Evaluation of CAT Variants A-89T, C389T, and C419T in Patients with Vitiligo in the Saudi Population

A novel missense variant in CAT gene causing acatalasemia with gangrenous periodontitis (Takahara's disease)

OBJECTIVES

Acatalasemia is a very rare disorder characterized by gangrenous oral ulcerations and is caused by biallelic variants in the CAT gene which encodes the catalase enzyme that decomposes the hydrogen peroxide molecules to remove their toxic effect. We report two siblings from a consanguineous Egyptian family presenting with joint hyperlaxity, loose dentitions with gangrenous periodontitis, and early loss of teeth.

STUDY DESIGN

The patients were clinically suspected to have the periodontal type of Ehlers-Danlos syndrome and thus genetic testing of C1S and C1R causative genes was carried out first by Sanger sequencing then exome sequencing (ES) was considered.

RESULTS

No pathogenic variants were detected in C1S and C1R genes then ES revealed a new homozygous missense variant in the CAT gene segregating in the family, c .635 T > G (p.Met212Arg).

CONCLUSION

We describe the first Egyptian cases with acatalasemia and expand the mutational spectrum of this rare disorder. Premature loss of teeth is an emerging finding in our cases and addresses the hazardous systemic manifestations associated with the disorder. The rarity of inherited orodental diseases renders the accurate diagnosis difficult and complicates the symptoms. Therefore, the use of advanced molecular technologies is highly advisable for early diagnosis and management of patients.

Extraciliary OFD1 Is Involved in Melanocyte Survival through Cell Adhesion to ECM via Paxillin

Primary cilia play a significant role in influencing cell fate, including apoptosis in multiple cell types. In the lesional epidermis of vitiligo patients, a reduced number of ciliated cells was observed. Our study also revealed a downregulation of oral-facial digital syndrome type 1 (OFD1) in the affected skin of vitiligo patients. However, it remains unknown whether primary cilia are involved in the control of melanocyte apoptosis. While both intraflagellar transport 88 (IFT88) and retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L) are associated with ciliogenesis in melanocytes, only the knockdown of OFD1, but not IFT88 and RPGRIP1L, resulted in increased melanocyte apoptosis. OFD1 knockdown led to a decrease in the expression of proteins involved in cell-extracellular matrix (ECM) interactions, including paxillin. The OFD1 amino acid residues 601-1012 interacted with paxillin, while the amino acid residues 1-601 were associated with ciliogenesis, suggesting that the OFD1 domains responsible for paxillin binding are distinct from those involved in ciliogenesis. OFD1 knockdown, but not IFT88 knockdown, inhibited melanocyte adhesion to the ECM, a defect that was restored by paxillin overexpression. In summary, our findings indicate that the downregulation of OFD1 induces melanocyte apoptosis, independent of any impairment in ciliogenesis, by reducing melanocyte adhesion to the ECM via paxillin.