Alternative titles; symbols
HGNC Approved Gene Symbol: TNNI3K
Cytogenetic location: 1p31.1 Genomic coordinates (GRCh38) : 1:74,235,387-74,544,428 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 1p31.1 | Cardiac conduction disease with or without dilated cardiomyopathy | 616117 | Autosomal dominant | 3 |
TNNI3K belongs to the MAPKKK (see MAP3K1, 600982) family of protein kinases and is expressed exclusively in cardiac myocytes (Zhao et al., 2003).
By searching EST databases for sequences expressed predominantly in heart, Zhao et al. (2003) identified TNNI3K. The deduced protein has 7 N-terminal ankyrin (see 612641) repeats, followed by a protein kinase domain and a C-terminal serine-rich domain. Northern blot analysis detected a 3.42-kb TNNI3K transcript in fetal and adult heart, but not in any other tissues examined. RNA dot blot analysis confirmed heart-specific TNNI3K expression. TNNI3K was variably expressed in all heart regions examined, with highest levels in interventricular septum and apex. Immunohistochemical analysis detected TNNI3K predominantly in nuclei of fetal and adult cardiac myocytes. TNNI3K was not detected in smooth muscle cells or endothelial cells. Western blot analysis detected TNNI3K protein at an apparent molecular mass of 93 kD.
Lai et al. (2008) stated that the human TNNI3K protein contains 835 amino acids.
By immunohistochemical analysis of mouse heart and differentiated HL-1 cardiac muscle cells, Tang et al. (2013) found that Tnni3K localized to sarcomeric Z discs.
Zhao et al. (2003) determined that the TNNI3K gene contains 25 exons and spans at least 320 kb.
By genomic sequence analysis, Zhao et al. (2003) mapped the TNNI3K gene to chromosome 1p31.1.
Patterson et al. (2017) reported that the mouse Tnni3k gene maps to chromosome 3.
Zhao et al. (2003) showed that human TNNI3K expressed in COS-7 cells had autocatalytic kinase activity. Mutation analysis revealed that lys490, a conserved residue within kinase subdomain II, was required for kinase activity. Yeast 2-hybrid analysis of a heart cDNA expression library revealed that TNNI3K interacted with cardiac troponin I (TNNI3; 191044), a key thin filament regulatory protein, and immunoprecipitation analysis confirmed the interaction. Zhao et al. (2003) hypothesized that TNNI3K may regulate cardiac contractility via its interaction with troponin.
Lai et al. (2008) found that overexpression of human TNNI3K promoted dimethyl-sulfoxide-induced differentiation in mouse P19CL6 cardiomyocytes in culture, increased beat frequency and contractile force, and increased the duration of spontaneous action potentials. These changes were accompanied by increased expression of alpha-actinin (see 102575) and suppressed phosphorylation of cardiac troponin. TNNI3K overexpression also enhanced epinephrine- and calcium-induced action potentials. TNNI3K countered apoptotic response of differentiated P19CL6 cells to heat stress and ultraviolet irradiation. In a mouse model of myocardial infarction, injection of TNNI3K-expressing P19CL6 cells into myocardium improved cardiac performance, attenuated ventricular remodeling, and reduced infarct size and apoptosis.
Using an in vitro kinase assay, Tang et al. (2013) found that TNNI3K autophosphorylated on tyrosine, threonine, and serine residues within the ankyrin repeats and serine-rich tail domain, indicating that it is a dual-function kinase. Expression of wildtype human TNNI3K in transgenic mice accelerated left-ventricular dysfunction, hypertrophy, and fibrosis in a pressure-overload model of cardiomyopathy. In contrast, biomechanical stress did not result in cardiomyopathy in transgenic mice expressing kinase-dead TNNI3K or in a naturally occurring Tnni3k-null mouse strain. Tang et al. (2013) concluded that TNNI3K may be either beneficial or injurious to cardiac function depending on the type of cardiac stress.
By surveying ventricular cells of 120 inbred mouse strains, Patterson et al. (2017) observed a greater than 7-fold range (2.3 to 17.0%) in the percentage of mononuclear cardiomyocytes. Two strains with high content of mononuclear diploid cardiomyocytes (MNDCMs) showed improved proliferation and functional and histologic recovery after permanent coronary artery ligation compared with 2 strains with low MNDCM numbers. Tnni3k expression across mouse strains negatively correlated with mononuclear cardiomyocyte frequency, and knockout of Tnni3k in low-MNDCM mice elevated MNDCM content and increased cardiomyocyte proliferation after injury. Overexpression of mouse Tnni3k in zebrafish promoted cardiomyocyte polyploidization and compromised heart regeneration after injury.
In a Caucasian family of German ancestry with cardiac conduction disease with or without dilated cardiomyopathy (CCDD; 616117), Theis et al. (2014) performed whole-exome sequencing and identified a heterozygous missense mutation in the TNNI3K gene (G526D; 613932.0001) on chromosome 1p31. The mutation segregated with disease in the family was not found in more than 7,600 exomes/genomes in publicly available databases.
Using whole-exome sequencing in a 3-generation pedigree with cardiac conduction system disease with or without ectopic tachycardia, Xi et al. (2015) identified a heterozygous missense mutation in the TNNI3K gene (T539A; 613932.0002). The mutation was confirmed by Sanger sequencing and segregated with the disease in the family. Xi et al. (2015) noted that the T539 residue has been shown to be key to controlling kinase activity and accessibility of the ligand-binding pocket to selective kinase inhibitors.
Using whole-exome sequencing in a 3-generation Chinese family with cardiac conduction disease and dilated cardiomyopathy, Fan et al. (2018) identified a heterozygous splice site mutation in the TNNI3K gene (613932.0003). The mutation was confirmed by Sanger sequencing and segregated with the disease in the family. The mutation was not found in the 1000 Genomes Project or dbSNP (build 132) databases or in 200 healthy local controls. Real-time qPCR analysis showed reduced TNNI3K mRNA expression of about 61% compared with controls, consistent with nonsense mediated decay.
In all 23 affected individuals from 3 unrelated large multigenerational families with CCDD, Podliesna et al. (2019) identified heterozygosity for the same missense mutation in the TNNI3K gene (E768K; 613932.0004). Functional analysis demonstrated significantly increased kinase activity with the E768K mutant, whereas there was reduced activity with the previously reported T539A mutant (613932.0002), and autophosphorylation was nearly abolished with the G526D mutant (613932.0001). Podliesna et al. (2019) concluded that more studies would be required to dissect pathways involving TNNI3K and to understand the pathogenetic mechanisms associated with TNNI3K variants.
Gan et al. (2021) found that knockin mice homozygous for a Tnni3k I685T mutation, corresponding to the human TNNI3K kinase domain I686T mutation, had normal Tnni3k expression levels in heart tissue compared to wildtype. However, the kinase activity of the I685T mutant was substantially reduced, leading to the development of left ventricular concentric remodeling, characterized by ventricular wall thickening and substantial reduction of cardiomyocyte aspect ratio. The mutant mice developed these conditions in the absence of fibrosis or hypertension, implying a primary cardiomyocyte etiology. Analysis with cultured cells showed that contractility, calcium dynamics, and protein kinase A (PKA; see 188830) signaling in response to isoproterenol were impaired in mutant cardiomyocytes, indicating diminished contractile reserve.
In 7 affected members of a Caucasian family of German ancestry with cardiac conduction disease with or without dilated cardiomyopathy (CCDD; 616117), Theis et al. (2014) identified heterozygosity for a c.1577G-A transition in exon 16 of the TNNI3K gene, resulting in a gly526-to-asp (G526D) substitution. The mutation was not found in 3 unaffected family members or in more than 7,600 exomes/genomes in publicly available databases. In vitro, the mutant peptide demonstrated abnormal aggregation and insolubility, in contrast to the completely soluble wildtype peptide. Immunohistochemical staining of ventricular tissue revealed markedly reduced TNNI3K expression in the sarcoplasm and nuclei of patient cardiomyocytes compared to controls.
By autophosphorylation assay in transfected HEK293A cells, Podliesna et al. (2019) observed that the G526D mutant nearly abolished TNNI3K kinase activity compared to wildtype protein.
In affected members of a 3-generation pedigree with conduction system disease (CCDD; 616117), some of whom also had congenital junctional ectopic tachycardia, Xi et al. (2015) identified a heterozygous c.1615A-G transition (c.1615A-G, NM_015978.2) in the TNNI3K gene, resulting in a thr539-to-ala (T539A) substitution at a conserved residue in the ATP-binding pocket. The mutation, which was found by whole-exome sequencing and confirmed by Sanger sequencing, segregated with the disease in the family. Xi et al. (2015) noted that the thr539 residue has been shown to be key to controlling kinase activity and accessibility of the ligand-binding pocket to selective kinase inhibitors.
By autophosphorylation assay in transfected HEK293A cells, Podliesna et al. (2019) observed significantly decreased levels of kinase activity with the T539A variant compared to wildtype protein.
In affected members of a 3-generation Chinese family with cardiac conduction disease and dilated cardiomyopathy (CCDD; 616117), Fan et al. (2018) identified a heterozygous splice site mutation (c.333+2T-C, NM_015978) in exon 4 of the TNNI3K gene, resulting in a premature stop codon. The mutation was confirmed by Sanger sequencing and segregated with the disease in the family. The mutation was not found in the 1000 Genomes Project or dbSNP (build 132) databases or in 200 healthy local controls. Real-time qPCR analysis showed reduced TNNI3K mRNA expression of about 61% in patient cells compared with controls, consistent with nonsense mediated decay.
In all 23 affected individuals from 3 unrelated large multigenerational families with cardiac conduction disease with or without dilated cardiomyopathy (CCDD; 616117), Podliesna et al. (2019) identified heterozygosity for a c.2302G-A transition (c.2302G-A, NM_015978.2) in exon 23 of the TNNI3K gene, resulting in a glu768-to-lys (E768K) substitution at a highly conserved residue within the C terminus. No clinical information was available for 3 additional family members who tested positive for the E768K variant, or for 1 obligate carrier. The mutation was very rare in the general population, with a minor allele frequency of 0.0016% in the gnomAD database. Autophosphorylation assay in transfected HEK293A cells demonstrated significantly increased kinase activity with the mutant compared to wildtype TNNI3K.
Fan, L.-L., Huang, H., Jin, J.-Y., Li, J.-J., Chen, Y.-Q., Zhao, S.-P., Xiang, R. Whole exome sequencing identifies a novel mutation (c.333+2T-C) of TNNI3K in a Chinese family with dilated cardiomyopathy and cardiac conduction disease. Gene 648: 63-67, 2018. [PubMed: 29355681] [Full Text: https://doi.org/10.1016/j.gene.2018.01.055]
Gan, P., Baicu, C., Watanabe, H., Wang, K., Tao, G., Judge, D. P., Zile, M. R., Makita, T., Mukherjee, R., Sucov, H. M. The prevalent I686T human variant and loss-of-function mutations in the cardiomyocyte-specific kinase gene TNNI3K cause adverse contractility and concentric remodeling in mice. Hum. Molec. Genet. 29: 3504-3515, 2021. [PubMed: 33084860] [Full Text: https://doi.org/10.1093/hmg/ddaa234]
Lai, Z.-F., Chen, Y.-Z., Feng, L.-P., Meng, X.-M., Ding, J.-F., Wang, L.-Y., Ye, J., Li, P., Cheng, X.-S., Kitamoto, Y., Monzen, K., Komuro, I., Sakaguchi, N., Kim-Mitsuyama, S. Overexpression of TNNI3K, a cardiac-specific MAP kinase, promotes P19CL6-derived cardiac myogenesis and prevents myocardial infarction-induced injury. Am. J. Physiol. Heart Circ. Physiol. 295: H708-H716, 2008. Note: Erratum: Am. J. Physiol. Heart Circ. Physiol. 295: H1815 only, 2008. [PubMed: 18552163] [Full Text: https://doi.org/10.1152/ajpheart.00252.2008]
Patterson, M., Barske, L., Van Handel, B., Rau, C. D., Gan, P., Sharma, A., Parikh, S., Denholtz, M., Huang, Y., Yamaguchi, Y., Shen, H., Allayee, H., Crump, J. G., Force, T. I., Lien, C.-L., Makita, T., Lusis, A. J., Kumar, S. R., Sucov, H. M. Frequency of mononuclear diploid cardiomyocytes underlies natural variation in heart regeneration. Nature Genet. 49: 1346-1353, 2017. [PubMed: 28783163] [Full Text: https://doi.org/10.1038/ng.3929]
Podliesna, S., Delanne, J., Miller, L., Tester, D. J., Uzunyan, M., Yano, S., Klerk, M., Cannon, B. C., Khongphatthanayothin, A., Laurent, G., Bertaux, G., Falcon-Eicher, S., Wu, S., Yen, H.-Y., Gao, H., Wilde, A. A. M., Faivre, L., Ackerman, M. J., Lodder, E. M.,. Bezzina, C. R. Supraventricular tachycardias, conduction disease, and cardiomyopathy in 3 families with the same rare variant in TNNI3K (p.glu768lys). Heart Rhythm 16: 98-105, 2019. [PubMed: 30010057] [Full Text: https://doi.org/10.1016/j.hrthm.2018.07.015]
Tang, H., Xiao, K., Mao, L., Rockman, H. A., Marchuk, D. A. Overexpression of TNNI3K, a cardiac-specific MAPKKK, promotes cardiac dysfunction. J. Molec. Cell. Cardiol. 54: 101-111, 2013. [PubMed: 23085512] [Full Text: https://doi.org/10.1016/j.yjmcc.2012.10.004]
Theis, J. L., Zimmermann, M. T., Larsen, B. T., Rybakova, I. N., Long, P. A., Evans, J. M., Middha, S., de Andrade, M., Moss, R. L., Wieben, E. D., Michels, V. V., Olson, T. M. TNNI3K mutation in familial syndrome of conduction system disease, atrial tachyarrhythmia and dilated cardiomyopathy. Hum. Molec. Genet. 23: 5793-5804, 2014. [PubMed: 24925317] [Full Text: https://doi.org/10.1093/hmg/ddu297]
Xi, Y., Honeywell, C., Zhang, D., Schwartzentruber, J., Beaulieu, C. L., Tetreault, M., Hartley, T., Marton, J., Vidal, S. M., Majewski, J., Aravind, L., Care4Rare Canada Consortium, Gollob, M., Boycott, K. M., Gow, R. M. Whole exome sequencing identifies the TNNI3K gene as a cause of familial conduction system disease and congenital junctional ectopic tachycardia. Int. J. Cardiol. 185: 114-116, 2015. [PubMed: 25791106] [Full Text: https://doi.org/10.1016/j.ijcard.2015.03.130]
Zhao, Y., Meng, X.-M., Wei, Y.-J., Zhao, X.-W., Liu, D.-Q., Cao, H.-Q., Liew, C.-C., Ding, J.-F. Cloning and characterization of a novel cardiac-specific kinase that interacts specifically with cardiac troponin I. J. Molec. Med. 81: 297-304, 2003. [PubMed: 12721663] [Full Text: https://doi.org/10.1007/s00109-003-0427-x]