TTN in Dilated Cardiomyopathy (DCM)

The role of rare variants in TTN as causative mutations in Dilated Cardiomyopathy is described below. By comparing the frequency of TTN variants in large DCM clinical cohorts to the background population rate in the ExAC database, the proportion of DCM patients with pathogenic mutations in TTN can be estimated, as well as the likelihood that a rare (population allele frequency <0.0001) TTN variant identified in a DCM patient is disease-causing. Summary data for different variant classes (all protein-altering variants, loss of function truncating variants and non-truncating variants) is highlighted - see the table below for full details of this analysis.


Excess of TTN truncating variants in DCM: 13.69% (p<0.0001)

Based on an analysis of rare truncating variants (MAF<0.0001 in ExAC) in TTN found in 460 DCM samples sequenced by OMGL and LMM and in reference samples of the ExAC population database.


Metrics by Variant Class:
All VarsTruncatingNon-Truncating
Excess in DCMn/a13.69%
p<0.0001
n/a
Etiological fraction n/a 0.95
0.93 - 0.96
n/a
Odds Ratio n/a 19.95
14.93 - 26.32
n/a

The Etiological Fraction (EF) is the proportion of affected carriers where the variant caused DCM. The Odds Ratio (OR) describes the odds of having a rare variant in the patient cohort to the odds in the ExAC cohort. Fisher's exact test p-values are displayed for case excess, 95% confidence intervals for EFs and ORs.



SourceSamples
Tested
Variant
Type
Variants
detected
Frequency
in DCM
Frequency
in ExAC
Case Excess
in DCM
Combined
(OMGL1 + LMM2)
460Truncating67 0.145650.008760.13689
OMGL1304Truncating45 0.148030.008760.13927
LMM2156Truncating22 0.141030.008760.13227

References

1. Roddy Walsh, Kate L. Thomson, James S. Ware, Birgit H. Funke, Jessica Woodley, Karen J. McGuire, Francesco Mazzarotto, Edward Blair, Anneke Seller, Jenny C. Taylor, Eric V. Minikel, Exome Aggregation Consortium, Daniel G. MacArthur, Martin Farrall, Stuart A. Cook and Hugh Watkins. Reassessment of Mendelian gene pathogenicity using 7,855 cardiomyopathy cases and 60,706 reference samples. Genet Med. 2016 doi:10.1038/gim.2016.90.

2. Pugh TJ, Kelly MA, Gowrisankar S, Hynes E, Seidman MA, Baxter SM, Bowser M, Harrison B, Aaron D, Mahanta LM, Lakdawala NK, McDermott G, White ET, Rehm HL, Lebo M, Funke BH. The landscape of genetic variation in dilated cardiomyopathy as surveyed by clinical DNA sequencing. Genet Med. 2014 Aug;16(8):601-8.