Micro RNAs and ageing Dr Felekkis 2014 (1)

MicroRNAs and Ageing

Dr Kyriacos Felekkis Assistant Professor-Department of Life and Health Sciences

Lead in Histopathology- University of Nicosia Medical School/ SGUL Medical Program

2nd Symposium. Pathways to Indefinite Lifespans. UNIC 24th of May 2014

"It is indeed remarkable that after a seemingly miraculous feat of

morphogenesis a complex metazoan should be unable to perform the much

simpler task of merely maintaining what is already formed."

Williams, G. C. (1957)


Ageing at the Cellular Level

• Cells are the functional units in the human body.

• Altered cellular processes translates to phenotypic changes in an organism at various stages: – Embryogenesis

– Development

– Growth

– Ageing

– Death


Cellular Pathways and Genes Involved in Ageing

• Insulin Signaling Pathway

• AMPK • MAP Kinase-JNK

pathway • mTOR pathway • Mitochondrial genes • DNA repair genes • Telomere

maintenance • Senesence

Smith-Vikos T. (2012), Journal of Cell Sciences, 125, 7-17.


Activity of Cellular Pathways can be Modified by Altering Gene Expression

Gene Expression = The conversion of

the information from the gene into mRNA via transcription and then to protein via translation resulting in the phenotypic manifestation of the gene

In early 2000 A major player in Gene Expression Regulation was discovered………

MicroRNAs (miRNAs)


http://www.biology-online.org/dictionary/Conversion

http://www.biology-online.org/dictionary/Gene

http://www.biology-online.org/dictionary/MRNA

http://www.biology-online.org/dictionary/Transcription

http://www.biology-online.org/dictionary/Protein

http://www.biology-online.org/dictionary/Translation

What are MicroRNA (miRNA)?

• MicroRNAs were first described in 1993 however the term miRNA was first used in 2001 in three articles in Science

–PubMed April 2014: 29413 publications • MicroRNA are small RNA molecules (19-25 nt) that are encoded by the

genome and function in the regulation of gene expression.

Ahmed et al. BMC Bioinformatics 2009 10:105 doi:10.1186/1471-2105-10-105

Pre- miRNA

miRNAs can be found in regions between genes (intergenic) or in introns of genes (intragenic). They are transcribed as single molecules or in clusters

Merchan et al. Genome Biology 2009 10:R136 doi:10.1186/gb-2009-10-12-r136


Biogenesis of miRNAs

• Pri-miRNA

• Pre-miRNA

• Mature miRNA

• Drosha

• Exportin-5

• Dicer

• RISC


Mechanism of action of miRNAs

• Mature miRNA hybridizes with partial complementarity to the 3’ UTR of the target mRNA and inhibits translation.

• Destruction of mRNA, e.t.c.

REDUCED PROTEIN LEVELS


Function of miRNAs

• Regulate expression of more than 70% of all the protein coding genes

• Regulators of various biological processes including embryonic development, cellular proliferation, differentiation and apoptosis

• MicroRNAs play a role in complicated diseases

– 70 human disease involve miRNAs

miRNA

miRNA

miRNA

miRNA

miRNA miRNA

miRNA Many-to-Many


Role of miRNAs in Ageing

• Recently being established

• Results from experimental models used in ageing research: – C. elegans (earthworm)

– D. melanogaster (fruit fly)

– M. musculus (mouse)

– Human cell lines

• Many miRNAs have been shown to be up- or down-regulated with ageing

• Several of these miRNAs have been identified as regulators of ageing


Role of miRNAs in Ageing Non-mammalian models- C. elegans

Anti- Ageing

• Lin-4

– Targets lin-14 and inhibits DAF-16 (Boehm and Slack,

2005)

• miR-71

– Targets IIS pathway

– DNA repair pathway (de Lancaster et al., 2010)

• miR-246 (de Lancaster et al., 2010)

Pro- Ageing

• miR-239

– Targets IIS pathway

• miR-34 (de Lancaster et al., 2010)


Role of miRNAs in Ageing Non-mammalian models- C. elegans

Anti- Ageing

• miR-14

– Suppressor of cell death (Xu et al.. 2003)

• miR-8

– Human homologue of miR-200

– Regulates body size processes

(Hyun et al., 2009)


Role of miRNAs in Ageing Mammalian models- Ageing Mouse

Adapted from Smith-Vikos T , and Slack F J J Cell Sci 2012;125:7-17

Oxidative Defense Maintain Healthy Liver

Mitochondrial Function Decreased Expression during Ageing Accounts for reduced RR

Target genes involved in muscle cell proliferation


Role of miRNAs in Ageing Mammalian models- Long and Short-lived Mouse

Adapted from Smith-Vikos T , and Slack F J J Cell Sci 2012;125:7-17

Ames dwarf mouse

Lives 70% longer

Polyamine Biosynthesis

ISS Pathway

Increased BCL2 Decreased apoptosis in the brain


Role of miRNAs in Ageing Mammalian models- Human Studies

• miR-141, miR-146a, miR-146b

• (Bhaumik et al., 2009)

Stress-Induced senescence

pathway

• miR-34a, miR-335

• (Bai et al., 2011)

Reactive Oxygen Species (ROS)

pathway

• miR-34a, miR-22

• (Xu et al., 2011) p53 and Rb pathways


Role of miRNAs in Evolution Major Regulators of Phenotypic Variability

miRNAs per gene

miRNAs binding sites per gene

Examined the relationship between miRNA and CNV genes Organisms adapted to the higher levels of protein expression by accumulation of binding sites for new miRNAs on those genes and at the same time by increasing the number of miRNA binding sites per mRNA molecule.



Increased number of miRNA-binding sites on CNV genes



Unique Regulation of CNV Genes in Humans

Pathways with tighter miRNA regulation- Only

Humans: Metabolic activities

pathways

Pathways whose tight regulation is lost in

humans: Disease pathways

It is possible that the unique nature of miRNA-CNV interactions might explain some of the physiological and pathological characteristics of the human lineage!


What next?

miR-146a

miR-146b

miR-141

miR-34a miR-335

miR-22

miR-93

miR-214

miR-669c

miR-101a

miR-720

miR-721

miR-7

miR-468

miR-542

miR-698 miR-71

miR-246

miR-8 miR-239


How can we use this knowledge Against Ageing

Circulating miRNAs as biomarkers for Ageing:

• miRNA can be released from cells to bodily fluids: – Urine, Blood, Saliva, Semen, Colostrum e.t.c.

• As free molecules or in exosomes

• Isolate and detected by: Microarray, Deep Sequencing, Real-Time PCR

• Identify “miRNA-signatures” that will indicate the presence of an ageing tissue



Use miRNA inhibitors and activators to interfere with the Ageing process

• Stable

• Systemic delivery

• High tissue absorbance

Bader A.G. and Lammers P., www.iptonline.com 2nd Symposium. Pathways to Indefinite Lifespans. UNIC 24th of May 2014

http://www.iptonline.com/


Understanding the interaction of miRNAs with various genomic elements through Evolution

• Identify the interaction between other genomic elements

• Role of those interactions in gene expression regulation

• Elucitation of the gene expression regulation network in humans will potentially unveil more ageing related therapeutic targets


“The idea is to die young as late as possible”- Ashley Montagu (1905-1999)

“Do not regret growing older. It is a privilege denied to many”-

Anonymous Author


Acknowledgements

• Department of Life and Health Sciences, University of Nicosia: – George Georgiou

– Nada Kubicova

• Molecular Medicine Research Center, University of Cyprus: – Dr Konstantinos Voskarides

– Prof. Constantinos Deltas

• Medical Research Center University of Heidelberg: – Prof. Norbert Gretz

– Dr Dweep Harsh

Micro RNAs and ageing Dr Felekkis 2014 (1)

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