Topic
Crotalus simus
About: Crotalus simus is a research topic. Over the lifetime, 18 publications have been published within this topic receiving 573 citations.
Papers
TL;DR: The increased concentration of the neurotoxins crotoxin and crotamine in South American rattlesnake venoms strongly argues that the gain of neurotoxicity and lethal venom activities to mammals may have represented the key axis along which overall venom toxicity has evolved during Crotalus durissus invasion of South America.
Abstract: We report a comparative venomic and antivenomic characterization of the venoms of newborn and adult specimens of the Central American rattlesnake, Crotalus simus, and of the subspecies cumanensis, durissus, ruruima, and terrificus of South American Crotalus durissus. Neonate and adult C. simus share about 50% of their venom proteome. The venom proteome of 6-week-old C. simus is predominantly made of the neurotoxic heterodimeric phospholipase A(2) (PLA(2) crotoxin) (55.9%) and serine proteinases (36%), whereas snake venom Zn(2+)-metalloproteinases (SVMPs), exclusively of class PIII, represent only 2% of the total venom proteins. In marked contrast, venom from adult C. simus comprises toxins from 7 protein families. A large proportion (71.7%) of these toxins are SVMPs, two-thirds of which belong to the PIII class. These toxin profiles correlate well with the overall biochemical and pharmacological features of venoms from adult (hemorrhagic) and newborn (neurotoxic) C. simus specimens. The venoms of the South American Crotalus subspecies belong to one of two distinct phenotypes. C. d. cumanensis exhibits high levels of SVMPs and low lethal potency (LD(50)), whereas C. d. subspecies terrificus, ruruima, and durissus have low SVMP activity and high neurotoxicity to mice. Their overall toxin compositions explain the outcome of envenomation by these species. Further, in all C. simus and C. durissus venoms, the concentration of neurotoxins (crotoxin and crotamine) is directly related with lethal activity, whereas lethality and metalloproteinase activity show an inverse relationship. The similar venom toxin profiles of newborn C. simus and adult C. durissus terrificus, ruruima, and durissus subspecies strongly suggests that the South American taxa have retained juvenile venom characteristics in the adult form (paedomorphism) along their North-South stepping-stone dispersal. The driving force behind paedomorphism is often competition or predation pressure. The increased concentration of the neurotoxins crotoxin and crotamine in South American rattlesnake venoms strongly argues that the gain of neurotoxicity and lethal venom activities to mammals may have represented the key axis along which overall venom toxicity has evolved during Crotalus durissus invasion of South America. The paedomorphic trend is supported by a decreasing LNC (lethal neurotoxicity coefficient, defined as the ratio between the average LD(50) of the venom and the crotoxin + crotamine concentration) along the North-South axis, coincident with the evolutionary dispersal pattern of the Neotropical rattlesnakes. The indistinguisable immunoreactivity patterns of Costa Rican and Venezuelan polyvalent antivenoms toward C. simus and C. durissus venoms strongly suggest the possibility of using these antivenoms indistinctly for the management of snakebites by adult C. simus and by certain C. d. cumanensis populations exhibiting a hemorrhagic venom phenotype. The antivenomic results also explain why the antivenoms effectively neutralize the hemorrhagic activity of adult C. simus venoms but does not protect against adult C. durissus sp. and newborn C. simus envenomations. The identification of evolutionary trends among tropical Crotalus, as reported here, may have an impact in defining the mixture of venoms for immunization to produce an effective pan-American anti-Crotalus antivenom.
234 citations
TL;DR: The findings support the view that understanding the phenotypic diversity of snake venoms requires a deep knowledge of the mechanisms regulating the transcriptional and translational activity of the venom gland and suggest a functional role for miRNAs.
Abstract: Understanding the processes that drive the evolution of snake venom is a topic of great research interest in molecular and evolutionary toxinology. Recent studies suggest that ontogenetic changes in venom composition are genetically controlled rather than environmentally induced. However, the molecular mechanisms underlying these changes remain elusive. Here we have explored the basis and level of regulation of the ontogenetic shift in the venom composition of the Central American rattlesnake, Crotalus s. simus using a combined proteomics and transcriptomics approach. Proteomic analysis showed that the ontogenetic shift in the venom composition of C. s. simus is essentially characterized by a gradual reduction in the expression of serine proteinases and PLA2 molecules, particularly crotoxin, a β-neurotoxic heterodimeric PLA2, concominantly with an increment of PI and PIII metalloproteinases at age 9–18 months. Comparison of the transcriptional activity of the venom glands of neonate and adult C. s. simus specimens indicated that their transcriptomes exhibit indistinguisable toxin family profiles, suggesting that the elusive mechanism by which shared transcriptomes generate divergent venom phenotypes may operate post-transcriptionally. Specifically, miRNAs with frequency count of 1000 or greater exhibited an uneven distribution between the newborn and adult datasets. Of note, 590 copies of a miRNA targeting crotoxin B-subunit was exclusively found in the transcriptome of the adult snake, whereas 1185 copies of a miRNA complementary to a PIII-SVMP mRNA was uniquely present in the newborn dataset. These results support the view that age-dependent changes in the concentration of miRNA modulating the transition from a crotoxin-rich to a SVMP-rich venom from birth through adulhood can potentially explain what is observed in the proteomic analysis of the ontogenetic changes in the venom composition of C. s. simus. Existing snake venom toxins are the result of early recruitment events in the Toxicofera clade of reptiles by which ordinary genes were duplicated, and the new genes selectively expressed in the venom gland and amplified to multigene families with extensive neofunctionalization throughout the approximately 112–125 million years of ophidian evolution. Our findings support the view that understanding the phenotypic diversity of snake venoms requires a deep knowledge of the mechanisms regulating the transcriptional and translational activity of the venom gland. Our results suggest a functional role for miRNAs. The impact of specific miRNAs in the modulation of venom composition, and the integration of the mechanisms responsible for the generation of these miRNAs in the evolutionary landscape of the snake's venom gland, are further challenges for future research.
191 citations
TL;DR: The results support the hypothesis that alterations of the distribution of miRNAs, modulating the translational activity of venom gland toxin-encoding mRNAs in response to an external cue, may contribute to the mechanism generating adaptive venom variability.
Abstract: Adult rattlesnakes within genus Crotalus express one of two distinct venom phenotypes, type I (hemorrhagic) and type II (neurotoxic). In Costa Rican Central American rattlesnake, ontogenetic changes in the concentration of miRNAs modulate venom type II to type I transition. Venomics and venom gland transcriptome analyses showed that adult C. simus and C. tzabcan expressed intermediate patterns between type II and type I venoms, whereas C. culminatus had a canonical type I venom. Neonate/juvenile and adult Mexican rattlesnakes showed notable inter- and intraspecific variability in the number, type, abundance and ontogenetic shifts of the transcriptional and translational venom gland activities. These results support a role for miRNAs in the ontogenetic venom compositional changes in the three congeneric Mexican rattlesnakes. It is worth noting the finding of dual-action miRNAs, which silence the translation of neurotoxic heterodimeric PLA2 crotoxin and acidic PLA2 mRNAs while simultaneously up-regulating S...
101 citations
TL;DR: There is a notorious difference in these venoms, particularly regarding the content of the potent neurotoxic phospholipase A2 complex 'crotoxin' of the rattlesnake Crotalus simus from Mexico.
83 citations
TL;DR: Proteomics analysis, in combination with in vitro and mouse tests, determined that the venom of C. basiliscus is mainly composed by SVMPs, which confer proteolytic and hemorrhagic activities to the venom, and the preclinical evaluation suggests that Birmex antivenom can be used to treat envenomations by Costa Rican adult C. simus snakebites.
44 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 3 |
| 2020 | 4 |
| 2019 | 1 |
| 2018 | 1 |
| 2017 | 4 |
| 2016 | 1 |