Girvan Malcolm

Small noncoding differentially methylated copy-number variants, including lncRNA genes, cause a lethal lung developmental disorder

An unanticipated and tremendous amount of the noncoding sequence of the human genome is transcribed. Long noncoding RNAs (lncRNAs) constitute a significant fraction of non-protein-coding transcripts; however, their functions remain enigmatic. We demonstrate that deletions of a small noncoding differentially methylated region at 16q24.1, including lncRNA genes, cause a lethal lung developmental disorder, alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV), with parent-of-origin effects. We identify overlapping deletions 250 kb upstream of FOXF1 in nine patients with ACD/MPV that arose de novo specifically on the maternally inherited chromosome and delete lung-specific lncRNA genes. These deletions define a distant cis-regulatory region that harbors, besides lncRNA genes, also a differentially methylated CpG island, binds GLI2 depending on the methylation status of this CpG island, and physically interacts with and up-regulates the FOXF1 promoter. We suggest that lung-transcribed 16q24.1 lncRNAs may contribute to long-range regulation of FOXF1 by GLI2 and other transcription factors. Perturbation of lncRNA-mediated chromatin interactions may, in general, be responsible for position effect phenomena and potentially cause many disorders of human development.

Neurodevelopmental Outcomes of Premature Infants Treated for Patent Ductus Arteriosus: A Population-Based Cohort Study.

OBJECTIVE To compare neurodevelopmental outcomes of extremely preterm infants diagnosed with patent ductus arteriosus (PDA) who were treated medically or surgically and those who were not diagnosed with PDA or who did not undergo treatment for PDA. STUDY DESIGN This retrospective population-based cohort study used data from a geographically defined area in New South Wales and the Australian Capital Territory served by a network of 10 neonatal intensive care units. Patients included all preterm infants born at <29 completed weeks of gestation between 1998 and 2004. Moderate/severe functional disability at 2-3 years corrected age was defined as developmental delay, cerebral palsy requiring aids, sensorineural or conductive deafness (requiring bilateral hearing aids or cochlear implant), or bilateral blindness (best visual acuity of <6/60). RESULTS Follow-up information at age 2-3 years was available for 1473 infants (74.8%). Compared with infants not diagnosed with a PDA or who did not receive PDA treatment for PDA, those with medically treated PDA (aOR, 1.622; 95% CI, 1.199-2.196) and those with surgically treated PDA (aOR, 2.001; 95% CI, 1.126-3.556) were at significantly greater risk for adverse neurodevelopmental outcomes at age 2-3 years. CONCLUSION Our results demonstrate that treatment for PDA may be associated with a greater risk of adverse neurodevelopmental outcome at age 2-3 years. This was particularly so among infants born at <25 weeks gestation. These results may support permissive tolerance of PDAs; however, reasons for this association remain to be elucidated through carefully designed prospective trials.

Pathogenetics of alveolar capillary dysplasia with misalignment of pulmonary veins

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a lethal lung developmental disorder caused by heterozygous point mutations or genomic deletion copy-number variants (CNVs) of FOXF1 or its upstream enhancer involving fetal lung-expressed long noncoding RNA genes LINC01081 and LINC01082. Using custom-designed array comparative genomic hybridization, Sanger sequencing, whole exome sequencing (WES), and bioinformatic analyses, we studied 22 new unrelated families (20 postnatal and two prenatal) with clinically diagnosed ACDMPV. We describe novel deletion CNVs at the FOXF1 locus in 13 unrelated ACDMPV patients. Together with the previously reported cases, all 31 genomic deletions in 16q24.1, pathogenic for ACDMPV, for which parental origin was determined, arose de novo with 30 of them occurring on the maternally inherited chromosome 16, strongly implicating genomic imprinting of the FOXF1 locus in human lungs. Surprisingly, we have also identified four ACDMPV families with the pathogenic variants in the FOXF1 locus that arose on paternal chromosome 16. Interestingly, a combination of the severe cardiac defects, including hypoplastic left heart, and single umbilical artery were observed only in children with deletion CNVs involving FOXF1 and its upstream enhancer. Our data demonstrate that genomic imprinting at 16q24.1 plays an important role in variable ACDMPV manifestation likely through long-range regulation of FOXF1 expression, and may be also responsible for key phenotypic features of maternal uniparental disomy 16. Moreover, in one family, WES revealed a de novo missense variant in ESRP1, potentially implicating FGF signaling in the etiology of ACDMPV.

A Comparison of the Ventilatory Response of Sleeping Newborn Lambs to Step and Progressive Hypoxaemia

1 Slight variations in the rate at which hypoxaemia develops may significantly alter the ventilatory response (VR) elicited. Here we have developed a technique to compare the VRs elicited from sleeping newborn lambs by specific (step versus progressive), short‐duration (≥ 5 min) episodes of hypoxaemia. The results may help us understand the limitations of using tests which deliver poorly defined stimuli to evaluate the postnatal development of the oxygen chemoreflex. 2 The VRs of five lambs elicited by a 5 min step or progressive reduction in the arterial oxygen saturation (Sa,O2) during quiet sleep were compared. Minute ventilation (V̇i, face mask) and Sa,O2 (pulse oximeter) were measured continuously. Alternate step (Sa,O2 reduced to 80–85 % within 60 s and maintained for a further 4 min) and progressive tests (progressive reduction in Sa,O2 to 80 % over 5 min) were administered daily between postnatal days 2–14. 3 There was a significant difference between the mean VR to step versus progressive hypoxaemia. The VR to a step challenge was biphasic (ΔV̇i=+32 ± 5% at 1 min and −1 ± 4% at 5 min; mean ±s.e.m.). Progressive hypoxaemia elicited a more subdued but sustained hyperpnoea (ΔV̇i=+11 ± 2% at 1 min and +11 ± 4% at 5 min). The difference between these two response profiles was statistically significant (P < 0.001). 4 Mean responses of lambs aged ≤ 5 days (4 ± 0.2 days) and ≥ 9 days (10 ± 0.3 days) were also compared. There was an upward shift in the position of step and progressive response curves of older lambs, reflecting primarily the increased vigour of the initial hyperpnoea elicited by step (ΔV̇i at 1 min =+20 ± 4% at 4 days vs.+40 ± 11 % at 10 days) as well as progressive (ΔV̇i at 1 min =+6 ± 2% at 4 days vs.+17 ± 5%at 10 days) hypoxaemia. 5 Qualitatively different VRs may be elicited from the newborn, depending upon the specific hypoxaemic profile administered. Therefore, to evaluate the significance of VRs elicited in response to classical, steady‐state hypoxia at different postnatal ages properly, the stimulus must be accurately described.

A key circulatory defence against asphyxia in infancy - the heart of the matter!

•  A rise in heart rate boosts cardiac output and blood pressure, improves perfusion and oxygen delivery, and speeds recovery during an emergency. •  Breathing efforts and lung inflation reflexively elevate heart rate during experimental asphyxia, and may rescue (‘auto resuscitate’) an animal from imminent death. •  We analysed whether this mechanism elevates heart rate when a healthy, sleeping infant is confronted by mild, progressive asphyxia. •  Term‐born infants aged 1–8 days rebreathed the expired gas for short periods to stimulate breathing and heart rate but not arousal from sleep. •  We show that a rising CO2 level during asphyxia is much more strongly cardio‐acceleratory than either vigorous breathing efforts or lung inflation. •  This excitatory action of CO2 on the heart develops soon after birth. •  We suggest that (i) the hypercapnia during asphyxia helps raise heart rate; (ii) excitation by respiratory manoeuvres alone is relatively weak and short lived and may not produce the sustained heart rate rise needed to counteract circulatory depression.

Dwell time and risk of central-line-associated bloodstream infection in neonates

BACKGROUND Umbilical venous catheters (UVCs) or peripherally inserted central catheters (PICCs), widely used in high-risk neonates, may have a threshold dwell time for subsequent increased risk of central-line-associated bloodstream infection (CLABSI). AIM To evaluate the CLABSI risks in neonates having either UVC, PICC, or those having both sequentially. METHODS The study included 3985 infants who had UVC or PICC inserted between 2007 and 2009 cared for in 10 regional neonatal intensive care units: 1392 having UVC only (group 1), 1317 PICC only (group 2), and 1276 both UVC and PICC (group 3). FINDINGS There were 403 CLABSIs among 6000 venous catheters inserted, totalling 43,302 catheter-days. CLABSI rates were higher in group 3 infants who were of lowest gestation (16.9 per 1000 UVC-days and 12.5 per 1000 PICC-days; median: 28 weeks) when compared with group 1 (3.3 per 1000 UVC-days; 37 weeks) and group 2 (4.8 per 1000 PICC-days; 30 weeks). Life table and Kaplan-Meier hazard analysis showed that UVC CLABSI rate increased stepwise to 42 per 1000 UVC-days by day 10, with the highest rate in group 3 (85 per 1000 UVC-days). PICC CLABSI rates remained relatively stable at 12-20 per 1000 PICC-days. Compared to PICC, UVC had a higher adjusted CLABSI risk controlled for dwell time. Among group 3, replacing UVC electively before day 4 may have a trend of lower CLABSI risk than late replacement. CONCLUSION There was no cut-off duration beyond which PICC should be removed electively. Early UVC removal and replacement by PICC before day 4 might be considered.

Mechanical ventilation in the newborn; a simplified approach. Part 1: Intermittent positive pressure ventilation

Positive pressure ventilation (PPV) is a frequent intervention in the neonatal intensive care unit. This article is directed towards paediatricians in training and attempts to cover the basics of PPV without being too technical. To do so we have employed an extensive use of graphics to illustrate the underlying principles.

Mechanical ventilation in the newborn; a simplified approach Part 2: High‐frequency ventilation

High frequency oscillatory ventilation (HFOV) is becoming an increasingly popular intervention in the neonatal intensive care unit. This article will attempt to explain the principles of HFOV. It is inherently more difficult to become skilled in this technique than in other forms of mechanical ventilation, so caution is warranted.