Abstract 12739: Gap Junction Protein Beta 4 Plays an Important Role In Cardiac Hypertrophy and Cardiac Function in Human and Zebrafish
Introduction: Gap junction protein beta 4 (GJB4) encodes a transmembrane connexin protein (Cx30.3) that is a component of gap junctions. Mutations in this gene remain unknown to be associated with hypertrophic cardiomyopathy (HCM) and cardiac dysfunction.
Hypothesis: Our hypothesis is that mutations in GJB4 can cause familial HCM, which can progresses into dilated-phase HCM (d-HCM).
Methods: We have previously examined a patient and her elder brother who both presented with complicated severe HCM and whose parents are married cousins. The elder brother had died suddenly as a child and the autopsy demonstrated the development of HCM. The patient was diagnosed with HCM, which progressed to d-HCM during the 20-year follow-up. The patient has recently undergone cardiac transplantation. The parents are healthy. We hypothesized that an autosomal recessive mutation caused their familial HCM. The whole-exome sequencing was performed from each of the three participants. We generated knockout zebrafish of GJB4 and ELP2 by CRISPER/Cas9 system and analysis the volume and function of ventricle at five days post fertilization (dpf).
Results: The gene exome analysis showed 34 single nucleotide polymorphisms (SNPs) that caused amino acid change for which the patient was homozygous and both parents were heterozygous after excluding all known common (>10%) SNP gene mutations in the dbSNP. Among them, GJB4 and ELP2 were the identified genes that are possibly associated with cardiac muscle. The PolyPhen-2 scores of mutations in GJB4 and ELP2 were 1.000 and 0.001 respectively. The identified missense mutation was a 981 A>C nucleotide transition in GJB4. The resultant E204A substitution replaces a polar carboxylic glutamate with a nonpolar alanine. The endodiastolic volume was significantly lower in GJB4-KO (94pl, p<0.01) and ELP2-KO (95pl, p<0.01) than in wild type (WT, 145pl) zebrafish at 5 dpf. Furthermore the ventricular ejection fraction was decreased in GJB4 KO (0.66, p<0.01) and unchanged in ELP2-KO (0.80) respectively compared with WT zebrafish (0.82).
Conclusions: These results indicate both that mutations in GJB4 and ELP2 can cause a familial form of HCM and that GJB4 especially may be a new target for treatment of cardiac function and hypertrophy.
Author Disclosures: R. Okamoto: None. I. Goto: None. Y. Nishimura: None. I. Kobayashi: None. R. Hashizume: None. K. Dohi: None. N. Yamada: None. T. Tanaka: None. M. Ito: None.
- © 2016 by American Heart Association, Inc.