What Do We Know about Dystroglycan?

Daniel Beltran

1 Outline

1. in epithelium and .

2. Role of dystroglycan.

3. and repair under normal conditions.

4. Dystroglycanopathies genetics.

5. Dystroglycanopathies muscle pathology.

2 Outline

1. Basement membrane in epithelium and skeletal muscle.

2. Role of dystroglycan.

3. Muscle contraction and repair under normal conditions.

4. Dystroglycanopathies genetics.

5. Dystroglycanopathies muscle pathology.

3 The body: Cells and connections

4 The human body: Cells and connections

Communication and …………… Contact

5 Basement Membrane

Basement membrane

6 Basement Membrane Functions

Adhesion Mechanic stability

Polarity

Survival

Compartmentalization Proliferation

More than just structure

7 Skeletal Muscle

8 Skeletal Muscle Basal Lamina

Kjaer (2004). Physiological Reviews, 84: 649. 9 Skeletal Muscle Basal lamina

Mouse skeletal muscle Human skeletal muscle

10

Goddeeris et al (2013). Nature, 503:136 Sabatelli et al (2003). Biochim Biophys Acta, 1638:57 Outline

1. Basement membrane in epithelium and skeletal muscle.

2. Role of dystroglycan.

3. Muscle contraction and repair under normal conditions.

4. Dystroglycanopathies genetics.

5. Dystroglycanopathies muscle pathology.

11 Dystroglycan

Basement Membrane

Laminin

α Dystroglycan Membrane β

Dystrophin

12 Basement Membrane compaction

Colognato 1999. JCB, 145:619 13 Outline

1. Basement membrane in epithelium and skeletal muscle.

2. Role of dystroglycan.

3. Muscle contraction and repair under normal conditions.

• Contraction. • Contraction induced muscle damage. • repair. • Satellite cells mediated muscle repair. • Debris clearance and extracellular remodeling.

14 Muscle Contraction

15 Transmission of force

DGC might contribute to “lateral transmission of force” from the to the lateral extracellular matrix.

16 Muscle Fiber Repair

Han et al (2007). Curr. Opin. Cell Biol., 19:409. 17 Satellite Cells

Satellite cells are quiescent unipotent stem cells, located underneath the basal lamina of adult skeletal muscle fibers

Basement membrane

18 From Yin et al (2013). Physiological Reviews, 93:23. Immune cells and fibroblasts 305:C241 , Physiol Cell

Neut

T cells Am Physiol J Mast (2014). (2014).

INFLAMMATION et al et

Lieber

Well integrated for a healthy muscle 19 Outline

1. Basement membrane in epithelium and skeletal muscle.

2. Role of dystroglycan.

3. Muscle contraction and repair under normal conditions.

4. Dystroglycanopathy .

5. Dystroglycanopathies muscle pathology.

20 Loss of α-Dystroglycan functional glycosylation

Normal Dystroglycanopathy Dystroglycanopathies spectrum

Congenital muscular dystrophy

CMD CMD w/ brain involvement Walker-Warburg LGMD no brain involvement Muscle-Eye-Brain (MEB) (WWS) Fukuyama-CMD (FCMD)

Severity

Adapted from Tobias Willer Dystroglycan Glycosylation Process

Generated byTobias Willer

23 Dystroglycanopathy candidate genes

Generated byTobias Willer

Introduction of exome sequencing Loss of α-Dystroglycan functional glycosylation

Normal Dystroglycanopathy Outline

1. Basement membrane in epithelium and skeletal muscle.

2. Role of dystroglycan.

3. Muscle contraction and repair under normal conditions.

4. Dystroglycanopathy genes.

5. Dystroglycanopathies muscle pathology.

• Contraction. • Contraction induced muscle damage. • Sarcolemma repair. • Satellite cells mediated muscle repair. • Debris clearance and extracellular remodeling.

26 Muscle Force Deficit

Lateral transmission of force

Dystrophic muscle displays considerable muscle weakness even in very early stages of the disease, prior to muscular atrophy.

Muscle as a unit 27 Model: αDG Large-glycan as a tunable scaffold for the basement membrane. Generated by Matt Goddeeris

Dystroglycan

28 Generated by Matt Goddeeris Basement Membrane compaction

Typical amount of glycan Reduced glycan

Large-KD Collagen Superstructure Collagen Superstructure BM { Superstructure Laminin Superstructure

Sarcolemma Sarcolemma 29 Laser membrane damage assay

Wild type Wild

Hypoglycosylated dystroglycan

Wild type dystroglycan Hypoglycosylated Fracture mechanics of the plasma membrane

Normal DGC

* Satellite cells

Dystroglycan plays a role in the attachment and/or stability of satellite cells.

Basal lamina components in the are known to govern satellite cell behavior; laminin-211 is particularly important.

Satellite cells in the muscles become exhausted, losing their regenerative capacity

Normal Ross et al (2012). Stem Cells, 30:2330. Proliferation is More fibronectin and α compromised in myd CSs collagen in myd β

DGpathy α β

From Yin et al (2013). Physiological Reviews, 93:23. 32 The human body: Cells and connections

Communication and …………… Contact

33 Immune cells and fibroblasts 305:C241 , Physiol Cell

Neut

T cells Am Physiol J Mast (2014). (2014).

INFLAMMATION et al et

Lieber

34 Possible Therapies

• Contraction. • Contraction induced muscle damage. • Muscle Fiber repair.

• Satellite cells fate. • Satellite cells exhaustion.

• Immune response and fibrosis.

35 Possible Therapies

Binding site

Agrin GalN β1,3 GlcN P ? n β1,4 Xyl GlcA Man LARGE Perlecan Pomt1/2 Laminin O α S/T α

Pharmacotherapy: β Upregulate glycosylation. Upregulate LARGE.

Gene Therapy: AAV delivery (FKRP, LARGE)

36 Possible Therapies

Pharmacotherapy: Vasodilator Anti inflammatories SCs directed therapies

Cell Therapy: Modification of patient SCs Cell Transplantation

Madaro & Bouche (2014). Biomed Res Int, 2014: 438675

37 THANK YOU!

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