A transcriptomic analysis of gene expression in the venom gland of the snake Bothrops alternatus (urutu)

<p>Abstract</p> <p>Background</p> <p>The genus <it>Bothrops </it>is widespread throughout Central and South America and is the principal cause of snakebite in these regions. Transcriptomic and proteomic studies have examined the venom composition of several species in this genus, but many others remain to be studied. In this work, we used a transcriptomic approach to examine the venom gland genes of <it>Bothrops alternatus</it>, a clinically important species found in southeastern and southern Brazil, Uruguay, northern Argentina and eastern Paraguay.</p> <p>Results</p> <p>A cDNA library of 5,350 expressed sequence tags (ESTs) was produced and assembled into 838 contigs and 4512 singletons. BLAST searches of relevant databases showed 30% hits and 70% no-hits, with toxin-related transcripts accounting for 23% and 78% of the total transcripts and hits, respectively. Gene ontology analysis identified non-toxin genes related to general metabolism, transcription and translation, processing and sorting, (polypeptide) degradation, structural functions and cell regulation. The major groups of toxin transcripts identified were metalloproteinases (81%), bradykinin-potentiating peptides/C-type natriuretic peptides (8.8%), phospholipases A₂(5.6%), serine proteinases (1.9%) and C-type lectins (1.5%). Metalloproteinases were almost exclusively type PIII proteins, with few type PII and no type PI proteins. Phospholipases A₂were essentially acidic; no basic PLA₂were detected. Minor toxin transcripts were related to L-amino acid oxidase, cysteine-rich secretory proteins, dipeptidylpeptidase IV, hyaluronidase, three-finger toxins and ohanin. Two non-toxic proteins, thioredoxin and double-specificity phosphatase Dusp6, showed high sequence identity to similar proteins from other snakes. In addition to the above features, single-nucleotide polymorphisms, microsatellites, transposable elements and inverted repeats that could contribute to toxin diversity were observed.</p> <p>Conclusions</p> <p><it>Bothrops alternatus </it>venom gland contains the major toxin classes described for other <it>Bothrops </it>venoms based on trancriptomic and proteomic studies. The predominance of type PIII metalloproteinases agrees with the well-known hemorrhagic activity of this venom, whereas the lower content of serine proteases and C-type lectins could contribute to less marked coagulopathy following envenoming by this species. The lack of basic PLA₂agrees with the lower myotoxicity of this venom compared to other <it>Bothrops </it>species with these toxins. Together, these results contribute to our understanding of the physiopathology of envenoming by this species.</p

Reduced antinociception in mice lacking neuronal nicotinic receptor subunits.

Nicotine exerts antinociceptive effects by interacting with one or more of the subtypes of nicotinic acetylcholine receptors (nAChRs) that are present throughout the neuronal pathways that respond to pain. To identify the particular subunits involved in this process, we generated mice lacking the alpha4 subunit of the neuronal nAChR by homologous recombination techniques and studied these together with previously generated mutant mice lacking the beta2 nAChR subunit. Here we show that the homozygous alpha4-/- mice no longer express high-affinity [3H]nicotine and [3H]epibatidine binding sites throughout the brain. In addition, both types of mutant mice display a reduced antinociceptive effect of nicotine on the hot-plate test and diminished sensitivity to nicotine in the tail-flick test. Patch-clamp recordings further reveal that raphe magnus and thalamic neurons no longer respond to nicotine. The alpha4 nAChR subunit, possibly associated with the beta2 nAChR subunit, is therefore crucial for nicotine-elicited antinociception.Journal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.info:eu-repo/semantics/publishe