Genome wide DNA methylation analysis of alveolar capillary dysplasia lung tissue reveals aberrant methylation of genes involved in development including the FOXF1 locus

Background Alveolar capillary dysplasia with or without misalignment of the pulmonary veins (ACD/MPV) is a lethal congenital lung disorder associated with a variety of heterozygous genomic alterations in the FOXF1 gene or its 60 kb enhancer. Cases without a genomic alteration in the FOXF1 locus have been described as well. The mechanisms responsible for FOXF1 haploinsufficiency and the cause of ACD/MPV in patients without a genomic FOXF1 variant are poorly understood, complicating the search for potential therapeutic targets for ACD/MPV. To investigate the contribution of aberrant DNA methylation, genome wide methylation patterns of ACD/MPV lung tissues were compared with methylation patterns of control lung tissues using the recently developed technique Methylated DNA sequencing (MeD-seq). Results Eight ACD/MPV lung tissue samples and three control samples were sequenced and their mutual comparison resulted in identification of 319 differentially methylated regions (DMRs) genome wide, involving 115 protein coding genes. The potentially upregulated genes were significantly enriched in developmental signalling pathways, whereas potentially downregulated genes were mainly enriched in O-linked glycosylation. In patients with a large maternal deletion encompassing the 60 kb FOXF1 enhancer, DNA methylation patterns in this FOXF1 enhancer were not significantly different compared to controls. However, two hypermethylated regions were detected in the 60 kb FOXF1 enhancer of patients harbouring a FOXF1 point mutation. Lastly, a large hypermethylated region overlapping the first FOXF1 exon was found in one of the ACD/MPV patients without a known pathogenic FOXF1 variation. Conclusion This is the first study providing genome wide methylation data on lung tissue of ACD/MPV patients. DNA methylation analyses in the FOXF1 locus excludes maternal imprinting of the 60 kb FOXF1 enhancer. Hypermethylation at the 60 kb FOXF1 enhancer might contribute to FOXF1 haploinsufficiency caused by heterozygous mutations in the FOXF1 coding region. Interestingly, DNA methylation analyses of patients without a genomic FOXF1 variant suggest that abnormal hypermethylation of exon 1 might play a role in some ACD/MPV in patients.

Nanoparticle Delivery of STAT3 Alleviates Pulmonary Hypertension in a Mouse Model of Alveolar Capillary Dysplasia

Background: Pulmonary hypertension (PH) is a common complication in patients with Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a severe congenital disorder associated with mutations in the FOXF1 gene. While the loss of alveolar microvasculature causes PH in ACDMPV patients, it is unknown whether increasing neonatal lung angiogenesis could prevent PH and right ventricular (RV) hypertrophy. Methods: We used echocardiography, RV catheterization, immunostaining and biochemical methods to examine lung and heart remodeling and RV output in Foxf1 WT/S52F mice carrying the S52F Foxf1 mutation (identified in ACDMPV patients). The ability of Foxf1 WT/S52F mutant embryonic stem cells (ESCs) to differentiate into respiratory cell lineages in vivo was examined using blastocyst complementation. Intravascular delivery of nanoparticles with a non-integrating Stat3 expression vector was used to improve neonatal pulmonary angiogenesis in Foxf1 WT/S52F mice and determine its effects on PH and RV hypertrophy. Results: Foxf1 WT/S52F mice developed PH and RV hypertrophy after birth. The severity of PH in Foxf1 WT/S52F mice directly correlated with mortality, low body weight, pulmonary artery muscularization and increased collagen deposition in the lung tissue. Increased fibrotic remodeling was found in human ACDMPV lungs. Mouse ESCs carrying the S52F Foxf1 mutation were used to produce chimeras via blastocyst complementation and to demonstrate that Foxf1 WT/S52F ESCs have a propensity to differentiate into pulmonary myofibroblasts. Intravascular delivery of nanoparticles carrying Stat3 cDNA protected Foxf1 WT/S52F mice from RV hypertrophy and PH, improved survival and decreased fibrotic lung remodeling. Conclusions: Nanoparticle therapies increasing neonatal pulmonary angiogenesis may be considered to prevent PH in ACDMPV.

Two cases of different genetic variants of alveolar capillary dysplasia associated with left-sided obstructive CHDs

Alveolar capillary dysplasia with misalignment of the pulmonary veins is an uncommon disorder that affects the lung vasculature development in the neonatal period and leads to pulmonary hypertension. We describe two patients with alveolar capillary dysplasia associated with left-sided obstructive heart defects with two different genetic variants. Our cases highlight the importance of early recognition of this disease in the setting of persistent and supra-systemic pulmonary hypertension despite surgical correction of the associated lesions. Identification of these cases will facilitate the development of a multidisciplinary approach and provide guidance to the affected families.

A Case of Alveolar Capillary Dysplasia with Misalignment of the Pulmonary Veins (ACD/MPV): The Importance of Early Genetic Testing

Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACD/MPV) is a rare, lethal condition caused by irregular pulmonary vascular maturation. Almost all cases present in the newborn period with ensuing respiratory decline within a couple days of life, ultimately leading to nearly 100% neonatal mortality. While the gold standard for diagnosis is lung biopsy, the identification of the Forkhead Box F1 (FOXF1) gene as the main genetic cause of ACD/MPV has allowed for a definitive diagnosis to be made without performing a high-risk procedure in a critically-ill neonate. This case report describes an ACD/MPV patient with hyperinsulinemia and refractory hypoglycemia as well as multiple anomalies who was found to have a novel pathogenic variant in the FOXF1 gene, identified via exome with copy number analysis, which results in premature protein termination (NM 001451.2 c.637 dup, p.Val213Glyfs*82). Our patient showcases the importance of early genetic testing to diagnose ACD/MPV given the substantial risk in obtaining a lung biopsy in a patient with hypoxemic respiratory failure, severe pulmonary hypertension, and vasodilator-induced pulmonary edema.