Correlation analysis of serum miR-145 and miR-210 with carotid artery stenosis and their predictive value for cerebral ischemic events.

OBJECTIVE: To analyze the significance of serum miR-145 and miR-210 expression levels in the diagnosis of carotid artery stenosis. METHODS: During the same period, 55 healthy individuals who received physical examination in the same hospital were recruited as controls and assigned to a non-stenosis group. Among the included patients, there were 45 cases of mild stenosis, 14 cases of moderate stenosis, and 6 cases of severe stenosis after carotid color Doppler ultrasonography. The expression levels of miR-145 and miR-210 in serum were measured using real-time fluorescence quantitative polymerase chain reaction (qPCR) technology. RESULTS: The expression levels of serum miR-145 and miR-210 in carotid artery stenosis group were significantly lower than those in non-stenosis group (p < 0.001). Multivariate Logistic regression analysis showed that smoking history, diabetes, hypertension and total cholesterol were positively correlated with the occurrence of carotid artery stenosis (p < 0.05). The expression levels of miR-145 and miR-210 were significantly negatively correlated with carotid artery stenosis (p < 0.001). In addition, patients with carotid artery stenosis and low expression levels of miR-145 and miR-210 had a greater risk of cerebral ischemia (p < 0.05). Cox regression analysis showed that the low expression of miR-145 and miR-210 were independent predictors of cerebral ischemic events. ROC analysis confirmed that miR-145 and miR-210 had good diagnostic efficacy in cerebral ischemia (p < 0.001). CONCLUSION: The decreased expression of miR-145 and miR-210 in serum is closely related to the diagnostic significance of carotid artery stenosis, and may be used to predict the occurrence of cerebral ischemic events.

Genetic continuity and change among the Indigenous peoples of California.

Before the colonial period, California harboured more language variation than all of Europe, and linguistic and archaeological analyses have led to many hypotheses to explain this diversity1. We report genome-wide data from 79 ancient individuals from California and 40 ancient individuals from Northern Mexico dating to 7,400-200 years before present (BP). Our analyses document long-term genetic continuity between people living on the Northern Channel Islands of California and the adjacent Santa Barbara mainland coast from 7,400 years BP to modern Chumash groups represented by individuals who lived around 200 years BP. The distinctive genetic lineages that characterize present-day and ancient people from Northwest Mexico increased in frequency in Southern and Central California by 5,200 years BP, providing evidence for northward migrations that are candidates for spreading Uto-Aztecan languages before the dispersal of maize agriculture from Mexico2-4. Individuals from Baja California share more alleles with the earliest individual from Central California in the dataset than with later individuals from Central California, potentially reflecting an earlier linguistic substrate, whose impact on local ancestry was diluted by later migrations from inland regions1,5. After 1,600 years BP, ancient individuals from the Channel Islands lived in communities with effective sizes similar to those in pre-agricultural Caribbean and Patagonia, and smaller than those on the California mainland and in sampled regions of Mexico.

The genetic legacy of African Americans from Catoctin Furnace.

Few African Americans have been able to trace family lineages back to ancestors who died before the 1870 United States Census, the first in which all Black people were listed by name. We analyzed 27 individuals from Maryland's Catoctin Furnace African American Cemetery (1774-1850), identifying 41,799 genetic relatives among consenting research participants in 23andMe, Inc.'s genetic database. One of the highest concentrations of close relatives is in Maryland, suggesting that descendants of the Catoctin individuals remain in the area. We find that many of the Catoctin individuals derived African ancestry from the Wolof or Kongo groups and European ancestry from Great Britain and Ireland. This study demonstrates the power of joint analysis of historical DNA and large datasets generated through direct-to-consumer ancestry testing.

[Genetic analysis of a Chinese pedigree affected with Congenital coagulation factor XII deficiency due to a c.1A>G start codon variant of F12 gene].

OBJECTIVE: To explore the clinical characteristics and genetic etiology of a consanguineous Chinese pedigree affected with Congenital coagulation factor XII (XII) deficiency. METHODS: Members of the pedigree who had visited Ruian People's Hospital on July 12, 2021 were selected as the study subjects. Clinical data of the pedigree were reviewed. Peripheral venous blood samples were taken from the subjects. Blood coagulation index and genetic testing were carried out. Candidate variant was verified by Sanger sequencing and bioinformatic analysis. RESULTS: This pedigree has comprised 6 individuals from 3 generations, including the proband, his father, mother, wife, sister and son. The proband was a 51-year-old male with kidney stones. Blood coagulation test showed that his activated partial thromboplastin time (APTT) was significantly prolonged, whilst the FXII activity (FXII:C) and FXII antigen (FXII:Ag) were extremely reduced. The FXII:C and FXII:Ag of proband's father, mother, sister and son have all reduced to about half of the lower limit of reference range. Genetic testing revealed that the proband has harbored homozygous missense variant of c.1A>G (p.Arg2Tyr) of the start codon in exon 1 of the F12 gene. Sanger sequencing confirmed that his father, mother, sister and son were all heterozygous for the variant, whilst his wife was of the wild type. By bioinformatic analysis, the variant has not been included in the HGMD database. Prediction with SIFT online software suggested the variant is harmful. Simulation with Swiss-Pbd Viewer v4.0.1 software suggested that the variant has a great impact on the structure of FXII protein. Based on the Standards and Guidelines for the Interpretation of Sequence Variants: A Joint Consensus Recommendation of the American College of Medical Genetics and Genomics (ACMG), the variant was rated as likely pathogenic. CONCLUSION: The c.1A>G (p.Arg2Tyr) variant of the F12 gene probably underlay the Congenital FXII deficiency in this pedigree. Above finding has further expanded the spectrum of F12 gene variants and provided a reference for clinical diagnosis and genetic counseling for this pedigree.

Entwined African and Asian genetic roots of medieval peoples of the Swahili coast.

The urban peoples of the Swahili coast traded across eastern Africa and the Indian Ocean and were among the first practitioners of Islam among sub-Saharan people1,2. The extent to which these early interactions between Africans and non-Africans were accompanied by genetic exchange remains unknown. Here we report ancient DNA data for 80 individuals from 6 medieval and early modern (AD 1250-1800) coastal towns and an inland town after AD 1650. More than half of the DNA of many of the individuals from coastal towns originates from primarily female ancestors from Africa, with a large proportion-and occasionally more than half-of the DNA coming from Asian ancestors. The Asian ancestry includes components associated with Persia and India, with 80-90% of the Asian DNA originating from Persian men. Peoples of African and Asian origins began to mix by about AD 1000, coinciding with the large-scale adoption of Islam. Before about AD 1500, the Southwest Asian ancestry was mainly Persian-related, consistent with the narrative of the Kilwa Chronicle, the oldest history told by people of the Swahili coast3. After this time, the sources of DNA became increasingly Arabian, consistent with evidence of growing interactions with southern Arabia4. Subsequent interactions with Asian and African people further changed the ancestry of present-day people of the Swahili coast in relation to the medieval individuals whose DNA we sequenced.

Perfluorooctanoic Acid (PFOA) Exposure Compromises Fertility by Affecting Ovarian and Oocyte Development.

PFOA, a newly emerging persistent organic pollutant, is widely present in various environmental media. Previous reports have proved that PFOA exposure can accumulate in the ovary and lead to reproductive toxicity in pregnant mice. However, the potential mechanism of PFOA exposure on fertility remains unclear. In this study, we explore how PFOA compromises fertility in the zebrafish. The data show that PFOA (100 mg/L for 15 days) exposure significantly impaired fertilization and hatching capability. Based on tissue sections, we found that PFOA exposure led to ovarian damage and a decrease in the percentage of mature oocytes. Moreover, through in vitro incubation, we determined that PFOA inhibits oocyte development. We also sequenced the transcriptome of the ovary of female zebrafish and a total of 284 overlapping DEGs were obtained. Functional enrichment analysis showed that 284 overlapping DEGs function mainly in complement and coagulation cascades signaling pathways. In addition, we identified genes that may be associated with immunity, such as LOC108191474 and ZGC:173837. We found that exposure to PFOA can cause an inflammatory response that can lead to ovarian damage and delayed oocyte development.

Large-scale migration into Britain during the Middle to Late Bronze Age.

Present-day people from England and Wales have more ancestry derived from early European farmers (EEF) than did people of the Early Bronze Age1. To understand this, here we generated genome-wide data from 793 individuals, increasing data from the Middle to the Late Bronze Age and Iron Age in Britain by 12-fold, and western and central Europe by 3.5-fold. Between 1000 and 875 BC, EEF ancestry increased in southern Britain (England and Wales) but not northern Britain (Scotland) due to incorporation of migrants who arrived at this time and over previous centuries, and who were genetically most similar to ancient individuals from France. These migrants contributed about half the ancestry of people of England and Wales from the Iron Age, thereby creating a plausible vector for the spread of early Celtic languages into Britain. These patterns are part of a broader trend of EEF ancestry becoming more similar across central and western Europe in the Middle to the Late Bronze Age, coincident with archaeological evidence of intensified cultural exchange2-6. There was comparatively less gene flow from continental Europe during the Iron Age, and the independent genetic trajectory in Britain is also reflected in the rise of the allele conferring lactase persistence to approximately 50% by this time compared to approximately 7% in central Europe where it rose rapidly in frequency only a millennium later. This suggests that dairy products were used in qualitatively different ways in Britain and in central Europe over this period.

[Effects of understory removal on soil microbial community composition in subtropical Phyllostachys edulis plantations]. / 林下植物剔除对毛竹林土壤微生物群落结构的影响.

We investigated the effects of understory removal on soil microbial community and soil physicochemical properties in a field experiment following random block design in subtropical moso bamboo (Phyllostachys edulis) plantations, which were widely contributed in middle subtropical area, aiming to assess the regulation mechanism of understory plants on soil microbial community. The results showed that understory removal significantly increased the contents of soil N, NO3--N, and soil available phosphorus, but decreased soil pH and the contents of soil NH4+-N and soil phosphorus (TP). Moreover, understory removal decreased total and bacterial PLFAs (B) and increasing soil fungal PLFAs (F), resulting in a higher F/B ratio. Redundancy analysis showed that changes in fungal PLFAs caused by understory removal were mainly attributed to soil acidification, while changes in bacterial PLFAs caused by understory removal were mainly due to the decreases in soil TP and pH. Furthermore, i14:0、i15:0 and i16:0 contributed to the decreases in bacterial biomass. Our results suggested that understory removal might not be suitable for the management of subtropical P. edulis plantations, as it would alter microbial community composition. The shift of soil microbial community from bacteria to fungi could inhibit microbial decomposition function.

Evaluation of minor drug-resistant viral variants in patients experiencing virological failure (VF) on a first-line regimen in Fujian Province by high-throughput sequencing.

BACKGROUND: It is largely unknown how frequently minor HIV drug-resistant variants at levels under limit of detection of conventional genotyping are present in patients experiencing virological failure (VF). Further, the clinical implications of minor drug-resistant variants at time of virologic failure are unknown. METHODS: Fifteen patients experiencing VF on a first-line regimen were evaluated by high-throughput sequencing and compared with the conventional Sanger genotype drug resistance detection method. RESULTS: NRTI drug resistant mutations (DRMs) were detected in a high proportion of subjects, with the most common being M184V and TAMs. Minor resistant mutations accounted for 19.27% of the total drug-resistant mutations in patients with VF. A mean of 1.7 additional mutations per subject were detected by high-throughput sequencing, the difference was statistically significant, and those additional low-abundance drug-resistant mutations increased the genotypic resistance scores in 10 of 11 subjects (90.9%). Among persons experiencing VF, minor variants possessing major PI (protease inhibitor) DRMs were present in a minority of cases, which was also the case in ARV-naive subjects, and suggests PIs may be effective in subjects experiencing VF on subsequent second-line PI-based antiretroviral regimen. The high-throughput sequencing results of mutations between ART failure subjects and treatment naïve subjects were also compared. Three novel mutations were then screened with higher frequencies in the ART failure subjects. CONCLUSIONS: It is important to guide the replacement of treatment programs and screening for new drug-resistant mutation sites, and the use of high-throughput sequencing methods can more comprehensively study the characteristics of drug-resistant viral variants of patients experiencing VF on a first-line regimen.

2,4-DCP compromises the fertilization capacity of mouse oocytes.

2,4-DCP (2,4-dichlorophenol) is an environmental estrogen that is ubiquitously distributed in the environment and widely used to produce herbicides and pharmaceutical intermediates. Although 2,4-DCP is suspected to have endocrine disruption, the reproductive toxicity of 2,4-DCP in mammals has not been adequately assessed. In the present study, we examined the effect of 2,4-DCP on the fertility of mouse eggs. The data showed that oral administration of 2,4-DCP (180 mg/kg/day for 7 days) compromises the fertilization rate of mouse oocytes. To further analyze the mechanism by which 2,4-DCP decreases fertilization, the key regulators and events during fertilization of mouse eggs were investigated. We found that the dynamics of cortical granules (CGs) were disrupted by showing the redistribution of CG free domain in 2,4-DCP-administered oocytes. This abnormality perturbed the sperm binding site in the zona pellucida (ZP) and dramatically reduced the number of sperm binding to the ZP of 2,4-DCP-administered oocytes. In addition, the abundance of Juno, a sperm receptor on the egg membrane, was also decreased and its distribution was mislocated in 2,4-DCP-administered oocytes. Finally, we validated that the defects of fertilization participants and events caused by 2,4-DCP might be mediated by the increased level of reactive oxygen species-induced apoptosis of oocytes. Therefore, we demonstrate that 2,4-DCP compromises the fertilization ability of mouse oocytes via inducing oxidative stress.

A Benziodoxole-Based Hypervalent Iodine(III) Compound Functioning as a Peptide Coupling Reagent.

1-Benzoyloxy-1,2-benziodoxol-3-(1H)-one (IBA-OBz), a readily available and bench stable benziodoxole-based iodine(III) reagent, can be employed for the synthesis of dipeptides from various standard and sterically hindered amino acids in the presence of (4-MeOC6H4)3P. The combined system of IBA-OBz/(4-MeOC6H4)3P is also successfully applied to the solid-phase peptide synthesis and a pentapeptide leu-enkephalin in unprotected form has been synthesized. Density functional theory calculations reveal that the rate-limiting step is nucleophilic attack of 4-dimethylaminopyridine (DMAP) onto IBA-OBz.

Melatonin ameliorates the fertilization capacity of oocytes exposed to 17α-ethynylestradiol.

17α-ethynylestradiol (EE2), a synthetic hormone that derives from the natural hormone estradiol, has been reported to alter the sex determination, sexual maturity and secondary sexual characteristics of exposed organisms. However, the adverse effects of EE2 on the oocyte quality have not fully determined. Here, we found that EE2 exposure compromised the fertilization capacity of mouse oocytes, while treatment of melatonin remarkably elevated the fertilization rate. Specifically, we observed that EE2 exposure led to the abnormal distribution and premature exocytosis of ovastacin, leading to the reduced number of sperm binding to the EE2-exposed oocytes. In addition, we found that the abundance of Juno, the sperm receptor on the oocyte membrane, was also diminished, which might be another potential cause leading to the fertilization failure of EE2-exposed oocytes. Finally, we demonstrated that melatonin improved the fertilization ability of EE2-exposed oocytes through eliminating the excessive ROS and inhibiting apoptosis.

Controllable Co@N-doped graphene anchored onto the NRGO toward electrocatalytic hydrogen evolution at all pH values.

We propose a synthetic strategy to synthesize cobalt nanoparticle cores encapsulated in tunable N-doped graphene shells on N-doped reduced graphene oxide as a highly efficient and stable pH-universal electrocatalyst. The superior performance is mainly attributed to the optimization of the electrocatalytic centre and the improvement of the electronic configuration.

Genomic analysis reveals rich genetic variation and potential targets of selection during domestication of castor bean from perennial woody tree to annual semi-woody crop.

Relatively, little is known about the genetic variation of woody trees during domestication. Castor bean (Ricinus communis L. Euphorbiaceae) is a commercially important nonedible annual oilseed crop and differs from its wild progenitors that have a perennial woody habit. Although castor bean is one of the oldest cultivated crops, its domestication origin, genomic variation, and potential targets of selection underlying domestication traits remain unknown. Here, we performed a phylogenetic analysis, which suggests that the wild accessions were distinctively separated from the cultivated accessions. Genome sequencing of three accessions (one each wild, landrace, and cultivar) showed a large number of genetic variants between wild and cultivated castor bean (ZB306 or Hale), and relatively few variants between cultivar ZB306 and Hale. Comparative genome analysis revealed many candidate genes of selection and key pathways potentially involved in the transition from a perennial woody tree to annual crop. Interestingly, among 16 oil-related genes only three showed evidence of selection and the remainder showed low genetic variation at the population level, suggesting strong purifying selection in both the wild and domesticated gene pools. These results extend our understanding of the origin, genomic variation, and domestication, and provide a valuable resource for future gene-trait associations and castor bean breeding.

Convergent eusocial evolution is based on a shared reproductive groundplan plus lineage-specific plastic genes.

Eusociality has convergently evolved multiple times, but the genomic basis of caste-based division of labor and degree to which independent origins of eusociality have utilized common genes remain largely unknown. Here we characterize caste-specific transcriptomic profiles across development and adult body segments from pharaoh ants (Monomorium pharaonis) and honey bees (Apis mellifera), representing two independent origins of eusociality. We identify a substantial shared core of genes upregulated in the abdomens of queen ants and honey bees that also tends to be upregulated in mated female flies, suggesting that these genes are part of a conserved insect reproductive groundplan. Outside of this shared groundplan, few genes are differentially expressed in common. Instead, the majority of the thousands of caste-associated genes are plastically expressed, rapidly evolving, and relatively evolutionarily young. These results emphasize that the recruitment of both highly conserved and lineage-specific genes underlie the convergent evolution of novel traits such as eusociality.

CD4+ TSCMs in the Bone Marrow Assist in Maturation of Antibodies against Influenza in Mice.

The bone marrow (BM) is not only a reservoir of hematopoietic stem cells but a repository of immunological memory cells. Further characterizing BM-resident memory T cells would be helpful to reveal the complicated relationship between the BM and immunological memory. In this study, we identified CD122high stem cell antigen-1 (Sca-1) high B cell lymphoma 2 (Bcl-2) high CD4+ stem cell-like memory T cells (TSCMs) as a distinct memory T cell subset, which preferentially reside in the BM, where they respond vigorously to blood-borne antigens. Interestingly, the natural CD4+ TSCMs homing to the BM colocalized with VCAM-1+ IL-15+ IL-7+ CXCL-12+ stromal cells. Furthermore, compared to spleen-resident CD4+ TSCMs, BM-resident TSCMs induced the production of high-affinity antibodies against influenza by B lymphocytes more efficiently. Taken together, these observations indicate that the BM provides an appropriate microenvironment for the survival of CD4+ TSCMs, which broadens our knowledge regarding the memory maintenance of antigen-specific CD4+ T lymphocytes.

[Resveratrol protects human sperm against cryopreservation-induced injury].

OBJECTIVE: To investigate the effects of resveratrol in the cryopreservation medium on the quality and function of post-thaw sperm. METHODS: Semen samples were obtained from 50 normozoospermic and 50 oligoasthenozoospermic men, liquefied and then cryopreserved in the glycerol-egg yolk-citrate (GEYC) medium with or without 30 µmol/L resveratrol. Sperm motility, viability and acrosome reaction (AR) were examined before and after thawing. Sperm lipid peroxidation and the level of reactive oxygen species (ROS) were measured using commercial malondialdehyde (MDA) and the ROS assay kit. Sperm mitochondrial membrane potential (MMP) and DNA damage were determined by Rhodamine 123 staining and TUNEL. RESULTS: The percentage of progressively motile sperm (PMS), total sperm motility, sperm viability, MMP and AR were significantly decreased (P <0.05) while the levels of sperm ROS, MDA and DNA fragmentation index (DFI) remarkably increased in both the normozoospermia and oligoasthenozoospermia groups after cryopreservation as compared with those in the fresh ejaculate (P <0.05). In comparison with the non-resveratrol control, the post-thaw sperm cryopreserved with 30 µmol/L resveratrol showed markedly higher PMS (ï¼»32.7 ± 4.8ï¼½ vs ï¼»43.1 ± 6.3ï¼½ %, P <0.05), total motility (ï¼»44.8 ± 6.9ï¼½ vs ï¼»56.9 ± 7.4ï¼½ %, P <0.05), viability (ï¼»52.3 ± 6.1ï¼½ vs ï¼»67.5 ± 5.6ï¼½ %, P <0.05), MMP (ï¼»56.5 ± 7.0ï¼½ vs ï¼»63.4 ± 7.5ï¼½ %, P <0.05) and AR (ï¼»16.6 ± 3.8ï¼½ vs ï¼»26.3 ± 4.7ï¼½ %, P <0.05) but lower ROS, MDA and DFI (all P <0.05) in the normozoospermia group, and so did the post-thaw sperm in the oligoasthenozoospermia group, with a particularly lower DFI (ï¼»28.5 ± 4.8ï¼½ vs ï¼»36.3 ± 5.7ï¼½%, P <0.01). CONCLUSIONS: Resveratrol in the cryopreservation medium can improve the quality and function of post-thaw human sperm by reducing cryopreservation-induced sperm injury and the level of ROS.

[Changes in regional homogeneity of brain activity in patients with diabetic peripheral].

OBJECTIVE: To investigate the abnormalities in regional homogeneity of brain activity in patients with diabetic peripheral neuropathy (DPN) using resting-state functional magnetic resonance imaging (rs-fMRI) and explore the association between brain activity changes and DPN. METHODS: A regional homogeneity (ReHo) approach was used to compare the local synchronization of rs-fMRI signals among 20 patients with painful DPN, 16 patients with painless DPN, and 16 type 2 diabetic patients without DPN (non-DPN group). RESULTS: Compared with the those without DPN, the patients with painful DPN showed high ReHo in the left inferior temporal gyrus and the right central posterior gyrus, and low ReHo in the posterior cingulate gyrus, right inferior parietal gyrus, and the left superior parietal gyrus (P < 0.05);the patients with painless DPN group showed high ReHo in the left inferior temporal gyrus, the right middle temporal gyrus, and the right superior frontal gyrus, and low ReHo in the left thalamus (P < 0.05).No significant differences in ReHo were found between the patients with painful DPN and painless DPN (P>0.05). CONCLUSIONS: The patients with DPN have altered ReHo in multiple brain regions and impairment of a default mode network, for which the left temporal gyrus may serve as a functional compensatory brain area. ReHo disturbance in the central right posterior gyrus may play a central role in the pain symptoms associated with painful DPN.

Effects of Vertical Glottal Duct Length on Intraglottal Pressures and Phonation Threshold Pressure in the Uniform Glottis.

According to Titze's 1988 derivations for phonation threshold pressure (PTP), there are a number of important variables that PTP depends upon. A primary one is the vertical glottal duct length T: PTP decreases if T is increased. Changing the length of T, however, may have a significant effect on other variables that PTP depends upon. This study examined the effects of lengthening the vertical uniform glottal duct on the transglottal and intraglottal pressures, and the derived transglottal pressure coefficients, for five glottal diameters (0.01, 0.02, 0.04, 0.08, and 0.16 cm) and three transglottal pressures (500, 1000, and 1500 Pa) for the uniform glottis by using the computational fluid dynamics code Fluent (for laminar, incompressible, two-dimensional flow). The results suggest the following: A longer vertical glottal duct length increases the intraglottal and transglottal pressures, and more so for smaller glottal diameters, and increases the transglottal pressure coefficient. In addition, unlike the transglottal pressure coefficient, the glottal entrance pressure coefficient is highly dependent on the vertical glottal duct length only for lower flows and Reynolds numbers, but is relatively independent of duct length, glottal diameter, and transglottal pressure above a flow value of approximately 50 cm3/s, suggesting that the entrance pressure coefficient is a relatively local phenomenon. These results suggest that the vertical glottal duct length and its effects need to be taken into consideration for vocal fold modeling, aeroacoustics purposes, and the estimation of PTP.

Population Genomic Analysis of a Pitviper Reveals Microevolutionary Forces Underlying Venom Chemistry.

Venoms are among the most biologically active secretions known, and are commonly believed to evolve under extreme positive selection. Many venom gene families, however, have undergone duplication, and are often deployed in doses vastly exceeding the LD50 for most prey species, which should reduce the strength of positive selection. Here, we contrast these selective regimes using snake venoms, which consist of rapidly evolving protein formulations. Though decades of extensive studies have found that snake venom proteins are subject to strong positive selection, the greater action of drift has been hypothesized, but never tested. Using a combination of de novo genome sequencing, population genomics, transcriptomics, and proteomics, we compare the two modes of evolution in the pitviper, Protobothrops mucrosquamatus. By partitioning selective constraints and adaptive evolution in a McDonald-Kreitman-type framework, we find support for both hypotheses: venom proteins indeed experience both stronger positive selection, and lower selective constraint than other genes in the genome. Furthermore, the strength of selection may be modulated by expression level, with more abundant proteins experiencing weaker selective constraint, leading to the accumulation of more deleterious mutations. These findings show that snake venoms evolve by a combination of adaptive and neutral mechanisms, both of which explain their extraordinarily high rates of molecular evolution. In addition to positive selection, which optimizes efficacy of the venom in the short term, relaxed selective constraints for deleterious mutations can lead to more rapid turnover of individual proteins, and potentially to exploration of a larger venom phenotypic space.