Ectodysplasin-A signaling is a key integrator in the lacrimal gland-cornea feedback loop.

A lack of ectodysplasin-A (Eda) signaling leads to dry eye symptoms, which have so far only been associated with altered Meibomian glands. Here, we used loss-of-function (Eda-/-) mutant mice to unravel the impact of Eda signaling on lacrimal gland formation, maturation and subsequent physiological function. Our study demonstrates that Eda activity is dispensable during lacrimal gland embryonic development. However, using a transcriptomic approach, we show that the Eda pathway is necessary for proper cell terminal differentiation in lacrimal gland epithelium and correlated with modified expression of secreted factors commonly found in the tear film. Finally, we discovered that lacrimal glands present a bilateral reduction of Eda signaling activity in response to unilateral corneal injury. This observation hints towards a role for the Eda pathway in controlling the switch from basal to reflex tears, to support corneal wound healing. Collectively, our data suggest a crucial implication of Eda signaling in the cornea-lacrimal gland feedback loop, both in physiological and pathophysiological conditions. Our findings demonstrate that Eda downstream targets could help alleviate dry eye symptoms.

The loop diuretic bumetanide blocks posttraumatic p75NTR upregulation and rescues injured neurons.

Injured neurons become dependent on trophic factors for survival. However, application of trophic factors to the site of injury is technically extremely challenging. Novel approaches are needed to circumvent this problem. Here, we unravel the mechanism of the emergence of dependency of injured neurons on brain-derived neurotrophic factor (BDNF) for survival. Based on this mechanism, we propose the use of the diuretic bumetanide to prevent the requirement for BDNF and consequent neuronal death in the injured areas. Responses to the neurotransmitter GABA change from hyperpolarizing in intact neurons to depolarizing in injured neurons. We show in vivo in rats and ex vivo in mouse organotypic slice cultures that posttraumatic GABA(A)-mediated depolarization is a cause for the well known phenomenon of pathological upregulation of pan-neurotrophin receptor p75(NTR). The increase in intracellular Ca(2+) triggered by GABA-mediated depolarization activates ROCK (Rho kinase), which in turn leads to the upregulation of p75(NTR). We further show that high levels of p75(NTR) and its interaction with sortilin and proNGF set the dependency on BDNF for survival. Thus, application of bumetanide prevents p75(NTR) upregulation and neuronal death in the injured areas with reduced levels of endogenous BDNF.

NKCC1-Deficiency Results in Abnormal Proliferation of Neural Progenitor Cells of the Lateral Ganglionic Eminence.

The proliferative pool of neural progenitor cells is maintained by exquisitely controlled mechanisms for cell cycle regulation. The Na-K-Cl cotransporter (NKCC1) is important for regulating cell volume and the proliferation of different cell types in vitro. NKCC1 is expressed in ventral telencephalon of embryonic brains suggesting a potential role in neural development of this region. The ventral telencephalon is a major source for both interneuron and oligodendrocyte precursor cells. Whether NKCC1 is involved in the proliferation of these cell populations remains unknown. In order to assess this question, we monitored several markers for neural, neuronal, and proliferating cells in wild-type (WT) and NKCC1 knockout (KO) mouse brains. We found that NKCC1 was expressed in neural progenitor cells from the lateral ganglionic eminence (LGE) at E12.5. Mice lacking NKCC1 expression displayed reduced phospho-Histone H3 (PH3)-labeled mitotic cells in the ventricular zone (VZ) and reduced cell cycle reentry. Accordingly, we found a significant reduction of Sp8-labeled immature interneurons migrating from the dorsal LGE in NKCC1-deficient mice at a later developmental stage. Interestingly, at E14.5, NKCC1 regulated also the formation of Olig2-labeled oligodendrocyte precursor cells. Collectively, these findings show that NKCC1 serves in vivo as a modulator of the cell cycle decision in the developing ventral telencephalon at the early stage of neurogenesis. These results present a novel mechanistic avenue to be considered in the recent proposed involvement of chloride transporters in a number of developmentally related diseases, such as epilepsy, autism, and schizophrenia.

Superior performance of decloaking chamber-based heat-induced epitope retrieval method improves the quantification of Olig2 cells in paraffin-embedded section of embryonic mouse brain.

BACKGROUND: Immunohistochemistry (IHC) studies in paraffin-embedded sections can be challenging due to epitope masking. To counteract this problem the microwave oven is widely used for heat-induced epitope retrieval (HIER). However, with this method important parameters cannot be specifically controlled, such as the intensity and duration of heating. NEW METHOD: We describe here a consistent and sensitive HIER method that uses a device for epitope retrieval in tissue sections, the decloaking chamber NxGen. With this method, heat temperature and time can be accurately set. Both qualitative (sensitivity and specificity of positive immunostaining) and quantitative (amount of positive-stained cells) analyses were compared between the microwave oven approach and the decloaking chamber, in paraffin-embedded sections from embryonic mouse brain. RESULTS: We found that the decloaking chamber-based HIER method was preferable to the commonly used microwave oven for the immunodetection and discrimination in mouse brain sections of single Olig2-positive cells, a marker of oligodendrocyte precursor cells. Both automated (ICY software) and manual counting (Adobe Photoshop software) showed a significant underestimation of Olig2-positive cells in microwave oven-treated sections compared to decloaking chamber-treatment. COMPARISON WITH EXISTING METHODS: Compared to other IHC procedures for cell automated quantification, the presently established protocol is easy to use, fast, and effective for the immunodetection and quantification of Olig2 in the developing mouse telencephalon. CONCLUSIONS: We conclude that the combination of decloaking chamber-based HIER method and spot detector in ICY software is a reliable and valuable tool, suited to basic research and clinical studies.

Heparan sulfate proteoglycan syndecan-3 is a novel receptor for GDNF, neurturin, and artemin.

Glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) are potent survival factors for dopaminergic neurons and motoneurons with therapeutic potential for Parkinson's disease. Soluble GFLs bind to a ligand-specific glycosylphosphatidylinositol-anchored coreceptor (GDNF family receptor α) and signal through the receptor tyrosine kinase RET. In this paper, we show that all immobilized matrix-bound GFLs, except persephin, use a fundamentally different receptor. They interact with syndecan-3, a transmembrane heparan sulfate (HS) proteoglycan, by binding to its HS chains with high affinity. GFL-syndecan-3 interaction mediates both cell spreading and neurite outgrowth with the involvement of Src kinase activation. GDNF promotes migration of cortical neurons in a syndecan-3-dependent manner, and in agreement, mice lacking syndecan-3 or GDNF have a reduced number of cortical γ-aminobutyric acid-releasing neurons, suggesting a central role for the two molecules in cortical development. Collectively, syndecan-3 may directly transduce GFL signals or serve as a coreceptor, presenting GFLs to the signaling receptor RET.