keep chromosome names in a bigwig file

Question

[Assa Yeroslaviz]

after an update of the rtracklyer package, I loose the names of chromosomes in my bigwigfile object.

I have a list of bigwig files, I'm reading into R for processing.

filesList <- list.files(path = "./bigWigFiles",pattern = ".bw", full.names = TRUE)
bigWigList <- lapply(X = filesList, FUN = import.bw, as="NumericList")

In rtracklayer version 1.38.3 the objkect has the names of the chromosome in a list

    > str(bigWigList[[1]])
Formal class 'SimpleNumericList' [package "IRanges"] with 4 slots
  ..@ elementType    : chr "numeric"
  ..@ elementMetadata: NULL
  ..@ metadata       :List of 1
  .. ..$ ranges:Formal class 'GRanges' [package "GenomicRanges"] with 6 slots
  .. .. .. ..@ seqnames       :Formal class 'Rle' [package "S4Vectors"] with 4 slots
  .. .. .. .. .. ..@ values         : Factor w/ 17 levels "chrI","chrII",..: 1 2 3 4 5 6 7 8 9 10 ...
  .. .. .. .. .. ..@ lengths        : int [1:17] 1 1 1 1 1 1 1 1 1 1 ...
  .. .. .. .. .. ..@ elementMetadata: NULL
  .. .. .. .. .. ..@ metadata       : list()
  .. .. .. ..@ ranges         :Formal class 'IRanges' [package "IRanges"] with 6 slots
  ...
  .. .. .. ..@ seqinfo        :Formal class 'Seqinfo' [package "GenomeInfoDb"] with 4 slots
  .. .. .. .. .. ..@ seqnames   : chr [1:17] "chrI" "chrII" "chrIII" "chrIV" ...
  .. .. .. .. .. ..@ seqlengths : int [1:17] NA NA NA NA NA NA NA NA NA NA ...
  .. .. .. .. .. ..@ is_circular: logi [1:17] NA NA NA NA NA NA ...
  .. .. .. .. .. ..@ genome     : chr [1:17] NA NA NA NA ...
  .. .. .. ..@ metadata       : list()
  ..@ listData       :List of 17
  .. ..$ chrI   : num [1:230218] 0 1 1 1 1 2 4 6 8 10 ...
  .. ..$ chrII  : num [1:813184] 8 14 24 30 37 44 56 58 64 67 ...
  .. ..$ chrIII : num [1:316620] 1 4 5 7 7 10 11 10 15 18 ...
  .. ..$ chrIV  : num [1:1531933] 7 7 15 17 20 22 24 30 34 37 ...
  .. ..$ chrIX  : num [1:439888] 15 42 69 87 98 111 127 146 161 185 ...
  .. ..$ chrV   : num [1:576874] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrVI  : num [1:270161] 0 3 3 4 6 8 10 11 11 11 ...
  .. ..$ chrVII : num [1:1090940] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrVIII: num [1:562643] 4 4 4 4 4 4 4 4 4 4 ...
  .. ..$ chrX   : num [1:745751] 16 42 55 70 82 102 114 120 132 142 ...
  .. ..$ chrXI  : num [1:666816] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrXII : num [1:1078177] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrXIII: num [1:924431] 0 1 1 1 1 1 1 1 1 1 ...
  .. ..$ chrXIV : num [1:784333] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrXV  : num [1:1091291] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrXVI : num [1:948066] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ chrmt  : num [1:85779] 33 52 70 71 73 80 83 84 85 87 ...

But in a different session with rtracklayer version 1.44.0 I don't have them anymore.

 str(bigWigList[[1]])
Formal class 'SimpleNumericList' [package "IRanges"] with 4 slots
  ..@ elementType    : chr "numeric"
  ..@ elementMetadata: NULL
  ..@ metadata       :List of 1
  .. ..$ ranges:Formal class 'GRanges' [package "GenomicRanges"] with 7 slots
  .. .. .. ..@ seqnames       :Formal class 'Rle' [package "S4Vectors"] with 4 slots
  .. .. .. .. .. ..@ values         : Factor w/ 17 levels "chrI","chrII",..: 1 2 3 4 5 6 7 8 9 10 ...
  .. .. .. .. .. ..@ lengths        : int [1:17] 1 1 1 1 1 1 1 1 1 1 ...
  .. .. .. .. .. ..@ elementMetadata: NULL
  .. .. .. .. .. ..@ metadata       : list()
  .. .. .. ..@ ranges         :Formal class 'IRanges' [package "IRanges"] with 6 slots
  ...
  .. .. .. .. .. ..@ seqnames   : chr [1:17] "chrI" "chrII" "chrIII" "chrIV" ...
  .. .. .. .. .. ..@ seqlengths : int [1:17] NA NA NA NA NA NA NA NA NA NA ...
  .. .. .. .. .. ..@ is_circular: logi [1:17] NA NA NA NA NA NA ...
  .. .. .. .. .. ..@ genome     : chr [1:17] NA NA NA NA ...
  .. .. .. ..@ elementMetadata:Formal class 'DataFrame' [package "S4Vectors"] with 6 slots
  .. .. .. .. .. ..@ rownames       : NULL
  .. .. .. .. .. ..@ nrows          : int 17
  .. .. .. .. .. ..@ listData       : Named list()
  .. .. .. .. .. ..@ elementType    : chr "ANY"
  .. .. .. .. .. ..@ elementMetadata: NULL
  .. .. .. .. .. ..@ metadata       : list()
  .. .. .. ..@ elementType    : chr "ANY"
  .. .. .. ..@ metadata       : list()
  ..@ listData       :List of 17
  .. ..$ : num [1:230218] 0 1 1 1 1 2 4 6 8 10 ...
  .. ..$ : num [1:813184] 8 14 24 30 37 44 56 58 64 67 ...
  .. ..$ : num [1:316620] 1 4 5 7 7 10 11 10 15 18 ...
  .. ..$ : num [1:1531933] 7 7 15 17 20 22 24 30 34 37 ...
  .. ..$ : num [1:439888] 15 42 69 87 98 111 127 146 161 185 ...
  .. ..$ : num [1:576874] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:270161] 0 3 3 4 6 8 10 11 11 11 ...
  .. ..$ : num [1:1090940] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:562643] 4 4 4 4 4 4 4 4 4 4 ...
  .. ..$ : num [1:745751] 16 42 55 70 82 102 114 120 132 142 ...
  .. ..$ : num [1:666816] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:1078177] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:924431] 0 1 1 1 1 1 1 1 1 1 ...
  .. ..$ : num [1:784333] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:1091291] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:948066] 0 0 0 0 0 0 0 0 0 0 ...
  .. ..$ : num [1:85779] 33 52 70 71 73 80 83 84 85 87 ...

For both versions I'm using the exact same command with the exact same bigwig file. Any idea what was changed, or how I can get the chromosome names into the output?

thanks Assa

[Assa Yeroslaviz]

I have figured out I can get them by calling them as such

   > levels(bigWigList[[1]]@metadata$ranges@seqnames)
 [1] "chrI"    "chrII"   "chrIII"  "chrIV"   "chrIX"   "chrV"    "chrVI"  
 [8] "chrVII"  "chrVIII" "chrX"    "chrXI"   "chrXII"  "chrXIII" "chrXIV" 
[15] "chrXV"   "chrXVI"  "chrmt"

But this looks a bit extreme. Is there a better way?

[Ram]

I think a better way to access them, instead of using slots directly, would be

as.character(seqnames(metadata(bigWigList[[1]])$ranges))

[Assa Yeroslaviz]

thanks for the suggestion. IMHO this is also not really a fixed solution, but just a different way to dodge the problem.

Previously it was possible to access them using the command names(bigWigList[[1]]) because they were saved with the data.

[Ram]

If you were able to access them previously, it might be worth starting a discussion with the developers on their recommended forum (mostly a GitHub issue here). It seems their listData slot has gone from being a named list to an unnamed list.