1p36 Deletion Syndrome and Left Ventricular Non-compaction Cardiomyopathy-Two Cases Report

Nonsense Variant PRDM16-Q187X Causes Impaired Myocardial Development and TGF-β Signaling Resulting in Noncompaction Cardiomyopathy in Humans and Mice

BACKGROUND

PRDM16 plays a role in myocardial development through TGF-β (transforming growth factor-beta) signaling. Recent evidence suggests that loss of PRDM16 expression is associated with cardiomyopathy development in mice, although its role in human cardiomyopathy development is unclear. This study aims to determine the impact of PRDM16 loss-of-function variants on cardiomyopathy in humans.

METHODS

Individuals with PRDM16 variants were identified and consented. Induced pluripotent stem cell-derived cardiomyocytes were generated from a proband hosting a Q187X nonsense variant as an in vitro model and underwent proliferative and transcriptional analyses. CRISPR (clustered regularly interspaced short palindromic repeats)-mediated knock-in mouse model hosting the Prdm16Q187X allele was generated and subjected to ECG, histological, and transcriptional analysis.

RESULTS

We report 2 probands with loss-of-function PRDM16 variants and pediatric left ventricular noncompaction cardiomyopathy. One proband hosts a PRDM16-Q187X variant with left ventricular noncompaction cardiomyopathy and demonstrated infant-onset heart failure, which was selected for further study. Induced pluripotent stem cell-derived cardiomyocytes prepared from the PRDM16-Q187X proband demonstrated a statistically significant impairment in myocyte proliferation and increased apoptosis associated with transcriptional dysregulation of genes implicated in cardiac maturation, including TGF-β-associated transcripts. Homozygous Prdm16Q187X/Q187X mice demonstrated an underdeveloped compact myocardium and were embryonically lethal. Heterozygous Prdm16Q187X/WT mice demonstrated significantly smaller ventricular dimensions, heightened fibrosis, and age-dependent loss of TGF-β expression. Mechanistic studies were undertaken in H9c2 cardiomyoblasts to show that PRDM16 binds TGFB3 promoter and represses its transcription.

CONCLUSIONS

Novel loss-of-function PRDM16 variant impairs myocardial development resulting in noncompaction cardiomyopathy in humans and mice associated with altered TGF-β signaling.

A Rare Case of an Infant With 1p36 Deletion Syndrome Presenting With Systolic Heart Failure Secondary to Severe Dilated Cardiomyopathy

1p36 deletion syndrome is a common terminal chromosomal deletion syndrome in humans. It is caused by the deletion of genetic material from a specific region in the short arm of chromosome 1. Symptoms range from seizure disorders, abnormalities of tone, visual and auditory disturbances. Cardiac abnormalities like left ventricular non-compaction (LVNC) and dilated cardiomyopathies (DCM) are commonly associated with this syndrome. This case report presents a 15-month-old female with dilated cardiomyopathy associated with 1p36 deletion syndrome, who has been followed from birth. Cardiac function was normal at birth with an ejection fraction of 65%. At three weeks of age, the patient presented with severe tachypnea, cyanosis, poor weight gain, and diaphoresis with feeding. Echocardiogram showed an ejection fraction of 22%. The patient was diagnosed with Modified Ross Heart Failure Class III. The patient was admitted to the cardiovascular intensive care unit where diuretics, phosphodiesterase inhibitors, and ionotropic agents were used to manage the heart failure. The patient relapsed two months later following a severe adenovirus infection. She was readmitted and heart failure medications were optimized. This patient has maintained a steady growth, meeting most milestones with no further relapse. The heterogeneity of 1p36 deletion syndrome presentation poses a diagnostic challenge for most clinicians. Cardiac involvements are very common and infants presenting with signs and symptoms of heart failure need to be screened for chromosomal abnormalities when other causes have been ruled out.