Abstract
Jalili syndrome denotes a recessively inherited combination of an eye disease (cone-rod dystrophy) and a dental disorder (amelogenesis imperfecta), which is caused by mutations in the CNNM4 gene. Whereas the ophthalmic consequences of these mutations have been studied comprehensively, the dental phenotype has obtained less attention. A defective transport of magnesium ions by the photoreceptors of the retina is assumed to account for the progressive visual impairment. Since magnesium is also incorporated in the mineral of dental hard tissues, we hypothesized that magnesium concentrations in defective enamel resulting from mutations in CNNM4 would be abnormal, if a similar deficiency of magnesium transport also accounted for the amelogenesis imperfecta. Thus, a detailed analysis of the dental hard tissues was performed in two boys of Kosovan origin affected by Jalili syndrome. Retinal dystrophy of the patients was diagnosed by a comprehensive eye examination and full-field electroretinography. A mutational analysis revealed a c.1312 dupC homozygous mutation in CNNM4, a genetic defect which had already been identified in other Kosovan families and putatively results in loss-of-function of the protein. The evaluation of six primary teeth using light and scanning electron microscopy as well as energy-dispersive X-ray spectroscopy showed that dental enamel was thin and deficient in mineral, suggesting a hypoplastic/hypomineralized type of amelogenesis imperfecta. The reduced mineral density of enamel was accompanied by decreased amounts of calcium, but significantly elevated levels of magnesium. In dentin, however, a similar mineral deficiency was associated with reduced magnesium and normal calcium levels. It is concluded that the c.1312 dupC mutation of CNNM4 results in mineralization defects of both enamel and dentin, which are associated with significantly abnormal magnesium concentrations. Thus, we could not disprove the hypothesis that a disrupted magnesium transport is involved in the development of the dental abnormalities observed in Jalili syndrome.
Highlights
The term Jalili syndrome (OMIM 217080) was proposed by Parry et al [1] for a recessively inherited combination of conerod dystrophy (CRD) and amelogenesis imperfecta (AI), which was observed in a large Arab kindred from the Gaza strip and first described by Jalili and Smith in 1988 [2]
We demonstrate that softening and discoloration of the dysplastic teeth are associated with significantly abnormal Mg concentrations in both dental hard tissues
In agreement with earlier investigations [3,5], the findings of this study showed that the c.1312 dupC homozygous mutation of CNNM4 results in AI of the hypoplastic/hypomineralized type
Summary
The term Jalili syndrome (OMIM 217080) was proposed by Parry et al [1] for a recessively inherited combination of conerod dystrophy (CRD) and amelogenesis imperfecta (AI), which was observed in a large Arab kindred from the Gaza strip and first described by Jalili and Smith in 1988 [2]. Cases from nine additional families (one from the Gaza strip, two from Kosovo, and the rest from various countries) have been reported. In these patients, ocular symptoms resulting from the retinal dystrophy became apparent early in life, usually in childhood. Ocular symptoms resulting from the retinal dystrophy became apparent early in life, usually in childhood They included photophobia, reduced vision, and nystagmus and sometimes progressed to nyctalopia [1,2,3,4,5,6]. Parry et al [1] claimed that the enamel of affected individuals appeared similar to that seen in hypomaturation type AI. Consistent taurodontism of permanent molars was noticed [1], but Michaelides et al [3] observed obliteration of the pulp chambers
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