The pathogenesis of the clinical features of oral-facial-digital syndrome type I

Primary cilia in hard tissue development and diseases

Bone and teeth are hard tissues. Hard tissue diseases have a serious effect on human survival and quality of life. Primary cilia are protrusions on the surfaces of cells. As antennas, they are distributed on the membrane surfaces of almost all mammalian cell types and participate in the development of organs and the maintenance of homeostasis. Mutations in cilium-related genes result in a variety of developmental and even lethal diseases. Patients with multiple ciliary gene mutations present overt changes in the skeletal system, suggesting that primary cilia are involved in hard tissue development and reconstruction. Furthermore, primary cilia act as sensors of external stimuli and regulate bone homeostasis. Specifically, substances are trafficked through primary cilia by intraflagellar transport, which affects key signaling pathways during hard tissue development. In this review, we summarize the roles of primary cilia in long bone development and remodeling from two perspectives: primary cilia signaling and sensory mechanisms. In addition, the cilium-related diseases of hard tissue and the manifestations of mutant cilia in the skeleton and teeth are described. We believe that all the findings will help with the intervention and treatment of related hard tissue genetic diseases.

Oro-facial-digital syndrome type I: a case report with novel features

Oro-facial-digital syndrome is a group of rare heterogeneous hereditary disorders characterized by abnormalities of the oral cavity, face and digits, along with varying degrees of mental retardation. Currently, Oro-facial-digital syndrome has been classified into 14 types and two additional unclassified variants have been proposed. Amongst the various variants described, Oro-facial-digital syndrome type I is the most common. We report an interesting subclinical sporadic case of Oro-facial-digital syndrome type I in a 21-year-old female patient. Interestingly, our patient presented with a few novel hitherto unreported clinical findings like midline pits in the philtrum area and a hamartomatous proliferation of tissue in the anterior maxillary alveolar gingival region. This case report highlights the importance of prudent histopathological-clinical correlation, which can direct the flow of clinical investigations leading to the detection and diagnosis of unsuspected conditions as learned in this case. We would also like to emphasize that comprehensive examination of new born for structural abnormalities of the orofacial region is crucial to early diagnosis of syndromes and subsequent referral for further evaluation and management.

Rubinstein-Taybi syndrome in a Saudi boy with distinct features and variants in both the CREBBP and EP300 genes: a case report

BACKGROUND

Rubinstein-Taybi syndrome (RSTS) Type 1 (OMIM 180849) is characterized by three main features: intellectual disability; broad and frequently angulated thumbs and halluces; and characteristic facial dysmorphism.

CASE PRESENTATION

We report on a Saudi boy with RSTS Type 1 and the following distinct features: a midline notch of the upper lip, a bifid tip of the tongue, a midline groove of the lower lip, plump fingers with broad / flat fingertips, and brachydactyly. The child was found to be heterozygous in the CREBBP gene for a sequence variant designated c.4963del, which is predicted to result in premature protein termination p.Leu1655Cysfs*89. The child and his father were also found to be heterozygous in the EP300 gene for a sequence variant designated c.586A > G, which is predicted to result in the amino-acid substitution p.Ile196Val.

CONCLUSION

Our report expands the clinical spectrum of RSTS to include several distinct facial and limb features. The variant of the CREBBP gene is known to be causative of RSTS Type 1. The variant in the EP300 gene is benign since the father carried the same variant and exhibited no abnormalities. However, functional studies are required to investigate if this benign EP300 variant influences the phenotype in the presence of disease-causing CREBBP gene mutations.

Wide-spread cone-shaped epiphyses in two Saudi siblings with Ellis-van Creveld syndrome

INTRODUCTION

Ellis-van Creveld (EVC) syndrome is one of the rarest ciliopathy syndromes. It is caused by mutations of the EVC and EVC2 genes which encode the EVC proteins present in the basal body of the primary cilium.

PRESENTATION OF CASES

We report on a Saudi family with two affected children. Gene analysis revealed a homozygous c.2T >A in exon 1 of the EVC gene. The most interesting finding in our patients was the wide - spread cone-shaped epiphyses in the hands and feet.

DISCUSSION

Although cone-shaped epiphyses is a known feature of EVC syndrome, it usually limited to the middle or proximal phalanges. The wide-spread cone-shaped epiphyses seen in our patients have not been previously reported.

CONCLUSION

EVC syndrome is very rare in the Middle East. We report on the first Saudi family with EVC syndrome confirmed by gene analysis. The most unique finding in our patients was the wide-spread cone-shaped epiphyses in the hands and feet. The abnormality is probably related to abnormal Indian hedgehog signaling in the primary cilium.

Expanding the allelic disorders linked to TCTN1 to include Varadi syndrome (Orofaciodigital syndrome type VI)

Varadi syndrome is a subtype of orofaciodigital syndrome (OFDS) that combines the typical features of OFDS and the posterior fossa features of Joubert syndrome. The only gene known to be mutated in Varadi syndrome is C5ORF42. In this report, we describe the phenotype of a patient with Varadi syndrome who is homozygous for a previously reported mutation in TCTN1 (NM_001082538.2:c.342-2A>G, p.Gly115Lysfs*8) and suggest that allelic disorders linked to TCTN1 include Varadi syndrome, in addition to Joubert syndrome and Meckel-Gruber syndrome.

GLI3-related polydactyly: a review

GLI3 mutations are known to be associated with nine syndromes/conditions in which polydactyly is a feature. In this review, the embryology, pathogenesis, and animal models of GLI3-related polydactyly are discussed first. This is followed by a detailed review of the genotype-phenotype correlations. Based on our review of the literature and our clinical experiences, we recommend viewing GLI3-related syndromes/conditions as four separate entities; each characterized by a specific pattern of polydactyly. These four entities are: the preaxial polydactyly type IV-Greig-acrocallosal spectrum, postaxial polydactyly types A/B, Pallister-Hall syndrome (PHS), and oral-facial-digital overlap syndrome. We also provide illustrative clinical examples from our practice including a family with a novel GLI3 mutation causing PHS. The review also introduces the term 'Forme Fruste' preaxial polydactyly and gives several conclusions/recommendations including the recommendation to revise the current criteria for the clinical diagnosis of PHS.

Consequences of Centrosome Dysfunction During Brain Development

Development requires cell proliferation, differentiation and spatial organization of daughter cells to occur in a highly controlled manner. The mode of cell division, the extent of proliferation and the spatial distribution of mitosis allow the formation of tissues of the right size and with the correct structural organization. All these aspects depend on cell cycle duration, correct chromosome segregation and spindle orientation. The centrosome, which is the main microtubule-organizing centre (MTOC) of animal cells, contributes to all these processes. As one of the most structurally complex organs in our body, the brain is particularly susceptible to centrosome dysfunction. Autosomal recessive primary microcephaly (MCPH), primordial dwarfism disease Seckel syndrome (SCKS) and microcephalic osteodysplastic primordial dwarfism type II (MOPD-II) are often connected to mutations in centrosomal genes. In this chapter, we discuss the consequences of centrosome dysfunction during development and how they can contribute to the etiology of human diseases.