Autosomal recessive polycystic kidney disease (ARPKD), usually considered to be a genetically homogeneous disease caused by mutations in PKHD1, has been associated with ciliary dysfunction. Here, we describe mutations in the DAZ interacting protein 1-like (DZIP1L) gene in patients with ARPKD, findings we have further validated by loss-of-function studies in mice and zebrafish. DZIP1L localizes to centrioles and at the distal end of basal bodies, and interacts with septin2, a protein implicated in maintenance of the periciliary diffusion barrier at the ciliary transition zone. Consistent with a defect in the diffusion barrier, we found that the ciliary membrane translocation of the PKD proteins, polycystin-1 and −2, is compromised in DZIP1L mutant cells. Together, these data provide the first conclusive evidence that ARPKD is not a homogeneous disorder, and establishes DZIP1L as a second gene involved in its pathogenesis.

Defects such as cleft lip with or without cleft palate (CL/P) are among the most common craniofacial birth defects in humans. In many cases, the underlying molecular and cellular mechanisms that result in these debilitating anomalies remain largely unknown. Perturbed hedgehog (HH) signalling plays a major role in craniofacial development, and mutations in a number of pathway constituents underlie craniofacial disease. In particular, mutations in the gene encoding the major HH receptor and negative regulator, patched1 (PTCH1), are associated with both sporadic and familial forms of clefting, yet relatively little is known about how PTCH1 functions during craniofacial morphogenesis. To address this, we analysed the consequences of conditional loss of Ptch1 in mouse neural crest cell-derived facial mesenchyme. Using scanning electron microscopy (SEM) and live imaging of explanted facial primordia, we captured defective nasal pit invagination and CL in mouse embryos conditionally lacking Ptch1. Our analysis demonstrates interactions between HH and FGF signalling in the development of the upper lip, and reveals cell-autonomous and non-autonomous roles mediated by Ptch1. In particular, we show that deletion of Ptch1 in the facial mesenchyme alters cell morphology, specifically in the invaginating nasal pit epithelium. These findings highlight a critical link between the neural crest cells and olfactory epithelium in directing the morphogenesis of the mammalian lip and nose primordia. Importantly, these interactions are critically dependent on Ptch1 function for the prevention of orofacial clefts.

Ciliopathies are a group of genetic disorders caused by defective assembly or dysfunction of the primary cilium, a microtubule-based cellular organelle that plays a key role in developmental signalling. Ciliopathies are clinically grouped in a large number of overlapping disorders, including the orofaciodigital syndromes (OFDS), the short rib polydactyly syndromes and Jeune asphyxiating thoracic dystrophy. Recently, mutations in the gene encoding the centriolar protein C2CD3 have been described in two families with a new sub-type of OFDS (OFD14), with microcephaly and cerebral malformations. Here we describe a third family with novel compound heterozygous C2CD3 mutations in two fetuses with a different clinical presentation, dominated by skeletal dysplasia with no microcephaly. Analysis of fibroblast cultures derived from one of these fetuses revealed a reduced ability to form cilia, consistent with previous studies in C2cd3-mutant mouse and chicken cells. More detailed analyses support a role for C2CD3 in basal body maturation; but in contrast to previous mouse studies the normal recruitment of the distal appendage protein CEP164 suggests that this protein is not sufficient for efficient basal body maturation and subsequent axonemal extension in a C2CD3-defective background.