# TOC
- 160520 RNA sample outlier
- 160526 WGS sample contamination
- 160527 PEER correction
- 160530 eQTL mapping
- 160603 RNA expression clustering
- 160604 phasing
- 160614 differential expression
- 160615 GWAS overlap
- 160618 colocalization
- 160627 sQTL
# 160527
# 160530
## 1 matrix_eQTL
1. prepare covariates
combine_covariates.R
2. prepare genotype data
bcftools
3. prepare expression data
normalize_rpkm.R
4. prepare genotype location
gen_snps_loc.R
5. prepare gene location
gen_gene_loc.R
6. find optimum number of PC and PEER factors:
find_optimal_num_PEER_factors_matrix_eQTL.sh
run_count_num_sig_association.sh
plot_num_eqtl_vs_cov.R
6. run matrix eQTL
run_matrix_eQTL.R
Conclusion:
3 PCs and 8 PEER factors give the most eQTLs
The output file is here:
$processed_data/find_optimum_num_PEER_factors_matrixeqtl/pc3.peer8.2.cis.txt
## 2 fastQTL
1. prepare genotype data
bcftools
2. prepare expression data
`gen_bed.R`
3. prepare covariates
`combine_covariates.R`
4. run fastqtl nominal pass
`run_fastqtl.nominal.sh`
5. compare fastqtl 10000 with 100000 permutations
`run_fastqtl.sh`
`qqplot_fastqtl_pvalue.R`
`compare_10000_100000_permutations.R`
`fastqtl_pvalue_corrections.R`
6. find optimal number of PC and PEER factors
`find_optimal_num_PEER_factors.sh`
`plot_num_egene_vs_cov.R`
7. compare number of eGenes with GTEx
`plot_num_egenes_vs_sample_size.R`
## 3 trans-eQTL (using matrix eQTL)
1. run trans eQTL using 3 PCs and 8 PEER factors
`run_matrix_eQTL.R`
# 160603 (expressiong clustering)
## 0 reference
[Figure](http://www.broadinstitute.org/collaboration/gtex_analysis/index.php/Temp_-_Transcriptome#4._Tissue_clustering.2FTissue_identity_from_Expression_Profiles)
[Method](http://www.broadinstitute.org/collaboration/gtex_analysis/index.php/Transcriptome_analysis_(CRG)#Clustering_of_gene_expression.)
## 1 gene expression clustering
0. run RNAseQC
`run_RNAseQC.sh`
1. copy rpkm into correct place
`prepare_gtex_rpkm.sh`
2. combine rpkm across all tissues, filter for genes >0.1 rpkm in >10 individuals
`combine_and_filter_rpkm.R`
3. hierarchical clustering
`hclust.R`
conclusion: HCASMC clustered with fibroblasts...
4. MDS
`mds.R`
5.
# 160604_phasing:
## compare the target VCF with reference VCF:
convert_chrom_names.sh
subset_vcf_to_first_4_col.sh
compare_vcf_with_reference.scratch.R
conclusion:
Many difference exists between the target and the reference VCF, especially in the ALT field. For example:
22_16858229 C C T A
These variants cannot be phased property, and conform-gt needs to be run.
## run conform-gt
make_list_of_non_caucasian_samples.hcasmc.R
make_list_of_non_EUR_samples.1kg.sh
run_conform_gt.sh
Result:
In total, the conformed VCF has 12523334 lines, compared to 15463398 lines in the original VCF file. The difference is 2940064 lines, or 19%.
## phasing:
run_beagle_phasing.sh # with reference
run_beagle_phasing_without_reference.sh # without reference
# 160614 (differential expression)
1. getting raw counts
2. run DESeq
## reference:
[fibroblast marker genes](https://www.researchgate.net/post/Which_genes_are_highly_expressed_in_fibroblast_cells)
[SMC marker genes](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2943591/)
# 160615
# 160618 (colocalization)
# TODO:
## reference
[CAD prevalance](https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6040a1.htm)
#### sQTL
# 160627 (sQTL)
# figures
normalize.R
intron_missingness_rate.pdf
# 160628 (beagle)
beagle_QC.R
R2_histogram.pdf
dosageR2_by_AFbin.pdf
dosageR2_by_AFbin_size_002.pdf
dosageR2_by_chrom.pdf
# TODO:
2. fine mapping
4. sQTL mapping
# 160629 (sqtl)
- map sQTLs with fastqtl nominal pass
- make qqplot and histogram
- diagnose enrichment of high pvalues
diagnostic_p_value_dist.R
gt6_count_vs_adj_min_pval.pdf
gt6_count_vs_mean_pval.pdf
gt6_count_vs_min_pval.pdf
mean_count_vs_adj_min_pval.pdf
mean_count_vs_mean_pval.pdf
mean_count_vs_min_pval.pdf
zero_count_vs_adj_mean_pval.pdf
zero_count_vs_mean_pval.pdf
zero_count_vs_min_pval.pdf
- plot number of sig. sqtl vs distance
+ plot_sqtl_vs_distance.R
* num_sig_sqtl_vs_dist.pdf
* num_sig_sqtl_within_intron_vs_dist.pdf
- visualize bam files
# 160705
# diagnose the p-value deflation problem.
- map sQTL on permuted data
+ sqtl.perm.histogram.pdf
+ sqtl.perm.qqplot.pdf
* observation: deflation still exists
- map sQTL on permuted data without PEER factors
+ sqtl.perm.histogram.noPEER.pdf
+ sqtl.perm.qqplot.noPEER.pdf
* observation: deflation disappeared
- map sQTL on permuted data with PEER factors using top 10000 introns
+ sqtl.perm.histogram.top10000.pdf
+ sqtl.perm.qqplot.top10000.pdf
* observation: deflation became small but still exists
- map sQTL on permuted data with 3,6,9,12,15 PEER factors (top 10000 introns)
+ sqtl.perm.histogram.top10000.peer{3,6,9,12,15}.pdf
+ sqtl.perm.qqplot.top10000.peer{3,6,9,12,15}.pdf
* observation: deflation lessens as the number of factors decreases
# 160708
# WASP correction
#### splicing QTLs (sQTLs)
#### 160629
(TBD) Leafcutter sQTL analysis
One of the top sIntrons for the SMAD3 loci is de novo. We visualized the loci by displaying RNAseq coverage summed across all samples on UCSC browser (figures/160629/smad3_loci_denovo_intron_RNAseq_coverage.png). The de novo intron is supported by some, but not much, RNAseq coverage. One sample, 1020301, does not show coverage in support of the de novo intron. One could suspect that this sample possesses a variant that favors against this intron.
#### 2D visualization (MDS, t-SNE)
#### 160603 MDS
TBA
#### 160729 t-SNE
t-SNE is a low-dimensional visualization method that preserves the distance of closely related points.
# combine_and_filter_rpkm.R
Genes were filtered with RPKM value > 0.1 in at least 80% of the samples. Genes that passes the filter are log transformed after an offset of 1. This resulted in gene expression profiles from a total of 16,383 genes.
# tsne.2.R
The mean of each gene are normalized to zero. We performed the Barnes-Hut version of t-SNE using a perplexity of 30 (default) and no preprocessing with PCA. The optimization procedure of t-SNE does not guarantee the that the final 2D visualization represent the global optimum. Therefore, we performed 1000 iterations and present the one with the lowest cost function. In this 2D visualization, HCP and HCM (serum fed and serum starved) overlaps each other. They are surrounded by fibroblast, heart, artery, stomach, pancreas, and muscle. (figures/160729/tsne.seed.25.pdf)
#### HCASMC specific genes
#### 160715
subsample.list.by.tissue.bl.R subsampled 10 individuals for each tissue and wrote the individuals to one txt file per tissue.
subsample.R generated subsampled gct files using lists generated by subsample.list.by.tissue.bl.R.
combine_read_counts.sh combined all gct files of HCASMC into one gct file.
find_housekeeping_genes.R found ~9,435 not differentially expressed across tissues with FDR 99%. The p-value distribution has a peak at 0 and another at 1 (see figures/160715/DE_p_value_distribution.pdf). In addition, p-value is inversely correlated with mean read depth. However, there are some genes with relatively high read depth and insignificant p-values (see figures/160715/mean_read_depth_vs_pvalue.pdf). The plot figures/160715/read_counts_across_tissue_for_DE_genes.pdf shows a couple examples of differentailly expressed genes. MDGA2 (ENSG00000139915.14) is a brain specific gene and FOXP1 (ENSG00000114861.14) is a transcription factor whose expression varies across tissue.
Eisenberg and Levanon reported 3804 housekeeping genes across 16 human tissues. They also provided a narrow list of 11 highly uniform genes. The plot figures/160715/read_counts_across_tissue_for_housing_keeping_genes_by_Levanon.pdf shows that some of reported housekeeping genes may not be uniformly expressed.
# find_house_keeping_gene.R
To select bona fide invariant housekeeping gene, we employ a equivalence testing procedure in an ANOVA framework. However, since ANOVA assumes samples are normally distribution with equal variances, we needed to transform the data. Among log(x), sqrt(x), x^(2/3) and variance stabilizing transformations, the first and last performed the best in making the distribution symmetric (figures/160715/compare_transformations.pdf). In terms of decompling variance from the mean, the last performed the best(figures/160715/mean_vs_variance.pdf). The figure figures/160715/expression_by_tissue_raw_count_vs_vsn.pdf shows pre and post variance stabilizating transformation. It is difficult to judge whether the variances are more constant, but expression outliers has smaller effects after VSN. In addition, the mean variance dependency has been reduced. The equivalence test is implemented in equivalence.R. The testing procedure follows chapter 7 of the book testing_statistical_hypotheses_of_equivalence_and_noninferiority. However, I did not carry on with this approach since I do not fully understand it.
# find_housekeeping_gene.2.R
An alternative approach is to set a minimum threshold on the expression value and a maximum threshold on the expression variance (as described in Levanon et al). These following filters:
(i) expression observed in all tissues;
(ii) low variance over tissues: standard-deviation [log2(RPKM)]<1;
(iii) no log2(rpkm) differed from the averaged by 1 (twofold) or more
identified 3391 housekeeping genes. Two examples of housekeeping and non-housekeeping genes are in figures/160715/{read_counts_for_hk_gene.pdf,read_counts_for_non_hk_gene.pdf}
# ruvseq.R
RUVSeq was used to correct for the unwanted hidden variables. The housekeeping genes selected using mean and variance threshold were used as control genes. Raw read counts (not corrected with size factors) was used as input to RUVSeq. Removing 20 hidden factors were sufficient, as the relative log expression for each sample is distributed with ~0 mean and similar variances (/srv/persistent/bliu2/HCASMC_eQTL/figures/160715/rle_and_pca_after_ruv.*.pdf)
# find_hcasmc_specific_genes.R (with RUVSeq correction)
The residuals from ruvseq.R was used as input. HCASMC specific gene were found using a rank based statistic described as follows. Given a list L1 of N numbers 1:N and a second list L2 of n numbers, the test calculates the probability that the maximum member of an arbitrary list of lengh n is less than the maximum memeber of the list L2. In particular, p=choose(max(L),n)/choose(N,n). P-values using permuted dataset shows that the test is well-calibrated (/srv/persistent/bliu2/HCASMC_eQTL/figures/160715/qqplot_pvalues.pdf)After BH adjustment, 5151 genes are statistically significant at FDR 5%. However, most of these genes does not make biological sense. For instance, many top hits are olfactory receptor genes (OR6C65, OR8H3), which should not be expressed in HCASMC at all. On the other hand, known HCASMC specific such as MYH10 has insignificant p-value (see processed_data/160715/hcasmc_specific_genes.txt). The unexpected pattern indicates that there may have been overcorrection. To address this, one can try regressing against less unwanted factors, or leaving out the top unwanted factors as these may capture true biological variation.
# ruvseq.2.R
I also tried using size factor corrected counts as input to RUVSeq. I rerun find_hcasmc_specific_gene.R using the residuals from ruvseq.2.R (results not saved) and the results were similar to ruvseq.R. This analysis eliminated library size as the reason for the unexpected results from find_hcasmc_specific_genes.R.
# find_hcasmc_specific_genes.2.R (no RUVSeq correction)
Previously overcorrection was suspect for the unexpected result from find_hcasmc_specific_genes.R. To test this hypothesis, I used the extreme case of no RUVSeq correction at all. Using size factor corrected read counts, all synthetic HCASMC genes (CALD1, VIM, MYH10, TPM4, RBP1) are significant hits. The top hits includes the following:
gene_id gene_name pvalue padjust
1 ENSG00000067208.10 EVI5 3.331360e-21 1.673360e-18
2 ENSG00000105825.7 TFPI2 3.331360e-21 1.673360e-18
3 ENSG00000130508.6 PXDN 3.331360e-21 1.673360e-18
4 ENSG00000133657.10 ATP13A3 3.331360e-21 1.673360e-18
5 ENSG00000134901.8 KDELC1 3.331360e-21 1.673360e-18
6 ENSG00000150093.14 ITGB1 3.331360e-21 1.673360e-18
7 ENSG00000164291.12 ARSK 3.331360e-21 1.673360e-18
8 ENSG00000172380.5 GNG12 3.331360e-21 1.673360e-18
9 ENSG00000173950.11 XXYLT1 3.331360e-21 1.673360e-18
10 ENSG00000179172.7 HNRNPCL1 3.331360e-21 1.673360e-18
EVI5 is ecotropic viral integration site 5. Most likely, this gene is upregulated due to Bovine serum virus.
TFPI2 is Tissue Factor Pathway Inhibitor 2. Upregulation of TFPI2 is observed in the study "The expression of tissue factor and tissue factor pathway inhibitor in aortic smooth muscle cells is up-regulated in synthetic compared to contractile phenotype."
PXDN is Peroxidasin which is part of extracellular matrix secretion.
ATP13A3 is a P-type ATPase which transport a variety of cations across the membrane. This is counter-intuitive since synthetic smooth muscle does not need to transport Ca2+.
The plot figures/160715/heatmap.2.pdf shows that HCASCM specific genes separates HCASMC from the other tissues.
# GSEA analysis
GSEA analysis shows that HCASMC specific genes are enriched in
1. MYC targets
2. unfolded protein response
3. protein secretion
4. epithelial mesenchymal transition
5. mTORC1 signaling (protein synthesis)
Enriched pathways are shown in figures/160715/gsea_enriched_pathways.png
# find_hcasmc_specific_genes.3.R
To understand whether each gene co-expression cluster correspond to any pathway, we performed hierarchical clustering using the top HCASMC-specific genes (FDR<1e-3, 4266 genes). A set of genes is assigned a cluster if the root of such cluster has height greater than or equal to the height of the root of the whole tree divided by 1.15 (note that this cutoff is ad hoc). A total of 4 clusters are formed, as shown in figures/160715/heatmap.3.pdf. PANTHER pathway analysis returned pathways specific to each of the 4 clusters (result stored in processed_data/160715/panther_hcasmc_specific_genes.{webarchive,txt}). Each gene cluster is enriched in multiple pathways. Note that the number of cluster can be tuned to maximize the number of discovered enriched pathways. However, I would like to discuss the current result before performing parameter tuning.
# find_hcasmc_specific_genes.4.R
A contrast is used to compare HCASMC to
1. all GTEx tissues
2. GTEx artery tissues
3. GTEx smooth muscle
4. GTEx heart
5. GTEx fibroblast
5. serum-free HCASMC
GSEA reports enriched pathway as follows:
1. all GTEx tissues
- hallmark
- upregulated
- cell cycle
- protein synethsis and and secretion
- downregulated
- KRAS signaling
- myogenesis
- KEGG
- up
- ribosome
- proteasome
- cell cycle
- DNA replication
- protein export
- down
- allograft rejection
- various immune pathways
- smooth muscle contraction
2. GTEx artery tissues
- hallmark
- same as above
- KEGG
- up
- same as above
- down
- KEGG_VASCULAR_SMOOTH_MUSCLE_CONTRACTION
- KEGG_DILATED_CARDIOMYOPATHY
- KEGG_COMPLEMENT_AND_COAGULATION_CASCADES
3. GTEx smooth muscle tissues
- hallmark
- same as above
- KEGG
- up
- same as above
- down
- KEGG_CALCIUM_SIGNALING_PATHWAY
- KEGG_VASCULAR_SMOOTH_MUSCLE_CONTRACTION
4. GTEx heart
- hallmark
- same as above
- KEGG
- KEGG_DILATED_CARDIOMYOPATHY
- KEGG_CARDIAC_MUSCLE_CONTRACTION
- KEGG_HYPERTROPHIC_CARDIOMYOPATHY_HCM
5. GTEx fibroblast
- hallmark
- same as above
- KEGG
- does not make sense??
6. HCASMC SF
- hallmark
- up
- same as above
- down
- HALLMARK_EPITHELIAL_MESENCHYMAL_TRANSITION (?)
- HALLMARK_MYOGENESIS
- HALLMARK_WNT_BETA_CATENIN_SIGNALING
- KEGG
- up
- KEGG_CARDIAC_MUSCLE_CONTRACTION (rank:31)
- KEGG_PROTEASOME
- KEGG_RNA_POLYMERASE
- down
- KEGG_RIBOSOME (?)
- KEGG_NOTCH_SIGNALING_PATHWAY
#### DE between serum-fed and serum-starved HCASMC
#### 160801:
# DESeq2_HCASMC_SF_vs_FBS.R
To test the effect of bovine serum exposure to HCASMC gene expression, I performed differential expression analysis with the DESeq2 package. Using 1% FDR, a total of 2472 genes are differentially expressed, among with 1380 are upregulated and 1092 are downregulated upon serum treatment (figures/160801/HCASMC_SF_vs_FBS.pdf). The top differentially expressed genes falls into the category of cell cycle regulators (e.g. CDC20, NEK2, SPC25, DLGAP5, MYBL2), platelet activeation and inflammatory response (KIF20A), inhibition of apoptosis (MYBL2) and ubiquitination (UBE2C).
# GSEA analysis:
To understand which pathways are perturbed upon serum stimulation, I performed GSEA analysis using the following 4 gene sets:
1. Hallmark
2. Cononical pathways (including BioCarta and KEGG)
3. Gene ontology Molecular function
4. Gene ontology Biological process
5. Transcription factor binding
In the hallmark gene sets, pathways activated in the FBS condition includes cell cycle regulation, and protein secretion.
Pathways activated in the SF condition is more convoluted: they include
1. coagulation
2. heme metabolism (erythroblast differentiation)
3. myogenesis
4. angiogenesis
5. inflammatary response
In the conanical pathway gene set, the FBS sets are enriched in the following pathways:
1. mitotic pathways
2. cardiac muscle, smooth muscle contraction (strange?)
the SF set are enriched with the following pathways:
1. Notch signalling
2. circadian expression
3. SMAD2/3 signaling etc
#### ATACseq variant scoring
The fa file contains 19 bp sequences
The bed file contains variant positions close but outside of the fa file sequences.
####
#### Fine-mapping by inspection
#### 160811
#### select top GWAS hits: extract_gwas_loci.R
I extracted the top GWAS hits from Nikpay 2015 NG. For each of the top GWAS hit, I extracted all tested genes (genes within 1MB from the variant) and plotted the association pvalue (../figures/160811/gwas_hits_gene_pval.pdf, using plot_gwas_hits_eqtl_pval.R). This plot suggests that two GWAS hits, rs273909 (SLC22A4-SLC22A5) and rs2521501 (FURIN-FES) are significantly associated with at least one gene (p-value <0.05). For rs273909, the top association is SLC22A4 (p<1.8e-4); for rs2521501, the top association is FES (p<2.0e-4). I then made locuszoom plot for both loci and observed coloclization at both loci. Notably, the top GWAS association overlaps the top eQTL association at rs2521501. Next, I made forestPM plot for both loci. For rs273909, HCASMC has the lowest p-value amonges all tissues. However, its m-value did not reach 0.9, likely due to small sample size. For rs2521501, artery, smooth muscle as well as HCASCM share low p-values, and all reached m-value of 0.9.
#### eCAVIAR
I ran eCAVIAR using a pipeline described in Farhad's paper.
1. select GWAS top variant
2. select the 50 up and downstream as the GWAS loci
3. select the eGenes for at least variant in all loci
4. run eCAVIAR for each genes @ each loci
There are 6 loci that have CLPP greater than 0.01
#### eGenes vs sample size
I plotted the number of eGenes vs sample size. The largest sample size is 361, and the smallest is 52. Figure "../figures/egenes_vs_sample_size/num_egenes_vs_sa_size.fullsize.pdf" shows regression on this range. HCASMC is slightly below the regression line. Figure "../figures/egenes_vs_sample_size/num_egenes_vs_sample_size.size150.pdf" shows regression from 52 to 150. In the latter, HCASMC seems to be on the regression line.
#### tarid:
This paper (http://www.cell.com/molecular-cell/abstract/S1097-2765(14)00565-6) suggests that the exon 2 of TARID binds GADD45A. GADD45A demethylate and activate transcription of TCF21 (figure5a_arab_2014_molecularCell.png). The variant rs2327429 is a GWAS-eQTL colocalized variant. This variant is in exon 2 of TARID and A -> T changes the stability of the secondary structure(tarid_2nd_structure.png, tarid_2nd_structure_rs2327429_A_T.png)
resources:
TARID transcript sequences: http://www.lncipedia.org/db/gene/TARID
TARID secondary structure
ref sequence: http://rna.tbi.univie.ac.at/cgi-bin/RNAfold.cgi?PAGE=3&ID=mj9aphLqq1
alt sequence: http://rna.tbi.univie.ac.at/cgi-bin/RNAfold.cgi?PAGE=3&ID=2cl2IX97FC
protein-RNA interaction:
Ref sequence: Prediction using RF classifier 0.8
Prediction using SVM classifier 0.77
Alt sequence:
Ref sequence: Prediction using RF classifier 0.8
Prediction using SVM classifier 0.78
RNAstructure prediction:
ref:
http://rna.urmc.rochester.edu/RNAstructureWeb/Servers/Predict1/ResultsPages/9299782801866953763/Results.html
alt:
http://rna.urmc.rochester.edu/RNAstructureWeb/Servers/Predict1/ResultsPages/19122644741555023435/Results.html
Another variant rs2329430, located in the "critical region" of TARID exon 2 (Arab 2014) seems to vary the RNA structure greatly. rs2329430 is a C/T variant.
# IMPUTATION
Three versions:
1. without reference
2. with 1kg p3v5a as reference (but not imputed)
3. with reference and impute into 1kg p3v5a
At first glance most imputed variants in (3) has low allele frequency. Makes sense because common allele would have been called by WGS.
# WASP
# CHT
when running CHT, don't forget to compile snp2h5 so the anaconda/lib versions are correct.
#### find_AHR_eQTLs_in_JUN_and_TCF21_peaks.R
A TCF21 and JUN peak within chr7:17,410,875-17,412,620 contains rs10265174, rs12699842, rs60457144. rs10265174 is the second most significant eQTL with p-value < 9e-5. Haploreg shows rs10265174 also changes the binding affinity of AP-1 and TCF4 (which has similar motif to TCF21). rs12699842 and rs60457144 are not tested due to low MAF.