Immunohistochemical localization of troponin-C in cultured neurons

Proteomic quantitative study of dorsal root ganglia and sciatic nerve in type 2 diabetic mice

OBJECTIVE

Peripheral neuropathy is the most common and debilitating complication of type 2 diabetes, leading to sensory loss, dysautonomia, hyperalgesia, and spontaneous noxious sensations. Despite the clinical and economic burden of diabetic neuropathy, no effective treatment is available. More preclinical research must be conducted in order to gain further understanding of the aetiology of the disease and elucidate new therapeutic targets.

METHODS

The proteome of lumbar dorsal root ganglia and sciatic nerve of BKS-db/db mice, which contain a mutation of the leptin receptor and are an established type 2 diabetes model, was characterized for the first time by tandem mass tag labelling and mass spectrometry analysis.

RESULTS

Proteomic analysis showed differentially expressed proteins grouped into functional clusters in db/db peripheral nerves compared to control mice, underlining reduced glycolytic and TCA cycle metabolism, higher lipid catabolism, upregulation of muscle-like proteins in DRG and downregulation in SCN, increased cytoskeleton-related proteins, a mild dysregulation of folding chaperones, activation of acute-phase and inflammatory response, and alterations in glutathione metabolism and oxidative stress related proteins.

CONCLUSIONS

Our data validate previous transcriptomic and metabolomic results and uncover new pathways altered in diabetic neuropathy. Our results point out that energetic deficiency could represent the main mechanism of neurodegeneration observed in diabetic neuropathy. These findings may provide important information to select appropriate targets to develop new therapeutic strategies.

Acute Simian Varicella Virus Infection Causes Robust and Sustained Changes in Gene Expression in the Sensory Ganglia

Primary infection with varicella-zoster virus (VZV), a neurotropic alphaherpesvirus, results in varicella. VZV establishes latency in the sensory ganglia and can reactivate later in life to cause herpes zoster. The relationship between VZV and its host during acute infection in the sensory ganglia is not well understood due to limited access to clinical specimens. Intrabronchial inoculation of rhesus macaques with simian varicella virus (SVV) recapitulates the hallmarks of VZV infection in humans. We leveraged this animal model to characterize the host-pathogen interactions in the ganglia during both acute and latent infection by measuring both viral and host transcriptomes on days postinfection (dpi) 3, 7, 10, 14, and 100. SVV DNA and transcripts were detected in sensory ganglia 3 dpi, before the appearance of rash. CD4 and CD8 T cells were also detected in the sensory ganglia 3 dpi. Moreover, lung-resident T cells isolated from the same animals 3 dpi also harbored SVV DNA and transcripts, suggesting that T cells may be responsible for trafficking SVV to the ganglia. Transcriptome sequencing (RNA-Seq) analysis showed that cessation of viral transcription 7 dpi coincides with a robust antiviral innate immune response in the ganglia. Interestingly, a significant number of genes that play a critical role in nervous system development and function remained downregulated into latency. These studies provide novel insights into host-pathogen interactions in the sensory ganglia during acute varicella and demonstrate that SVV infection results in profound and sustained changes in neuronal gene expression.

IMPORTANCE

Many aspects of VZV infection of sensory ganglia remain poorly understood, due to limited access to human specimens and the fact that VZV is strictly a human virus. Infection of rhesus macaques with simian varicella virus (SVV), a homolog of VZV, provides a robust model of the human disease. Using this model, we show that SVV reaches the ganglia early after infection, most likely by T cells, and that the induction of a robust innate immune response correlates with cessation of virus transcription. We also report significant changes in the expression of genes that play an important role in neuronal function. Importantly, these changes persist long after viral replication ceases. Given the homology between SVV and VZV, and the genetic and physiological similarities between rhesus macaques and humans, our results provide novel insight into the interactions between VZV and its human host and explain some of the neurological consequences of VZV infection.

Differences in brain transcriptomes of closely related Baikal coregonid species

The aim of this work was to get deeper insight into genetic factors involved in the adaptive divergence of closely related species, specifically two representatives of Baikal coregonids—Baikal whitefish (Coregonus baicalensis Dybowski) and Baikal omul (Coregonus migratorius Georgi)—that diverged from a common ancestor as recently as 10–20 thousand years ago. Using the Serial Analysis of Gene Expression method, we obtained libraries of short representative cDNA sequences (tags) from the brains of Baikal whitefish and omul. A comparative analysis of the libraries revealed quantitative differences among ~4% tags of the fishes under study. Based on the similarity of these tags with cDNA of known organisms, we identified candidate genes taking part in adaptive divergence. The most important candidate genes related to the adaptation of Baikal whitefish and Baikal omul, identified in this work, belong to the genes of cell metabolism, nervous and immune systems, protein synthesis, and regulatory genes as well as to DTSsa4 Tc1-like transposons which are widespread among fishes.

Neural activity imaging with genetically encoded calcium indicators

Genetically encoded calcium indicators (GECIs), together with modern microscopy, allow repeated activity measurement, in real time and with cellular resolution, of defined cellular populations. Recent efforts in protein engineering have yielded several high-quality GECIs that facilitate new applications in neuroscience. Here, we summarize recent progress in GECI design, optimization, and characterization, and provide guidelines for selecting the appropriate GECI for a given biological application. We focus on the unique challenges associated with imaging in behaving animals.

The phenomics and expression quantitative trait locus mapping of brain transcriptomes regulating adaptive divergence in lake whitefish species pairs (Coregonus sp.)

We used microarrays and a previously established linkage map to localize the genetic determinants of brain gene expression for a backcross family of lake whitefish species pairs (Coregonus sp.). Our goals were to elucidate the genomic distribution and sex specificity of brain expression QTL (eQTL) and to determine the extent to which genes controlling transcriptional variation may underlie adaptive divergence in the recently evolved dwarf (limnetic) and normal (benthic) whitefish. We observed a sex bias in transcriptional genetic architecture, with more eQTL observed in males, as well as divergence in genome location of eQTL between the sexes. Hotspots of nonrandom aggregations of up to 32 eQTL in one location were observed. We identified candidate genes for species pair divergence involved with energetic metabolism, protein synthesis, and neural development on the basis of colocalization of eQTL for these genes with eight previously identified adaptive phenotypic QTL and four previously identified outlier loci from a genome scan in natural populations. Eighty-eight percent of eQTL-phenotypic QTL colocalization involved growth rate and condition factor QTL, two traits central to adaptive divergence between whitefish species pairs. Hotspots colocalized with phenotypic QTL in several cases, revealing possible locations where master regulatory genes, such as a zinc-finger protein in one case, control gene expression directly related to adaptive phenotypic divergence. We observed little evidence of colocalization of brain eQTL with behavioral QTL, which provides insight into the genes identified by behavioral QTL studies. These results extend to the transcriptome level previous work illustrating that selection has shaped recent parallel divergence between dwarf and normal lake whitefish species pairs and that metabolic, more than morphological, differences appear to play a key role in this divergence.

Effects of anoxia, aglycemia, and acidosis on cytosolic Mg2+, ATP, and pH in rat sensory neurons

Sensory neurons can detect ischemia and transmit pain from various organs. Whereas the primary stimulus in ischemia is assumed to be acidosis, little is known about how the inevitable metabolic challenge influences neuron function. In this study we have investigated the effects of anoxia, aglycemia, and acidosis upon intracellular Mg(2+) concentration [Mg(2+)](i) and intracellular pH (pH(i)) in isolated sensory neurons. Anoxia, anoxic aglycemia, and acidosis all caused a rise in [Mg(2+)](i) and a fall in pH(i). The rise in [Mg(2+)](i) in response to acidosis appears to be due to H(+) competing for intracellular Mg(2+) binding sites. The effects of anoxia and aglycemia were mimicked by metabolic inhibition and, in a dorsal root ganglia (DRG)-derived cell line, the rise in [Mg(2+)](i) during metabolic blockade was closely correlated with fall in intracellular ATP concentration ([ATP](i)). Increase in [Mg(2+)](i) during anoxia and aglycemia were therefore assumed to be due to MgATP hydrolysis. Even brief periods of anoxia (<3 min) resulted in rapid internal acidosis and a rise in [Mg(2+)](i) equivalent to a decline in MgATP levels of 15-20%. With more prolonged anoxia (20 min) MgATP depletion is estimated to be around 40%. With anoxic aglycemia, the [Mg(2+)](i) rise occurs in two phases: the first beginning almost immediately and the second after an 8- to 10-min delay. Within 20 min of anoxic aglycemia [Mg(2+)](i) was comparable to that observed following complete metabolic inhibition (dinitrophenol + 2-deoxyglucose, DNP + 2-DOG) indicating a near total loss of MgATP. The consequences of these events therefore need to be considered in the context of sensory neuron function in ischemia.

Proteomics study of neuropathic and nonneuropathic dorsal root ganglia: altered protein regulation following segmental spinal nerve ligation injury

Peripheral nerve injury is often followed by the development of severe neuropathic pain. Nerve degeneration accompanied by inflammatory mediators is thought to play a role in generation of neuropathic pain. Neuronal cell death follows axonal degeneration, devastating a vast number of molecules in injured neurons and the neighboring cells. Because we have little understanding of the cellular and molecular mechanisms underlying neuronal cell death triggered by nerve injury, we conducted a proteomics study of rat 4th and 5th lumbar (L4 and L5) dorsal root ganglion (DRG) after L5 spinal nerve ligation. DRG proteins were displayed on two-dimensional gels and analyzed through quantitative densitometry, statistical validation of the quantitative data, and peptide mass fingerprinting for protein identification. Among approximately 1,300 protein spots detected on each gel, we discovered 67 proteins that were tightly regulated by nerve ligation. We find that the injury to primary sensory neurons turned on multiple cellular mechanisms critical for the structural and functional integrity of neurons and for the defense against oxidative damage. Our data indicate that the regulation of metabolic enzymes was carefully orchestrated to meet the altered energy requirement of the DRG cells. Our data also demonstrate that ligation of the L5 spinal nerve led to the upregulation in the L4 DRG of the proteins that are highly expressed in embryonic sensory neurons. To understand the molecular mechanisms underlying neuropathic pain, we need to comprehend such dynamic aspect of protein modulations that follow nerve injury.

Peripheral nervous system-specific genes identified by subtractive cDNA cloning

An improved method for constructing and screening subtractive cDNA libraries has been used to identify 46 mRNA transcripts that are expressed selectively in neonatal rat dorsal root ganglia (DRG) as judged by Northern blots and in situ hybridization. Sequence analysis demonstrates that both known (e.g. peripherin, calcitonin gene-related peptide, myelin P0) and novel identifiable transcripts (e.g. C-protein-like, synuclein-like, villin-like) are present in the library. Half of the transcripts (23) are undetectable in liver, kidney, heart, spleen, cerebellum, and cerebral cortex. Of the DRG-specific transcripts, 12 contain putative open reading frames that show no identity with known proteins. The construction of such a subtractive library thus provides us with both known and novel markers, and identifies new predicted DRG-specific proteins. In addition, the DRG-specific clones provide probes to define the regulatory elements that specify peripheral nervous-system-specific gene expression.

Calbindin D-28k and parvalbumin in the rat nervous system

This paper describes the distribution of structures stained with mono- and polyclonal antibodies to the calcium-binding proteins calbindin D-28k and parvalbumin in the nervous system of adult rats. As a general characterization it can be stated that calbindin antibodies mainly label cells with thin, unmyelinated axons projecting in a diffuse manner. On the other hand, parvalbumin mostly occurs in cells with thick, myelinated axons and restricted, focused projection fields. The distinctive staining with antibodies against these two proteins can be observed throughout the nervous system. Calbindin D-28k is primarily associated with long-axon neurons (Golgi type I cells) exemplified by thalamic projection neurons, strionigral neurons, nucleus basalis Meynert neurons, cerebellar Purkinje cells, large spinal-, retinal-, cochlear- and vestibular ganglion cells. Calbindin D-28k occurs in all major pathways of the limbic system with the exception of the fornix. Calbindin D-28k is, however, also found in some short-axon cells (Golgi type II), represented by spinal cord interneurons in layer II and interneurons of the cerebral cortex. It is also detectable in some ependymal cells and abundantly occurs in vegetative centres of the hypothalamus. The "paracrine core" of the nervous system and its adjunct (1985, Nieuwenhuys, Chemoarchitecture of the Brain. Springer, Berlin) is very rich in calbindin D-28k. The distribution of calbindin D-28k-positive neurons is very similar to that of the dihydroperydine subtype of calcium channels. Most of the cells containing calbindin D-28k are vulnerable to neurodegenerative processes. Parvalbumin-immunoreactive neurons have a different, and mostly complementary distribution compared with those which react with calbindin D-28k antisera, but in a few cases (Purkinje cells of the cerebellum, spinal ganglion neurons), both calcium-binding proteins co-exist in the same neuron. Many parvalbumin-immunoreactive cells in the central nervous system are interneurons (Golgi type II) and, to a lesser extent, long-axon cells (Golgi type I), whereas conditions are vice versa in the peripheral nervous system. Intrinsic parvalbuminic neurons are prominent in the cerebral cortex, hippocampus, cerebellar cortex and spinal cord. Long-axon parvalbumin-immunoreactive neurons are, for example, the Purkinje cells, neurons of the thalamic reticular nucleus, globus pallidus, substantia nigra (pars reticulata) and a subpopulation among large spinal-, retinal-, cochlear- and vestibular ganglion cells. Parvalbumin is rich in cranial nerve nuclei related to eye movements. In addition to nervous elements, parvalbumin immunoreactivity occurs in a few ependymal cells and in some pillar cells of the organ of Corti.(ABSTRACT TRUNCATED AT 400 WORDS)