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The repertoire of equine intestinal alpha-defensins.

Bruhn O, Paul S, Tetens J, Thaller G - BMC Genomics (2009)

Bottom Line: These effector molecules of the innate immune system act as endogenous antibiotics to protect the organism against infections with pathogenic microorganisms.In other cases the same genomic exons were found in different transcripts.Interestingly, the peptides were not found in other species of the Laurasiatheria to date.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Animal Breeding and Husbandry, Christian-Albrechts-University of Kiel, Hermann-Rodewald-Strasse 6, D-24118 Kiel, Germany. obruhn@tierzucht.uni-kiel.de

ABSTRACT

Background: Defensins represent an important class of antimicrobial peptides. These effector molecules of the innate immune system act as endogenous antibiotics to protect the organism against infections with pathogenic microorganisms. Mammalian defensins are classified into three distinct sub-families (alpha-, beta- and theta-defensins) according to their specific intramolecular disulfide-bond pattern. The peptides exhibit an antimicrobial activity against a broad spectrum of microorganisms including bacteria and fungi. Alpha-Defensins are primarily synthesised in neutrophils and intestinal Paneth cells. They play a role in the pathogenesis of intestinal diseases and may regulate the flora of the intestinal tract. An equine intestinal alpha-defensin (DEFA1), the first characterised in the Laurasiatheria, shows a broad antimicrobial spectrum against human and equine pathogens. Here we report a first investigation of the repertoire of equine intestinal alpha-defensins. The equine genome was screened for putative alpha-defensin genes by using known alpha-defensin sequences as matrices. Based on the obtained sequence information, a set of oligonucleotides specific to the alpha-defensin gene-family was designed. The products generated by reverse-transcriptase PCR with cDNA from the small intestine as template were sub-cloned and numerous clones were sequenced.

Results: Thirty-eight equine intestinal alpha-defensin transcripts were determined. After translation it became evident that at least 20 of them may code for functional peptides. Ten transcripts lacked matching genomic sequences and for 14 alpha-defensin genes apparently present in the genome no appropriate transcript could be verified. In other cases the same genomic exons were found in different transcripts.

Conclusions: The large repertoire of equine alpha-defensins found in this study points to a particular importance of these peptides regarding animal health and protection from infectious diseases. Moreover, these findings make the horse an excellent species to study biological properties of alpha-defensins. Interestingly, the peptides were not found in other species of the Laurasiatheria to date. Comparison of the obtained transcripts with the genomic sequences in the current assembly of the horse (EquCab2.0) indicates that it is yet not complete and/or to some extent falsely assembled.

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Phylogeny of the mammals based on the Bayesian phylogenetic tree according to Murphy et al. [41]. In underlined species α-defensin genes and transcripts are known. In species underlined with a dashed line, α-defensin genes in the genome are only known by in silico approaches [20]. The asterisked species have no α-defensin genes.
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Figure 4: Phylogeny of the mammals based on the Bayesian phylogenetic tree according to Murphy et al. [41]. In underlined species α-defensin genes and transcripts are known. In species underlined with a dashed line, α-defensin genes in the genome are only known by in silico approaches [20]. The asterisked species have no α-defensin genes.

Mentions: Alpha-defensin transcripts were formerly only known in primates, glires and horses. In recent studies the existence of α-defensin genes was observed in the genomes of the opossum [19], the elephant and the hedgehog tenrec [20]. According to the Bayesian phylogenetic tree of mammals [41], the horse is classified into the group of the Laurasiatheria as well as cattle, dog, bat and hedgehog (Fig. 4). Nothing is known about the existence of α-defensins in bat and hedgehog, and no α-defensin gene was found in cattle [21] and dog [22]. Whereas α-defensin genes exist in basal mammals like opossum, elephant and hedgehog tenrec and in the group of Euarchontoglires, the Equidae are the only known family expressing α-defensin genes within the group of Laurasiatheria. In future studies it will be necessary to clarify why cattle and dog presumably lost their complete set of α-defensin genes while the horse increased the gene number extensively. Additionally, the presence or absence of α-defensins in the closest relatives of the horse like tapir and rhinoceros (which form together with the horse the group of Perissodactyla) has to be analysed. This may lead to new aspects in the development, reorganisation and separation of defensin genes. It is very unlikely that α-defensins evolved independently within the Equidae, indicated by the high analogy between the amino acid sequences of the horse compared with known α-defensins from primates and glires [18]. It is assumed that α-defensins evolved from one or two ancestral genes by gene-duplication [22,42]. According to the observation that platypus being the most basal mammal that already has been sequenced has four α-defensin genes [43], one can hypothesise that α-defensins may have been lost independently in different clades during the divergence of the phylogenetic tree.


The repertoire of equine intestinal alpha-defensins.

Bruhn O, Paul S, Tetens J, Thaller G - BMC Genomics (2009)

Phylogeny of the mammals based on the Bayesian phylogenetic tree according to Murphy et al. [41]. In underlined species α-defensin genes and transcripts are known. In species underlined with a dashed line, α-defensin genes in the genome are only known by in silico approaches [20]. The asterisked species have no α-defensin genes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2803202&req=5

Figure 4: Phylogeny of the mammals based on the Bayesian phylogenetic tree according to Murphy et al. [41]. In underlined species α-defensin genes and transcripts are known. In species underlined with a dashed line, α-defensin genes in the genome are only known by in silico approaches [20]. The asterisked species have no α-defensin genes.
Mentions: Alpha-defensin transcripts were formerly only known in primates, glires and horses. In recent studies the existence of α-defensin genes was observed in the genomes of the opossum [19], the elephant and the hedgehog tenrec [20]. According to the Bayesian phylogenetic tree of mammals [41], the horse is classified into the group of the Laurasiatheria as well as cattle, dog, bat and hedgehog (Fig. 4). Nothing is known about the existence of α-defensins in bat and hedgehog, and no α-defensin gene was found in cattle [21] and dog [22]. Whereas α-defensin genes exist in basal mammals like opossum, elephant and hedgehog tenrec and in the group of Euarchontoglires, the Equidae are the only known family expressing α-defensin genes within the group of Laurasiatheria. In future studies it will be necessary to clarify why cattle and dog presumably lost their complete set of α-defensin genes while the horse increased the gene number extensively. Additionally, the presence or absence of α-defensins in the closest relatives of the horse like tapir and rhinoceros (which form together with the horse the group of Perissodactyla) has to be analysed. This may lead to new aspects in the development, reorganisation and separation of defensin genes. It is very unlikely that α-defensins evolved independently within the Equidae, indicated by the high analogy between the amino acid sequences of the horse compared with known α-defensins from primates and glires [18]. It is assumed that α-defensins evolved from one or two ancestral genes by gene-duplication [22,42]. According to the observation that platypus being the most basal mammal that already has been sequenced has four α-defensin genes [43], one can hypothesise that α-defensins may have been lost independently in different clades during the divergence of the phylogenetic tree.

Bottom Line: These effector molecules of the innate immune system act as endogenous antibiotics to protect the organism against infections with pathogenic microorganisms.In other cases the same genomic exons were found in different transcripts.Interestingly, the peptides were not found in other species of the Laurasiatheria to date.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Animal Breeding and Husbandry, Christian-Albrechts-University of Kiel, Hermann-Rodewald-Strasse 6, D-24118 Kiel, Germany. obruhn@tierzucht.uni-kiel.de

ABSTRACT

Background: Defensins represent an important class of antimicrobial peptides. These effector molecules of the innate immune system act as endogenous antibiotics to protect the organism against infections with pathogenic microorganisms. Mammalian defensins are classified into three distinct sub-families (alpha-, beta- and theta-defensins) according to their specific intramolecular disulfide-bond pattern. The peptides exhibit an antimicrobial activity against a broad spectrum of microorganisms including bacteria and fungi. Alpha-Defensins are primarily synthesised in neutrophils and intestinal Paneth cells. They play a role in the pathogenesis of intestinal diseases and may regulate the flora of the intestinal tract. An equine intestinal alpha-defensin (DEFA1), the first characterised in the Laurasiatheria, shows a broad antimicrobial spectrum against human and equine pathogens. Here we report a first investigation of the repertoire of equine intestinal alpha-defensins. The equine genome was screened for putative alpha-defensin genes by using known alpha-defensin sequences as matrices. Based on the obtained sequence information, a set of oligonucleotides specific to the alpha-defensin gene-family was designed. The products generated by reverse-transcriptase PCR with cDNA from the small intestine as template were sub-cloned and numerous clones were sequenced.

Results: Thirty-eight equine intestinal alpha-defensin transcripts were determined. After translation it became evident that at least 20 of them may code for functional peptides. Ten transcripts lacked matching genomic sequences and for 14 alpha-defensin genes apparently present in the genome no appropriate transcript could be verified. In other cases the same genomic exons were found in different transcripts.

Conclusions: The large repertoire of equine alpha-defensins found in this study points to a particular importance of these peptides regarding animal health and protection from infectious diseases. Moreover, these findings make the horse an excellent species to study biological properties of alpha-defensins. Interestingly, the peptides were not found in other species of the Laurasiatheria to date. Comparison of the obtained transcripts with the genomic sequences in the current assembly of the horse (EquCab2.0) indicates that it is yet not complete and/or to some extent falsely assembled.

Show MeSH
Related in: MedlinePlus