Welcome to the repository for the "Transcript expression-aware annotation improves rare variant discovery and interpretation" manuscript. Here we'll outline how to get transcript expression values for your variant file and isoform expression expression matrix of interest, and outline the commands and code to recreate analyses in the pre-print.
You will need
- A variant file that has columns for chrom, pos, ref and alt
- An isoform expression matrix
- The ability to use Hail locally or on a cloud platform
You can have additional columns in your variant file, which will be maintained, and only new columns of transcript-expression annotation will be added. Your isoform expression matrix must start with two columns : 1. transcript_id and 2. gene_id. The remaining columns can be any samples or tissues. If you have biological replicates, they should be numbered with a '.' delimiter (e.g. MuscleSkeletal.1, MuscleSkeletal.2, MuscleSkeletal.3).
Instructions to set up Hail can be found in the Hail docs
If you're unable to set up Hail in your local environment, we have released the pext values for every possible SNV in the genome in both a tsv and HT format in the folder: gs://gnomad-public/papers/2019-tx-annotation/pre_computed/
More information about this file's format is below.
Please be aware that while we don't expect any issues, the files may be iterated upon until publication of the manuscript!
We will walk through an example of annotating de novo variants in autism and developmental delay / intellectual disability with the GTEx v7 dataset.
We recommend using hailctl dataproc from the Hail team for Google Cloud. Note that this is a successor to cloudtools from Ben Neale's lab.
You will need the gnomAD and tx-annotation init scripts, which are both publically available. To start a cluster:
hailctl dataproc start tutorial --init gs://gnomad-public/papers/2019-tx-annotation/tx-annotation-init.sh --num-preemptible-workers 8 --packages gnomad==0.3 --vep GRCh37 --requester-pays-allow-all --region us-central1
Note that after version 02.34 Hail has moved VEP to a requestor pays bucket, so if using vep, must add a requestor pays. Also note that since we develoepd this package, the gnomAD repo has migrated over to the Broad Github. This has resulted in some changes that we've adapted our code to, but clusters now start with --packages gnomad==0.3.
My last update of the code used Hail 0.2.40-216e3cc7271c. Note Hail changes quite frequently. My last run-through of the tutorial was with version 0.2.40-216e3cc7271c.
Also note that in tx_annotation, vep_config is hard coded as vep_config = vep_config_path("GRCh37"). If you're on Grch38, please specify vep_config = vep_config_path("GRCh38") for proper VEP annotation.
To connect to the clustter
hailctl dataproc connect tutorial nb --zone us-central1-f
And start a Hail Jupyter notebook
If you have your region coded in, you won't need the --region and --zone flags on the start and cluster commands. In my last iteration, I needed to do this, so leaving it in.
The variant file we'll be using for the tutorial is available at : gs://gnomad-public/papers/2019-tx-annotation/data/de_novo_variants/asd_ddid_de_novos.txt
This is what the first line of the file looks like :
DataSet CHROM POSITION REF ALT GENE_NAME VEP_functional_class_canonical MPC loftee group ASC_v15_VCF 1 94049574 C A BCAR3 splice_donor_variant NA HC Control
Again, we will only use the chrom, pos, ref, alt columns, and will add additional columns. The VEP columns in the file are based on the canonical trasncript, so we will re-VEP.
Note that unless the variant file you're using is already available as HT that's been vep'd in Hail, we recommend running VEP since the pext code uses the nested VEP format for calculation.
This is how to import the file into Hail, define the variant field, vep, and write the MT. Note that this VEP configuration will also annotate with LOFTEE v.1.0
0 - At the top of your script specify from tx_annotation import * which will start a Hail environment, and import necessary parts of the gnomAD repository.
1 - Import file as a table
rt = hl.import_table("gs://gnomad-public/papers/2019-tx-annotation/data/de_novo_variants/asd_ddid_de_novos.txt")2 - Define the variant in terms of chrom:pos:ref:alt and have Hail parse it, which will create locus and alleles fields
rt = rt.annotate(variant=rt.CHROM + ':' + rt.POSITION + ":" + rt.REF + ":" + rt.ALT)
rt = rt.annotate(** hl.parse_variant(rt.variant))
rt = rt.key_by(rt.locus, rt.alleles)3 - Make a MT from the Table, and repartition for speed (rule of thumb is ~2k variants per partition)
mt = hl.MatrixTable.from_rows_table(rt)
mt = mt.repartition(10)4 - VEP and write out the MT
annotated_mt = hl.vep(mt, vep_config)
annotated_mt.write("gs://gnomad-public/papers/2019-tx-annotation/results/de_novo_variants/asd_ddid_de_novos.vepped.021819.mt")For GRCh37 in the paper, I used annotated_mt = hl.vep(mt, “gs://hail-common/vep/vep/vep85-loftee-gcloud.json”) however, since then the gnomAD team has made updates to their core function, so vep_or_lookup_vep(mt.rows()) may also work. Note that this latter function only takes HT, hence mt.rows().
We'll use the GTEx v7 isoform expression file. Here is what the header of the file looks like
transcript_id gene_id GTEX-1117F-0226-SM-5GZZ7 GTEX-1117F-0426-SM-5EGHI GTEX-1117F-0526-SM-5EGHJ
ENST00000373020.4 ENSG00000000003.10 26.84 4.13 13.54
We've replaced the sample names with unique tissue names, so that samples with the same tissue are labelled as WholeBlood.1, WholeBlood.2, WholeBlood.3 etc:
transcript_id gene_id Adipose-Subcutaneous.1 Muscle-Skeletal.2 Artery-Tibial.3 ENST00000373020.8 ENSG00000000003.14 26.32 3.95 13.23
Make sure the file is bgzip'd.
We first need to get the median expression of all transcripts per tissue. This can be carried out using the get_gtex_summary() function (the function name is a misnomer, as it can work on non-GTEx files).
isoform_tpms_path = /path/to/text/file/with/isoform/quantifications.tsv.bgz
tx_summary_ht_path = /path/to/matrix_table/file/you/want/to/create
get_gtex_summary(isoform_tpms_path,tx_summary_ht_path)For the manuscript we ran:
gtex_v7_isoform_tpms_path = "gs://gnomad-public/papers/2019-tx-annotation/data/GRCH37_hg19/reheadered.GTEx_Analysis_2016-01-15_v7_RSEMv1.2.22_transcript_tpm.txt.gz"
gtex_v7_tx_summary_ht_path = "gs://gnomad-public/papers/2019-tx-annotation/data/GRCH37_hg19/GTEx.V7.tx_medians.021420.ht"
get_gtex_summary(gtex_v7_isoform_tpms_path,gtex_v7_tx_summary_ht_path )If you'd like to get mean isoform expression accross tissues and not median, add get_medians = False to the command. If you want to also export the median isoform expression per tissue file as a tsv, add make_per_tissue_file = True
Running the above commands on the GTEx v7 dataset creates: gs://gnomad-public/papers/2019-tx-annotation/data/GRCH37_hg19/GTEx.V7.tx_medians.021420.ht which is the file used for the analyses in the manuscript and the file you can use for your annotation GTEx v7 annotation.
You'll need to create separate file with gene expression values per tissue, with the tissue names matching the median isoform expression file. Here, we define gene expression as the sum of transcript expression from RSEM. So we use the median isoform file we created.
gtex_v7_gene_maximums_ht_path = "gs://gnomad-public/papers/2019-tx-annotation/data/GRCH37_hg19/GTEx.v7.gene_expression_per_gene_per_tissue.021420.ht"
get_gene_expression(gtex_v7_tx_summary_ht_path, gtex_v7_gene_maximums_ht_path)All you have to do at this point is import your VEP'd variant matrix table, and run the tx_annotate() function!
1 - Import VEP'd variant MT, and median isoform expression MT:
mt, gtex = read_tx_annotation_tables(ddid_asd_de_novos, gtex_v7_tx_summary_ht_path, "mt")2 - Run tx_annotation
ddid_asd = tx_annotate_mt(mt, gtex,
tx_annotation_type = "proportion",
gene_maximums_ht_path =gtex_v7_gene_maximums_ht_path,
filter_to_csqs=all_coding_csqs)This command by default will remove certain GTEx tissues with <100 samples, reproductive tissues, or cell lines (specified in tx_annotation_resources and in the manuscript).
- If you don't want to remove these tissues (or if you are not working with GTEx) specify
tissues_to_filter = None. - If you'd like to get the non-normalized ext values instead of pext, specify
tx_annotation_type = "expression". - Not specifying
filter_to_csqs=all_coding_csqswill add pext values to non-coding variants (which may be desired behavior based on your goals). Note that splice variants are considered coding variants here. The description of coding csqs is available intx_annotation_resourcesasall_coding_csqs. - If you're only interested in getting pext for a certain group of genes, you can specify that with
filter_to_genes. This will return the same file, but will only add the pext values to the genes of interest. An example of adding pext while specifying genes is below (under the ClinVar - gnomAD comparison section)
The function returns your variant MT with a new field called tx_annotation (ddid_asd_de_novos_with_pext above).
At this point, you can choose what annotation you want to use for a given variant (for example, you may be interested in any pLoF variant, or variants found on certain set of transcripts, or just variants found on the canonical transcript - the last of which sort of defeats the point of using this method). In the manuscript we used the worst consequence accross transcripts, which is the context for which we see this method being most powerful. If you'd also like to use the worst consequence, and pull out pext values for the worst consequence, we have helper functions available:
At this point you will remove all variants that did not receive a pext value (e.g. if you specific filter_to_csqs = all_coding_csqs this will remove noncoding variants). At this point, we don't support the OS annotation in LOFTEE, which add pLoF annotations to missense and synonymous variants (for example, a synonymous variant can be called LOFTEE HC in the latest LOFTEE release if it's predicted to affect splicing). We therefore replace OS annotations with the original annotation (ie. we replace the HC for a synonymous variant with ""). Finally, we extract the worst consequence, and create one column per tissue.
1 - Remove variants that did not receive a pext annotation (ie. noncoding variants)
ddid_asd = ddid_asd.filter_rows(~hl.is_missing(ddid_asd.tx_annotation))2 - Overwrite LOFTEE OS variants with original variant annotation
ddid_asd = ddid_asd.annotate_rows(tx_annotation=ddid_asd.tx_annotation.map(fix_loftee_beta_nonlofs))3 - Pull out worst consequence
ddid_asd = pull_out_worst_from_tx_annotate(ddid_asd)At this point you can write out the file with ddid_asd.rows().export("gs://out_file.bgz")
This will create the transcript annotated de novo variant file used in Figure 4 of the manuscript. We've exported the result of this code snippet here: gs://gnomad-public/papers/2019-tx-annotation/results/de_novo_variants/asd_ddid_de_novos.tx_annotated.021520.tsv.bgz
6) Optional (but highly recommended): get max pext per gene to filter genes where pext will be misquantified
We note that for a minority of genes, when RSEM assigns higher relative expression to non-coding transcripts, the sum of the value of coding transcripts can be much smaller than the gene expression value for the transcript, resulting in low pext scores for all coding variants in the gene, and thus resulting in possible filtering of all variants for a given gene. In many cases this appears to be the result of spurious non-coding transcripts with a high degree of exon overlap with true coding transcripts.
To get around this artifact from affecting our analyses, you can calculate the maximum pext score for all variants across all protein coding genes, and removed any gene where the maximum pext score is below a given threshold
context_max_per_gene = /path/to/tsv/file/of/pext/per/gene/you/want/to/create.tsv
mt, gtex = read_tx_annotation_tables(context_ht_path, gtex_v7_tx_summary_ht_path, 'ht')
context_annotated = tx_annotate_mt(mt, gtex, "proportion",
gene_maximums_ht_path=gtex_v7_gene_maximums_ht_path,
filter_to_csqs=all_coding_csqs)
mt_annotated.write(context_annotated, overwrite=True)
identify_maximum_pext_per_gene(context_annotated, context_max_per_gene)For the manuscript, this is gs://gnomad-public/papers/2019-tx-annotation/data/GRCH37_hg19/all.genes.max.pext.GTEx.v7.021520.tsv.bgz
and for all analyses in the paper, we've filtered out genes where max pext is < 0.2
Here we'll detail the commands for obtaining pext values for some of the analyses in manuscript. This will go over the analysis of:
- Getting baselevel expression values for a gene (Figure 2B)
- Comparison of highly conserved and unconserved regions (Figure 3A)
- Comparison of % variant filtered with pext < 0.1 in haploinsufficient disease genes (Figure 4A)
Note that scripts for these and other analyses are availabel in /analyses/ folder in this repository. The paths to the files are available in tx_annotation_resources.py If you find something is missing, please e-mail me at [email protected]
The idea here is that you annotate the expression of a given position as opposed to a variant consequence pair. The baselevel pext value will always be higher than any of the variant annotation pext values, because the base value is just the sum of the expression of protein coding transcripts that overlap the coding base. This baselevel value is what we show in the gnomAD browser. Just because a position has a high baselevel value though, does not mean that say, a pLoF at that position has a high pext value.
We get these baselevel values by using the sites table of all possible variant in the genome. We sum of the expression of all transcripts overlapping that base, where there's a coding consequence.
- TCF4
from tx_annotation import *
mt, gtex = read_tx_annotation_tables(context_ht_path, gtex_v7_tx_summary_ht_path, "ht")
gene_baselevel= get_baselevel_expression_for_genes(mt, gtex, gene_list = {'TCF4'})
gene_baselevel.export("gs://gnomad-public/papers/2019-tx-annotation/results/baselevel_pext/TCF4.baselevel.ext.021319.tsv.bgz")The resulting file is used in Fig2B and Supp Fig 4.
You can specify any number of genes you want in gene_list. If you don't specify any genes, it will annotate all positions in the exome.
Also found in /analyses/conservation_analysis.py
1 - Read in baselevel expresison and phyloCSF files
phylocsf = hl.import_table(phylocsf_file_path, impute = True)
all_baselevel_ht = hl.read_table(all_baselevel_ht_path)
phylocsf = phylocsf.annotate(chrom = phylocsf.chromosome_name.replace("chr",""))Note that all_baselevel_ht_path is the file used to create the tx_annotation tracks in the gnomAD browser
Remove tissues that were filtered from the manuscript from this file, to maintain consistency & recalculate the mean pext
all_baselevel_ht = all_baselevel_ht.drop(*v7_tissues_to_drop)
tissues = set(all_baselevel_ht.row) - {'ensg', 'symbol', 'locus', 'mean_proportion', 'mean_prop_correct'}
all_baselevel_ht = all_baselevel_ht.annotate(mean_prop_conservation=hl.mean(
hl.filter(lambda e: ~hl.is_nan(e),[all_baselevel_ht[tissue_id] for tissue_id in tissues]), filter_missing=True))2 - Define regions of high and low conservation, and filter remaning regions
phylocsf = phylocsf.annotate(conservation_type = hl.case(missing_false=True)
.when(phylocsf.max_score > 1000, "high")
.when(phylocsf.max_score < -100, "low")
.default('filter'))
phylocsf = phylocsf.filter(phylocsf.conservation_type != "filter")3 - Make intervals in the phyloCSF file
phylocsf = phylocsf.annotate(chrom = phylocsf.chromosome_name.replace("chr",""))
phylocsf = phylocsf.annotate(interval =
hl.interval(hl.locus(phylocsf.chrom, phylocsf.start_coordinate),
hl.locus(phylocsf.chrom, phylocsf.end_coordinate)),
interval_name =
phylocsf.chrom + ":" +
hl.str(phylocsf.start_coordinate) + "-" +
hl.str(phylocsf.end_coordinate) )
phylocsf = phylocsf.key_by(phylocsf.interval)4 - Filter the baselevel expression file to the intervals of high or low conservation in the phyloCSF file
all_baselevel_ht = all_baselevel_ht.annotate(**phylocsf[all_baselevel_ht.locus])
all_baselevel_ht= all_baselevel_ht.filter(hl.is_defined(all_baselevel_ht.conservation_type), keep=True)5- Get mean pext in these intervals
mean_proportion_in_interval = (all_baselevel_ht.group_by(symbol = all_baselevel_ht.symbol,
ensg = all_baselevel_ht.ensg,
enst = all_baselevel_ht.transcript_id,
interval = all_baselevel_ht.interval_name,
conservation_type = all_baselevel_ht.conservation_type).
aggregate(mean_of_mean_pext =
hl.agg.filter(~hl.is_nan(all_baselevel_ht.mean_prop_conservation),
hl.agg.mean(all_baselevel_ht.mean_prop_conservation))))6 - Export the file for plotting
mean_proportion_in_interval.export("gs://gnomad-public/papers/2019-tx-annotation/results/conservation.phylocsf.vs.pext.021520.tsv.bgz")This also serves as an example of annotating only a subset of genes in a variant table.
Here we will annotate variants in HI genes in the gnomAD exomes sites HT, the gnomAD genomes sites HT, and the ClinVar HT with pext values.
out_dir = "gs://gnomad-public/papers/2019-tx-annotation/results/gene_list_comparisons/"
1 - Import HI genes
hi_genes = import_gene_list(curated_haploinsufficient_genes, gene_column="ENSGID", ensg=True)There are two options for importing gene lists, either importing ENSG IDs, or importing gene symbols. gene_column refers to the column in the file that contains your gene names, if the values are ENSGs, specify ensg = True. You can specify peek = True if you'd like to just like to import the gene list file and take a peek without doing anything.
2 - Annotate gnomAD exomes
mt, gtex = read_tx_annotation_tables(gnomad_release_mt_path, gtex_v7_tx_summary_ht_path, "ht")
mt = mt.filter_rows(hl.len(mt.filters) == 0)
mt_gnomad_hi = tx_annotate_mt(mt, gtex,"proportion",
filter_to_csqs=lof_csqs,
filter_to_genes=hi_genes, gene_column_in_mt="gene_id")
mt_gnomad_hi = mt_gnomad_hi.filter_rows(~hl.is_missing(mt_gnomad_hi.tx_annotation))
mt_gnomad_hi = pull_out_worst_from_tx_annotate(mt_gnomad_hi)
mt_gnomad_hi.rows().export("%sHI_genes.gnomad.exomes.r2.1.tx_annotated.021420.tsv.bgz" %out_dir)
- `gene_column_in_mt` is one of either `gene_id` (ENSG) or `gene_symbol` and tells the function which VEP field to look to filter to genes.
- `mt = mt.filter_rows(hl.len(mt.filters) == 0)` filters variants to only those that are RF PASS.3 - Annotate gnomAD genomes
mt_genomes, gtex = read_tx_annotation_tables(gnomad_genomes_release_mt_path, gtex_v7_tx_summary_ht_path, "ht")
mt_genomes = mt_genomes.filter_rows(hl.len(mt_genomes.filters) == 0)
mt_gnomad_hi = tx_annotate_mt(mt, gtex,"proportion",
filter_to_csqs=lof_csqs,
filter_to_genes=hi_genes, gene_column_in_mt="gene_id")
mt_gnomad_hi = mt_gnomad_hi.filter_rows(~hl.is_missing(mt_gnomad_hi.tx_annotation))
mt_gnomad_hi = pull_out_worst_from_tx_annotate(mt_gnomad_hi)
mt_gnomad_hi.rows().export("%sHI_genes.gnomad.genomes.r2.1.tx_annotated.021420.tsv.bgz" %out_dir)4 - Annotate ClinVar
clinvar_mt, gtex = read_tx_annotation_tables(clinvar_ht_path, gtex_v7_tx_summary_ht_path, "ht")
mt_clinvar_hi = tx_annotate_mt(clinvar_mt, gtex,"proportion",
filter_to_csqs=lof_csqs, filter_to_genes=hi_genes,
gene_column_in_mt="gene_id")
mt_clinvar_hi = mt_clinvar_hi.filter_rows(~hl.is_missing(mt_clinvar_hi.tx_annotation))
mt_clinvar_hi = pull_out_worst_from_tx_annotate(mt_clinvar_hi)
mt_clinvar_hi = mt_clinvar_hi.annotate_rows(**mt_clinvar_hi.info)
mt_clinvar_hi = mt_clinvar_hi.drop("vep", "tx_annotation","info")
mt_clinvar_hi.rows().export("%sHI_genes.clinvar.alleles.single.b37.tx_annotated.021420.tsv.bgz" %out_dir)The fields are dropped to save space.