Present and future of antisense therapy for splicing modulation in inherited metabolic disease

Abstract

The number of mutations identified deep in introns which activate or create novel splice sites resulting in pathogenic pseudoexon inclusion in mRNA continues to grow for inherited metabolic disease (IMD) and other human genetic diseases. A common characteristic is that the native splice sites remain intact thus retaining the potential for normal splicing. Antisense oligonucleotides (AO) have been shown to modulate the splicing pattern by steric hindrance of the recognition and binding of the splicing apparatus to the selected sequences. In the case of pseudoexons, AO force the use of the natural splice sites, recovering normally spliced transcripts encoding functional protein. This review summarizes the present knowledge of antisense splicing modulation as a molecular therapy approach for pseudoexon-activating mutations, with a focus in IMD. Although the feasibility of treatment for patients with IMD has yet to be proven, it appears to be clinically promising, as positive results have been reported in cellular and animal models of disease, and antisense therapy for splicing modulation is currently in the clinical trials phase for Duchenne muscular dystrophy patients. Here, we review the most recent advances in AO stability, targeting and delivery, and other issues to be considered for an effective treatment in the clinical setting. Although the number of patients who can be potentially treated is low for each IMD, it represents an excellent therapeutical option as a type of personalized molecular medicine which is especially relevant for diseases for which there is, to date, no efficient treatment.

Pseudoexon exclusion by antisense therapy in 6-pyruvoyl-tetrahydropterin synthase deficiency

“…Many of these new exons in our genome are transposable sequence elements derived from short or long interspersed nuclear elements (SINEs or LINES, respectively), with primarily SINE-Alu sequences as a prominent source of new exons in the eukaryotic transcriptome [Vorechovsky, 2010]. Several examples of this pathogenic mechanism have been reported in human genetic disorders such as cystic fibrosis, ataxia telangiestasia, and several inherited metabolic disorders, including organic acidemias, phosphomanomutase deficiency, and 6-pyruvoyltetrahydropterin synthase deficiency [Perez et al, 2010].…”

Intron and Its Splicing Mechanism and Their Connection with Human Disease

“…In the pseudoexon events, AO give pressure to use of the natural splice sites, regaining normally spliced transcripts resulted with functional protein. Some positive results were obtained from antisense splicing modulation as a molecular therapy approach for pseudoexon-activating mutations, resulted with IMD disease and Duchenne muscular dystrophy 12 .…”

Antisense Mediated Splicing Modulation For Inherited Metabolic Diseases: Challenges for Delivery

“…The common feature is hyperammonemia that is highly toxic to the development of the central nervous system (Lanpher et al, 2003). In the most frequent urea cycle defect, ornithine transcarbamylase (OTC) deficiency (MIM 311250), analysis of hepatic biopsies identified up to three different pseudoexon insertions caused by point mutations creating novel 3¢ or 5¢ splice sites (Ogino et al, 2007;Engel et al, 2008 Desviat et al, 2006;Perez et al, 2010;Brasil et al, 2011;Sanaker et al, 2012;Perez et al, 2013). ESE, exonic splicing enhancer; 3¢ss, 3¢ splice site; 5¢ss, 5¢ splice site.…”

“…In line with this, antisense treatment in cells from IMD patients carrying intronic pseudoexon activating mutations in different gene defects responsible for organic acidemias (OAs) (PCCA, MIM 232000; PCCB, MIM 232050; and MUT, MIM 609058), monoamine neurotransmitter deficiencies (PTS, MIM 616719), glycosylation defects (PMM2, MIM 601785), and lysosomal disorders (NPC1, MIM 607623) among others (Fig. 1A), has resulted in complete recovery of protein and activity up to wild-type levels (Perez et al, 2010).…”