Characterization of the 3'UTR of the BTD gene and identification of regulatory elements and microRNAs

Abstract

Reduced biotinidase activity is associated with a spectrum of deficiency ranging from total deficiency to heterozygous levels, a finding that is not always explained by the pathogenic variants observed in the BTD gene. The investigation of miRNAs, regulatory elements and variants in the 3'UTR region may present relevance in understanding the genotype-phenotype association. The aims of the study were to characterize the regulatory elements of the 3'UTR of the BTD gene and identify variants and miRNAs which may explain the discrepancies observed between genotype and biochemical phenotype. We evaluated 92 individuals with reduced biotinidase activity (level of heterozygotes = 33, borderline = 35, partial DB = 20 or total DB= 4) with previously determined BTD genotype. The 3'UTR of the BTD gene was Sanger sequenced. In silico analysis was performed to identify miRNAs and regulatory elements. No variants were found in the 3'UTR. We found 97 possible miRNAs associated with the BTD gene, 49 predicted miRNAs involved in the alanine, biotin, citrate and pyruvate metabolic pathways and 5 genes involved in biotin metabolism. Six AU-rich elements were found. Our data suggest variants in the 3'UTR of BTD do not explain the genotype-phenotype discrepancies found in Brazilian individuals with reduced biotinidase.

A Different Approach to the Evaluation of the Genotype-Phenotype Relationship in Biotinidase Deficiency: Repeated Measurement of Biotinidase Enzyme Activity

“…[2] There have been many studies to date evaluating the relationship between genotypes and phenotypes in biotinidase enzyme de ciency, however biotinidase enzyme activity measurements were made only once or twice in most of them. [2][3][4][5][6][7][8][9][10][11][12][13] As biotinidase enzyme activity measurements may be affected by such external factors as age, prematurity, neonatal jaundice and the temperature of the sample during storage or transport, [1; 4; 14; 15] it is suggested that a diagnosis of biotinidase enzyme de ciency should be based on multiple measurements of plasma biotinidase enzyme activity. [4] We believe that repeated measurement of biotinidase enzyme activity during the clinical follow-up of patients with biotinidase enzyme de ciency can lead to a better evaluation of the genotype and phenotype relationship and the exclusion of external factors.…”