The various regulatory functions of long noncoding RNAs in apoptosis, cell cycle, and cellular senescence.

Long noncoding RNAs (lncRNAs) are a group of noncoding cellular RNAs involved in significant biological phenomena such as differentiation, cell development, genomic imprinting, adjusting the enzymatic activity, regulating chromosome conformation, apoptosis, cell cycle, and cellular senescence. The misregulation of lncRNAs interrupting normal biological processes has been implicated in tumor formation and metastasis, resulting in cancer. Apoptosis and cell cycle, two main biological phenomena, are highly conserved and intimately coupled mechanisms. Hence, some cell cycle regulators can influence both programmed cell death and cell division. Apoptosis eliminates defective and unwanted cells, and the cell cycle enables cells to replicate themselves. The improper regulation of apoptosis and cell cycle contributes to numerous disorders such as neurodegenerative and autoimmune diseases, viral infection, anemia, and mainly cancer. Cellular senescence is a tumor-suppressing response initiated by environmental and internal stress factors. This phenomenon has recently attained more attention due to its therapeutic implications in the field of senotherapy. In this review, the regulatory roles of lncRNAs on apoptosis, cell cycle, and senescence will be discussed. First, the role of lncRNAs in mitochondrial dynamics and apoptosis is addressed. Next, the interaction between lncRNAs and caspases, pro/antiapoptotic proteins, and also EGFR/PI3K/PTEN/AKT/mTORC1 signaling pathway will be investigated. Furthermore, the effect of lncRNAs in the cell cycle is surveyed through interaction with cyclins, cdks, p21, and wnt/ß-catenin/c-myc pathway. Finally, the function of essential lncRNAs in cellular senescence is mentioned.

Autosomal recessive cardiomyopathy and sudden cardiac death associated with variants in MYL3.

PURPOSE: Variants in genes encoding sarcomeric proteins are the most common cause of inherited cardiomyopathies. However, the underlying genetic cause remains unknown in many cases. We used exome sequencing to reveal the genetic etiology in patients with recessive familial cardiomyopathy. METHODS: Exome sequencing was carried out in three consanguineous families. Functional assessment of the variants was performed. RESULTS: Affected individuals presented with hypertrophic or dilated cardiomyopathy of variable severity from infantile- to early adulthood-onset and sudden cardiac death. We identified a homozygous missense substitution (c.170C>A, p.[Ala57Asp]), a homozygous translation stop codon variant (c.106G>T, p.[Glu36Ter]), and a presumable homozygous essential splice acceptor variant (c.482-1G>A, predicted to result in skipping of exon 5). Morpholino knockdown of the MYL3 orthologue in zebrafish, cmlc1, resulted in compromised cardiac function, which could not be rescued by reintroduction of MYL3 carrying either the nonsense c.106G>T or the missense c.170C>A variants. Minigene assay of the c.482-1G>A variant indicated a splicing defect likely resulting in disruption of the EF-hand Ca2+ binding domains. CONCLUSIONS: Our data demonstrate that homozygous MYL3 loss-of-function variants can cause of recessive cardiomyopathy and occurrence of sudden cardiac death, most likely due to impaired or loss of myosin essential light chain function.

Motor neuron diseases caused by a novel VRK1 variant - A genotype/phenotype study.

BACKGROUND: Motor neuron disorders involving upper and lower neurons are a genetically and clinically heterogenous group of rare neuromuscular disorders with overlap among spinal muscular atrophies (SMAs) and amyotrophic lateral sclerosis (ALS). Classical SMA caused by recessive mutations in SMN1 is one of the most common genetic causes of mortality in infants. It is characterized by degeneration of anterior horn cells in the spinal cord, leading to progressive muscle weakness and atrophy. Non-SMN1-related spinal muscular atrophies are caused by variants in a number of genes, including VRK1, encoding the vaccinia-related kinase 1 (VRK1). VRK1 variants have been segregated with motor neuron diseases including SMA phenotypes or hereditary complex motor and sensory axonal neuropathy (HMSN), with or without pontocerebellar hypoplasia or microcephaly. RESULTS: Here, we report an association of a novel homozygous splice variant in VRK1 (c.1159 + 1G>A) with childhood-onset SMA or juvenile lower motor disease with brisk tendon reflexes without pontocerebellar hypoplasia and normal intellectual ability in a family with five affected individuals. We show that the VRK1 splice variant in patients causes decreased splicing efficiency and a mRNA frameshift that escapes the nonsense-mediated decay machinery and results in a premature termination codon. CONCLUSIONS: Our findings unveil the impact of the variant on the VRK1 transcript and further support the implication of VRK1 in the pathogenesis of lower motor neuron diseases.

Spectrum of MYBPC3 Gene Mutations in Patients with Hypertrophic Cardiomyopathy, Reporting Two Novel Mutations from North-West of Iran.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is the leading cause of sudden cardiac death (SCD) in children and young adults and is the most frequent genetically determined cardiovascular disease following autosomal dominant pattern of inheritance. A number of genes have been shown to be responsible for HCM including MYBPC3. Cmybc, the protein encoded by MYBPC3 is a sarcomeric thick filament protein that interacts with titin, myosin, and actin to control sarcomeric gathering. Mutations in the MYBPC3 gene have been found to be associated with a history of sudden cardiac death in HCM patients. The main objective of the present study was to investigate the type and frequency of mutations in the MYBPC3 gene in HCM patients from the North-West of Iran. METHODS: All the exons and exon-intron flanking regions of the MYBPC3 gene were assessed by PCR-SSCP, and the PCR products with divergent pattern of bands on polyacrylamide gel were sent for bi-directional sequencing. RESULTS: Mutational screening of a cohort of 42 HCM cases led to the identification of 14 MYBPC3 variations. Three cases out of those variations were frameshift, 1 case was splice site, 3 cases were missense, 2 cases were synonymous, and 5 cases were intronic variants. MYBPC3 mutations (28.5%) represent the most prevalent cause of inherited HCM. The age of onset was 39.3 in MYBPC3 carrier patients. Multiple gene mutations were recognized in 1 case (2.3%). CONCLUSIONS: The results obtained from the present study indicate a significant role of MYBPC3 gene mutations in HCM disease and can be used for pre-symptomatic diagnosis of at risk family members of affected individuals.

Clinical utility of measuring expression levels of Stanniocalcin 2 in patients with colorectal cancer.

Stanniocalcin 2 (STC2) is a novel member of the Stanniocalcin family, the function of which remains unclear. Its expression is clinically significant in several cancers. The aim of this study was to evaluate the clinical value of measuring expression levels of STC2 in colorectal cancer (CRC) patients. A total of 47 tumor and matched tumor-free margin samples were obtained during surgery. The STC2 mRNA expression level in tumor and marginal tissue was examined by real-time quantitative PCR. STC2 mRNA expression levels were higher in tumor tissues than the control. (r=0.36, p≤0.02). mRNA expression level of STC2 was significantly associated with tumor size (p≤0.05) and histologic grade (p≤0.05). Our study demonstrated that STC2 was significantly expressed in CRC patients, relative to the control. STC2 can therefore be used as a biomarker to differentiate between tumor borders and margins. Analysis of STC2 gene expression during surgery could be useful in reducing surgical error in tumor removal and increasing overall success of surgery with improved tumor clearance. However, in some cases such as where the tumor is end-stage, the expression of such a biomarker may not be clinically beneficial to record. The consideration of marginal samples as a control group can help reduce the effect of confounding factors such as racial and individual differences.