A Pilot Study on Human CYP1B1 Gene Mutations in Three Cases with Primary Congenital Glaucoma in Calabar: Benefits for Disease Management

Background: Primary congenital glaucoma (PCG) is an inherited ocular congenital anomaly of the trabecular meshwork and anterior chamber angle, which results in optic nerve damage due to increase intraocular pressure if not properly managed. We explore CYPIBI gene mutations in three cases of primary congenital glaucoma, their family members in Calabar, helping to discuss future options for the disease management.

Methods: Clinical and molecular screenings were conducted on three cases of PCG, six parent and six siblings of the PCG patients recruited for this study. 51 unrelated, age-matched controls comprising 30 children control and 21 adult control were selected from individuals attending the eye clinic for general eye examinations that has no glaucoma or history of glaucoma. 2-3 ml of blood was collected from each participant, DNA extracted from blood, and PCR amplifications were carried out on exon 3. 25 μl of amplicon was utilized for bidirectional sequencing. The nucleotide sequences of the CYPIBI gene were edited from chromatograms using Bioedit software. Multiple sequence alignment and pairwise comparison of CYPIBI gene was carried out in the MEGA 6 software. Statistical analyses were performed using SPSS version 20 software. Significant level was set at P<0.05.

Results: Two missense mutations of CYPIBI gene namely: g.291G>C (p.Q97H) and 344C>T (P.T115M) were observed in this pilot study after the in-silico analysis. The g.291G>C mutation that resulted in an amino acid substitution of glutamine by histidine at position 97(p.Q97H) was observed in all the 3 cases of PCG, their parent (six) and siblings. The g.344C>T was detected in only one PCG patient. Two deletions of CYPIB1 gene namely: g.378-380delATG and g.535delG were also observed in this study. The g.378-380delATG was detected in all the PCG cases, their parents while g.535delG was seen in only one PCG patient that was 28 months old boy. These CYPIBI gene mutations were absents in all the controls.

Conclusion: This pilot study identified some CYPIBI gene mutations, which were peculiar to PCG cases, their parents and other family members. It suggests hereditary form of the disease although further studies are needed. This forms a baseline research for further molecular studies among PCG patients.