STARSMini-Symposium

Skeletal Muscle:Development, Adaptation & Disease

“Gain Without Pain”

Rhonda Bassel-Duby, Ph.D.Associate Professor of Molecular Biology

Diagram of Skeletal Muscle

Myoglobin Immunohistochemistry

Subtypes of Skeletal Myofibers

Type I (slow)Type I (slow) Type Type IIaIIa Type Type IIb IIb (fast)(fast)

white, glycolyticfatigue rapidlyrapid force developmentinsulin-resistant

red, oxidativefatigue-resistantslow contractioninsulin-sensitive

endurance training, nerve stimulation

inactivity, disease, hypogravity

Establishing Myofiber SpecializationPreprogramming of myoblasts

Pattern imposed by motor nerve

tonic

phasic

Cross-innervation Switches Fiber Types

Buller et al.,19 60

Electrical Stimulation Model

unstimulated stimulated

Molecular Marker of Muscle Plasticity

myoglobin

Electrical Signals Alter Intracellular Calcium

time (min)60 120 180 240 3000

0

0.2

0.4

[Ca

2+] i(µM

)

time (sec)

01 2 3 4 5 60

[Ca

2+] i(µM

)0.5

1.0

200 ms

10 Hz continuous 100 Hz intermittent

0.5mv

EMG

Type I fibers Type II fibers

Genetic Reprogramming of Skeletal Muscleneural activity

Ca2+

GSK3

MCIP

HDAC

Myofiber specialization (fiber type)

NFAT

calcineurin

PGC-1MEF2

CaMK

Genetic Manipulation of Signal Transduction Pathways in Muscle

Voluntary Running Cages

Voluntary Wheel Running Enhances Muscle Oxidative Capacity

Sedentary 4 wk run

Genetic Reprogramming of Skeletal Muscleneural activity

Myofiber specialization (fiber type)

NFAT

calcineurin

Ca2+

Genetic Manipulation of Signal Transduction Pathways in Muscle

Calcineurin Promotes Slow Fiber Transformation

MCK 4.8 kb calcineurin hGH

MCK-CnA*Wild-type

Slow myosin ATPase(gastrocnemius)

Naya et al. J Biol Chem, 1999.

Genetic Reprogramming of Skeletal Muscleneural activity

Ca2+

MEF2

CaMK

Myofiber specialization (fiber type)

Expression of CaMKIV* in Skeletal Muscle

MCK 4.8 kb hGHCaMKIV*

CaMKIV*

CaMKIV-brainCaMKIV-testis

brai

nhe

art

lung

liver

stom

ach

kidn

eysp

leen

test

issk

. mus

cle

CaMKIV*

tubulin

sole

usPL

AED

LW

V

sol e

usPL

AED

LW

V

Wild-type

MCK-CaMK

CaMK Promotes Slow Fibers Transformation

Wild-type

MCK-CaMK

Wu et al. Science, 2002.

CaMK Stimulates Mitochondrial Biogenesis

MC

K-C

aMK

Wild

-type

Wu et al. Science, 2002.

MCK-CaMK Muscle Shows Improved Function

Wu et al. Science, 2002.

Genetic Reprogramming of Skeletal Muscleneural activity

Myofiber specialization (fiber type)

NFAT

calcineurin

PGC-1MEF2

CaMK

Ca2+

PGC-1α Promotes Slow Fiber Transformation

MCK 4.8 kb hGHPGC-1α WT TgSol Pl Sol Pl

PGC-1α

* *

WT Tg

WT Tg

myoglobin

Tn I-slow

cytochrome c

tubulin

Hind limb Soleus/GastrocnemiusWT Tg

Lin et al. Nature, 2002.

PGC-1α Promotes Slow Fiber Transformation

Wild-type

MCK-PGC-1

metachromatic stain anti-myosin (slow)

MCK-PGC-1 Muscle is More Resistant to Fatigue

WT

Stim

ulat

ion

time

(min

)

2

4

6

8

10

12

14

16

P<0.01

MCK-PGC-1αLin et al. Nature, 2002.

Genetic Reprogramming of Skeletal Muscleneural activity

Ca2+

Myofiber specialization (fiber type)

NFAT

calcineurin

PGC-1MEF2

CaMK

Calcineurin Enhances Insulin-StimulatedGlucose Transport in Muscle

0

5

10

15

2deo

xygl

ucos

e U

ptak

e(n

mol

/mg/

20 m

in)

Wild-typeEDL

MCK-CnA*EDL

insulininsulin

-+

Ryder et al. JBC, 2003

Calcineuirn Modulates Insulin-Stimulated Glucose Uptake in Muscle

IRS1

GLUT4 Pool

GlucoseInsulin

PI3-K

AktEnhanced

Glucose UptakeCalcineurin

Neural activity

[Ca2+ ]

Modified Gene Program

Genetic Reprogramming of Skeletal Muscleneural activity

Ca2+

GSK3

MCIP

HDAC

Myofiber specialization (fiber type)

NFAT

calcineurin

PGC-1MEF2

CaMK

Skeletal Muscle Regenerates

satellite cells

Muscle Regeneration

quiescent satellite cells proliferating satellite cells

quiescent satellite cells

Growing Muscle on Synthetic Fibers

Acknowledgements

Hai Wu Daniel GarryJoseph GarciaFritz Thurmond

Sandy WilliamsEric Olson

Jim RichardsonJohn Shelton

Bruce SpiegelmanJiandie LinHarvard Medical School

Jeffrey Ryder

Frank NayaEva ChinDarrell NeuferElizabeth Cronin Jim Stull

George Ordway

Karolinska, Sweden