Cyclopia and defective axial patterning in mice lacking Sonic hedgehog gene function

Targeted gene disruption in the mouse shows that the Sonic hedgehog (Shh) gene plays a critical role in patterning of vertebrate embryonic tissues, including the brain and spinal cord, the axial skeleton and the limbs. Early defects are observed in the establishment or maintenance of midline structures, such as the notochord and the floorplate, and later defects include absence of distal limb structures, cyclopia, absence of ventral cell types within the neural tube, and absence of the spinal column and most of the ribs. Defects in all tissues extend beyond the normal sites of Shh transcription, confirming the proposed role of Shh proteins as an extracellular signal required for the tissue-organizing properties of several vertebrate patterning centres.

Floor plate and motor neuron induction by different concentrations of the amino-terminal cleavage product of sonic hedgehog autoproteolysis

The differentiation of floor plate cells and motor neurons can be induced by Sonic hedgehog (SHH), a secreted signaling protein that undergoes autoproteolytic cleavage to generate amino- and carboxy-terminal products. We have found that both floor plate cells and motor neurons are induced by the amino-terminal cleavage product of SHH (SHH-N). The threshold concentration of SHH-N required for motor neuron induction is about 5-fold lower than that required for floor plate induction. Higher concentrations of SHH-N can induce floor plate cells at the expense of motor neuron differentiation. Our results suggest that the induction of floor plate cells and motor neurons by the notochord in vivo is mediated by exposure of neural plate cells to different concentrations of the amino-terminal product of SHH autoproteolytic cleavage.

Top-down processing mediated by interareal synchronization

Perception and cortical responses are not only driven "bottom-up" by the external stimulus but are altered by internal constraints such as expectancy or the current behavioral goal. To investigate neurophysiological mechanisms of such top-down effects, we analyzed the temporal interactions of neurons on different levels of the cortical hierarchy during perception of stimuli with varying behavioral significance. We found that interareal interactions in a middle-frequency range (theta and alpha; 4-12 Hz) strongly depend on the associated behavior, with a phase relationship and a layer specificity indicating a top-down-directed interaction. For novel unexpected stimuli, presumably processed in a feed-forward fashion, no such interactions occurred but high-frequency interactions (gamma; 20-100 Hz) were observed. Thus corticocortical synchronization reflects the internal state of the animal and may mediate top-down processes.

Sonic hedgehog is essential to foregut development

Congenital malformation of the foregut is common in humans, with an estimated incidence of 1 in 3000 live births, although its aetiology remains largely unknown. Mice with a targeted deletion of Sonic hedgehog (Shh) have foregut defects that are apparent as early as embryonic day 9.5, when the tracheal diverticulum begins to outgrow. Homozygous Shh-null mutant mice show oesophageal atresia/stenosis, tracheo-oesophageal fistula and tracheal and lung anomalies, features similar to those observed in humans with foregut defects. The lung mesenchyme shows enhanced cell death, decreased cell proliferation and downregulation of Shh target genes. These results indicate that Shh is required for the growth and differentiation of the oesophagus, trachea and lung, and suggest that mutations in SHH and its signalling components may be involved in foregut defects in humans.

Discharge of noradrenergic locus coeruleus neurons in behaving rats and monkeys suggests a role in vigilance

Recordings from noradrenergic locus coeruleus (LC) neurons in behaving rats and monkeys revealed that these cells decrease tonic discharge during sleep and also during certain high arousal behaviors (grooming and consumption) when attention (vigilance) was low. Sensory stimuli of many modalities phasically activated LC neurons. Response magnitudes varied with vigilance, similar to results for tonic activity. The most effective and reliable stimuli for eliciting LC responses were those that disrupted behavior and evoked orienting responses. Similar results were observed in behaving monkeys except that more intense stimuli were required for LC responses. Our more recent studies have examined LC activity in monkeys performing an "oddball" visual discrimination task. Monkeys were trained to release a lever after a target cue light that occurred randomly on 10% of trials; animals had to withhold responding during non-target cues. LC neurons selectively responded to the target cues during this task. During reversal training, LC neurons lost their response to the previous target cue and began responding to the new target light in parallel with behavioral reversal. Cortical event-related potentials were elicited in this task selectively by the same stimuli that evoked LC responses. Injections of lidocaine, GABA, or a synaptic decoupling solution into the nucleus paragigantocellularis in the rostral ventrolateral medulla, the major afferent to LC, eliminated responses of LC neurons to sciatic nerve stimulation or foot- or tail-pinch. This indicates that certain sensory information is relayed to LC through the excitatory amino acid (EAA) input from the ventrolateral medulla. The effect of prefrontal cortex (PFC) activation on LC neurons was examined in anesthetized rats. Single pulse PFC stimulation had no pronounced effect on LC neurons, consistent with our findings that this area does not innervate the LC nucleus. However, trains of PFC stimulation substantially activated most LC neurons. Thus, projections from the PFC may activate LC indirectly or through distal dendrites, suggesting a circuit whereby complex stimuli may influence LC neurons. The above results, in view of previous findings for postsynaptic effects of norepinephrine, are interpreted to reveal a role for the LC system in regulating attentional state or vigilance. The roles of major inputs to LC from the ventrolateral and dorsomedial medulla in sympathetic control and behavioral orienting responses, respectively, are integrated into this view of the LC system. It is proposed that the LC provides the cognitive complement to sympathetic function.

Essential role for Sonic hedgehog during hair follicle morphogenesis

The hair follicle is a source of epithelial stem cells and site of origin for several types of skin tumors. Although it is clear that follicles arise by way of a series of inductive tissue interactions, identification of the signaling molecules driving this process remains a major challenge in skin biology. In this study we report an obligatory role for the secreted morphogen Sonic hedgehog (Shh) during hair follicle development. Hair germs comprising epidermal placodes and associated dermal condensates were detected in both control and Shh -/- embryos, but progression through subsequent stages of follicle development was blocked in mutant skin. The expression of Gli1 and Ptc1 was reduced in Shh -/- dermal condensates and they failed to evolve into hair follicle papillae, suggesting that the adjacent mesenchyme is a critical target for placode-derived Shh. Despite the profound inhibition of hair follicle morphogenesis, late-stage follicle differentiation markers were detected in Shh -/- skin grafts, as well as cultured vibrissa explants treated with cyclopamine to block Shh signaling. Our findings reveal an essential role for Shh during hair follicle morphogenesis, where it is required for normal advancement beyond the hair germ stage of development.

Induction of midbrain dopaminergic neurons by Sonic hedgehog

Midbrain dopaminergic neurons, whose loss in adults results in Parkinson's disease, can be specified during embryonic development by a contact-dependent signal from floor plate cells. Here we show that the amino-terminal product of Sonic hedgehog autoproteolysis (SHH-N), an inductive signal expressed by floor plate cells, can induce dopaminergic neurons in vitro. We show further that manipulations to increase the activity of cyclic AMP-dependent protein kinase A, which is known to antagonize hedgehog signaling, can block dopaminergic neuron induction by floor plate cells. Our results and those of other studies indicate that SHH-N can function in a dose-dependent manner to induce different cell types within the neural tube. Our results also provide the basis for a potential cell transplantation therapy for Parkinson's disease.

Manifestation of the limb prepattern: limb development in the absence of sonic hedgehog function

The secreted protein encoded by the Sonic hedgehog (Shh) gene is localized to the posterior margin of vertebrate limb buds and is thought to be a key signal in establishing anterior-posterior limb polarity. In the Shh(-/-) mutant mouse, the development of many embryonic structures, including the limb, is severely compromised. In this study, we report the analysis of Shh(-/-) mutant limbs in detail. Each mutant embryo has four limbs with recognizable humerus/femur bones that have anterior-posterior polarity. Distal to the elbow/knee joints, skeletal elements representing the zeugopod form but lack identifiable anterior-posterior polarity. Therefore, Shh specifically becomes necessary for normal limb development at or just distal to the stylopod/zeugopod junction (elbow/knee joints) during mouse limb development. The forelimb autopod is represented by a single distal cartilage element, while the hindlimb autopod is invariably composed of a single digit with well-formed interphalangeal joints and a dorsal nail bed at the terminal phalanx. Analysis of GDF5 and Hoxd11-13 expression in the hindlimb autopod suggests that the forming digit has a digit-one identity. This finding is corroborated by the formation of only two phalangeal elements which are unique to digit one on the foot. The apical ectodermal ridge (AER) is induced in the Shh(-/-) mutant buds with relatively normal morphology. We report that the architecture of the Shh(-/-) AER is gradually disrupted over developmental time in parallel with a reduction of Fgf8 expression in the ridge. Concomitantly, abnormal cell death in the Shh(-/-) limb bud occurs in the anterior mesenchyme of both fore- and hindlimb. It is notable that the AER changes and mesodermal cell death occur earlier in the Shh(-/-) forelimb than the hindlimb bud. This provides an explanation for the hindlimb-specific competence to form autopodial structures in the mutant. Finally, unlike the wild-type mouse limb bud, the Shh(-/-) mutant posterior limb bud mesoderm does not cause digit duplications when grafted to the anterior border of chick limb buds, and therefore lacks polarizing activity. We propose that a prepattern exists in the limb field for the three axes of the emerging limb bud as well as specific limb skeletal elements. According to this model, the limb bud signaling centers, including the zone of polarizing activity (ZPA) acting through Shh, are required to elaborate upon the axial information provided by the native limb field prepattern.

Specification of ventral neuron types is mediated by an antagonistic interaction between Shh and Gli3

Specification of distinct neuron types in the ventral spinal cord is thought to be mediated by a graded concentration of Sonic hedgehog (Shh), a secreted signaling protein. Shh is made in the notochord, the most ventral part of the spinal cord, and in mice lacking Shh, ventral cell types are reduced or absent. The response to Shh depends on transcription factors of the Gli family, but the detailed mechanism is not understood. Here we show that Gli3 represses ventral fates in a dose-dependent manner. Whereas Shh -/- mutant mice show reductions in several classes of ventral interneurons and a complete absence of motor neurons, these cell types were rescued in Shh-/-;Gli3 -/- double mutants. This rescue of the Shh null phenotype depended on the level of Gli3 function; a partial rescue was observed in Shh-/-;Gli3 +/- embryos. We propose that Shh is required to antagonize Gli3, which would otherwise repress ventral fates. Differences between rostral and caudal regions suggest that other signaling molecules-in addition to Shh-may be involved in specifying ventral fates, particularly in the caudal region of the spinal cord.

Long-range sclerotome induction by sonic hedgehog: direct role of the amino-terminal cleavage product and modulation by the cyclic AMP signaling pathway

A long-range signal encoded by the Sonic hedgehog (Shh) gene has been implicated as the ventral patterning influence from the notochord that induces sclerotome and represses dermomyotome in somite differentiation. Long-range effects of hedgehog (hh) signaling have been suggested to result either from local induction of a secondary diffusible signal or from the direct action of the highly diffusible carboxy-terminal product of HH autoproteolytic cleavage. Here we provide evidence that the long-range somite patterning effects of SHH are instead mediated by a direct action of the amino-terminal cleavage product. We also show that pharmacological manipulations to increase the activity of cyclic AMP-dependent protein kinase A can selectively antagonize the effects of the amino-terminal cleavage product. Our results support the operation of a single evolutionarily conserved signaling pathway for both local and direct long-range inductive actions of HH family members.

A sonic hedgehog-independent, retinoid-activated pathway of neurogenesis in the ventral spinal cord

Sonic hedgehog (Shh) is thought to control the generation of motor neurons and interneurons in the ventral CNS. We show here that a Shh-independent pathway of interneuron generation also operates in the ventral spinal cord. Evidence for this parallel pathway emerged from an analysis of the induction of ventral progenitors that express the Dbx homeodomain proteins and of Evx1/2 (V0) and En1 (V1) neurons. Shh signaling is sufficient to induce Dbx cells and V0 and V1 neurons but is not required for their generation in vitro or in vivo. Retinoids appear to mediate this parallel pathway. These findings reveal an unanticipated Shh-independent signaling pathway that controls progenitor cell identity and interneuron diversity in the ventral spinal cord.

Potent excitatory influence of prefrontal cortex activity on noradrenergic locus coeruleus neurons

An influence of the prefrontal cortex on noradrenergic locus coeruleus neurons would have profound implications for the function of the locus coeruleus system. Although the medial prefrontal cortex does not substantially innervate the core of the nucleus locus coeruleus, evidence indicates that the medial prefrontal cortex projects to regions containing locus coeruleus dendrites; indirect medial prefrontal cortex-locus coeruleus projections are also possible. Here, we examined influences of prefrontal cortex activity on locus coeruleus firing rates by activating or inactivating the medial prefrontal cortex while recording impulse activity of locus coeruleus neurons extracellularly in anaesthetized rats. Most of our electrical stimulation experiments were conducted in rats which underwent lesions of the ascending dorsal bundle of noradrenergic fibres from the locus coeruleus to eliminate locus coeruleus projections to the prefrontal cortex, because antidromic activation of locus coeruleus from the prefrontal cortex affects even non-driven locus coeruleus neurons through collaterals. Single pulse stimulation (1 mA, 0.3-0.5 ms) of the dorsomedial (frontal region 2) or prelimbic region of the medial prefrontal cortex synaptically activated 13/16 (81%) or 16/56 (29%) locus coeruleus neurons, respectively. Train stimulation (20 Hz for 0.5 s) synaptically activated greater percentages of locus coeruleus cells, 11/12 cells (92%) for the dorsomedial prefrontal cortex, and 41/50 cells (82%) for the prelimbic cortex. No inhibitory responses in the locus coeruleus were obtained with dorsomedial prefrontal stimulation, and weak inhibition was found in 16% of locus coeruleus cells with prelimbic stimulation. Electrical stimulation of more lateral frontal cortex (Fr1 area) had no effects on locus coeruleus activity. Chemical stimulation of the dorsomedial prefrontal cortex with L-glutamate (10 or 100 mM) or D,L-homocysteic acid (10 mM) phasically activated 15/26 (55%) locus coeruleus cells, and 15/68 cells (22%) with prelimbic stimulation; such activation was sometimes followed by long-lasting oscillatory activity. No locus coeruleus cells exhibited purely inhibitory responses with chemical stimulation of any prefrontal cortex site. Inactivation of the dorsomedial or prelimbic region of the prefrontal cortex with lidocaine microinjection (2%, 180 or 300 nl) reduced locus coeruleus firing rates in 6/10 (60%) or 7/19 (37%) locus coeruleus cells, respectively. In no case did lidocaine in any prefrontal cortex site activate a locus coeruleus neuron. These results indicate that the medial prefrontal cortex provides a potent excitatory influence on locus coeruleus neurons. The fact that inactivation of the medial prefrontal cortex suppressed locus coeruleus firing indicates that the medial prefrontal cortex also provides a resting tonic excitatory influence on locus coeruleus activity.

Coordinate regulation and synergistic actions of BMP4, SHH and FGF8 in the rostral prosencephalon regulate morphogenesis of the telencephalic and optic vesicles

We investigated the roles of bare morphogenetic protein (BMP), sonic hedgehog (SHH) and fibroblast growth factor (FGF)-expressing signaling centers in regulating the patterned outgrowth of the telencephalic and optic vesicles. Implantation of BMP4 beads in the anterior neuropore of stage 10 chicken embryos repressed FGF8 and SHH expression. Similarly, loss of SHH expression in Shh mutant mice leads to increased BMP signaling and loss of Fgf8 expression in the prosencephalon. Increased BMP signaling and loss of FGF and SHH expression was correlated with decreased proliferation, increased cell death, and hypoplasia of the telencephalic and optic vesicles. However, decreased BMP signaling, through ectopic expression of Noggin, a BMP-binding protein, also caused decreased proliferation and hypoplasia of the telencephalic and optic vesicles, but with maintenance of Fgf8 and Shh expression, and no detectable increase in cell death. These results suggest that optimal growth requires a balance of BMP, FGF8 and SHH signaling. We suggest that the juxtaposition of Fgf8, Bmp4 and Shh expression domains generate patterning centers that coordinate the growth of the telencephalic and optic vesicles, similar to how Fgf8, Bmp4 and Shh regulate growth of the limb bud. Furthermore, these patterning centers regulate regional specification within the forebrain and eye, as exemplified by the regulation of Emx2 expression by different levels of BMP signaling. In summary, we present evidence that there is cross-regulation between BMP-, FGF- and SHH-expressing signaling centers in the prosencephalon which regulate morphogenesis of, and regional specification within, the telencephalic and optic vesicles.

Products, genetic linkage and limb patterning activity of a murine hedgehog gene

The hedgehog (hh) segmentation gene of Drosophila melanogaster encodes a secreted signaling protein that functions in the patterning of larval and adult structures. Using low stringency hybridization and degenerate PCR primers, we have isolated complete or partial hh-like sequences from a range of invertebrate species including other insects, leech and sea urchin. We have also isolated three mouse and two human DNA fragments encoding distinct hh-like sequences. Our studies have focused upon Hhg-1, a mouse gene encoding a protein with 46% amino acid identity to hh. The Hhg-1 gene, which corresponds to the previously described vhh-1 or sonic class, is expressed in the notochord, ventral neural tube, lung bud, hindgut and posterior margin of the limb bud in developing mouse embryos. By segregation analysis the Hhg-1 gene has been localized to a region in proximal chromosome 5, where two mutations affecting mouse limb development previously have been mapped. In Drosophila embryos, ubiquitous expression of the Hhg-1 gene yields effects upon gene expression and cuticle pattern similar to those observed for the Drosophila hh gene. We also find that cultured quail cells transfected with a Hhg-1 expression construct can induce digit duplications when grafted to anterior or mid-distal but not posterior borders within the developing chick limb; more proximal limb element duplications are induced exclusively by mid-distal grafts. Both in transgenic Drosophila embryos and in transfected quail cells, the Hhg-1 protein product is cleaved to yield two stable fragments from a single larger precursor. The significance of Hhg-1 genetic linkage, patterning activity and proteolytic processing in Drosophila and chick embryos is discussed.

Involvement of neurogranin in the modulation of calcium/calmodulin-dependent protein kinase II, synaptic plasticity, and spatial learning: a study with knockout mice

Neurogranin/RC3 is a neural-specific Ca(2+)-sensitive calmodulin (CaM)-binding protein whose CaM-binding affinity is modulated by phosphorylation and oxidation. Here we show that deletion of the Ng gene in mice did not result in obvious developmental or neuroanatomical abnormalities but caused an impairment of spatial learning and changes in hippocampal short- and long-term plasticity (paired-pulse depression, synaptic fatigue, long-term potentiation induction). These deficits were accompanied by a decreased basal level of the activated Ca(2+)/CaM-dependent kinase II (CaMKII) ( approximately 60% of wild type). Furthermore, hippocampal slices of the mutant mice displayed a reduced ability to generate activated CaMKII after stimulation of protein phosphorylation and oxidation by treatments with okadaic acid and sodium nitroprusside, respectively. These results indicate a central role of Ng in the regulation of CaMKII activity with decisive influences on synaptic plasticity and spatial learning.

Sonic hedgehog controls epaxial muscle determination through Myf5 activation

Sonic hedgehog (Shh), produced by the notochord and floor plate, is proposed to function as an inductive and trophic signal that controls somite and neural tube patterning and differentiation. To investigate Shh functions during somite myogenesis in the mouse embryo, we have analyzed the expression of the myogenic determination genes, Myf5 and MyoD, and other regulatory genes in somites of Shh null embryos and in explants of presomitic mesoderm from wild-type and Myf5 null embryos. Our findings establish that Shh has an essential inductive function in the early activation of the myogenic determination genes, Myf5 and MyoD, in the epaxial somite cells that give rise to the progenitors of the deep back muscles. Shh is not required for the activation of Myf5 and MyoD at any of the other sites of myogenesis in the mouse embryo, including the hypaxial dermomyotomal cells that give rise to the abdominal and body wall muscles, or the myogenic progenitor cells that form the limb and head muscles. Shh also functions in somites to establish and maintain the medio-lateral boundaries of epaxial and hypaxial gene expression. Myf5, and not MyoD, is the target of Shh signaling in the epaxial dermomyotome, as MyoD activation by recombinant Shh protein in presomitic mesoderm explants is defective in Myf5 null embryos. In further support of the inductive function of Shh in epaxial myogenesis, we show that Shh is not essential for the survival or the proliferation of epaxial myogenic progenitors. However, Shh is required specifically for the survival of sclerotomal cells in the ventral somite as well as for the survival of ventral and dorsal neural tube cells. We conclude, therefore, that Shh has multiple functions in the somite, including inductive functions in the activation of Myf5, leading to the determination of epaxial dermomyotomal cells to myogenesis, as well as trophic functions in the maintenance of cell survival in the sclerotome and adjacent neural tube.

Anorectal malformations caused by defects in sonic hedgehog signaling

Anorectal malformations are a common clinical problem affecting the development of the distal hindgut in infants. The spectrum of anorectal malformations ranges from the mildly stenotic anus to imperforate anus with a fistula between the urinary and intestinal tracts to the most severe form, persistent cloaca. The etiology, embryology, and pathogenesis of anorectal malformations are poorly understood and controversial. Sonic hedgehog (Shh) is an endoderm-derived signaling molecule that induces mesodermal gene expression in the chick hindgut. However, the role of Shh signaling in mammalian hindgut development is unknown. Here, we show that mutant mice with various defects in the Shh signaling pathway exhibit a spectrum of distal hindgut defects mimicking human anorectal malformations. Shh null-mutant mice display persistent cloaca. Mutant mice lacking Gli2 or Gli3, two zinc finger transcription factors involved in Shh signaling, respectively, exhibit imperforate anus with recto-urethral fistula and anal stenosis. Furthermore, persistent cloaca is also observed in Gli2(-/-);Gli3(+/-), Gli2(+/-);Gli3(-/-), and Gli2(-/-);Gli3(-/-) mice demonstrating a gene dose-dependent effect. Therefore, Shh signaling is essential for normal development of the distal hindgut in mice and mutations affecting Shh signaling produce a spectrum of anorectal malformations that may reveal new insights into their human disease equivalents.

Limb-patterning activity and restricted posterior localization of the amino-terminal product of Sonic hedgehog cleavage

BACKGROUND

Sonic hedgehog (Shh), a vertebrate homolog of the Drosophila segment polarity gene hedgehog (hh), has been implicated in patterning of the developing chick limb. Such a role is suggested by the restricted expression of Shh along the posterior limb bud margin, and by the observation that heterologous cells expressing Shh have limb-polarizing activity resembling that of cells from the polarizing region of the posterior limb bud margin. It has not been demonstrated, however, that the Sonic hedgehog protein (SHH) alone is sufficient for limb patterning. SHH has been shown to undergo autoproteolytic cleavage in vitro, yielding two smaller products. It is of interest, therefore, to determine whether processing of SHH occurs in the developing limb and how such processing influences the function of SHH.

RESULTS

We demonstrate that SHH is proteolytically processed in developing chick limbs. Grafts of cells expressing SHH protein variants that correspond to individual cleavage products demonstrate that the ability to induce patterned gene expression and to impose morphological pattern upon the limb bud is limited to the amino-terminal product (SHH-N) of SHH proteolytic cleavage. We also demonstrate that bacterially synthesized and purified SHH-N, released from implanted beads, is sufficient for limb-patterning activity. Finally, we show that the endogenous amino-terminal cleavage product is tightly localized to the posterior margin of the limb bud.

CONCLUSIONS

Our data show that, of the two cleavage products resulting from SHH autoproteolysis, SHH-N expressed in grafted heterologous cells or supplied in purified form is sufficient to impose pattern upon the developing limb. Moreover, the restricted localization of the endogenous amino-terminal SHH cleavage product to the posterior border of the chick limb bud makes it unlikely that its patterning activity results from it being distributed in a broad gradient across the antero-posterior axis. More consistent with the observed localization is a model in which the amino-terminal SHH cleavage product exerts its patterning effects by local induction in or near the polarizing region, initiating a cascade of gene expression that ultimately extends across the developing limb.

Rosiglitazone does not improve cognition or global function when used as adjunctive therapy to AChE inhibitors in mild-to-moderate Alzheimer's disease: two phase 3 studies

INTRODUCTION

Two phase 3 studies evaluated the efficacy and safety of rosiglitazone (RSG), a type 2 diabetes treatment, in an extended release (RSG XR) form as adjunctive therapy to ongoing acetylcholine esterase inhibitor (AChEI) treatment in AD (REFLECT-2, adjunctive to donepezil; REFLECT-3, to any AChEI). An open-label extension study (REFLECT-4) assessed RSG XR long-term safety.

METHODS

In these two double-blind, placebo-controlled studies, subjects with mild-to-moderate probable AD were randomized within 2 apolipoprotein E (APOE) allelic strata (APOE ε4-positive, APOE ε4-negative) to once daily placebo, 2 mg RSG XR, or 8 mg RSG XR for 48 weeks (REFLECT-2, N=1,496; REFLECT-3, N=1,485). Co-primary efficacy endpoints were change from baseline in Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and Clinical Dementia Rating scale - Sum of Boxes (CDR-SB) scores at week 48. Three populations were analyzed: APOE4-negative, all subjects except APOE ε4 homozygotes, and the full intent-to-treat population.

RESULTS

No statistically or clinically relevant differences between treatment groups were observed on the a priori primary endpoints in REFLECT-2 or REFLECT-3. Edema was the most frequent adverse event with RSG in each study (14% and 19%, respectively, at 8 mg RSG XR).

CONCLUSIONS

No evidence of statistically or clinically significant efficacy in cognition or global function was detected for 2 mg or 8 mg RSG XR as adjunctive therapy to ongoing AChEIs. There was no evidence of an interaction between treatment and APOE status. Safety and tolerability of RSG XR was consistent with the known profile of rosiglitazone.

Hoxd-12 differentially affects preaxial and postaxial chondrogenic branches in the limb and regulates Sonic hedgehog in a positive feedback loop

Several 5′ members of the Hoxd cluster are expressed in nested posterior-distal domains of the limb bud suggesting a role in regulating anteroposterior pattern of skeletal elements. While loss-of-function mutants have demonstrated a regulatory role for these genes in the developing limb, extensive functional overlaps between various different Hox genes has hampered elucidation of the roles played by individual members. In particular, the function of Hoxd-12 in the limb remains obscure. Using a gain-of-function approach, we find that Hoxd-12 misexpression in transgenic mice produces apparent transformations of anterior digits to posterior morphology and digit duplications, while associated tibial hemimelia and other changes indicate that formation/growth of certain skeletal elements is selectively inhibited. If the digital arch represents an anterior bending of the main limb axis, then the results are all reconcilable with a model in which Hoxd-12 promotes formation of postaxial chondrogenic condensations branching from this main axis (including the anteriormost digit) and selectively antagonizes formation of ‘true’ preaxial condensations that branch from this main axis (such as the tibia). Hoxd-12 misexpression can also induce ectopic Sonic hedgehog (Shh) expression, resulting in mirror-image polydactyly in the limb. Misexpression of Hoxd-12 in other lateral plate derivatives (sternum, pelvis) likewise phenocopies several luxoid/luxate class mouse mutants that all share ectopic Shh signalling. This suggests that feedback activation of Shh expression may be a major function of Hoxd-12. Hoxd-12 can bind to and transactivate the Shh promoter in vitro. Furthermore, expression of either exogenous Hoxd-11 or Hoxd-12 in cultured limb bud cells, together with FGF, induces expression of the endogenous Shh gene. Together these results suggest that certain 5′ Hoxd genes directly amplify the posterior Shh polarizing signal in a reinforcing positive feedback loop during limb bud outgrowth.

Potential production platform of n-butanol in Escherichia coli

We proposed a potential production platform of n-butanol in Escherichia coli. First, a butyrate-conversion strain was developed by removal of undesired genes and recruiting endogenous atoDA and Clostridium adhE2. Consequently, this E. coli strain grown on the M9 mineral salt with yeast extract (M9Y) was shown to produce 6.2g/L n-butanol from supplemented butyrate at 36h. The molar conversion yield of n-butanol on butyrate reaches 92%. Moreover, the production platform was advanced by additional inclusion of a butyrate-producing strain. This strain was equipped with a pathway comprising atoDA and heterologous genes for the synthesis of butyrate. Without butyrate, the butyrate-conversion and the butyrate-producing strains were co-cultured in M9Y medium and produced 5.5g/L n-butanol from glucose at 24h. The production yield on glucose accounts for 69% of the theoretical yield. Overall, it indicates a promise of the developed platform for n-butanol production in E. coli.

Expression of murine Lhx5 suggests a role in specifying the forebrain

A LIM homeobox gene, Lim5, is known to be expressed in the forebrain of Xenopus and zebrafish (Toyama et al. [1995] Dev. Biol. 170:583-593). Results from developmental and comparative studies of its mouse ortholog, Lhx5, indicate that this gene may play important roles in forebrain development. Lhx5 expression is detected in the most anterior portion of the neural tube at the headfold stage, overlapping partially with Otx2 expression domain. After neural tube closure, Lhx5 is expressed as a transverse stripe, covering most of the diencephalic primordium. This expression recedes to restricted areas as Dlx gene expression occurs. By midgestation, both genes, Lhx5 and Dlx5, are expressed in the diencephalon and ventral telencephalon in an alternating complementary pattern. It may be that Dlx inhibits Lhx5, and this may represent a step of early regionalization of the forebrain. Lhx5 is also expressed in midbrain, hindbrain, and spinal cord, overlapping extensively with Lhx1 starting from day E10.5 of gestation. The early, persistent, and dynamic expression of Lhx5 suggests a regulatory function in forebrain formation.

Histocompatibility antigens controlled by the I region of the murine H-2 complex. I. Mapping of H-2A and H-2C loci

Skin grafts were reciprocally exchanged in pairs of congenic lines identical in all genes except those located in the central portion of the H-2 complex. Seven such lines were tested: 6R, B10.AQR, A.TL, A.TH, 7R, 9R, and B10.HTT. In all donor-recipient combinations at least some grafts were rejected. In combinations differing at the IA subregion (and other central H-2 regions or subregions), all first-set grafts were rejected within 3 wk after transplantation, and all second-set grafts were rejected within 10 days. In combinations differing at the IC subregion (and other central regions, but not at the IA subregion) between 60 and 100% of first-set grafts were rejected, but some grafts survived for over 100 days. Most of the second-set grafts were rejected within 1 mo after grafting. This behavior of skin grafts indicated the presence of two histocompatibility loci in the I region, a strong one and a weak one. This conclusion was confirmed by genetic mapping which placed the strong locus in the IA subregion and the weak locus in the IC subregion. We designate the former locus H-2A and the latter H-2C. The same strain combinations used for the skin grafting were also used for determination of the capacity of I-region antigens to function as targets in the in vitro cell-mediated lymphocytotoxicity (CML) assay. Spleen cells from mice presensitized in vivo by skin grafting were restimulated in vitro and tested against 51Cr-labeled concanavalin A or lipopolysaccharide blasts. The testing revealed the presence in the I region of two loci coding for CML-target antigens. The two loci comapped with the H-2A and H-2C loci and were most likely identical to them. As in the skin grafting test, in the CML test, the H-2A antigens evoked stronger response than the H-2C antigens. Rejection of skin grafts across the H-2A and H-2C loci was accompanied by the production of Ia antibodies. Direct cytotoxic and absorption tests with Ia antibodies directed against antigens coded for by the IC subregion revealed the presence of IaC antigens on epidermal cells. We suggest that the products of Ia loci might function as transplantation antigens.

Response of locus coeruleus neurons to footshock stimulation is mediated by neurons in the rostral ventral medulla

While it is well documented that locus coeruleus neurons are potently activated by foot-pinch or sciatic nerve stimulation, little is known about the circuit producing this sensory response. Previous work in our laboratory has identified the medullary nucleus paragigantocellularis as a major excitatory afferent to the locus coeruleus. Here, we use local microinjections into the paragigantocellularis to test whether this nucleus is a link in the pathway mediating the activation of locus coeruleus neurons by subcutaneous footpad stimulation, or footshock, in anesthetized rats. Lidocaine HCl microinjected into the paragigantocellularis reversibly attenuated footshock-evoked activation of 50 out of 56 locus coeruleus cells, with responses in 20 cells completely blocked. Microinjections of GABA into the paragigantocellularis reduced the footshock-evoked responses of 17 out of 27 locus coeruleus cells (seven complete blocks); microinjections of the GABAB agonist baclofen had no effect (0 out of 11 cells blocked). Microinjections of a synaptic decoupling cocktail of manganese and cadmium also attenuated locus coeruleus activation in eight out of nine cells with two complete blocks. With each agent, the most effective injection placement for complete blockade of responses was the ventromedial paragigantocellularis; injections bordering this region attenuated responses, while those outside of the paragigantocellularis (dorsal medullary reticular formation, nucleus tractus solitarius, or facial nucleus), or vehicle injections, were ineffective. These results are consistent with previous findings that pharmacologic blockade of paragigantocellularis-evoked locus coeruleus activity also blocks footshock-evoked responses of locus coeruleus neurons [Ennis and Aston-Jones (1988) J. Neurosci. 8, 3644-3657], and support the view that this somatosensory response, and perhaps other sensory-evoked responses of locus coeruleus neurons, involve the nucleus paragigantocellularis.

A 5-hydroxytryptamine2 agonist augments gamma-aminobutyric acid and excitatory amino acid inputs to noradrenergic locus coeruleus neurons

We examined the effects of the 5-hydroxytryptamine2 receptor agonist, (+-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, on spontaneous and evoked discharge of locus coeruleus neurons in the rat. Extracellular recordings were obtained from single locus coeruleus neurons while (+-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane was injected systemically or locally into the locus coeruleus. Systemic, but not local, administration of (+-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane decreased spontaneous discharge of locus coeruleus neurons in a dose-dependent manner while simultaneously increasing responses evoked by somatosensory stimulation, consistent with previous studies using 5-hydroxytryptamine2 agonists. Increased responsiveness was observed after both low- and high-intensity stimulation and, in the latter, resulted from the addition of a second, longer latency response after (+-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane administration, when cells typically responded to each stimulation with two driven spikes instead of one. Both of these effects could be completely reversed by systemic administration of the 5-hydroxytryptamine2 receptor antagonist, ketanserin. Furthermore, we report that: (i) the (+/-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane-induced decrease in spontaneous firing was blocked by local infusion of the GABA antagonists bicuculline or picrotoxin into the locus coeruleus, but not by local infusion of the alpha-2 adrenoceptor antagonist, idazoxan; and (ii) the enhancement of locus coeruleus sensory responses after high-intensity stimulation was blocked by local application of the selective antagonist of N-methyl-D-aspartate receptors, 2-amino-5-phosphonopentanoic acid, but not by local infusion of the preferential antagonist of non-N-methyl-D-aspartate receptors, 6-cyano-7-nitroquinoxaline-2,3-dione. Together, these results lead us to propose that systemic 5-hydroxytryptamine2 agonists influence locus coeruleus indirectly, causing tonic activation of a GABAergic input to the locus coeruleus, and facilitating sensory inputs that act via excitatory amino acid receptors within locus coeruleus.