Clinical Ophthalmology (Sep 2021)
A Genotype–Phenotype Analysis of the Bardet–Biedl Syndrome in Puerto Rico
Abstract
Gabriel A Guardiola,1 Fabiola Ramos,2 Natalio J Izquierdo,3 Armando L Oliver2 1Department of Medicine, Universidad Central del Caribe School of Medicine, Bayamon, PR, USA; 2Department of Ophthalmology, University of Puerto Rico School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR, USA; 3Department of Surgery, University of Puerto Rico School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR, USACorrespondence: Natalio J Izquierdo 369 De Diego, Torre San Francisco, Suite 310, San Juan, PR, 00923, USATel +1 787 402-0201Email [email protected]: Bardet–Biedl syndrome is a complex heterogeneous ciliopathy caused by genetic mutations. Although establishing genotype–phenotype correlations has been challenging, some regional variations have been previously reported. Due to its relative geographic isolation, Puerto Rico has a greater prevalence of Bardet–Biedl syndrome than do other regions. We sought to characterize the most frequent genotypic variations in a local cohort of Bardet–Biedl syndrome patients and report any genotypic–phenotypic trends.Methods: Twenty-seven patients from an ophthalmology clinic in Puerto Rico with genetically confirmed Bardet–Biedl syndrome took a questionnaire inquiring about their most common symptoms. Ophthalmological information was obtained from patient records. The frequencies of the genotypic variations and symptoms were calculated.Results: In the study population, BBS1 was the most prevalent mutated gene, followed by BBS7. In the BBS1 group, we found homozygotes for c.1169T>G (p.Met390Arg) and c.1645G>T (p.Glu549*), and compound heterozygotes for c.1169T>G (p.Met390Arg) and c.1645G>T (p.Glu549*), with one patient having c.1645G>T (p.Glu549*) and c.432+1G>A (splice donor). All the BBS7 patients were homozygous for c.632C>T (p.Thr211Ile). Compared to BBS7, we found that BBS1 patients generally had a milder ocular and systemic phenotype. However, when analyzing different BBS1 variants, patients with mutations in c.1645G>T (p.Glu549*), both compound heterozygous and homozygous, had more severe systemic phenotypes, overall.Conclusion: Our study was the first detailed genotype–phenotype analysis of the Bardet–Biedl syndrome in Puerto Rico. Genetic mutations in BBS1 and BBS7 seem to be the most common culprits behind Bardet–Biedl syndrome in this population. Although patients diagnosed with BBS1 are likely to display milder systemic features, this was not the case with our BBS1 patients having the c.1645G>T (p.Glu549*) mutation. Further studies should focus on the c.1645G>T (p.Glu549*) mutation’s impact on the BBS1 gene and protein product.Keywords: ciliopathy, compound heterozygotes, retinitis pigmentosa, polydactyly
