Kelly Gu & Jackie Tsao

AMYLOID PRECURSOR PROTEIN REGULATES NEUROGENESIS BY

ANTAGONIZING MIR-574-5P IN THE DEVELOPING CEREBRAL CORTEX

Defining APPDefining miRNAPurposeSetup: Why miR-574-5p?Connection b/w APP and miRNAmiRnA-574-5p in depthResults: Proliferation, Migration,

DifferentiationImplications

OUTLINE

Transmembrane glycoprotein

Developing and mature brain

Cleaved by enzymes to release amyloid beta

This study: APP and microRNA

AMYLOID PRECURSOR PROTEIN (APP)

Defi ne microRNA Regulates genes to promote neurogenesis

Regulates: 1. migration of neurons2. Neurogenesis/

diff erentiation from a neural progenitor cell (NPC)

Defi ning NPC: biological cell that tends to diff erentiate into a specifi c type of cell

MICRO RNA (miRNA)

How APP regulates microRNAHow microRNA regulates proliferation,

migration, and differentiation

APP deficiency enhances neurogenesis…“but the mechanisms underlying this process are not known.” (citation) Proves relationship, not mechanism

Absence or presence of APP

PURPOSE

Microarray: looks for what APP is regulating

Found that several different microRNAs are regulated

The miRNA that was the most upregulated miR-574-5p

WHY miR-574-5P?

UPREGULATION OF MIR-574-5P IN THE CORTEX OF APP KO MICE

EXPRESSION OF miR-574-5p IN THE DEVELOPING CORTEX

Wild Type (WT) Knockout (KO)

APP negatively regulates miRNA in the cortex and the neural progenitors

APP to 0 miRNA-574-5p

Abnormal clumping of APP product in the brain

*Increase in APP≠AD

APP AND miRNA

A. APP KO = 574 upregulated B. Overexpression of APP = reduced 574 expressionC. Overexpression of APP in APP-KO NPCs decreases the upregulated 574 transcriptsD. Expression of 574 or anti-574 DID NOT aff ect the APP protein level (downstream target)

APP AND miRNA

Function via base pairing with complementary sequences of mRNA molecules

gene silencing via translational repression or targeted degradation

Essential for brain morphogenesis and neurogenesis

The specifics of miRNA-574-5p

Proliferation MigrationDiff erentiationAll three have to be tightly coordinatedessential for the proper development of the nervous

system

BREAKDOWN

APP

miRNA

neurogenesis, differentiation, and migration

proliferation

neural progenitor pool

NPC’s specializing

neurons are born

A STEP FURTHER

miRNA-574-5p

*Differentiation is involved in neurogenesis

Pathogenesis of ADDeveloping and adult brainAblation of APP in mice enhance neural

progenitor cells differentiation during embryonic development

Discovery: APP controls growth and maturation of brain cells

APP may control the balance between proliferation and differentiation of NPCs through the regulation of specific miRNAs

RESULTS

PROVING THE EFFECTS OF microRNA

microRNA APP increases proliferationWhen DNA synthesizes creates nucleotides

When neural progenitor cells are transfected with the miR-574-5p, there is 40% reduction in BrdU incorporation

PROLIFERATION

Migration of the NPCs

Subventricular zone (start) = where neurons develop

Cortical cortex (finish) = where neurons end up

MIGRATION

MIGRATION

1. miR-574-4p expression was knocked down in SVZ progenitor cells through electroporation.

2. Traced the migration process.

3. One day after: 62% of the transfected cells present in the SVZ

4. Normal migration: cells primarily distributed throughout CP, with limited number left in SVZ

5. miR-574-4p knockdown cells display a defect in ability to migrate into the CP

APP miRNA differentiation

Neurogenesis and Differentiation

NPCs from APP-knockout mice: 40-50% increase in neurogenesis compared with wild type

NPCs from miRNA-574-5p knockdown: 59% reduction in cells entering the CP

DIFFERENTIATION

miR-574-5p maintains the balance between NPCs

proliferation and differentiation in vitroregulates neuronal cell migration during

cortical development

CONCLUSION

NEUROGENESIS

PROLIFERATION

New therapeutic drugsNew biomarkersPotentially use the 574 as a biomarker miR-574-5p = important molecule that

regulates multiple phases of neurogenesis in embryonic cortex and

APP-mediated effects on neural stem cell fate

IMPLICATIONS (LAST SLIDE)

Zhang, W., Thevapriya, S., Kim, P.J., Yu, W.P., Je, H.S., Tan, E.K., Zeng, L.. (2014). Amyloid precursor protein regulates neurogenesis by antagonizing miR-574-5p in the developing cerebral cortex. Nature Communications, 5 3330. Retrieved from http://www.nature.com/ncomms/2014/140303/ncomms4330/full/ncomms4330.html#/discussion

“APP is your friend and your enemy.”

“It’s like wheat in the winter. You want a good amount.”

CITATIONS