Roles of lncRNAs in brain development and pathogenesis: Emerging therapeutic opportunities

The human genome is pervasively transcribed, producing a majority of short and long noncoding RNAs (lncRNAs) that can influence cellular programs through a variety of transcriptional and post-transcriptional regulatory mechanisms. The brain houses the richest repertoire of long noncoding transcripts, which function at every stage during central nervous system development and homeostasis. An example of functionally relevant lncRNAs is species involved in spatiotemporal organization of gene expression in different brain regions, which play roles at the nuclear level and in transport, translation, and decay of other transcripts in specific neuronal sites. Research in the field has enabled identification of the contributions of specific lncRNAs to certain brain diseases, including Alzheimer's disease, Parkinson's disease, cancer, and neurodevelopmental disorders, resulting in notions of potential therapeutic strategies that target these RNAs to recover the normal phenotype. Here, we summarize the latest mechanistic findings associated with lncRNAs in the brain, focusing on their dysregulation in neurodevelopmental or neurodegenerative disorders, their use as biomarkers for central nervous system (CNS) diseases in vitro and in vivo, and their potential utility for therapeutic strategies.

Osmotic core-shell polymeric implant for sustained BDNF AntagoNAT delivery in CNS using minimally invasive nasal depot (MIND) approach

The development of drug delivery strategies for efficacious therapeutic administration directly into the central nervous system (CNS) in a minimally invasive manner remains a major obstacle hindering the clinical translation of biological disease-modifying therapeutics. A novel direct trans-nasal delivery method, termed 'Minimally-Invasive Nasal Depot' (MIND), has proved to be successful in providing high CNS uptake and brain distribution of blood-brain barrier (BBB) impermeant therapeutics via direct administration to the olfactory submucosal space in a rodent model. The present study describes the engineering of custom-made implants with a unique architecture of an "osmotically-active core" entrapping the therapeutic and a "biodegradable polymeric shell" to enable long-acting delivery using the MIND procedure. The MIND-administered implant provided sustained CNS delivery of brain derived neurotrophic factor (BDNF) AntagoNATs for up to 4 weeks in Sprague Dawley rats resulting in significant endogenous BDNF protein upregulation in several brain tissues. The biocompatibility of such core-shell implants coupled with their substantial pharmacokinetic advantages and safety of the MIND procedure highlights the practical utility and translational potential of this synergistic approach for treatment of chronic age-related neurodegenerative diseases.

Minimally Invasive Nasal Depot (MIND) technique for direct BDNF AntagoNAT delivery to the brain

The limitations of central nervous system (CNS) drug delivery conferred by the blood-brain barrier (BBB) have been a significant obstacle in the development of large molecule therapeutics for CNS disease. Though significantly safer than direct CNS administration via intrathecal (IT) or intracerebroventricular (ICV) injection, the topical intranasal delivery of CNS therapeutics has failed to become clinically useful due to a variety of practical and physiologic drawbacks leading to high dose variability and poor bioavailability. This study describes the minimally invasive nasal depot (MIND) technique, a novel method of direct trans-nasal CNS drug delivery which overcomes the dosing variability and efficiency challenges of traditional topical trans-nasal, trans-olfactory strategies by delivering the entire therapeutic dose directly to the olfactory submucosal space. We found that the implantation of a depot containing an AntagoNAT (AT) capable of de-repressing brain derived neurotrophic factor (BDNF) expression enabled CNS distribution of ATs with significant and sustained upregulation of BDNF with efficiencies approaching 40% of ICV delivery. As the MIND technique is derived from common outpatient rhinological procedures routinely performed in Ear, Nose and Throat (ENT) clinics, our findings support the significant translational potential of this novel minimally invasive strategy as a reliable therapeutic delivery approach for the treatment of CNS diseases.

Upregulation of Haploinsufficient Gene Expression in the Brain by Targeting a Long Non-coding RNA Improves Seizure Phenotype in a Model of Dravet Syndrome

Dravet syndrome is a devastating genetic brain disorder caused by heterozygous loss-of-function mutation in the voltage-gated sodium channel gene SCN1A. There are currently no treatments, but the upregulation of SCN1A healthy allele represents an appealing therapeutic strategy. In this study we identified a novel, evolutionary conserved mechanism controlling the expression of SCN1A that is mediated by an antisense non-coding RNA (SCN1ANAT). Using oligonucleotide-based compounds (AntagoNATs) targeting SCN1ANAT we were able to induce specific upregulation of SCN1A both in vitro and in vivo, in the brain of Dravet knock-in mouse model and a non-human primate. AntagoNAT-mediated upregulation of Scn1a in postnatal Dravet mice led to significant improvements in seizure phenotype and excitability of hippocampal interneurons. These results further elucidate the pathophysiology of Dravet syndrome and outline a possible new approach for the treatment of this and other genetic disorders with similar etiology.

Basic biology and therapeutic implications of lncRNA

Long non-coding RNAs (lncRNA), a class of non-coding RNA molecules recently identified largely due to the efforts of FANTOM, and later GENCODE and ENCODE consortia, have been a subject of intense investigation in the past decade. Extensive efforts to get deeper understanding of lncRNA biology have yielded evidence of their diverse structural and regulatory roles in protecting chromosome integrity, maintaining genomic architecture, X chromosome inactivation, imprinting, transcription, translation and epigenetic regulation. Here we will briefly review the recent studies in the field of lncRNA biology focusing mostly on mammalian species and discuss their therapeutic implications.