Search

Background: Biotinidase (BTD, encoded by the BTD gene) deficiency is an autosomal recessive neurometabolic disease caused by abnormal BTD activity in the biotin cycle. The clinical symptoms of patients, which are mainly neurocutaneous, range from mild to severe based on the enzyme activity level. This study aimed to identify BTD gene mutations in suspected BTD deficiency patients for the first time in the southwest of Iran and evaluate their genotype-phenotype correlations., Methods: 11 clinically and biochemically suspected patients from nine unrelated families and their available family members were subjected to Sanger sequencing. Segregation analysis was performed for novel mutation. The effect of each mutation on protein stability and hydropathicity, as well as the pathogenicity prediction of all detected mutations were assessed using various in silico analysis tools., Results: Six mutations including a novel and five previously reported mutations were identified in patients with different ethnicities. Three out of five known mutations were reported for the first time in Iran. Various common clinical manifestations and a rarely reported coexistence of celiac disease in biotinidase deficiency patients were observed. The novel missense variant c.787G > A (p.Glu263Lys) was detected in exon 4 of the BTD gene, within the biotinidase-like domain of the BTD protein. This variation was found in two cousins of a family, both developed the same initial clinical presentation. In silico analyses revealed that this missense substitution decreased protein stability and increased protein hydrophilicity. Additionally, the known frameshift mutation c.1264delG (p.val422serfster59), was the most frequent allele in the studied population. We also predicted and visualized the effects of the novel and frameshift mutations on protein structure., Conclusion: Our findings expanded the mutational spectrum of the BTD gene and provided valuable data on genotype-phenotype correlations, which helps in genetic counseling. Furthermore, the necessity of performing molecular analysis along with enzymatic analysis was highlighted by this study., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biotinidase deficiency (BTD) is an autosomal recessive disorder characterized by impaired recycling of the water-soluble vitamin biotin which leads to a spectrum of clinical manifestations ranging from mild to severe, including mainly neurological and cutaneous symptoms. Biotin supplementation is a cornerstone of treatment, but diagnosis often relies on measuring serum enzyme activity, which needs to be confirmed by genetic analysis. Thus, molecular methods become necessary in the differential diagnosis of BTD. Accordingly, countries with a high-incidence have implemented next-generation sequencing (NGS) techniques to newborn screening programs for BT. Nevertheless, NGS platforms, while well-established, present challenges in cost, labor, accessibility, and duration for newborn screening programs targeting BTD, therefore these limitations necessitate the exploration of alternative systems to ensure efficient and widespread screening. Here, third-generation sequencing platforms, notably Oxford Nanopore Technology (ONT), present promising solutions to the associated challenges. Hence, in the present study, we aimed to develop an ONT-based assay for the screening of BTD gene. After designing and optimizing primers for long-PCR using reference DNA, we assessed the performance of the ONT assay in BTD patients previously diagnosed by enzyme assay and confirmed using Illumina-based sequencing. The results demonstrate a strong correlation between the two methods, indicating the reliability of the ONT-based assay. Moreover, this first in-house single gene testing specifically tailored for BTD successfully detected previously known genetic variants with high sequencing depths, affirming the effectiveness of ONT-based sequencing in human genetics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biotinidase is the enzyme that is necessary for the recycling of the vitamin, biotin. Biotinidase deficiency is an autosomal recessively inherited metabolic disorder. If untreated, individuals with biotinidase deficiency usually develop neurological and cutaneous symptoms that can result in coma or death. Symptomatic individuals can be markedly improved by treating them with pharmacological doses of biotin; however, some clinical features may be irreversible. Fortunately, essentially all symptoms can be prevented if treatment is initiated at birth or before the symptoms develop. Because of this, the disorder is currently screened for in newborns in all states in the United States and in many countries around the world. This is the story of one laboratory's work in bringing basic science research from the discovery of the disorder to its translation into clinical medicine and its impact on the individuals with the disorder and their families., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Biotinidase deficiency (BTD) is an inherited disorder with severe clinical manifestations if not treated early. 63,119 neonates were tested for BTD according to a 3-step protocol. Biotinidase activity was initially estimated through standard colorimetric method on dried blood spots, then the suspected samples were subjected to molecular analysis of the BT gene and determination of BT activity in serum through an HPLC method. 14 infants with partial BTD (incidence 1:4508) were detected. Nine of them were homozygotes (D444H/D444H), and 4 compound heterozygotes carrying D444H combined with Q456H, T532M, C186Y and R157H, respectively. All were asymptomatic and supplemented with 10mg biotin. Although the number of screened neonates is rather small, it may be suggested that the incidence of the partial BTD infants is the highest ever reported. Detection of BTD should be added to the Greek national neonatal screening program., (Copyright © 2013. Published by Elsevier B.V.)