Contents

Original Authors: James W. MacDonald, Lori Shepherd
Presenting Authors: Lori Shepherd
Date: 25 July, 2019

Objective: Learn about Bioconductor resources for caching files and gene and genome annotation.

1 ChipDb/OrgDb Exercises

Load the example ChipDb and OrgDb libraries. While most of these questions either object can be used, OrgDb should be used unless a specific ChipDb object is available for your given experiment/research.

# Example orgDb
library(org.Hs.eg.db)

# Example chipDb
library(hugene20sttranscriptcluster.db)

  1. What is the central key for each of these AnnoDb objects? Can you print out the first 10 keys for each?

  2. Can all of the available columns be used as keytypes for each of these?

  3. What gene symbol corresponds to Entrez Gene ID 1000?

  4. What is the Ensembl Gene ID for PPARG?

  5. What is the UniProt ID for GAPDH?

  6. How many of the probeset ids from the ChipDb map to a single gene? How many don’t map to a gene at all?

  7. Get all the gene alias for a given Entrez Gene ID displayed as a CharacterList. What are the alias for Entrez Gene ID 1000?

2 TxDb/EnsDb

Load the TxDb library.

library(TxDb.Hsapiens.UCSC.hg19.knownGene)
library(EnsDb.Hsapiens.v86)

  1. How many Bioconductor TxDb packages are there? How many EnsDb packages are there?

  2. What information can be inferred from the name? What about for TxDb.Ggallus.UCSC.galGal4.refGene and TxDb.Rnorvegicus.BioMart.igis?

  3. What do you think is the central key for TxDb objects? What other keytypes can be used? Can all of the available columns be used as keytypes?

  4. List all the genomic positions of the transcripts by gene.

  5. List all the promoter regions 1000bp upstream and 200bp download

  6. How many transcripts does PPARG have, according to UCSC? And does Ensembl agree? Is it right to compare these results?

  7. How many genes are between 2858473 and 3271812 on chr2 in the hg19 genome?
    • Hint: you make a GRanges object

3 Organism.Db

We didn’t discuss Organism.Db packages. They combined the data from OrgDb and TxDb. The limitation is there are only three available in Bioconductor: Human, Rat, Mouse. Organism.dplyr has many more species available and is the recommened package to use even for these three species.

But… for practice, Try these:

library(Homo.sapiens)

  1. Get all the GO terms for BRCA1

  2. What gene does the UCSC transcript ID uc002fai.3 map to?

  3. How many other transcripts does that gene have?

  4. Get all the transcripts from the hg19 genome build, along with their Ensembl gene ID, UCSC transcript ID and gene symbol

4 Organism.dplyr

Use the light version for exercise.

library(Organism.dplyr)
src <- src_organism(dbpath = hg38light())

  1. How many supported organisms are implemented in Organism.dplyr?

  2. Display the ensembl Id and genename description for symbol “NAT2”.

  3. Show all the alias for “NAT2” in the database.

  4. Get all the promoter regions.

  5. Extract the “id” table.

  6. Display Gene ontology (GO) information for gene symbol “Nat2”.

5 BSgenome

Load the libraries

library(BSgenome)
library(BSgenome.Hsapiens.UCSC.hg19)

  1. How many BSgenomes are there in Bioconductor?

  2. Get the sequence from UCSC hg19 builds for chromosome 1. And print the frequency of each letter.

  3. Get the sequence corresponding to chr6 35310335-35395968. Get the complement and reverse complement of it.

  4. Get the sequences for all transcripts of the TP53 gene

6 AnnotationHub

Load AnnotationHub. This section depends on internet. You may not be able to run this section without internet access.

library(AnnotationHub)

  1. How many resources are available in AnnotationHub?

  2. How many resources are on AnnotationHub for Atlantic salmon (Salmo salar)?

  3. Get the most recent Ensembl build for domesticated dog (Canis familiaris) and make a TxDb

  4. Get information on the following ids “AH73986”, “AH73881”,“AH64538”, “AH69344”.

7 biomaRt

Load biomaRt. This section depends on internet. You may not be able to run this section without internet access.

library(biomaRt)

  1. List available marts

  2. Use mart corresponding to Ensembl Genes 97 and list available datasets.

  3. Create mart with Homo sapiens ensembl genes dataset

  4. Get the Ensembl gene IDs and HUGO symbol for Entrez Gene IDs 672, 5468 and 7157

  5. What do you get if you query for the ‘gene_exon’ for GAPDH?

  6. What are the avaiable search terms?

8 BiocFileCache

Load BiocFileCache. This section depends on internet. You many not be able to run this section without internet access.

library(BiocFileCache)

  1. Create a temporary cache using tempdir(). We use a temporary directory so it will be cleaned up at the end. If using to manage file would want a more permanent location.

  2. What is the path to your cache?

  3. What columns do we store in the database by default?

  4. Get a file path to save an object so that it is tracked in the cache. Assume the object will be saved as a RData object.

  5. Add a remote resource to the cache. The httpbin site has mock urls that can be used for testing “http://httpbin.org/get”.

  6. Add another remote resource to the cache but do not automatically download. Call this resource “TestNoDownload” You can use the same url as above or any of your choosing.

  7. Check that the resources have been added to the cache. Do a query for resources matching “Test”. How many resources match?

  8. Do resources need to be updated?

  9. Make a data.frame of metadata and add it to the cache. Do a query that would use the metadata.