Light plays a pivotal role in the regulation of affective behaviors. However, the precise circuits that mediate the impact of light on depressivelike behaviors are not well understood. Here, we show that light influences depressive-like behaviors through a disynaptic circuit linking the retina and the lateral habenula (LHb). Specifically, M4type melanopsin-expressing retinal ganglion cells (RGCs) innervate GABA neurons in the thalamic ventral lateral geniculate nucleus and intergeniculate leaflet (vLGN/IGL), which in turn inhibit CaMKIIa neurons in the LHb. Specific activation of vLGN/IGL-projecting RGCs, activation of LHbprojecting vLGN/IGL neurons, or inhibition of postsynaptic LHb neurons is sufficient to decrease the depressive-like behaviors evoked by longterm exposure to aversive stimuli or chronic social defeat stress. Furthermore, we demonstrate that the antidepressive effects of light therapy require activation of the retina-vLGN/IGL-LHb pathway. These results reveal a dedicated retina-vLGN/ IGL-LHb circuit that regulates depressive-like behaviors and provide a potential mechanistic explanation for light treatment of depression.

Background The blood-brain barrier (BBB) formed by brain endothelial cells (ECs) interconnected by tight junctions (TJs) is essential for the homeostasis of the central nervous system (CNS). Although studies have shown the importance of various signaling molecules in BBB formation during development, little is known about the molecular basis regulating the integrity of the adult BBB. Methods and Results Using a mouse model with tamoxifen-inducible EC-restricted disruption of ctnnb1 (iCKO), here we show that endothelial β-catenin signaling is essential for maintaining BBB integrity and CNS homeostasis in adult. The iCKO mice developed severe seizures accompanied by neuronal injury, multiple brain petechial hemorrhages, and CNS inflammation, and all died postictal. Disruption of endothelial β-catenin induced BBB breakdown and downregulation of specific TJ proteins Claudin-1 and -3 in adult brain ECs. The clinical relevance of the data is indicated by the observation of decreased expression of Claudin-1 and nuclear β-catenin in brain ECs of hemorrhagic lesions of hemorrhagic stroke patients. Conclusion These results demonstrate the prerequisite role of endothelial β-catenin in maintaining the integrity of adult BBB. The results suggest that BBB dysfunction secondary to defective β-catenin transcription activity is a key pathogenic factor in hemorrhagic stroke, seizure activity and CNS inflammation.

Retinitis pigmentosa (RP) constitutes a group of genetically heterogeneous progressive photoreceptor degenerations leading to blindness and affecting 50,000-100,000 people in the U.S. alone. Over 20 different RP loci have been mapped, of which six have been identified. Three of these encode members of the rod photoreceptor visual transduction cascade: rhodopsin, the rod cGMP-gated cation channel alpha subunit, and the beta subunit of cGMP-phosphodiesterase (PDEB). As null mutations in PDEB cause some cases of RP and since both alpha and beta subunits are required for full phosphodiesterase activity, we examined the gene encoding the alpha subunit of cGMP phosphodiesterase (PDEA) in 340 unrelated patients with RP. We found three point mutations in PDEA in affected members of two pedigrees with recessive RP. Each mutation alters an essential functional domain of the encoded protein and likely disrupts its catalytic function. PDEA is the seventh RP gene identified, highlighting the extensive genetic heterogeneity of the disorder and encouraging further investigation into the role of other members of the phototransduction cascade in RP.

IntroductionAt a certain point in development, axons in the mammalian central nervous system (CNS) lose their ability to regenerate after injury. The mechanisms of this growth failure are unclear. According to the prevailing view, CNS regenerative failure reflects both the intrinsic inability of adult CNS neurons to survive and reinitiate axonal growth and the lack of a permissive environment for such growth (Bregman, 1998;Chen and Tonegawa, 1998;Goldberg and Barres, 2000;Horner and Gage, 2000). Proposed potential growth obstacles within the CNS include myelin-associated inhibitory molecules, glial scarring after injury, and lack of growth-promoting substrates and neurotrophic factors (Fournier and Strittmatter, 2001;Goldberg and Barres, 2000;Morgenstern et al., 2002). Successful regeneration in the adult CNS may require manipulating both the intrinsic features of injured neurons and the CNS environment. Despite the recent identification of growth-inhibitory molecules and their receptors (McGee and Strittmatter, 2003), two pertinent questions remain unanswered. What are the essential intrinsic and environmental components for promoting CNS regeneration, and how can the axonal growth potential lost during development be restored in the mature CNS?Optic nerve injury is a standard model for studying CNS regeneration. Rodent retinal ganglion cells (RGCs), whose axons form the optic nerve, normally cannot regenerate their axons through an injured optic nerve. When provided with permissive substrate or given a novel treatment, only a small population of severed axons are induced to regenerate; the regeneration is slow, and the axons stop extending before they reach their targets Yin et al., 2003). Rodent RGCs lose their intrinsic ability for axon elongation before birth (Chen et al., 1995;Goldberg et al., 2002). Developing RGCs have two distinct stages of axonal growth -elongation and arborization -distinguished by contrasting rates of axon extension (Goldberg and Barres, 2000;Jhaveri et al., 1991). Embryonic RGC axons elongate about 10 times faster than mature ones (0.5-2.0 mm/d versus 40-60 µm/d). This difference has been attributed primarily to the maturational change in the intrinsic property of neurons and contributes critically to the failure of optic nerve regeneration (Goldberg et al., 2002).RGCs lose their intrinsic capacity for axonal elongation at embryonic day 18 (E18), before the onset of growth inhibition in the CNS environment (Chen and Tonegawa, 1998). Such a developmental scheme offers an opportunity to characterize and uncover independently the intrinsic and environmental elements in optic nerve regenerative failure. Naturally, the first important question is what determines the intrinsic regenerative capacity of RGC axons. Previously we showed that one determining factor is the anti-apoptotic gene Bcl-2 (Chen et al., 1997). In lower vertebrates (e.g. fish and frog), CNS neurons upregulate Bcl-2 after injury and readily regenerate axons and re-establish topographically organized connections (Cristin...

Background The integrity of endothelial monolayer is a sine qua non for vascular homeostasis and maintenance of tissue fluid balance. However, little is known about the signaling pathways regulating regeneration of the endothelial barrier following inflammatory vascular injury. Methods and Results Employing genetic and pharmacological approaches, we demonstrated that endothelial regeneration selectively requires activation of p110γPI3K signaling, which thereby mediates the expression of the endothelial reparative transcription factor FoxM1. We observed that FoxM1 induction in the pulmonary vasculature was inhibited in mice treated with p110γ-selective inhibitor and in Pik3cg−/− mice following LPS challenge. Pik3cg−/− mice exhibited persistent lung inflammation induced by sepsis and sustained increase in vascular permeability. Restoration of expression of either p110γ or FoxM1 in pulmonary endothelial cells of Pik3cg−/− mice restored endothelial regeneration and normalized the defective vascular repair program. We also observed diminished expression of p110γ in pulmonary vascular endothelial cells of ARDS patients, suggesting that impaired p110γ-FoxM1 vascular repair signaling pathway is a critical factor in persistent leaky lung microvessels and edema formation in the disease. Conclusions We identify p110γ as the critical mediator of endothelial regeneration and vascular repair following sepsis-induced inflammatory injury. Thus, activation of p110γ-FoxM1 endothelial regeneration may represent a novel strategy for the treatment of inflammatory vascular diseases.

We recently found that 5-lipoxygenase (5-LOX) is activated to produce cysteinyl leukotrienes (CysLTs), and CysLTs may cause neuronal injury and astrocytosis through activation of CysLT(1) and CysLT(2) receptors in the brain after focal cerebral ischemia. However, the property of astrocyte responses to in vitro ischemic injury is not clear; whether 5-LOX, CysLTs, and their receptors are also involved in the responses of ischemic astrocytes remains unknown. In the present study, we performed oxygen-glucose deprivation (OGD) followed by recovery to induce ischemic-like injury in the cultured rat astrocytes. We found that 1-h OGD did not injure astrocytes (sub-lethal OGD) but induced astrocyte proliferation 48 and 72 h after recovery; whereas 4-h OGD moderately injured the cells (moderate OGD) and led to death 24-72 h after recovery. Inhibition of phospholipase A(2) and 5-LOX attenuated both the proliferation and death. Sub-lethal and moderate OGD enhanced the production of CysLTs that was inhibited by 5-LOX inhibitors. Sub-lethal OGD increased the expressions of CysLT(1) receptor mRNA and protein, while moderate OGD induced the expression of CysLT(2) receptor mRNA. Exogenously applied leukotriene D(4) (LTD(4)) induced astrocyte proliferation at 1-10 nM and astrocyte death at 100-1,000 nM. The CysLT(1) receptor antagonist montelukast attenuated astrocyte proliferation, the CysLT(2) receptor antagonist BAY cysLT2 reversed astrocyte death, and the dual CysLT receptor antagonist BAY u9773 exhibited both effects. In addition, LTD(4) (100 nM) increased the expression of CysLT(2) receptor mRNA. Thus, in vitro ischemia activates astrocyte 5-LOX to produce CysLTs, and CysLTs result in CysLT(1) receptor-mediated proliferation and CysLT(2) receptor-mediated death.

At a certain point in development, axons in the mammalian CNS undergo a profound loss of intrinsic growth capacity, which leads to poor regeneration after injury. Overexpression of Bcl-2 prevents this loss, but the molecular basis of this effect remains unclear. Here, we report that Bcl-2 supports axonal growth by enhancing intracellular Ca 2 þ signaling and activating cAMP response element binding protein (CREB) and extracellular-regulated kinase (Erk), which stimulate the regenerative response and neuritogenesis. Expression of Bcl-2 decreases endoplasmic reticulum (ER) Ca 2 þ uptake and storage, and thereby leads to a larger intracellular Ca 2 þ response induced by Ca 2 þ influx or axotomy in Bcl-2-expressing neurons than in control neurons. Bcl-x L , an antiapoptotic member of the Bcl-2 family that does not affect ER Ca 2 þ uptake, supports neuronal survival but cannot activate CREB and Erk or promote axon regeneration. These results suggest a novel role for ER Ca 2 þ in the regulation of neuronal response to injury and define a dedicated signaling event through which Bcl-2 supports CNS regeneration.

A novel serine/threonine protein phosphatase (PPase) designated PP7 was identified from cDNA produced from human retina RNA. PP7 has a molecular mass of ϳ75 kDa, and the deduced amino acid sequence of PP7 contains a phosphatase catalytic core domain that possesses all of the invariant motifs of the PP1, PP2A, PP2B, PP4, PP5, and PP6 gene family. However, PP7 has unique N-and C-terminal regions and shares <35% identity with the other known PPases. The unique C-terminal region of PP7 contains multiple Ca 2؉ binding sites (i.e. EF-hand motifs). This region of PP7 is similar to the Drosophila retinal degeneration C gene product (rdgC), and PP7 and rdgC share 42.1% identity. Unlike the other known PPases, the expression of PP7 is not ubiquitous; PP7 was only detected in retina and retinal-derived Y-79 retinoblastoma cells. Expression of recombinant human PP7 in baculovirus-infected SF21 insect cells produces an active soluble enzyme that is capable of utilizing phosphohistone and p-nitrophenyl phosphate as substrates. The activity of recombinant PP7 is dependent on Mg 2؉ and is activated by calcium (IC 50 Х 250 M). PP7 is not affected by calmodulin and is insensitive to inhibition by okadaic acid, microcystin-LR, calyculin A, and cantharidin.