Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution

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  Image Credit: WikiCommons Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution Abstract The comparison of chromosome-level genomes allows biologists to investigate new axes of organismal evolution. Spiders comprise a significant proportion of known arachnid diversity, with many complex morphologies and unique natural histories, yet comparative genomics in spiders has been limited due to the number of available genomes. We present a de novo chromosomal reference genome of a mature male tarantula, Aphonopelma marxi, and comparatively examine spider genome evolution across the Order Araneae. Using PacBio HiFi and Hi-C sequencing, the final 6.5 Gb assembly consists of 17 autosomes, 1 X chromosome, and 127 unplaced scaffolds, with an N50 of 370 Mb and Arachnida (odb10; 2934 genes) BUSCO of 96.7%. By comparing 20 additional spider genomes from 15 families, we find mygalomo...

The action of marimastat, a metalloprotease inhibitor, on the coagulant, hemorrhagic, and neuromuscular activities of Lachesis muta (South American bushmaster) venom

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The action of marimastat, a metalloprotease inhibitor, on the coagulant, hemorrhagic, and neuromuscular activities of Lachesis muta (South American bushmaster) venom

Abstract

Snake venom metalloproteases (SVMP) play a major role in various pathophysiological effects of snakebite envenomation, and marimastat (MMT), a selective metalloprotease inhibitor, has been investigated as a potential ancillary treatment for attenuating SVMP-mediated effects. In this work, the effect of MMT on the coagulant, hemorrhagic and neuromuscular activities of Lachesis muta (South American bushmaster) venom was assessed experimentally in vitro and in vivo and compared with therapeutic anti-Bothrops/Lachesis antivenom (AV) produced by the Instituto Butantan. MMT (0.03-3.0 mM) significantly reduced the proteolytic (caseinolytic) activity of the venom (20 μg), without affecting the esterolytic activity. The clotting activity (expressed as the minimum coagulant dose: 7.5 μg/ml) was unaffected by 0.03 mM MMT, whereas AV (antivenom:venom ratio of 1:3 v/w) completely prevented this effect. Thrombin-like activity was significantly attenuated only by AV, whereas both agents failed to prevent venom-induced factor X activation; the venom did not activate prothrombin. The venom showed α- and β-fibrinogenolytic activities. MMT partially reduced the α-chain fibrinogenolysis only at 5 min of incubation, whereas AV was ineffective; MMT abolished the β-chain fibrinogenolysis at 5 min of incubation and significantly delayed this alteration at 30 and 90 min of incubation, whereas AV produced greater inhibition of β-fibrinogenolysis after 30 and 90 min of incubation. Hemorrhagic activity was partially attenuated by MMT and abolished by AV. Venom (100 μg/ml) caused neuromuscular blockade that was attenuated by MMT alone or in combination with AV, and the resulting myonecrosis and cell vacuolization were attenuated by MMT and AV. MMT showed no additional protection when combined with AV in any of the activities tested. Together, these findings show that snake venom metalloproteases are involved to varying degrees in several activities of L. muta venom, some of which are also inhibited by therapeutic antivenom.
Proença-Hirata, V. S., Oliveira, I. N., Souza-Gomes, G. C., Dias, S. R., Ghirotti, H. A., Azevedo, S. N., Demico, P. J., Pacagnelli, F. L., Giuffrida, R., Nai, G. A., Silva, N. J., Torres-Bonilla, K. A., Paulesini, E., Hyslop, S., De Morais-Zani, K., & Floriano, R. S. (2026). The action of marimastat, a metalloprotease inhibitor, on the coagulant, hemorrhagic, and neuromuscular activities of Lachesis muta (South American bushmaster) venom. Toxicon, 109105. https://doi.org/10.1016/j.toxicon.2026.109105