitro. Here we describe use of one component of the regimen that additionally contains novel phorbol esters possessing HIV latency-reversal properties.

AIM OF THE STUDY

We sought to document experiences of traditional medicine users, assess the ability of traditional medicine components to reverse HIV latency in vitro, and identify pure compounds that conferred these activities.

MATERIALS AND METHODS

Experiences of two HIV-positive traditional medicine users (patients) were documented using qualitative interview techniques. Latency reversal activity was assessed using a cell-based model (J-Lat, clone 9.2). Crude plant extracts were fractionated by open column chromatography and reverse-phase HPLC. Compound structures were elucidated using NMR spectroscopy and mass spectrometry.

RESULTS

Patients using the 3-step regimen reported improved health over several years despite no reported use of standard HIV therapies. Crude extracts from Croton megalobotrys Müll Arg. ("Mukungulu"), the third component of the 3-step regimen, induced HIV expression in J-lat cells to levels comparable to the known LRA prostratin. Co-incubation with known LRAs and pharmacological inhibitors indicated that the active agent(s) in C. megalobotrys were likely to be protein kinase C (PKC) activator(s). Consistent with these results, two novel phorbol esters (Namushen 1 and 2) were isolated as abundant components of C. megalobotrys and were sufficient to confer HIV latency reversal in vitro.

CONCLUSION

We have identified novel LRAs of the phorbol ester class from a medicinal plant used in HIV/AIDS management. These data, combined with self-reported health effects and previously-described in vitro anti-HIV activities of this traditional 3-step regimen, support the utility of longitudinal observational studies of patients undergoing this regimen to quantify its effects on plasma viral loads and HIV reservoir size in vivo.

ABCA8 Regulates Cholesterol Efflux and High-Density Lipoprotein Cholesterol Levels

Objective—

High-density lipoproteins (HDL) are considered to protect against atherosclerosis in part by facilitating the removal of cholesterol from peripheral tissues. However, factors regulating lipid efflux are incompletely understood. We previously identified a variant in adenosine triphosphate–binding cassette transporter A8 ( ABCA8 ) in an individual with low HDL cholesterol (HDLc). Here, we investigate the role of ABCA8 in cholesterol efflux and in regulating HDLc levels.

Approach and Results—

We sequenced ABCA8 in individuals with low and high HDLc and identified, exclusively in low HDLc probands, 3 predicted deleterious heterozygous ABCA8 mutations (p.Pro609Arg [P609R], IVS17-2 A>G and p.Thr741Stop [T741X]). HDLc levels were lower in heterozygous mutation carriers compared with first-degree family controls (0.86±0.34 versus 1.17±0.26 mmol/L; P =0.005). HDLc levels were significantly decreased by 29% ( P =0.01) in Abca8b −/− mice on a high-cholesterol diet compared with wild-type mice, whereas hepatic overexpression of human ABCA8 in mice resulted in significant increases in plasma HDLc and the first steps of macrophage-to-feces reverse cholesterol transport. Overexpression of wild-type but not mutant ABCA8 resulted in a significant increase (1.8-fold; P =0.01) of cholesterol efflux to apolipoprotein AI in vitro. ABCA8 colocalizes and interacts with adenosine triphosphate–binding cassette transporter A1 and further potentiates adenosine triphosphate–binding cassette transporter A1–mediated cholesterol efflux.

Conclusions—

ABCA8 facilitates cholesterol efflux and modulates HDLc levels in humans and mice.

Mechanisms of Action of Novel Influenza A/M2 Viroporin Inhibitors Derived from Hexamethylene Amiloride

The increasing prevalence of influenza viruses with resistance to approved antivirals highlights the need for new anti-influenza therapeutics. Here we describe the functional properties of hexamethylene amiloride (HMA)-derived compounds that inhibit the wild-type and adamantane-resistant forms of the influenza A M2 ion channel. For example, 6-(azepan-1-yl)-N-carbamimidoylnicotinamide ( 9: ) inhibits amantadine-sensitive M2 currents with 3- to 6-fold greater potency than amantadine or HMA (IC50 = 0.2 vs. 0.6 and 1.3 µM, respectively). Compound 9: competes with amantadine for M2 inhibition, and molecular docking simulations suggest that 9: binds at site(s) that overlap with amantadine binding. In addition, tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-biphenyl]-4-carboxylate ( 27: ) acts both on adamantane-sensitive and a resistant M2 variant encoding a serine to asparagine 31 mutation (S31N) with improved efficacy over amantadine and HMA (IC50 = 0.6 µM and 4.4 µM, respectively). Whereas 9: inhibited in vitro replication of influenza virus encoding wild-type M2 (EC50 = 2.3 µM), both 27: and tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-biphenyl]-4-carboxylate ( 26: ) preferentially inhibited viruses encoding M2(S31N) (respective EC50 = 18.0 and 1.5 µM). This finding indicates that HMA derivatives can be designed to inhibit viruses with resistance to amantadine. Our study highlights the potential of HMA derivatives as inhibitors of drug-resistant influenza M2 ion channels.

Screening of the Pan-African natural product library identifies ixoratannin A-2 and boldine as novel HIV-1 inhibitors

The continued burden of HIV in resource-limited regions such as parts of sub-Saharan Africa, combined with adverse effects and potential risks of resistance to existing antiretroviral therapies, emphasize the need to identify new HIV inhibitors. Here we performed a virtual screen of molecules from the pan-African Natural Product Library, the largest collection of medicinal plant-derived pure compounds on the African continent. We identified eight molecules with structural similarity to reported interactors of Vpu, an HIV-1 accessory protein with reported ion channel activity. Using in vitro HIV-1 replication assays with a CD4+ T cell line and peripheral blood mononuclear cells, we confirmed antiviral activity and minimal cytotoxicity for two compounds, ixoratannin A-2 and boldine. Notably, ixoratannin A-2 retained inhibitory activity against recombinant HIV-1 strains encoding patient-derived mutations that confer resistance to protease, non-nucleoside reverse transcriptase, or integrase inhibitors. Moreover, ixoratannin A-2 was less effective at inhibiting replication of HIV-1 lacking Vpu, supporting this protein as a possible direct or indirect target. In contrast, boldine was less effective against a protease inhibitor-resistant HIV-1 strain. Both ixoratannin A-2 and boldine also inhibited in vitro replication of hepatitis C virus (HCV). However, BIT-225, a previously-reported Vpu inhibitor, demonstrated antiviral activity but also cytotoxicity in HIV-1 and HCV replication assays. Our work identifies pure compounds derived from African plants with potential novel activities against viruses that disproportionately afflict resource-limited regions of the world.

Identification of four novel genes contributing to familial elevated plasma HDL cholesterol in humans

While genetic determinants strongly influence HDL cholesterol (HDLc) levels, most genetic causes underlying variation in HDLc remain unknown. We aimed to identify novel rare mutations with large effects in candidate genes contributing to extreme HDLc in humans, utilizing family-based Mendelian genetics. We performed next-generation sequencing of 456 candidate HDLc-regulating genes in 200 unrelated probands with extremely low (≤10th percentile) or high (≥90th percentile) HDLc. Probands were excluded if known mutations existed in the established HDLc-regulating genes ABCA1, APOA1, LCAT, cholesteryl ester transfer protein (CETP), endothelial lipase (LIPG), and UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 2 (GALNT2). We identified 93 novel coding or splice-site variants in 72 candidate genes. Each variant was genotyped in the proband's family. Family-based association analyses were performed for variants with sufficient power to detect significance at P < 0.05 with a total of 627 family members being assessed. Mutations in the genes glucokinase regulatory protein (GCKR), RNase L (RNASEL), leukocyte immunoglobulin-like receptor 3 (LILRA3), and dynein axonemal heavy chain 10 (DNAH10) segregated with elevated HDLc levels in families, while no mutations associated with low HDLc. Taken together, we have identified mutations in four novel genes that may play a role in regulating HDLc levels in humans.

Aminoadamantanes with persistent in vitro efficacy against H1N1 (2009) influenza A

A series of 2-adamantanamines with alkyl adducts of various lengths were examined for efficacy against strains of influenza A including those having an S31N mutation in M2 proton channel that confer resistance to amantadine and rimantadine. The addition of as little as one CH₂ group to the methyl adduct of the amantadine/rimantadine analogue, 2-methyl-2-aminoadamantane, led to activity in vitro against two M2 S31N viruses A/Calif/07/2009 (H1N1) and A/PR/8/34 (H1N1) but not to a third A/WS/33 (H1N1). Solid state NMR of the transmembrane domain (TMD) with a site mutation corresponding to S31N shows evidence of drug binding. But electrophysiology using the full length S31N M2 protein in HEK cells showed no blockade. A wild type strain, A/Hong Kong/1/68 (H3N2) developed resistance to representative drugs within one passage with mutations in M2 TMD, but A/Calif/07/2009 S31N was slow (>8 passages) to develop resistance in vitro, and the resistant virus had no mutations in M2 TMD. The results indicate that 2-alkyl-2-aminoadamantane derivatives with sufficient adducts can persistently block p2009 influenza A in vitro through an alternative mechanism. The observations of an HA1 mutation, N160D, near the sialic acid binding site in both 6-resistant A/Calif/07/2009(H1N1) and the broadly resistant A/WS/33(H1N1) and of an HA1 mutation, I325S, in the 6-resistant virus at a cell-culture stable site suggest that the drugs tested here may block infection by direct binding near these critical sites for virus entry to the host cell.

Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning

The human neocortex has numerous specialized functional areas whose formation is poorly understood. Here, we describe a 15-base pair deletion mutation in a regulatory element of GPR56 that selectively disrupts human cortex surrounding the Sylvian fissure bilaterally including "Broca's area," the primary language area, by disrupting regional GPR56 expression and blocking RFX transcription factor binding. GPR56 encodes a heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor required for normal cortical development and is expressed in cortical progenitor cells. GPR56 expression levels regulate progenitor proliferation. GPR56 splice forms are highly variable between mice and humans, and the regulatory element of gyrencephalic mammals directs restricted lateral cortical expression. Our data reveal a mechanism by which control of GPR56 expression pattern by multiple alternative promoters can influence stem cell proliferation, gyral patterning, and, potentially, neocortex evolution.

Abstract 155: Mutations In ABCA8 Result In HDL Deficiency And Cholesterol Efflux Defects

The molecular basis of extreme HDL-C levels is incompletely understood. To identify mutations in novel putative HDL genes, we sequenced select genes in 80 unrelated individuals with extreme low HDLc (HDL %ile≤10th) and as controls, 120 individuals with high HDL (HDL %ile≥90th). We identified two variants in ABCA8 in subjects with low HDL-C levels. The E18-2T>C mutation is located in a highly conserved region and gives rise to a disruption of a splice site. The G>C variant occurs at a site conserved in vertebrates, at position 64425884 (build HG18), and results in Pro609Arg substitution. No ABCA8 mutations were identified in HHDL individuals. These represent the first mutations identified in ABCA8, which belongs to the family of ATP binding cassette transporters. Family expansion followed by genotyping identified additional mutation carriers and first degree relative controls in whom segregation analyses were performed. Compared with controls, mutation carriers showed a significant 32.6% decrease in plasma HDLc levels and decreased HDL percentiles (HDLc: controls = 1.23±0.26, mutation carriers = 0.83±0.37, mmol/L, p=0.0007; HDL%ile: controls = 41.8±21.2, mutation carriers = 17.3±19.2, p=0.004, n=23 controls and 12 carriers). No changes in LDLc, triglycerides or BMI were observed. Since mutations in ABCA8 reduce plasma HDLc levels, we assessed the role of ABCA8 in lipid efflux. Cholesterol efflux to lipid-free APOA-I was significantly reduced by 62.1% in fibroblasts from the proband with the E18-2 T>C mutation. In comparison, fibroblasts from heterozygous ABCA1 mutation carriers showed a 30-60% decrease in efflux to APOA-I depending on mutation severity. Wild type and P609R ABCA8 cDNA clones were generated from human liver RNA. A significant ~200% increase in cholesterol efflux to lipid free APOA-I was observed with wild type ABCA8, further suggesting that ABCA8 is a lipid transporter. A significant 75% decrease in the efflux of cholesterol to lipid-free APOA-I (p=0.02) was observed with the mutant P609R ABCA8 protein compared to wild-type. We show here that ABCA8 is a cholesterol transporter, and that mutations in ABCA8 are a novel cause for reduced plasma HDLc levels in humans.

Two novel mutations in apolipoprotein C3 underlie atheroprotective lipid profiles in families

Apolipoprotein C3 (APOC3) mutations carriers typically display high plasma high-density lipoprotein cholesterol (HDL-C) and low triglycerides (TGs). We set out to investigate the prevalence and clinical consequences of APOC3 mutations in individuals with hyperalphalipoproteinemia. Two novel mutations (c.-13-2A>G and c.55+1G>A) and one known mutation (c.127G>A;p.Ala43Thr) were found. Lipid profiles and apoCIII isoform distributions were measured. c.55+1G>A mutation carriers displayed higher HDL-C percentiles (35.6 ± 35.8 vs 99.0 ± 0, p = 0.002) and lower TGs (0.51 (0.37-0.61) vs 1.42 (1.12-1.81) mmol/l, p = 0.007) and apoCIII levels (4.24 ± 1.57 vs 7.33 ± 3.61 mg/dl, p = 0.18). c.-13-2A>G mutation carriers did not display significantly different HDL-C levels (84.0 ± 30.0 vs 63.7 ± 45.7, p = 0.50), a trend towards lower TGs [0.71 (0.54 to 0.78) vs 0.85 (0.85 to -) mmol/l, p = 0.06] and significantly lower apoCIII levels (3.09 ± 1.08 vs 11.45 ± 1.06 mg/dl, p = 0.003). p.Ala43Thr mutation carriers displayed a trend towards higher HDL-C percentiles (91.2 ± 31.8 vs 41.0 ± 29.7 mmol/l, p = 0.06) and significantly lower TGs [0.58 (0.36-0.63) vs 0.95 (0.71-1.20) mmol/l, p = 0.02] and apoCIII levels (4.92 ± 2.33 vs 6.60 ± 1.60, p = 0.25). Heterozygosity for APOC3 mutations results in high HDL-C and low TGs and apoCIII levels. This favourable lipid profile in patients with genetically low apoCIII levels holds promise for current studies investigating the potential of apoCIII inhibition as a novel therapeutic in cardiovascular disease prevention.

The impact of partial and complete loss-of-function mutations in endothelial lipase on high-density lipoprotein levels and functionality in humans

BACKGROUND

Endothelial lipase is a phospholipase with activity against high-density lipoprotein. Although a small number of mutations in LIPG have been described, the role of LIPG in protection against atherosclerosis is unclear.

METHODS AND RESULTS

We identified 8 loss-of-function (LOF) mutations in LIPG in individuals with high-density lipoprotein cholesterol. Functional analysis confirmed that most rare mutations abolish lipase activity in vitro, indicating complete LOF, whereas 2 more common mutations N396S and R476W reduce activity by ≈50%, indicating partial LOF and implying ≈50% and ≈75% remaining endothelial lipase function in heterozygous complete LOF and partial LOF mutation carriers, respectively. complete LOF mutation carriers had significantly higher plasma high-density lipoprotein cholesterol levels compared with partial LOF mutation carriers. Apolipoprotein B-depleted serum from complete LOF carriers showed significantly enhanced cholesterol efflux acceptor capacity, whereas only trends were observed in partial LOF carriers. Carriers of LIPG mutations exhibited trends toward reduced coronary artery disease in 4 independent cohorts (meta-analysis odds ratio, 0.7; P=0.04).

CONCLUSIONS

Our data suggest that the impact of LIPG mutations is directly related to their effect on endothelial lipase function and support that antagonism of endothelial lipase function improves cardioprotection.

Segregation of LIPG, CETP, and GALNT2 mutations in Caucasian families with extremely high HDL cholesterol

To date, few mutations are described to underlie highly-elevated HDLc levels in families. Here we sequenced the coding regions and adjacent sequence of the LIPG, CETP, and GALNT2 genes in 171 unrelated Dutch Caucasian probands with HDLc≥90th percentile and analyzed segregation of mutations with lipid phenotypes in family members. In these probands, mutations were most frequent in LIPG (12.9%) followed by GALNT2 (2.3%) and CETP (0.6%). A total of 6 of 10 mutations in these three genes were novel (60.0%), and mutations segregated with elevated HDLc in families. Interestingly, the LIPG mutations N396S and R476W, which usually result in elevated HDLc, were unexpectedly found in 6 probands with low HDLc (i.e., ≤10th percentile). However, 5 of these probands also carried mutations in ABCA1, LCAT, or LPL. Finally, no CETP and GALNT2 mutations were found in 136 unrelated probands with low HDLc. Taken together, we show that rare coding and splicing mutations in LIPG, CETP, and GALNT2 are enriched in persons with hyperalphalipoproteinemia and segregate with elevated HDLc in families. Moreover, LIPG mutations do not overcome low HDLc in individuals with ABCA1 and possibly LCAT and LPL mutations, indicating that LIPG affects HDLc levels downstream of these proteins.

Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans

The scavenger receptor class B, member 1 (SR-BI), is a key cellular receptor for high-density lipoprotein (HDL) in mice, but its relevance to human physiology has not been well established. Recently a family was reported with a mutation in the gene encoding SR-BI and high HDL cholesterol (HDL-C). Here we report two additional individuals with extremely high HDL-C (greater than the 90th percentile for age and gender) with rare mutations in the gene encoding SR-BI. These mutations segregate with high HDL-C in family members of each proband and are associated with a 37% increase in plasma HDL-C in heterozygous individuals carrying them. Both mutations occur at highly conserved positions in the large extracellular loop region of SR-BI and are predicted to impair the function of the SR-BI protein. Our findings, combined with the prior report of a single mutation in the gene encoding SR-BI, further validate that mutations in SR-BI are a rare but recurring cause of elevated HDL-C in humans.

Increased risk of coronary artery disease in Caucasians with extremely low HDL cholesterol due to mutations in ABCA1, APOA1, and LCAT

Mutations in ABCA1, APOA1, and LCAT reduce HDL cholesterol (HDLc) in humans. However, the prevalence of these mutations and their relative effects on HDLc reduction and risk of coronary artery disease (CAD) are less clear. Here we searched for ABCA1, APOA1, and LCAT mutations in 178 unrelated probands with HDLc <10th percentile but no other major lipid abnormalities, including 89 with ≥1 first-degree relative with low HDLc (familial probands) and 89 where familial status of low HDLc is uncertain (unknown probands). Mutations were most frequent in LCAT (15.7%), followed by ABCA1 (9.0%) and APOA1 (4.5%), and were found in 42.7% of familial but only 14.6% of unknown probands (p=2.44∗10(-5)). Interestingly, only 16 of 24 (66.7%) mutations assessed in families conferred an average HDLc <10th percentile. Furthermore, only mutation carriers with HDLc <5th percentile had elevated risk of CAD (odds ratio (OR)=2.26 for 34 ABCA1 mutation carriers vs. 149 total first-degree relative controls, p=0.05; OR=2.50 for 26 APOA1 mutation carriers, p=0.04; OR=3.44 for 38 LCAT mutation carriers, p=1.1∗10(-3)). These observations show that mutations in ABCA1, APOA1, and LCAT are sufficient to explain >40% of familial hypoalphalipoproteinemia in this cohort. Moreover, individuals with mutations and large reductions in HDLc have increased risk of CAD. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Comprehensive EMX2 genotyping of a large schizencephaly case series

Schizencephaly is a brain malformation disorder characterized by one or more full-thickness clefts through the cerebral cortex. While initial reports suggested that EMX2 mutations are a common cause of schizencephaly, more recent evidence suggests that EMX2 mutations are not a common cause of this malformation. To determine the frequency of EMX2 mutations in patients with schizencephaly, we sequenced EMX2 in a cohort of 84 affected probands. No pathologic mutations were identified in this cohort, suggesting that EMX2 mutations are an uncommon cause of schizencephaly.

Disease-associated mutations affect GPR56 protein trafficking and cell surface expression

Bilateral frontoparietal polymicrogyria (BFPP) is a congenital brain malformation resulting in irregularities on the surface of the cortex, where normally convoluted gyri are replaced by numerous (poly) and noticeably smaller (micro) gyri. Individuals with BFPP suffer from epilepsy, mental retardation, language impairment and motor developmental delay. Mutations in the gene-encoding G protein-coupled receptor 56 (GPR56) cause BFPP; however, it remains unclear how these mutations affect GPR56 function. Here, we examine the biochemical properties and protein trafficking of wild-type and mutant GPR56. We demonstrate that GPR56 protein undergoes two major modifications, GPS domain-mediated protein cleavage and N-glycosylation, and that the N-terminal fragment can be released from the cell surface. In contrast to the wild-type protein, disease-associated GPR56 missense mutations in the tip of the N-terminal domain (R38Q, R38W, Y88C and C91S) produce proteins with reduced intracellular trafficking and poor cell surface expression, whereas the two mutations in the GPS domain (C346S and W349S) produce proteins with dramatically impaired cleavage that fail to traffic beyond the endoplasmic reticulum. Cell-trafficking impairments are abrogated in part by pharmacological chaperones that can partially rescue mutant GPR56 cell surface expression. These data demonstrate that some BFPP-associated mutations in GPR56 impair trafficking of the mutant protein to the plasma membrane, thus providing insights into how BFPP-associated mutations affect GPR56 function.

Single-cell transcriptional profiles and spatial patterning of the mammalian olfactory epithelium

In order to gain insights into the regulatory control of neuronal diversity in the mammalian olfactory system, we have identified the transcriptional profile of individual olfactory neurons. A single cell microarray strategy was performed to search for candidate genes involved in the molecular specification of dorso-ventral zones of olfactory receptor (OR) expression. Several transcripts were identified that display differential expression in distinct OR zones, including a novel family of genes, the Lozenge-like (Lzl) genes which share sequence consensus motifs with Lozenge, a transcription factor involved in the patterning of the Drosophila olfactory and visual systems.

EMX2-independent familial schizencephaly: Clinical and genetic analyses

Schizencephaly is a human brain malformation distinguished by full-thickness unilateral or bilateral clefts through the neocortex. Heterozygous mutations in the EMX2 locus are reported to give rise to schizencephaly. However, the comprehensive identification of causative genetic loci is precluded by a lack of large pedigrees and genome-wide linkage analyses. We present here a large Turkish pedigree with three individuals with schizencephaly. The similarity of clinical signs in affected individuals strongly suggests an underlying genetic cause; however, genome-wide linkage analysis rules out EMX2 linkage and instead suggests additional candidate loci. These results indicate that genetic forms of schizencephaly are likely to be heterogeneous.