OBSTRUCTIVE APNEAS IN A MOUSE MODEL OF CONGENITAL CENTRAL HYPOVENTILATION SYNDROME

RationaleCongenital Central Hypoventilation Syndrome is characterized by life-threatening sleep hypoventilation, and is caused by PHOX2B gene mutations, most frequently the PHOX2B27Ala/+ mutation. Patients require lifelong ventilatory support. It is unclear whether obstructive apneas are part of the syndrome. ObjectivesTo determine whether Phox2b27Ala/+ mice, which presented main symptoms of Congenital Central Hypoventilation Syndrome and died within hours after birth, also presented obstructive apneas and investigate potential underlying mechanisms. MethodsApneas were classified as central, obstructive or mixed by using an original system combining pneumotachography and laser detection of abdominal movement immediately after birth. Some respiratory nuclei involved in airway patency were analyzed by immunohistochemistry and electrophysiology in brainstem-spinal cord preparation. Measurements and Main ResultsThe median (interquartile range) of obstructive apnea frequency was 2.3/min (1.5-3.3) in Phox2b27Ala/+ pups versus 0.6/min (0.4-1.0) in wildtypes (P < 0.0001). Obstructive apnea duration was 2.7s (2.3-3.9) in Phox2b27Ala/+ pups versus 1.7s (1.1- 1.9) in wildtypes (P < 0.0001). Central and mixed apneas presented similar, significant differences. In Phox2b27Ala/+ preparations, hypoglossal nucleus had fewer neurons (P < 0.05) and smaller size (P < 0.01), compared to wildtypes. Importantly, coordination of phrenic and hypoglossal activities was disrupted, as shown by the longer and variable delay of hypoglossal with respect to phrenic onset, compared to wildtypes (P < 0.001). ConclusionsThe Phox2b27Ala/+ mutation predisposed pups not only to hypoventilation and central apneas, but also obstructive and mixed apneas likely due to hypoglossal dysgenesis. These results call for attention toward obstructive events in infants with Congenital Central Hypoventilation Syndrome. Subject category15.1 Animal Models of Sleep Apnea