A novel mutation in the OFD1 (Cxorf5) gene may contribute to oral phenotype in patients with oral-facial-digital syndrome type 1

OFD1: One gene, several disorders

The OFD1 protein is necessary for the formation of primary cilia and left–right asymmetry establishment but additional functions have also been ascribed to this multitask protein. When mutated, this protein results in a variety of phenotypes ranging from multiorgan involvement, such as OFD type I (OFDI) and Joubert syndromes (JBS10), and Primary ciliary dyskinesia (PCD), to the engagement of single tissues such as in the case of retinitis pigmentosa (RP23). The inheritance pattern of these condition differs from X‐linked dominant male‐lethal (OFDI) to X‐linked recessive (JBS10, PCD, and RP23). Distinctive biological peculiarities of the protein, which can contribute to explain the extreme clinical variability and the genetic mechanisms underlying the different disorders are discussed. The extensive spectrum of clinical manifestations observed in OFD1‐mutated patients represents a paradigmatic example of the complexity of genetic diseases. The elucidation of the mechanisms underlying this complexity will expand our comprehension of inherited disorders and will improve the clinical management of patients.

Odontoblast differentiation is regulated by an interplay between primary cilia and the canonical Wnt pathway

Primary cilium is a protruding cellular organelle that has various physiological functions, especially in sensory reception. While an avalanche of reports on primary cilia have been published, the function of primary cilia in dental cells remains to be investigated. In this study, we focused on the function of primary cilia in dentin-producing odontoblasts. Odontoblasts, like most other cell types, possess primary cilia, which disappear upon the knockdown of intraflagellar transport protein 88. In cilia-depleted cells, the expression of dentin sialoprotein, an odontoblastic marker, was elevated, while the deposition of minerals was slowed. This was recapitulated by the activation of canonical Wnt pathway, also decreased the ratio of ciliated cells. In dental pulp cells, as they differentiated into odontoblasts, the ratio of ciliated cells was increased, whereas the canonical Wnt signaling activity was repressed. Our results collectively underscore the roles of primary cilia in regulating odontoblastic differentiation through canonical Wnt signaling. This study implies the existence of a feedback loop between primary cilia and the canonical Wnt pathway.

Orofaciodigital syndrome type II (Mohr syndrome): a case report

Background

Orofacial digital syndrome is a rare genetic disorder with oral cavity, facial and digits anomalies. Orofacial digital syndrome type II, also called the “Mohr syndrome” is a very rare subtype that has been reported scarcely in Asia especially in Japanese patients.

Case presentation

The case is an Iranian 5-year old girl who had been admitted for orthopedic surgery. She surprisingly had pre and postaxial polydactyly of all the four limbs concurrent with syndromic face and most of the features of Orofaciodigital syndrome type II.

Conclusion

Mohr syndrome, anesthesia and surgical considerations are discussed in this case report. It is recommended to consider these considerations and the possibility of OFDS in every child with pre and postaxial polydactyly of the four limbs and to try to distinguish type II from other types of ODFS.

Oral-Facial-Digital Syndrome Type 1: Further Clinical and Molecular Delineation in 2 New Families

OBJECTIVE

Oral-facial-digital syndrome type 1 (OFD1) [OMIM 311200] is a rare genetic disorder associated with congenital anomalies of the oral cavity, face, and digits. This condition is associated with mutations in the OFD1 gene. Our objective was to recruit patients with the OFD1 clinical phenotype without genetic confirmation, aiming to identify genetic variants in the OFD1 gene.

DESIGN

Three patients from 2 unrelated families were recruited into our study. We employed a variety of genomic techniques on these patients, including candidate gene analysis, array comparative genomic hybridization, whole-exome sequencing, and whole-genome sequencing.

RESULTS

We investigated 3 affected patients from 2 unrelated families with a clinical diagnosis of OFD1. We discovered a novel pathogenic dominant missense mutation c.635G>C (p.Arg212Pro) in the OFD1 gene in one family. A novel frameshift, loss-of-function mutation c.306delA (p.Glu103LysfsTer42) was detected in the affected patient in the second family.

CONCLUSIONS

These new genetic variants will add to the spectrum of known OFD1 mutations associated with the OFD1 disorder. Our study also confirms the variable phenotypic presentation of OFD1 and its well-recognized association with central nervous system malformations and renal anomalies. Molecular diagnostic confirmation achieved in these families will have positive implications for their medical management.

Truncating mutations in exons 20 and 21 of OFD1 can cause primary ciliary dyskinesia without associated syndromic symptoms

BACKGROUND

Primary ciliary dyskinesia (PCD) is a motile ciliopathy, whose symptoms include airway infections, male infertility and situs inversus. Apart from the typical forms of PCD, rare syndromic PCD forms exist. Mutations of the X-linked OFD1 gene cause several syndromic ciliopathies, including oral-facial-digital syndrome type 1, Joubert syndrome type 10 (JBTS10), and Simpson-Golabi-Behmel syndrome type 2, the latter causing the X-linked syndromic form of PCD. Neurological and skeletal symptoms are characteristic for these syndromes, with their severity depending on the location of the mutation within the gene.

OBJECTIVES

To elucidate the role of motile cilia defects in the respiratory phenotype of PCD patients with C-terminal OFD1 mutations.

METHODS

Whole-exome sequencing in a group of 120 Polish PCD patients, mutation screening of the OFD1 coding sequence, analysis of motile cilia, and magnetic resonance brain imaging.

RESULTS

Four novel hemizygous OFD1 mutations, in exons 20 and 21, were found in men with a typical PCD presentation but without severe neurological, skeletal or renal symptoms characteristic for other OFD1-related syndromes. Magnetic resonance brain imaging in two patients did not show a molar tooth sign typical for JBTS10. Cilia in the respiratory epithelium were sparse, unusually long and displayed a defective motility pattern.

CONCLUSION

Consistent with the literature, truncations of the C-terminal part of OFD1 (exons 16-22) almost invariably cause a respiratory phenotype (due to motile cilia defects) while their impact on the primary cilia function is limited. We suggest that exons 20-21 should be included in the panel for regular mutation screening in PCD.