Biallelic DAW1 variants cause a motile ciliopathy characterized by laterality defects and subtle ciliary beating abnormalities

PURPOSE

The clinical spectrum of motile ciliopathies includes laterality defects, hydrocephalus, and infertility as well as primary ciliary dyskinesia when impaired mucociliary clearance results in otosinopulmonary disease. Importantly, approximately 30% of patients with primary ciliary dyskinesia lack a genetic diagnosis.

METHODS

Clinical, genomic, biochemical, and functional studies were performed alongside in vivo modeling of DAW1 variants.

RESULTS

In this study, we identified biallelic DAW1 variants associated with laterality defects and respiratory symptoms compatible with motile cilia dysfunction. In early mouse embryos, we showed that Daw1 expression is limited to distal, motile ciliated cells of the node, consistent with a role in left-right patterning. daw1 mutant zebrafish exhibited reduced cilia motility and left-right patterning defects, including cardiac looping abnormalities. Importantly, these defects were rescued by wild-type, but not mutant daw1, gene expression. In addition, pathogenic DAW1 missense variants displayed reduced protein stability, whereas DAW1 loss-of-function was associated with distal type 2 outer dynein arm assembly defects involving axonemal respiratory cilia proteins, explaining the reduced cilia-induced fluid flow in particle tracking velocimetry experiments.

CONCLUSION

Our data define biallelic DAW1 variants as a cause of human motile ciliopathy and determine that the disease mechanism involves motile cilia dysfunction, explaining the ciliary beating defects observed in affected individuals.

Clinical exome sequencing reveals locus heterogeneity and phenotypic variability of cohesinopathies

PURPOSE

Defects in the cohesin pathway are associated with cohesinopathies, notably Cornelia de Lange syndrome (CdLS). We aimed to delineate pathogenic variants in known and candidate cohesinopathy genes from a clinical exome perspective.

METHODS

We retrospectively studied patients referred for clinical exome sequencing (CES, N = 10,698). Patients with causative variants in novel or recently described cohesinopathy genes were enrolled for phenotypic characterization.

RESULTS

Pathogenic or likely pathogenic single-nucleotide and insertion/deletion variants (SNVs/indels) were identified in established disease genes including NIPBL (N = 5), SMC1A (N = 14), SMC3 (N = 4), RAD21 (N = 2), and HDAC8 (N = 8). The phenotypes in this genetically defined cohort skew towards the mild end of CdLS spectrum as compared with phenotype-driven cohorts. Candidate or recently reported cohesinopathy genes were supported by de novo SNVs/indels in STAG1 (N = 3), STAG2 (N = 5), PDS5A (N = 1), and WAPL (N = 1), and one inherited SNV in PDS5A. We also identified copy-number deletions affecting STAG1 (two de novo, one of unknown inheritance) and STAG2 (one of unknown inheritance). Patients with STAG1 and STAG2 variants presented with overlapping features yet without characteristic facial features of CdLS.

CONCLUSION

CES effectively identified disease-causing alleles at the mild end of the cohensinopathy spectrum and enabled characterization of candidate disease genes.

Achy breaky makey wakey heart? A randomised crossover trial of musical prompts

OBJECTIVE

Compared with no music (NM), does listening to 'Achy breaky heart' (ABH) or 'Disco science' (DS) increase the proportion of prehospital professionals delivering chest compressions at 2010 guideline-compliant rates of 100-120 bpm and 50-60 mm depths?

METHODS

A randomised crossover trial recruiting at an Australian ambulance conference. Volunteers performed three 1-min sequences of continuous chest compressions on a manikin accompanied by NM, repeated choruses of ABH and DS, prerandomised for order.

RESULTS

37 of 74 participants were men; median age 37 years; 61% were paramedics, 20% students and 19% other health professionals. 54% had taken cardiopulmonary resuscitation training within 1 year. Differences in compression rate (mode, IQR) were significant for NM (105, 99-116) versus ABH (120, 107-120) and DS (104, 103-107) versus ABH (p<0.001) but not NM versus DS (p=0.478). Differences in proportions of participants compressing at 100-120 bpm were significant for DS (61/74, 82%) versus NM (48/74, 65%, p=0.007) and DS versus ABH (47/74, 64%, p=0.007) but not NM versus ABH (p=1). Differences in compression depth were significant for NM (48 mm, 46-59 mm) versus DS (54 mm, 44-58 mm, p=0.042) but not NM versus ABH (54 mm, 43-59 mm, p=0.065) and DS versus ABH (p=0.879). Differences in proportions of subjects compressing at 50-60 mm were not significant (NM 31/74 (42%); ABH 32/74 (43%); DS 29/74 (39%); all p>0.5).

CONCLUSIONS

Listening to DS significantly increased the proportion of prehospital professionals compressing at 2010 guideline-compliant rates. Regardless of intervention more than half gave compressions that were too shallow. Alternative audible feedback mechanisms may be more effective.

Effect of listening to Nellie the Elephant during CPR training on performance of chest compressions by lay people: randomised crossover trial

OBJECTIVES

To determine whether listening to music during cardiopulmonary resuscitation (CPR) training increases the proportion of lay people delivering chest compressions of 100 per minute.

DESIGN

Prospective randomised crossover trial.

SETTING

Large UK university.

PARTICIPANTS

130 volunteers (81 men) recruited on an opportunistic basis. Exclusion criteria included age under 18, trained health professionals, and cardiopulmonary resuscitation (CPR) training within the past three months.

INTERVENTIONS

Volunteers performed three sequences of one minute of continuous chest compressions on a skill meter resuscitation manikin accompanied by no music, repeated choruses of Nellie the Elephant (Nellie), and That's the Way (I like it) (TTW) according to a pre-randomised order.

MAIN OUTCOME MEASURES

Rate of chest compressions delivered (primary outcome), depth of compressions, proportion of incorrect compressions, and type of error.

RESULTS

Median (interquartile range) compression rates were 110 (93-119) with no music, 105 (98-107) with Nellie, and 109 (103-110) with TTW. There were significant differences within groups between Nellie v no music and Nellie v TTW (P<0.001) but not no music v TTW (P=0.055). A compression rate of between 95 and 105 was achieved with no music, Nellie, and TTW for 15/130 (12%), 42/130 (32%), and 12/130 (9%) attempts, respectively. Differences in proportions were significant for Nellie v no music and Nellie v TTW (P<0.001) but not for no music v TTW (P=0.55). Relative risk for a compression rate between 95 and 105 was 2.8 (95% confidence interval 1.66 to 4.80) for Nellie v no music, 0.8 (0.40 to 1.62) for TTW v no music, and 3.5 (1.97 to 6.33) for Nellie v TTW. The number needed to treat for listening to Nellie v no music was 5 (4 to 10)-that is, the number of cardiac arrests required during which lay responders listen to Nellie to facilitate one patient receiving compressions at the correct rate (v no music) would be between four and 10. A greater proportion of compressions were too shallow when participants listened to Nellie v no music (56% v 47%, P=0.022).

CONCLUSIONS

Listening to Nellie the Elephant significantly increased the proportion of lay people delivering compression rates at close to 100 per minute. Unfortunately it also increased the proportion of compressions delivered at an inadequate depth. As current resuscitation guidelines give equal emphasis to correct rate and depth, listening to Nellie the Elephant as a learning aid during CPR training should be discontinued. Further research is required to identify music that, when played during CPR training, increases the proportion of lay responders providing chest compressions at both the correct rate and depth.