transgenerational epigenetic effects: implications for cancer

Transgenerational epigenetic effects:

Implications for cancer risk and prevention

AICR’s 2013 Annual Research Conference onFood, Nutrition, Physical Activity and CancerNovember 7-8, 2913Hyatt Regency Bethesda

No Relevant Financial Relationships

Epigenetics

Phenotypic: inheritance of phenotypic variation without changes in DNA sequence

across cell divisions (mitosis)

sometimes across generations (meiosis)

Molecular: gene expressionRNA biologyprotein functions

Conventional epigenetics

From totipotency to differentiation

Genetically identical cells,with distinct and heritable functions

Molecular changes – epigenetic code- DNA (methylation, histone modification)

- RNA (chemical modification, translation, editing)- Protein functions

Reversible, e.g. iPSCs

Transgenerational epigenetic effects

Phenotypes and disease riskresult from environmental exposures

and genetic variantsin previous generations

,Heritable and familial, and ‘feel’ genetic,but individuals were not exposed to the

environmental factors, and did not inherit the genetic variants

Instead, epigenetic marks are inherited

Environmental effects

Chemical – diet, toxins, drugs

Physical – temperature, irradiation

Biological – social, stress

Genetic effects

Violate the rulesof Mendelian inheritance

Many traits and diseases

But generally need to control environment and genetics to detect

in a robust way

Multigenerational Exposure vsTransgenerational Exposures

Males PregnantGeneration Non-pregnant females females

F0 Individual (F0) Individual (F0)Gametes (F1) Fetus (F1)

F-gametes (F2)

F1 Individual (F1) Individual (F1)Gametes (F2) Gametes (F2)



Transgenerational - two parts

Diet - paternal- eating habits

- obesity- liver disease?

- liver cancer, colon cancer?

Testicular cancer - maternal- no diet effect, but exercise?

- reversible

Diet-induced obesity:

Gene - diet interactions

B6 on HFHSA/J on HFHSB6 on LFLS A/J on LFLS

0 25 50 75 100 125 1500

10

20

30

40

50

60

Age (days)

Bod

y W

eigh

t (gr

ams)

N ~ 25, Error Bars = 1 SD

NormalDiet

High fat, high sucroseor low fat, low sucrose(58% vs 11% saturated fat)

B6, obese only with a HFHS diet

A/J, lean regardless of diet

On High Fat, High Sucrose Diet: B6 A/J

Obesity

Insulin resistance

Hypertension

Cardiovascular disease Risk

XXXX

Genetics of disease Genetics of health

Nadeau and Topol, Nat. Genet. 2006; Shao et al. PNAS, 2008; Hill et al., Hum Mol Genet, 2009

XNon‐alcoholicsteatohepatitis

B6 and A/J: Contrasting models of disease

XHepatocellularcarcinoma

……

……

……

……

A/JB6 B6-Chr 1A B6-Chr 19A

, ,

Singer and Hill et al. Science 2004, Shao et al. PNAS 2008

Chromosome Substitution Strains (CSSs):A genome survey of individual genotypes

…

• CSSs partition the genome in a stable, defined and non-overlapping manner

• Genetic variation is controlled in a precise and reproducible manner

Many chromosomes confer resistance to diet-induced obesity

0 20 40 60 80 100 120 140 1600

10

20

30

40

50

Age (days)

Bod

y W

eigh

t (gr

ams)

0 20 40 60 80 100 120 140 1600

10

20

30

40

50

Age (days) B

ody

Wei

ght (

gram

s)

18 obesity-resistant 4 obese

92A

62BL

A QTL for transgenerational studies

161A

30 Mb

3 Mb

QTL

Strain

B6 161A

p < 0.001

p < 0.01

p < 0.0001

Glu

cose

(mg/

dl)

Insu

lin (u

g/l)

Bod

y w

eigh

t (g)

8 of the 12 genes in the 161A interval maintain histone methylation in sperm

Parental effects on diet-induced obesity

(B6 x 161A)F1 x (B6 x 161A)F1

B6 161AB6/161Aobese lean

if no transgenerational effectsBreeders on standard dietTest mice on high-fat diet

Transgenerational inheritance

B6 161A “B6” 161AGenotype:

Parents:

p value:

B6 161A (B6x161A)F1 (B6x161A)F1

< 10-8 < 0.0005 < 0.0005(relative to B6)

< 0.0001

F2 F3F2

“B6”

“B6”

P0

P0

Transgenerational inheritance to sons


Parents:

p value:

B6 161A (B6x161A)F1 (B6x161A)F1

< 10-8 < 0.0005 < 0.0005(relative to B6)

< 0.0001

F2 F3F2

“B6”

“B6”

Transgenerational inheritance to grandsons


Parents:

p value:

B6 161A (B6x161A)F1 (B6x161A)F1

< 10-8 < 0.0005 < 0.0005(relative to B6)

< 0.0001

F2 F3F2

“B6”

“B6”

Parental effects on diet-induced obesity

(B6 x 161A)F1 x (B6 x 161A)F1

B6 161AB6/161Aobese lean

if no transgenerational effectsBreeders on standard dietTest mice on high-fat diet

Transgenerational inheritance to grandsons


Parents:

p value:

B6 161A (B6x161A)F1 (B6x161A)F1

< 10-8 < 0.0005 < 0.0005(relative to B6)

< 0.0001

F2 F3F2

“B6”

“B6”

Testicular cancer

One of the most heritable cancers,but highly complicated genetics

Conventional and epigenetic inheritance

- maternal lineage- transgenerational

- reversible

129/Sv: Mouse model of TGCTs

Germ cells, the mother of all stem cells

• Spontaneous TGCTs occur at a measurable frequency only in the 129 family of inbred strains

• What do we know?Genetically controlled, but complex

Stems cells are primordial germ cells (PGCs) Age of onset (E11.5-E12.5)Evident at 3-4 weeks of ageModifier genes – Pten, Kitl, p53, and Dnd1

Apobec1 (cytidine deaminase) effects

• Increases risk in the paternal germ-lineage

• A conventional modifier effectl

ko/++/+



• Reduces risk in the maternal germ-lineage

• Acts in a transgenerational manner

• Only a partial loss of function

ko/++/+

Parental: 129 +/+ 7 %

♀ transmission ♂ transmission

N1 1.6 % * (191) na

N2 1.8 % * (168) 0.7 % * (151)

N3 2.6 % (*) (117) 0.0 % * (59)

Persistence of epigenetic effects: female germ-lineage

effect persists for 3 generations

Parental 129 +/+ 7 %

♀ transmission ♂ transmission

N1 na 7.2 % (125)

N2 5.4% (130) 4.5 % (157)

N3 4.7% (129) 1.8 % (*) (55)

Persistence of epigenetic effects: male germ-lineage

no change in baseline rate



• Reduces risk in the maternal germ-lineage

• Acts in a transgenerational manner

• Only a partial loss of function

ko/++/+

ko/+ ♀ x +/+

+/+ x ko/+ ♂

0% *

♀ germ line

+/+ x ko/+ ♂

+/+ x ko/+ ♂

9%

ko/+ ♀ x +/+

ko/+ ♀ x +/+

0% *

ko/+ ♀ x +/+

ko/+ ♀ x +/+ ko/+ ♀ x +/+

Switch to ♂: +1 generation

Switch to ♂: +2 generations

Switch Switch

ko/+ ♂:

ko/+ ♂:

ko/+ ♂:

Switching parental origin

ko/+ ♀ x +/+

13% *

♂ germ line

0%

+/+ x ko/+ ♂

14%*

Switch to ♀: +1 generation

Switch to ♀: +2 generations

Switch

+/+ x ko/+ ♂ +/+ x ko/+ ♂

+/+ x ko/+ ♂ +/+ x ko/+ ♂ +/+ x ko/+ ♂

ko/+ ♀ x +/+

ko/+ ♀ x +/+

Switch

ko/+ ♂:

ko/+ ♂:

ko/+ ♂:

Switching parental origin

Emerging principlesof transgenerational inheritance

1. Induced in females, males, or both2. Inherited through females, males, or both3. Environment, genetics, or both4. Large and common as conventional effects5. Reversible6. Design, control, replication!7. Heterogeneity?8. Generalizations?

Persistence of memory

Environment Genetics

Physiological stress

Homeostatic and epigenetic response in soma

Heritable epigenetic changes in germline

Adaptation, that we detect as aberrations and disease

Jason HeaneyVicki Nelson

Jennifer ZechelSteph DoernerJohn Giesinger

Soha YazbekDavid Buchner

Ghunwa NakouziPaola Raska

Philip AndersonAnnie Hill

Sabrina SpiezioElaine Leung

NCI, NCRR, and NIH Pioneer Award

Eric Lander, Broad InstituteJosephine Lam, Cleveland ClinicNick Davidson, Washington Univ.

transgenerational epigenetic effects: implications for cancer

Documents