A novel missense mutation in the transcription factor FOXF1 cosegregating with infantile hypertrophic pyloric stenosis in the extended pedigree linked to IHPS5 on chromosome 16q24

High-level gonosomal mosaicism for a pathogenic non-coding CNV deletion of the lung-specific FOXF1 enhancer in an unaffected mother of an infant with ACDMPV

BACKGROUND

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) results from haploinsufficiency of the mesenchymal transcription factor FOXF1 gene. To date, only one case of an ACDMPV-causative CNV deletion inherited from a very-low level somatic mosaic mother has been reported.

METHODS

Clinical, histopathological, and molecular studies, including whole genome sequencing, chromosomal microarray analysis, qPCR, and Sanger sequencing, followed by in vitro fertilization (IVF) with preimplantation genetic testing (PGT) were used to study a family with a deceased neonate with ACDMPV.

RESULTS

A pathogenic CNV deletion of the lung-specific FOXF1 enhancer in the proband was found to be inherited from an unaffected mother, 36% mosaic for this deletion in her peripheral blood cells. The qPCR analyses of saliva, buccal cells, urine, nail, and hair samples revealed 19%, 18%, 15%, 19%, and 27% variant allele fraction, respectively, indicating a high recurrence risk. Grandparental studies revealed that the deletion arose on the mother's paternal chromosome 16. PGT studies revealed 44% embryos with the deletion, reflecting high-level germline mosaicism.

CONCLUSION

Our data further demonstrate the importance of parental testing in ACDMPV families and reproductive usefulness of IVF with PGT in families with high-level parental gonosomal mosaicism.

Clinical, Histopathological, and Molecular Diagnostics in Lethal Lung Developmental Disorders

Lethal lung developmental disorders are a rare but important group of pediatric diffuse lung diseases presenting with neonatal respiratory failure. On the basis of histopathological appearance at lung biopsy or autopsy, they have been termed: alveolar capillary dysplasia with misalignment of the pulmonary veins, acinar dysplasia, congenital alveolar dysplasia, and other unspecified primary pulmonary hypoplasias. However, the histopathological continuum in these lethal developmental disorders has made accurate diagnosis challenging, which has implications for recurrence risk. Over the past decade, genetic studies in infants with alveolar capillary dysplasia with misalignment of the pulmonary veins have revealed the causative role of the dosage-sensitive FOXF1 gene and its noncoding regulatory variants in the distant lung-specific enhancer at chromosome 16q24.1. In contrast, the molecular bases of acinar dysplasia and congenital alveolar dysplasia have remained poorly understood. Most recently, disruption of the TBX4-FGF10-FGFR2 epithelial-mesenchymal signaling pathway has been reported in patients with these lethal pulmonary dysplasias. Application of next-generation sequencing techniques, including exome sequencing and whole-genome sequencing, has demonstrated their complex compound inheritance. These data indicate that noncoding regulatory elements play a critical role in lung development in humans. We propose that for more precise lethal lung developmental disorder diagnosis, a diagnostic pathway including whole-genome sequencing should be implemented.

Highly Sensitive Blocker Displacement Amplification and Droplet Digital PCR Reveal Low-Level Parental FOXF1 Somatic Mosaicism in Families with Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins

Detection of low-level somatic mosaicism [alternate allele fraction (AAF) ≤ 10%] in parents of affected individuals with the apparent de novo pathogenic variants enables more accurate estimate of recurrence risk. To date, only a few systematic analyses of low-level parental somatic mosaicism have been performed. Herein, highly sensitive blocker displacement amplification, droplet digital PCR, quantitative PCR, long-range PCR, and array comparative genomic hybridization were applied in families with alveolar capillary dysplasia with misalignment of pulmonary veins. We screened 18 unrelated families with the FOXF1 variant previously determined to be apparent de novo (n = 14), of unknown parental origin (n = 1), or inherited from a parent suspected to be somatic and/or germline mosaic (n = 3). We identified four (22%) families with FOXF1 parental somatic mosaic single-nucleotide variants (n = 3) and copy number variant deletion (n = 1) detected in parental blood samples and an AAF ranging between 0.03% and 19%. In one family, mosaic allele ratio in tissues originating from three germ layers ranged between <0.03% and 0.65%. Because the ratio of parental somatic mosaicism have significant implications for the recurrence risk, this study further implies the importance of a systematic screening of parental samples for low-level and very-low-level (AAF ≤ 1%) somatic mosaicism using methods that are more sensitive than those routinely applied in diagnostics.

A recurrent 8 bp frameshifting indel in FOXF1 defines a novel mutation hotspot associated with alveolar capillary dysplasia with misalignment of pulmonary veins

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal lung developmental disease. Affected infants manifest with severe respiratory distress and refractory pulmonary hypertension and uniformly die in the first month of life. Heterozygous point mutations or copy-number variant deletions involving FOXF1 and/or its upstream lung-specific enhancer on 16q24.1 have been identified in the vast majority of ACDMPV patients. We have previously described two unrelated families with a de novo pathogenic frameshift variant c.691_698del (p.Ala231Argfs*61) in the exon 1 of FOXF1. Here, we present a third unrelated ACDMPV family with the same de novo variant and propose that a direct tandem repeat of eight consecutive nucleotides GCGGCGGC within the ~4 kb CpG island in FOXF1 exon 1 is a novel mutation hotspot causative for ACDMPV.

Co-occurrence of infantile hypertrophic pyloric stenosis and congenital heart defects: a nationwide cohort study

BACKGROUND

Recent studies suggest that infantile hypertrophic pyloric stenosis (IHPS) and congenital heart defects (CHDs) may share some genetic risk factors, but little is known about the co-occurrence of the two conditions in patients.

METHODS

Our study cohort included 2,212,756 persons born in Denmark 1977-2013. We identified patients with IHPS and CHD in the National Patient Register. Using log-linear Poisson regression, we estimated the (incidence) rate ratios (RRs) comparing the rate of IHPS among children with a CHD diagnosis (exposed) and the rate among those without such a diagnosis.

RESULTS

Twenty-seven thousand three hundred and fifty-seven children in the cohort were diagnosed with CHD out of whom 85 developed IHPS (RR = 2.62, 95% confidence interval (CI) 2.09-3.22]). The results were similar for those with and without other congenital malformations, for preterm and term deliveries, and for both sexes. There was, however, a significant effect of calendar period (P = .003). In the period 1977-1996, the RR of IHPS given a CHD diagnosis was 1.96 (95% CI 1.41-2.64); in the period 1997-2014, the RR was 3.75 (95% CI 2.74-4.99).

CONCLUSION

CHD was associated with an increased risk of IHPS. Further research is needed to delineate molecular-level mechanisms that may affect both conditions.

Genes and transcription factors related to the adverse effects of maternal type I diabetes mellitus on fetal development

PURPOSE

Maternal type I diabetes mellitus (T1DM) increases the risk of adverse pregnancy outcomes, but the corresponding mechanism is unclear. This study aims to investigate the mechanism underlying the adverse pregnancy outcomes of maternal T1DM.

METHODS

Gene expression microarray (GSE51546) was down-loaded from the Gene Expression Omnibus. This dataset included 12 umbilical cord samples from the newborns of T1DM mothers (T1DM group, N = six) and non-diabetic mothers (control group, N = six).

RESULTS

Consequently, 1051 differentially expressed genes (DEGs) were found between the two groups. The up-regulated DEGs enriched in 30 KEGG pathways. HLA-DPA1, HLA-DMA, HLA-DMB, HLA-DQA1, HLA-DQA2 and HLA-DRA enriched in "Type I diabetes mellitus". This pathway was strongly related to 14 pathways, most of which were associated with diseases. Then, a protein-protein interaction network was constructed, and 45 potential key DEGs were identified. The 45 DEGs enriched in pathways such as "Rheumatoid arthritis", "Chemokine signaling pathway" and "Cytokine-cytokine receptor interaction" (e.g. CXCL12 and CCL5). Transcription factors (TFs) of key DEGs were predicted, and a TF-DEG regulatory network was constructed.

CONCLUSIONS

Some genes (e.g. CXCL12 and CCL5) and their TFs were significantly and abnormally regulated in the umbilical cord tissue from the pregnancies of T1DM mothers compared to that from non-T1DM mothers.

Infantile Hypertrophic Pyloric Stenosis: An Epidemiological Review

Infantile hypertrophic pyloric stenosis (IHPS) is the most common gastrointestinal disease among infants. IHPS occurs as an isolated condition or together with other congenital anomalies. Association with genetic and environmental factors, bottle feeding, younger maternal age, maternal smoking, and erythromycin administration in the first two weeks of life has been shown. Familial aggregation has been described and a family history is seen in 47.9 percent of siblings. Infants typically present with projectile vomiting associated with symptoms of failure to thrive. An olive-like mass palpable in the right upper abdominal quadrant is being reported less frequently because of earlier diagnosis by ultrasound. IHPS is generally corrected through laparoscopic pyloromyotomy. Endoscopic pyloric balloon dilation is a novel alternative. Further studies on different populations, the general population, and familial segregation to determine the prevalence, influence, and mode of familial aggregation and correlation with environmental factors are needed to determine the etiology of IHPS.

Pyloric stenosis: an enigma more than a century after the first successful treatment

Despite hypertrophic pyloric stenosis (HPS) being one of the most frequently treated pediatric surgical conditions, its etiology remains incompletely understood. We review the diagnosis and treatment of this condition with an emphasis on the evolution of surgical techniques that led to laparoscopic pyloromyotomy, the most frequently performed technique for HPS today. In addition, we review key developments in the understanding of HPS etiology and treatment, including the postulated etiology of work-induced hypertrophy of the pylorus, its association with prokinetic macrolide antibiotics, and the emerging role of atropine sulfate as a medical treatment for HPS or a rescue treatment for incomplete myotomy.