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. 2018 Jun 20;27(18):3272–3282. doi: 10.1093/hmg/ddy233

Figure 1.

Figure 1.

Troponin complex structure, variation, and developmental expression. (A) The slow fiber troponin complex is composed of TNNT1 (gray), TNNI1 (green) and TNNC1 (orange) protein subunits. Six pathogenic variants of TNNT1 are indicated by blue arrows (see text and Table 2 for references). The p.Glu180Ter mutation causing Amish nemaline myopathy (ANM) by cleaving the 83 carboxy-terminal amino acids. The residual protein fragment does not bind TNNI1, TNNC1 or tropomyosin, and is rapidly degraded in sarcoplasm. (B) During the course of embryological development, immature TNNT isoforms (embryonic TNNT3 and cardiac TNNT2; green) are expressed in skeletal muscle. Beginning around birth and progressing through the first 3–6 months of life, these are replaced by mature TNNT3 (blue) and TNNT1 (red) proteins, closely paralleling the course of muscle weakness and atrophy in children with ANM (black).