Pregnancy in patients with VHL disease induces cerebellar hemangioblastoma progression and causes a high VHL disease-related pregnancy complication rate. We recommend intensified surveillance of patients with VHL disease, especially of cerebellar hemangioblastomas during preconception care and pregnancy.
Background
In the past decade, we and others have reported three families with rare genetic variants in TNNI3K, encoding the cardiac-specific troponin-I interacting kinase (TNNI3K), co-segregating with a mixed, but highly penetrant, cardiac phenotype that features predominant atrial/junctional tachycardia occurring in combination with cardiac conduction disease and dilated cardiomyopathy. We demonstrated that while the p.Thr539Ala and p.Gly526Asp TNNI3K variants had decreased auto-phosphorylation activity the p.Glu768Lys variant, present in 3 independent families, leads to increased auto-phosphorylation levels, in line with the finding that increased levels of Tnni3k expression are associated with slower atrial-ventricular conduction in mice.
Objective
Identifying new genetic variants in the TNNI3K gene associated with cardiac disease and assessing their impact on TNNI3K auto-phosphorylation levels.
Methods
Through next generation sequencing of a panel of genes associated with cardiac disease we assessed TNNI3K in patients with cardiac arrhythmias and cardiomyopathies. All variants identified were assessed in vitro for effects on auto-phosphorylation. Briefly, wild-type and mutant TNNI3K constructs were transfected into HEK293 cells, protein was extracted after 48 hours and analyzed with anti-flag and anti-phospho-tyrosine antibodies on Western blot.
Results
We identified 7 novel and rare variants in TNNI3K in 11 additional probands, with predominantly cardiac conduction disease, with or without dilated cardiomyopathy, and atrial-ventricular-re-entry-tachycardia (AVNRT). Of these, multiple variants were found to have aberrant auto-phosphorylation including almost absent auto-phosphorylation capacity for one (TNNI3K-p.Val510Leu). All three-independent wild type TNNI3K transfected HEK293 cell lysates showed similar phosphorylated TNNI3K levels and the kinase-dead negative control demonstrated no phosphorylation activity.
Conclusion
We here present 7 novel genetic variants in TNNI3K in patients with a remarkable overlap in cardiac phenotype consisting mainly of AVNRT and cardiac conduction disease. We further show that some of these variants alter the auto-phosphorylation of TNNI3K. These results indicate a more prevalent role of variants in TNNI3K in human cardiac disease and a possible in vitro functional assay to assess the pathogenicity of such variants.
Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): The Dutch Research Council (NWO Talent Scheme VIDI-91718361)
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