Promoter Variant Alters Expression of the Autophagic BECN1 Gene: Implications for Clinical Manifestations of Machado-Joseph Disease

Abstract

Autophagy is especially important in disorders where accumulation of the mutant protein is a hallmark, such as the Machado-Joseph disease/spinocerebellar ataxia type 3 (MJD/SCA3). We analyzed the promoter of the BECN1 gene, whose overexpression has been reported to exert neuroprotective effects in MJD, with the aim of finding variants that could be associated with expression levels of beclin-1 and could be tested as modifiers of onset and disease severity. A fragment encompassing the BECN1 promoter was sequenced in 95 MJD subjects and 120 controls. The impact of the variation detected on transcription factors (TFs) binding affinity was evaluated in silico and inferences concerning levels of expression were confirmed by fluorescence-based quantitative real-time PCR in a subset of 28 MJD subjects and 26 controls. Four previously described (rs60221525, rs116943570, rs34882610, and rs34037822) and one novel (c.-933delG) variants were identified. In silico analysis performed for the most frequent variants-rs60221525 C allele and rs116943570 T allele-predicted an impact of the presence of these alleles on TF binding affinity. BECN1 expression levels were in agreement with the in silico predictions, showing a tendency for decreased levels in samples with the rs60221525 C allele and for increased levels in samples with the rs116943570 T allele. MJD patients carrying the rs60221525 C allele presented a tendency for earlier estimated age at onset. Moreover, patients with the rs60221525 C allele presented a more severe clinical picture, compared to patients without this allele. The analysis of a larger number of patients from different cohorts, currently unavailable, would be required to confirm these results.

Genetic analysis of the CITED2 gene promoter in isolated and sporadic congenital ventricular septal defects

“…The promoter, regulatory region of DNA located 5′ upstream of a gene, plays an essential role in transcriptional regulation. It is well reported that DNA sequence variations in the gene promoter region may be associated with alterations in gene expression levels, putatively leading to disease 9,10 . Consequently, the analysis of promoter DNA sequence variations is important for the reason that it improves the diagnosis of disease‐causing DNA promoter variations and also expands our understanding of the role of transcriptional regulation in human disease.…”

Recent advances in understanding dominant spinocerebellar ataxias from clinical and genetic points of view

“…Other studies have also demonstrated an imbalance between autophagy and apoptosis in SCA3. For example, an increase has been reported in the levels of BECN1 , encoding the proautophagic Beclin 1 protein 46 , and BCL2/BAX ratio has been shown to be lower in pre-ataxic SCA3 carriers than in controls 47 , enhancing apoptotic processes.…”

Cathelicidins and defensins antimicrobial host defense peptides in the treatment of TB and HIV: Pharmacogenomic and nanomedicine approaches towards improved therapeutic outcomes

“…Chung et al report that although vitamin D and cathelicidin lead to HIV autophagy, it does lead to HIV-1 inhibition [ 20 ]. As ATG6 is located downstream of LL-37 and its expression is dependent on the presence of LL-37 [ 20 ], it is unclear whether genetic variants in the Beclin-1 promoter region (rs60221525, rs116943570, rs34882610, and rs34037822 and c.–933delG [ 32 ]) will impact its overall function in inducing autophagy. Additional studies are needed to understand the role of using LL-37 in the presence of these polymorphisms in Beclin-1 and its potential impact on overall management of TB and HIV.…”