Characterising the variation of MSTN across livestock animals would be fundamental in identifying elite animals possessing the double muscling trait and bringing them in breeding policy for improved meat production

1. Myostatin (MSTN) and its
Applications in Animal Breeding
Dr Wani AAhad
M.V.Sc
Animal Biotechnology
SKUAST-K

2.  Recent advancements in sequencing and genotyping technologies
have enabled a rapid evolution in methods for meat animal selection.
 New tools will become available for meat producers to implement
in the endeavor to efficiently produce high quality meat for today’s
consumer.
 The ultimate objective of improving meat quality either by
breeding or rearing factors.
Introduction

3. Introduction
 For genetic purposes, polymorphisms in some key genes have been
reported for their association with meat quality traits.
 The sequencing of the bovine genome has dramatically increased
the number of available gene polymorphisms.
 The association of these new polymorphisms with the variability in
meat quality (e.g. tenderness, marbling) for different breeds in
different rearing systems will be a very important issue.

4.  For rearing purposes, global gene expression profiling at the
mRNA or protein level has already shown that previously
unsuspected genes may be associated either with muscle
development or growth, and may lead to the development of new
molecular indicators of tenderness or marbling.
 Some of these genes are specifically regulated by genetic and
nutritional factors or differ between different meat cuts.
(Hocquette et al., 2007)
Introduction

5. Genes influencing Growth traits
S.No. GENE CHROMOSOME
1 MSTN: Myostatin (GDF-8) 2
2 CAST: Calpastatin 5
3 CLPG: Callipyge 18
4 LEP: Leptin gene 3
5 Casein: α casein 6
6 GH: Growth Hormone 19
7 GHR: Bovine Growth Hormone Receptor 20
8 IGF-I: Insulin Like Growth Factor I 5
9 POU1F1: Pituitary Specific Transcription Factor-1 1

6.  An Example for meat trait, a visibly distinct muscular hypertrophy,
commonly known as double muscling, occurs with high frequency
in the Belgian Blue and Piedmontese cattle breeds.
 Kambadur et al ., (1997) have evaluated this gene as a candidate
gene for double-muscling condition by cloning the bovine myostatin
cDNA and examining the expression pattern and sequence of the
gene in normal and double-muscled cattle.
 Moreover, sequence analysis reveals mutations in heavy-muscled
cattle of both breeds.
Contd…

7.  Myostatin is almost only expressed in
skeletal muscle.
 Myostatin could first be detected at day 9.5
post-coitum.
 Myostatin knock-out mice muscles weigh
2-3 times more than those of wild type
animals.
 Hyperplasia (more fibres) and hypertrophy
(larger fibres); more DNA.
(McPherron et al., 1997)
Discovery of Myostatin Gene (GDF-8)
WILD TYPE
KNOCK OUT MICE

8.  Myostatin (MSTN/GDF8) is a member of the
transforming growth factor-β super family.
 It is produced by skeletal muscle and acts as a
negative regulator of muscle growth.
 It has an essential role in the regulation of
muscle growth and meat quality.
(Zhang et al., 2013)
Myostatin Gene

9. MSTN gene
 The myosatin prepropeptide is made
up of 3 subunits:
1. C-terminal peptide
2. Signal Sequence
3. N-terminal peptide
 For myostatin to be in its active form:
It needs to cleaved free from the
propeptide complex:
•Protease.

10. MSTN gene
Location 2q11-q12
Size 6.2 kbp
Exons 3
Introns 2

11. Physiological Action
 Myostatin and Activin interact and activate a heterodimeric receptor complex,
comprising activin receptor 2 (ACVR2) and activin receptor-like kinase 4 (ALK4).
 Myostatin/activin signaling in myofibers is mediated by phosphorylation and
nuclear translocation of Smad2 or Smad3 (Small mothers against decapentaplegic)
transcription factors, and formation of heterodimers with Smad4.
 Smad4 complex binds to the promoters in the target genes & forms a
transcription repressor complex.
(Rehfeldt et al., 2000)

12. Contd…
 Myostatin represses the levels of myogenic regulatory
factors (MyoD, Myf4, Myf5 and myogenin), leading to the
inhibition of myogenic differentiation.
 Myostatin inhibits myogenic differentiation factor (MyoD)
activity and expression via Smad 3 resulting the failure of the
myoblasts to differentiate into myotubes (Mature Muscle
Fibers).
(Rehfeldt et al., 2000)

13.  Myostatin also inhibits Akt (Protein Kinase B /
Serine/theronine specific protein kinase).
 That is responsible to cause Muscle hypertrophy.
 Through activation of protein synthesis.
(Sartori et al., 2014)
How does myostatin inhibit
growth?

14.  Furthermore, MSTN has been shown to
directly prevent Cell Cycle G1 to S phase
transition by decreasing the levels of Cyclin
dependent kinase complex 2 ( CDK2).
(McKoy et al., 2007)
Contd…

15. Myostatin inhibitors
 Obviously, bodybuilders are very keen to inhibit myostatin in
order to promote muscle growth further.
 Like:
 MYOSTAT
 MYO-ZAP
 MYO BLAST
 MYO-X

16. Super
TGF

17. MSTN gene Polymorphism
 Mutations in the MSTN gene can inactivate its expression or
produce a non-functional protein, which leads to dramatic
muscularity and a “double-muscling” phenomenon in many
species.
(Grisolia et al., 2009)
 It has been considered as an important candidate gene for growth
and development of domestic animals .
 MSTN has a key role in muscle growth and is believed to have
potential applications in breeding and animal husbandry.
(Supakorn, 2009; Zhang et al., 2012)

18. Natural Myostatin mutations
occur
 Natural myostatin mutations can occur as well:
 McPherron et al. (1997) found in Belgian Blue
and Piedmontese cattle a natural myostatin
mutation resulting in non-functional myostatin
and increased muscle size.
Figure: A fullblood Belgian Blue bull showing the
double muscling phenotype
(McPherron et al., 1997)

19. Contd…
 Missense mutation g.368A>C
(p.Lys49Thr) in Exon-1 has effects
on the MSTN protein structure and
on the biological function of the
MSTN protein.
(Grobet et al., 1998)
(Beaver, 2006)

20.  The genetic improvement of animals is a fundamental, incessant,
and complex process.
Conclusion
 In recent years many methods have been developed and tested.
 The genetic polymorphism at the DNA sequence level has
provided a large number of markers and revealed potential utility of
application in animal breeding.
 The invention of polymerase chain reaction (PCR) in accordance
with the constantly increasing accuracy in DNA sequencing
methods also represents a milestone in this endeavor.

21. Conclusion
 Identification of myostatin polymorphisms that can interrupt
function.
 Opens the door for widespread screening of possible carrier
animals and breeding.
 Strategies that can take advantage of the useful nature of a
myostatin knockout while selecting against undesirable companion
traits.

22.  Plans already underway to screen large numbers of various
livestock breeds and species will help producers to identify the
mutation within their own herds and develop a breeding strategy to
maximize its potential.
Conclusion
 With these varied approaches to exploiting myostatin mutations
may represent a significant gain for several livestock industries.
 The two century-long drive to explore myostatin has been a
study in tenacity for the livestock industry in particular,
embodying the best outcome of perseverance and creative
problem solving.