Posts Tagged ‘transposable elements’

Dfam 3.2 Release

July 9, 2020

Dfam is proud to announce the release of Dfam 3.2.  This release represents a significant step in the expansion of Dfam by providing early access to uncurated, de novo generated families.  As a demonstration of this new capability, we imported a set of 336 RepeatModeler generated libraries produced by Fergal Martin and Denye Ogeh at the European Bioinformatics Institute (EBI).  Also in this release, Dfam now provides family alignments to the RepeatMasker TE protein database aiding in the discovery of related families and in the classification of uncurated TEs.

Uncurated Family Support

In addition to the fully curated libraries for the model organisms human, mouse, zebrafish, worm and fly, Dfam also includes curated libraries for seven other species.  While a fully curated library is the ultimate goal, support for uncurated families has become an essential aspect of a TE resource due to the increasing rate at which new species are being sequenced and the need to have at least a simple TE masking library available.

By standardizing the storage and tracking of uncurated families, it becomes possible to use these datasets to crudely mask an assembly, provide a first approximation of the TE content, and create a starting point for community curation efforts.  Due to the redundancy and fragmentation inherent in these datasets, we do not compute genome-specific thresholds or generate genome coverage plots for these families.  The latest update to the web portal includes new interfaces for uncurated families and some existing interfaces now include an option to include/omit uncurated families.

In this release, Dfam now contains RepeatModeler de novo-produced libraries for an additional 336 species as the result of the collaboration with EBI researchers (denoted with the new uncurated accession prefix “DR”).  Notable taxa expansions include sauropsida (lizards and birds) and fishes (bony and cartilaginous) (Table1). Also included are Amphibia, Viridiplantae and additional species in Mammalia. 

Table 1. De novo-identified TE families from additional species

SpeciesNumber (species)RetrotransposonsDNA transposonsOther
Mammalia471830137812567
Sauropsida164293261168827192
Amphibia6178120316107
Actinopterygii (bony fishes)116275205136177006
Chondrichthyes (cartilaginous fishes)516711982273
Viridiplantae (green plants)28964121687

Aligned Protein Features

In previous versions of Dfam, hand-curated coding regions were provided for a select set of families.  The protein products of these curated sequences were placed in the RepeatMasker TE protein database for use with the RepeatProteinMask tool.  In this release we have used this database with BLASTX to produce alignments to all Dfam families including the uncurated entries.  The resulting alignments are displayed alongside the curated coding regions as the new “aligned” feature track (Figure 1).

Figure 1. Feature track and details for BLASTX alignments to TE protein database.

Website improvements

Several minor improvements have been made to the interface since the previous release.  The browse page now provides links to download the families selected by the query/filter options as HMM, EMBL or FASTA records.  The Seed tab of the Families page now displays the average Kimura divergence of the seed alignment instances to the consensus.

Curation with Dfam: new data and platform updates

March 17, 2020

DNA transposon termini signatures

The Dfam consortium is excited to announce the generation and release of terminal repeat sequence signatures for class II DNA transposable elements. The termini of class II elements are crucial for movement, and as such, can be used to classify de novo DNA transposable element families in new genomic sequences (Figure 1).

Figure 1. Major subgroups of class II DNA transposons.

The LOGOs of the termini can be viewed on the “Classifications” tab on the Dfam website and are organized by class II subclasses (e.g., Crypton, Helitron, TIR, etc.) (Figure 2). This allows for easy visualization of the base conservation at each position in the terminal sequences and comparisons between the 5’ and 3’ termini (Figure 2). In addition, the termini profiles are available for download as a .HMM file.

Figure 2. Termini signature visualization on the Dfam website (www.dfam.org) sample. Base conservation can be seen via the LOGOs of the 5’, 3’ and combined edge (termini) HMMs. The movement type can be seen preceding DNA transposons that move via a common mechanism (e.g. “Circular dsDNA intermediate). The number of families used to generate the LOGOs are indicated, as well as the subclass named (e.g. “Crypton_A”). Additional notes on the termini, when relevant, are also available.

Community data submissions

We have taken the first small step towards a community-driven data curation platform by developing a new data submission system.  At the start this will facilitate the process of uploading data to the site for processing by the curators. As we move forward, further aspects of the curation process will be made available to the community.  Upon creating an account and logging in, users can submit files to Dfam using our web-based upload page. Here you will also find information about submission requirements and how different levels of library quality are handled in Dfam.