Background Congenital central hypoventilation syndrome (CCHS) is a rare life-threatening disorder of respiratory and autonomic regulation. It is classically caused by dominant mutations in the transcription factor PHOX2B. The objective of the present study was to identify the molecular cause of a recessive form of central hypoventilation with autonomic dysfunction.

Methods Here, we used homozygosity mapping and whole-genome sequencing in a consanguineous family with CCHS in combination with functional analyses in CRISPR/Cas9 engineered mice.

Results We report on a consanguineous family with three affected children, all tested PHOX2B mutation negative, presenting with alveolar hypoventilation and symptoms of autonomic dysregulation. Whole-genome sequencing revealed a homozygous frameshift mutation in exon 25 of the MYO1H gene (c.2524_2524delA) segregating with the phenotype in the family. MYO1H encodes for the unconventional myosin IH, which is thought to function as a motor protein in intracellular transport and vesicle trafficking. We show that Myo1h is broadly expressed in the mouse lower medulla, including the CO₂-sensitive Phox2b+ retrotrapezoid neurons. To test the pathogenicity of the variant, we engineered two Myo1h mutant mouse strains: the first strain (Myo1h*) resembling the human mutation and the second being a full knock-out (Myo1h^FS ). Whole-body plethysmography studies in Myo1h* newborns with the re-engineered human mutation revealed hypoventilation and a blunted response to CO₂, recapitulating the breathing phenotype observed in the kindred.

Conclusions Our results identify MYO1H as an important gene in CO₂ sensitivity and respiratory control and as the cause of a rare recessive form of congenital central hypoventilation.