Report of a rare case of congenital mitral valve prolapse with chronic kidney disease--reconsidered genotype-phenotypic correlations

Abstract

Background: Mitral valve prolapse (MVP) is a common cardiovascular disease defined as a late systolic click or mitral valve lobes that move up into the left atrium during ventricular systole, with or without mitral insufficiency. Dachsous catherin-related 1 (DCHS1) is one of the two known pathogenic genes associated with MVP. However, there is little information about the renal dysfunction caused by MVP and DCHS1 mutations.

Methods: We analyzed the genetic etiology in a rare case of 9-year-old boy affected by chronic renal failure with MVP. Subsequently, we constructed stable cell lines overexpressing wild-type DCHS1 or mutant DCHS1 (c.8309G>A, p.R2770Q) to evaluate the influence of the DCHS1 mutation on the proliferation, apoptosis, and autophagy.

Results: Complete exome sequencing and pedigree verification revealed a mutation p.R2770Q (c.8309G>A) in exon 21 of the DCHS1 gene carried by the patient, which may affect the DNA binding. No such mutation was detected in his parents, indicating that this was a new mutation. Potential functional impact of sequence variants was predicted using in silico prediction programs including SIFT, Polyphen2, and Condel. This variant was determined to be a pathogenic mutation that has not been reported elsewhere. Subsequently, we used a stable DCHS1 gene-mutated HK-2 cell line to analyse proliferation, apoptosis, and autophagy, showed that kidney volume decreased with increasing cell death associated with a reduced proliferation.

Conclusions: Our analysis revealed a heterozygous variation of DCHS1 in a child with MVP. Our observations highlight previously unrecognized phenotypes of the currently recognized MVP genotype, including distinct chronic renal failure.

Keywords: DCHS1 mutation; chronic renal failure; genotype-phenotype correlations; mitral valve prolapse.

FIGURE 1

Clinical, radiological, and genetic findings of the patient. (a) CT examination indicates bilateral renal atrophy, especially the left kidney. (b) Ultrasonic cardiogram (c) Pedigree chart of the patient's family. I1, I2, and II1 represent the father, mother, and patient, respectively, and the arrows represent the proband. Black represents DCHS1 mutation. (d) Genetic analysis shows a heterozygous DCHS1 mutation, c.8309G>A was identified in the patient, but not in her parents. (e) Sequence chromatograms of the rare (p.R2770Q) missense in silico‐predicted deleterious variants identified in this study.

FIGURE 2

Efficiency of DCHS1 c.8309G>A (p.R2770Q) mutation in cultured HK‐2 cells. (a) Efficiency of DCHS1 c.8309G>A (p.R2770Q) mutation in HK‐2 cells was determined by qRT‐PCR. Control: wild‐type; DCHS1‐WT: DCHS1 was cloned to construct HK‐2 stable cell line; DCHS1‐Mut: DCHS1 (c.8309G>A, p.R2770Q) was cloned to construct HK‐2. (b) Western blot analysis of the efficiency of DCHS1‐Mut: in HK‐2 cells. (c) OD values of the three groups of cells at 24, 48, and 72 hr were measured by CCK‐8 assay. Western blot analysis of the expression of cyclin D1 and CDK4 protein. **p < 0.01.

FIGURE 3

DCHS1‐Mut promotes HK‐2 cell apoptosis and autophagy. (a) Flow cytometric analysis of apoptotic cells was quantified by Annexin V‐FITC/PI double‐staining. (b) Western blot analysis of the presence of cleaved‐Caspase‐3 and cleaved‐PARP. (c) Western blot analysis of the expression of Beclin1, LC3B‐I, and LC3B‐II. (d) Immunofluorescence analysis of LC3B expression. LC3B was labeled green with Alexa Fluor 488‐conjugated secondary antibodies, cell nuclei were stained blue with DAPI. Scale bars: 50 μm. *p < 0.05, **p < 0.001.