hichipper QC report

2017-12-29

hichipper, version 0.7.1.

Summary Tables

HCASMC_Rep2 HCASMC_Rep3 HCASMC_Rep1
Total PETs 228769936 234135569 259296589
% Reads in Anchors 56.59 58.70 56.99
% HQ Unique Mapped 91.31 88.65 90.66
% Long Range Interaction 7.57 7.36 7.65
% in Loops 0.66 0.72 0.69

The first summary table notes how many PETs are in each sample and what fraction were mapped with high-quality. First, the “% Reads in Anchors” takes all unique, mappable pairs (whether they are valid, dangling, self-circle, etc. doesn’t matter) and determines what fraction have both overlapping with anchor loci. Note, this numer should give an indication of the ChIP quality, but it may be sensitive to how peaks are determined with padding, etc. While the “% HQ Unique Mapped” reads should be self explanatory, the “% Long Range Interaction” value represents the number of intrachromosomal reads longer than the minimum length (default 5Kb) specified by the user and is a good approximation for the efficacy of the in situ ligation. Finally, the “% in Loops” is the fraction of total reads that are in loops, defined by high-quality, mapped intrachromosomal, anchor-mapped, between min and max lengths (default 5Kb and 2Mb). If the proportion of loops reads is low but the proportion of long range interactions is high, this suggests that the ChIP efficiency is relatively low.


HCASMC_Rep2 HCASMC_Rep3 HCASMC_Rep1
Intrachromasomal PETs 34638408 33039279 38083613
% Reads < 5Kb 38.56 36.41 36.06
% Reads in 5KB-2Mb 49.98 52.13 52.07
% Reads > 2Mb 11.47 11.46 11.87

The second summary table shows the total number of intrachromosomal pets and the distance that they span binned by the max and min user defined distances. Only reads in the middle are used when making loops but all are used for anchor calling. If the very long interactions are disproportionately abundant, the proximity ligation step may not have been effective. In contrast, if the short range interactions are disproportionately abundant, issues with the in situ ligation likely occurred in the experiment.


Loop Width Distribution Histogram

Above is a histogram of the loop widths greater than the minimum distance supplied in the parameters. Note that the loops smaller than the minimum distance have been filtered to make the histogram more interpretable (refer to the table above to see the proportion of very loops below the minimum distance, which are likely self-ligations).

Raw Read Stats

HCASMC_Rep2 HCASMC_Rep3 HCASMC_Rep1
Total_PETs 228,769,936 234,135,569 259,296,589
Mapped_unique_quality 208,887,301 207,563,111 235,087,439
Mapped_unique_quality_valid 39,311,012 37,614,264 43,440,534
Valid_Intra 34,638,408 33,039,279 38,083,613
Valid_Intra_<5Kb 13,354,869 12,028,753 13,731,711
Valid_Intra_5Kb-2Mb 17,311,591 17,224,077 19,831,177
Valid_Intra_>2Mb 3,971,948 3,786,449 4,520,725
Valid_Intra_anchor_5Kb-2Mb 1,518,708 1,676,595 1,779,738
HQ_Reads_In_Anchors 129,471,316 137,427,428 147,766,356

Proportional Read Stats

HCASMC_Rep2 HCASMC_Rep3 HCASMC_Rep1
Total_PETs 100.00 100.00 100.00
Mapped_unique_quality 91.31 88.65 90.66
Mapped_unique_quality_valid 17.18 16.07 16.75
Valid_Intra 15.14 14.11 14.69
Valid_Intra_<5Kb 5.84 5.14 5.30
Valid_Intra_5Kb-2Mb 7.57 7.36 7.65
Valid_Intra_>2Mb 1.74 1.62 1.74
Valid_Intra_anchor_5Kb-2Mb 0.66 0.72 0.69
Long_Range_Interactions 7.57 7.36 7.65

Number of Anchor Peaks

sample npeaks
HCASMC_Rep2 84598
HCASMC_Rep3 84598
HCASMC_Rep1 84598

The number of anchor peaks used in each sample. In lowly sequenced samples, these numbers may be low and be responsible for the lack of PETs mapping into loops.