RAB23 loss-of-function mutation causes context-dependent ciliopathy in Carpenter syndrome.

Area of Science:

• Cell Biology
• Genetics
• Developmental Biology

Background:

• Primary cilia are crucial signaling organelles; their dysfunction causes human ciliopathies.
• RAB23, a GTPase, regulates Hedgehog signaling and ciliary transport.
• Mutations in RAB23 cause Carpenter syndrome (CS), sharing traits with ciliopathies, but the link is unclear.

Purpose of the Study:

• To investigate the in vivo role of RAB23 in primary cilia function.
• To elucidate the relationship between RAB23 loss-of-function and ciliopathy pathogenesis.
• To confirm Carpenter syndrome as a ciliopathy.

Main Methods:

• Generated and analyzed Rab23 loss-of-function models: conditional knockout (CKO) mice, patient-derived induced pluripotent stem cells (iPSCs), and zebrafish morphants.
• Assessed primary cilia formation, ciliation frequency, and cilia length in various cell types.
• Evaluated Hedgehog signaling pathway activation in Rab23-deficient cells.

Main Results:

• Rab23-CKO mutants exhibited developmental and phenotypic traits mirroring human ciliopathies and CS.
• Primary cilia formation was perturbed in a cell-type specific manner across all models.
• Neurons showed reduced ciliation frequency, while other cell types displayed shortened cilia or normal ciliation with altered length.

Conclusions:

• RAB23 deficiency leads to cell-type specific primary cilia dysfunction, underlying CS pathology.
• This study provides the first in vivo evidence for RAB23's context-specific role in primary cilia.
• Direct evidence of primary cilia anomalies in CS patient-derived cells confirms CS as a ciliopathy.