UPR activation specifically modulates glutamate neurotransmission in the cerebellum of a mouse model of autism.

An increasing number of rare mutations linked to autism spectrum disorders have been reported in genes encoding for proteins involved in synapse formation and maintenance, such as the post-synaptic cell adhesion proteins neuroligins. Most of the autism-linked mutations in the neuroligin genes map on the extracellular protein domain. The autism-linked substitution R451C in Neuroligin3 (NLGN3) induces a local misfolding of the extracellular domain, causing defective trafficking and retention of the mutant protein in the endoplasmic reticulum (ER). The activation of the unfolded protein response (UPR), due to misfolded proteins accumulating in the ER, has been implicated in pathological and physiological conditions of the nervous system. It was previously shown that the over-expression of R451C NLGN3 in a cellular system leads to the activation of the UPR. Here, we have investigated whether this protective cellular response is detectable in the knock-in mouse model of autism endogenously expressing R451C NLGN3. Our data showed up-regulation of UPR markers uniquely in the cerebellum of the R451C mice compared to WT littermates, at both embryonic and adult stages, but not in other brain regions. Miniature excitatory currents in the Purkinje cells of the R451C mice showed higher frequency than in the WT, which was rescued inhibiting the PERK branch of UPR. Taken together, our data indicate that the R451C mutation in neuroligin3 elicits UPR in vivo, which appears to trigger alterations of synaptic function in the cerebellum of a mouse model expressing the R451C autism-linked mutation.

Altered localization and functionality of TAR DNA Binding Protein 43 (TDP-43) in niemann- pick disease type C.

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized by the occurrence of visceral and neurological symptoms. At present, the molecular mechanisms causing neurodegeneration in this disease are unknown. Here we report the altered expression and/or mislocalization of the TAR-DNA binding protein 43 (TDP-43) in both NPC mouse and in a human neuronal model of the disease. We also report the neuropathologic study of a NPC patient's brain, showing that while TDP-43 is below immunohistochemical detection in nuclei of cerebellar Purkinje cells, it has a predominant localization in the cytoplasm of these cells. From a functional point of view, the TDP-43 mislocalization, that occurs in a human experimental neuronal model system, is associated with specific alterations in TDP-43 controlled genes. Most interestingly, treatment with N-Acetyl-cysteine (NAC) or beta-cyclodextrin (CD) can partially restore TDP-43 nuclear localization. Taken together, the results of these studies extend the role of TDP-43 beyond the Amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD)/Alzheimer disease (AD) spectrum. These findings may open novel research/therapeutic avenues for a better understanding of both NPC disease and the TDP-43 proteinopathy disease mechanism.

A marked paucity of granule cells in the developing cerebellum of the Npc1(-/-) mouse is corrected by a single injection of hydroxypropyl-ß-cyclodextrin.

In this study we show that postnatal development of cerebellar granule neurons (GNs) is defective in Npc1(-/-) mice. Compared to age-matched wild-type littermates, there is an accelerated disappearance of the external granule layer (EGL) in these mice. This is due to a premature exit from the cell cycle of GN precursors residing at the level of the EGL. As a consequence, the size of cerebellar lobules of these mice displays a 20%-25% reduction compared to that of age-matched wild-type mice. This size reduction is detectable at post-natal day 28 (PN28), when cerebellar GN development is completed while signs of neuronal atrophy are not yet apparent. Based on the analysis of EGL thickness and the determination of proliferating GN fractions at increasing developmental times (PN8-PN14), we trace the onset of this GN developmental defect during the second postnatal week. We also show that during this developmental time Shh transcripts undergo a significant reduction in Npc1(-/-) mice compared to age-matched wild-type mice. In light of the mitogenic activity of Shh on GNs, this observation further supports the presence of defective GN proliferation in Npc1(-/-) mice. A single injection of hydroxypropyl-ß-cyclodextrin at PN7 rescues this defect, restoring the normal patterns of granule neuron proliferation and cerebellar lobule size. To our knowledge, these findings identify a novel developmental defect that was underappreciated in previous studies. This defect was probably overlooked because Npc1 loss-of-function does not affect cerebellar foliation and causes the internal granule layer and molecular layer to decrease proportionally, giving rise to a normally appearing, yet harmoniously smaller, cerebellum.

Cholesterol metabolism-associated molecules in late onset Alzheimer's disease.

Alzheimer’s disease (AD) is the most common cause of dementia and, with an aging population, poses a huge public health problem. Although a small per cent is caused by single gene changes, most AD is sporadic and unexplained. Of many modifying factors, changes in brain cholesterol homeostasis are the best studied. We present a review of the role of altered cholesterol metabolism and hypercholesterolemia in APP processing and Abeta generation. We also provide an overview of the potential pharmacological modulation of cholesterol homeostasis in the brain by cholesterol-lowering agents and beta-cyclodextrins.