Characterization of MHC class II genes in the critically endangered European eel (Anguilla anguilla)

Bracamonte, Seraina E.; Baltazar‐Soares, Miguel; Eizaguirre, Christophe

doi:10.1007/s12686-015-0501-z

Cited by 12 publications

(25 citation statements)

References 66 publications

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“…The importance of duplicated genes as a reservoir of raw genetic material and its contribution in evolution has been recognized for long [67], but very little is known about AMPs copy number variation and their location within amphibian genomes. Earlier studies have shown the presence of more than one MHC class II loci in several species [68][69][70], but before our study this was not described for AMPs along a latitudinal gradient in ranids.…”

Section: Copy Number and Trans-species Polymorphism Variationcontrasting

confidence: 50%

Antimicrobial peptide and sequence variation along a latitudinal gradient in two anurans

et al. 2020

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Background: While there is evidence of both purifying and balancing selection in immune defense genes, largescale genetic diversity in antimicrobial peptides (AMPs), an important part of the innate immune system released from dermal glands in the skin, has remained uninvestigated. Here we describe genetic diversity at three AMP loci (Temporin, Brevinin and Palustrin) in two ranid frogs (Rana arvalis and R. temporaria) along a 2000 km latitudinal gradient. We amplified and sequenced part of the Acidic Propiece domain and the hypervariable Mature Peptide domain (~150-200 bp) in the three genes using Illumina Miseq and expected to find decreased AMP genetic variation towards the northern distribution limit of the species similarly to studies on MHC genetic patterns. Results: We found multiple loci for each AMP and relatively high gene diversity, but no clear pattern of geographic genetic structure along the latitudinal gradient. We found evidence of trans-specific polymorphism in the two species, indicating a common evolutionary origin of the alleles. Temporin and Brevinin did not form monophyletic clades suggesting that they belong to the same gene family. By implementing codon evolution models we found evidence of strong positive selection acting on the Mature Peptide. We also found evidence of diversifying selection as indicated by divergent allele frequencies among populations and high Theta k values. Conclusion: Our results suggest that AMPs are an important source of adaptive diversity, minimizing the chance of microorganisms developing resistance to individual peptides.

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Section: Copy Number and Trans-species Polymorphism Variationcontrasting

confidence: 50%

Antimicrobial peptide and sequence variation along a latitudinal gradient in two anurans

et al. 2020

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“…In this study, 25 alleles were found from 459 valid sequences. The polymorphisms of mcaIIa have been reported in many fish species (Bracamonte et al ., ; Liu et al ., ; Liu, Liu, Wang, et al ., ; Liu, Liu, Zhao, et al ., ; Shen et al ., ; Wynne et al ., ; Xu et al ., , ; Yang et al ., ). For example, 37 different mcaIIa alleles were found from the E. coioides (Yang et al ., ).…”

Section: Discussionmentioning

confidence: 99%

“…In this study, 25 alleles were found from 459 valid sequences. The polymorphisms of mcaIIa have been reported in many fish species (Bracamonte et al, 2015; al., 2016). These results indicate that the mcaIIa gene is highly polymorphic in fishes.…”

Section: Discussionmentioning

confidence: 99%

MHC class IIA polymorphisms and their association with resistance–susceptibility to Streptococcus agalactiae in Nile tilapia, Oreochromis niloticus

Gao

Zhao

et al. 2018

Journal of Fish Biology

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The association between major histocompatibility complex (MHC) class IIA polymorphisms and the severity of infection by Streptococcus agalactiae was investigated using 40 susceptible and 40 resistant individuals of Nile tilapia Oreochromis niloticus. Twenty‐five alleles were identified from 80 individuals, which belong to 22 major allele types. High polymorphism of mhcIIa gene and at least two loci were discovered in O. niloticus. In peptide‐binding region (PBR) and non‐PBR, the ratio of nonsynonymous substitution (dN) to synonymous substitution (dS) was 1.294 (>1) and 1.240 (>1), suggesting that the loci are evolving under positive balancing selection. Association analysis showed that the allele, orni‐daa*0501, was significantly associated with resistance to S. agalactiae, while the alleles, orni‐daa*1101, orni‐daa*1301, orni‐daa*1401 and orni‐daa*1201, were associated with susceptibility to S. agalactiae. To confirm these correlations, another independent challenge experiment was performed in the Huizhou population of the O. niloticus. The frequency distribution showed that the orni‐daa*1101 allele was significantly more frequent in the Huizhou‐Susceptible group (HZ‐SG) than in the Huizhou‐Resistant group (HZ‐RG) (P < 0.05), which was consistent with the first challenge. However, orni‐daa*0501 did not present in HZ‐SG and HZ‐RG and the distribution frequencies of the orni‐daa*1201, orni‐daa*1301 and orni‐daa*1401 alleles were not significantly more frequent in HZ‐SG than in HZ‐RG. These results indicate that the orni‐daa*1101 allele confers susceptibility to S. agalactia infection. These results suggest that the diversity of exon 2 of mcaIIa alleles could be used to explore the association between disease susceptibility or resistance and the multiformity of mcaIIa and to achieve the molecular‐assisted selection of O. niloticus with enhanced disease resistance.

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“…Also, the utility of dN/dS ratios to detect balancing selection depends on the degree of polymorphism within species, as saturation of synonymous sites may lead to biased dN/dS estimations in highly divergent allelic lineages (Castric and Vekemans 2007;Fijarczyk and Babik 2015). Thus, these limitations should be openly acknowledged and further tested, as nucleotide substitution rates remain among the most popular measures of balancing selection acting on MHC genes, even at the level of a single species or population (e.g., Knafler et al 2014;Bracamonte et al 2015;Eimes et al 2015;Jaeger et al 2016;Jarvi et al 2016).…”

Section: Discussionmentioning

confidence: 99%

Coloniality and migration are related to selection on MHC genes in birds

2016

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The major histocompatibility complex (MHC) plays a key role in pathogen recognition as a part of the vertebrate adaptive immune system. The great diversity of MHC genes in natural populations is maintained by different forms of balancing selection and its strength should correlate with the diversity of pathogens to which a population is exposed and the rate of exposure. Despite this prediction, little is known about how life-history characteristics affect selection at the MHC. Here, we examined whether the strength of balancing selection on MHC class II genes in birds (as measured with nonsynonymous nucleotide substitutions, dN) was related to their social or migratory behavior, two life-history characteristics correlated with pathogen exposure. Our comparative analysis indicated that the rate of nonsynonymous substitutions was higher in colonial and migratory species than solitary and resident species, suggesting that the strength of balancing selection increases with coloniality and migratory status. These patterns could be attributed to: (1) elevated transmission rates of pathogens in species that breed in dense aggregations, or (2) exposure to a more diverse fauna of pathogens and parasites in migratory species. Our study suggests that differences in social structure and basic ecological traits influence MHC diversity in natural vertebrate populations.

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Characterization of MHC class II genes in the critically endangered European eel (Anguilla anguilla)

Cited by 12 publications

References 66 publications

Antimicrobial peptide and sequence variation along a latitudinal gradient in two anurans

Antimicrobial peptide and sequence variation along a latitudinal gradient in two anurans

MHC class IIA polymorphisms and their association with resistance–susceptibility to Streptococcus agalactiae in Nile tilapia, Oreochromis niloticus

Coloniality and migration are related to selection on MHC genes in birds

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