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Miro1-mediated mitochondrial dynamics in Breast Cancer

An in-depth analysis of the Mouse Model

Ali A. Termos

March 4^th, 2025

Cunniff Lab

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What is Miro1?

Sources: [ 1 ] , [ 6 ]

Miro1 AlphaFold Prediction (v2.3.2)

Confidence for predicted structure

GTPase Domains

Ca²⁺ EF-hand motifs

C-terminal Tail

Miro1 GTPase Activity

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Role of Miro1

Resources are Localized

Microtubule

Kinesin

Track 2

Track 1

Mitochondrion

Miro1

Cell

ATP & mROS

Adaptor Protein

Mitochondrial Trafficking

Local region

Sources: [ 1 ] , [ 5 ]

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Breast cancer relevance

Source: [ 6 ]

Survival Analysis of MIRO1…

Breast Cancer Patients (TCGA)

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Mouse model: involved genes

Sources: [ 2 ] , [ 4 ] , [ 5 ]

MTB

MIC

Floxed Miro1

MMTV-LTR

rtTA

Miro1

Exon 1

Miro1

Exon 2

Miro1

Exon 3

Miro1

Exon 4

LoxP

Tet-o

PyVmT

IRES

CRE

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Mouse model: how it works?

Sources: [ 2 ] , [ 4 ] , [ 5 ]

MTB

MIC

Floxed Miro1

MMTV-LTR

rtTA

Tet-o

PyVmT

IRES

CRE

Mammary Gland Development

Estrogen

Doxycycline

Weeks

Infused

Food

Miro1

Exon 1

Miro1

Exon 2

Miro1

Exon 3

Miro1

Exon 4

LoxP

CRE

rtTA

+

Mammary Epithelial Cell

8

PyVmT

SRC

MAPK & PI3K

Pathways

Cell Transformation

PyVmT

rtTA

We run our experiments at the age of sexual maturity, which is around 8 weeks
Mammary glands of female mice at that time are flooded with estrogen
Alongside Estrogen, the presence of Doxycycline infused food pellets, we can activate the model
Estrogen binds the MTB promoter, expressing in turn rtTA
Which itself forms a complex with doxycycline and that complex binds to MIC’s promoter Tet-o, which activates MIC
This leads to the expression of PyVMT and CRE
CRE finds its way to Miro1 and cuts at the LoxP sites, knocking out Miro1
At the same time, PyVmT is being expressed, binding to the inner membrane of the cell
It acts as a docking station for a non-receptor tyrosine kinase called SRC
Through a cascade of phosphorylation events, SRC kinases bind PyVmT, activating in turn the MAPK & PI3K pathways
Which triggers downstream signaling that leads to cell transformation
This is how the model concurrently triggers cancer formation and Miro1 knockout.

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Mouse model: mice setup

Sources: [ 3 ] , [ 5 ]

Gene Legend

Miro1

Floxed Miro1

MTB

MIC

MTB ; MIC ; WT

MTB ; MIC ; HET

MTB ; MIC ; fl / fl

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Mouse model: confirming the transgenes

Source: [ 5 ]

Floxed Miro1

Miro1

Exon 1

Miro1

Exon 2

Miro1

Exon 3

Miro1

Exon 4

LoxP

Miro1

Exon 1

Miro1

Exon 2

Miro1

Exon 3

Miro1

Exon 4

Genotyping…

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Mouse model: observed phenotypes

Source: [ 5 ]

Hematoxylin and Eosin (H&E) staining…

No Doxycycline

Corresponding genotypes:

+

Legend

Miro1 Gene

LoxP Sequence

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Mouse model: stats

Source: [ 5 ]

% Tumor-free Mice

% Lung Metastasis of Mice

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References

[ 1 ] Eberhardt, E. L., Ludlam, A. V., Tan, Z., & Cianfrocco, M. A. (2020). Miro: A molecular switch at the center of mitochondrial regulation. Protein Science, 29 (6), 1269–1284. https://doi.org/10.1002/pro.3839

[ 2 ] Guy, C. T., R. D. Cardiff, and W. J. Muller. Induction of Mammary Tumors by Expression of Polyomavirus Middle T Oncogene: A Transgenic Mouse Model for Metastatic Disease, 1992.

[ 3 ] Nguyen, T. T., Oh S. S., Weaver D., Lewandowska A., Maxfield D., Schuler M. H., Smith N. K., Macfarlane J., Saunders G., Palmer C. A., Debattisti V., Koshiba T., Pulst S., Feldman E. L., Hajnóczky G., Shaw J. M. Loss of Miro1-directed mitochondrial movement results in a novel murine model for neuron disease. Proc Natl Acad Sci U S A, vol. 111, no. 35, Sep. 2, 2014, pp. E3631-40. doi: 10.1073/pnas.1402449111. Epub 2014 Aug 18. PMID: 25136135; PMCID: PMC4156725.

[ 4 ] Rao, T., J. J. Ranger, H. W. Smith, S. H. Lam, L. Chodosh, and W. J. Muller. Inducible and coupled expression of the polyomavirus middle T antigen and Cre recombinase in transgenic mice: An in vivo model for synthetic viability in mammary tumour progression. Breast Cancer Research, vol. 16, no. 1, Jan. 2014, doi: 10.1186/bcr3603.

[ 5 ] Termos, R., A. Muskat, N. Shannon, M. McCoy, A. A. Termos, C. Palmer, T. Messier, M. Chang, and B. Cunniff. Tissue-specific Miro1 knockdown inhibits mouse breast cancer tumorigenesis. (In progress).

[ 6 ] Uhlen, M., Zhang C., Lee S., Sjöstedt E., Fagerberg L., Bidkhori G., Benfeitas R., Arif M., Liu Z., Edfors F., Sanli K., von Feilitzen K., Oksvold P., Lundberg E., Hober S., Nilsson P., Mattsson J., Schwenk J. M., Brunnström H., Glimelius B., Sjöblom T., Edqvist P. H., Djureinovic D., Micke P., Lindskog C., Mardinoglu A., Ponten F. A pathology atlas of the human cancer transcriptome. Science (1979), vol. 357, no. 6352, Aug. 18, 2017, eaan2507. doi: 10.1126/science.aan2507. PMID: 28818916.

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Thank you

Q&A