PMC7680847_01
The clinical data and genetic analysis of the patient with MMP21 variant. (A) Chest X-ray of the patient indicating dextrocardia. (B) Sanger DNA sequencing chromatogram demonstrating the homozygosity for an MMP21 stopgain variant (c.G496T; p.G166*). (C) The sequence encoding the signal peptide and propeptide is before the red dotted line, the subsequent sequence encodes matrix metalloproteinase-21, the red arrow indicates the variant identified in this study, and the numbers and black arrows indicate the family in Table 2 and position of MMP21 variants, respectively. Domain structure of MMP21. SP, signal peptide; PG_binding, putative peptidoglycan-binding domain; ZnMc superfamily, zinc-dependent metalloprotease; HX superfamily, hemopexin-like repeats.
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F1
He was diagnosed with complex CHD, mirror-image dextrocardia (Figure 1A), single-ventricle, pulmonary stenosis, and transposition of the great arteries, without PCD. After filtration of the WES data (Table 1), we finally identified a biallelic stopgain variant (c.G496T; p.G166*) in MMP21 and further confirmed it by Sanger sequencing (Figure 1B). This variant caused a truncated MMP21 mRNA containing only the signal peptide and propeptide, while the coding sequence of matrix metalloproteinase-21 was almost entirely absent (Figure 1C).