Left ventricular non-compaction (LVNC), is a hereditary cardiomyopathy with limited treatments. Our previous study linked phosphodiesterase 4D interacting protein (PDE4DIP) to LVNC development. To explore the functional role of PDE4DIP activation in regulating cell polarity, skeleton, and energy metabolism, and to elucidate its mechanisms driving LVNC development, bioinformatics analysis was performed to compare its expression in LVNC patients and normal subjects. Overexpression and knockdown of PDE4DIP were constructed in H9C2 cells and neonatal Sprague–Dawley rat primary cardiomyocytes, respectively. Electron microscopy, MitoTracker-Green staining, and an ATP kit were employed to assess mitochondria’s morphology and functional status. Real-time quantitative PCR, western blotting, and immunofluorescence assays were employed to detect the expression of cell polarity-, skeleton-, and Rho-ROCK signaling-related genes and proteins. Cell scratching and CCK-8 assays were employed to detect cell migration and proliferation abilities of H9C2, respectively. We found that PDE4DIP expression was increased in the LVNC-derived human-induced pluripotent stem cell-derived cardiomyocytes compared with normal subjects. Furthermore, overexpression of PDE4DIP induced cytoskeletal disorganization, decreased ATP content and cell migration, and increased cell proliferation and mitochondrial vacuolation. Moreover, the knockdown of PDE4DIP promoted cytoskeleton formation and contributed to increased ATP content and elevated cell migration. Mechanically, overexpression of PDE4DIP inhibited cell polarity-, skeleton-, and Rho-ROCK signaling-related genes and proteins, which could be increased by knockdown of PDE4DIP, suggesting that a critical regulation of PDE4DIP to Rho-ROCK pathway. This discovery suggests that PDE4DIP contributes to the development of LVNC by regulating cell polarity, skeleton, and energy metabolism through the Rho-ROCK pathway.

Cyanotic congenital heart disease (CCHD), a term describing the most severe congenital heart diseases are characterized by the anatomic malformation of a right to left shunt. Although the incidence of CCHD are far less than the that of congenital heart diseases (CHD), patients with CCHD always present severe clinical features such as hypoxia, dyspnea, and heart failure. Chronic hypoxia induces hypoxemia that significantly contributes to poor prognosis in CCHD. Current studies have demonstrated that the prolyl-4-hydroxylase2 (PHD2, encoded by EGLN1)/hypoxia-inducible factor-1A (HIF-1A) pathway is a key regulator of hypoxic response. Thus, we aim to assess the associations of single polymorphisms (SNPs) of the EGLN1 gene and hypoxic response in CCHD. A missense variant of EGLN1 c.380G>C (rs1209790) was found in 46 patients (46/126), with lower hypoxia incidence and higher rate of collateral vessel formation, compared with the wild type (P < 0.05). In vitro experiments, during hypoxia, EGLN1 mutation reduced EGLN1 expression compared with the wild type, with higher HIF-1A, VEGF and EPO expression levels in the mutant. No difference in HK1 expression was observed between the mutant and wild type. CCHD patients with c.380G>C showed improved response to hypoxia compared with the wild-type counterparts. The EGLN1 c.380G>C mutation improves hypoxic response through the PHD2/HIF-1A pathway, which may provide a molecular mechanism for hypoxic response in CCHD. The effects of the EGLN1 c.380G>C mutation on CCHD prognosis deserve further investigation.