CIROZ variants cause heterotaxy syndrome and is specifically expressed in Gastruloids

Heterotaxy syndrome (HTX) is a rare disease caused by the disruption of left-right asymmetric development, and is often accompanied by congenital heart disease (CHD). However, the regulatory mechanism of breaking symmetry is still incompletely understood. Gastruloids can recapitulate the key characteristics of early embryogenesis, serving as a valuable in vitro model for studying left-right asymmetric development. In this study, we identified novel compound heterozygous CIROZ nonsense and missense variants in a proband with HTX by using whole-exome sequencing (WES) technology. To investigate the pathogenic mechanism, we generated Ciroz -knockout mice and found that they displayed laterality defects and died within 24 hours of birth. Furthermore, we found that Ciroz is specifically expressed in gastruloids differentiated from mouse embryonic stem cells. Collectively, our findings highlight the necessity of CIROZ in regulating left-right asymmetric development, providing a theoretical basis for genetic counseling and precision treatment of HTX.