looking for the appropriate size: genetics under control

Looking for the appropriate size: genetics under control

Crazy about Biomedicine– May 2013Ana FerreiraDevelopment and Growth Control Lab

I. Genetics

Definition Mendelian Genetics

Drosophila melanogaster: The Fruit Fly

Historical view of the fly Drosophila as a model organism

II. Developmental Biology

DefinitionHistorial view

III. Growth Control:

The different parameters Our system: the fly wing Systemic vs Organ-autonomous Growth Control

Size Control and Human Disease

Summary

I. Genetics

Genetics

Genetics deals with the molecular structure and function of genes,

gene behavior in the context of a cell or organism, patterns of

inheritance from parent to offspring, and gene distribution,

variation and change in populations

is a discipline of biology, is the science of genes, heredity, and variation in living organisms

GENETICS + ORGANISM EXPERIENCES

=

FINAL OUTCOME

Mendelian and Classic Genetics

Gregor Mendel(1822 - 1884)

observed that organisms inherit traits by way of discrete units of inheritance, which are now called genes

studied the nature of inheritance in plants

traced the inheritance patterns of certain traits in plants and described them mathematically

studied the segregation of heritable traits in pea plants

Pisum sativum

Discrete Inheritance and Mendel’s Laws

29,000 pea plants

Grow easily, develop pure-bred strains, and control their pollination


Dominant trait

Alleles: is one of a number of alternative forms of the same gene


3:1 ratio

diploid species: each individual has two copies of each gene, one inherited from each parent

organisms with two different alleles of a given gene are called heterozygous

organisms with two copies of the same allele of a given gene are called homozygous


(WW)

Purple

(Ww)

Purple

(ww)

White

heterozygoushomozygous homozygous


(WW)

Purple

(Ww)

Purple

(ww)

White

Genotype(set of alleles)

Phenotype(observable traits)

heterozygoushomozygous homozygous

one allele is called dominant

other allele is called recessive

W W


3:1 ratio


The Law of Dominance: In a cross between contrasting homozygous

individuals, only one form of the trait will appear in the F1 generation -

this trait is the dominant trait

1





1

The Law of Segregation: when any individual produces gametes, the

copies of a gene separate so that each gamete receives only one copy

(allele) - a gamete will receive one allele or the other

2

The Law of Independent Assortment: alleles responsible for different

traits are distributed to gametes (and thus the offspring) independently

of each other





1

The Law of Segregation: when any individual produces gametes, the

copies of a gene separate so that each gamete receives only one copy

(allele) - a gamete will receive one allele or the other

2

3

Drosophila melanogaster

Drosophila melanogaster: the fruit fly

Charles W. Woodworth (1865 - 1940)

1900 – First to breed Drosophila in the Lab

Historical view of Drosophila

Thomas Hunt Morgan (1866 - 1945)

1933 – Nobel Prize in Physiology or Medicine for the role played by chromosomes in heredity

1900 – Started to work with Drosophila (study of mutation)

1910 – First mutation was found (white)


1911 – Genes are on chromosomes

Hermann Joseph Müller (1890 - 1967)

1946 – Nobel Prize in Physiology or Medicine for the discovery of the genetics effects of Radiation (X-ray mutagenesis)


Eric Wieschaus(1947 - )

Janni Nusslein-Volhard(1942 - )

Edward B. Lewis(1918 - 2004)

1995 – Nobel Prize in Physiology or Medicine for revealing the genetic control of embryonic development


Jules A. Hoffmann(1941 - )

Bruce A. Beutler(1957 - )

Ralph M. Steinman(1943 – 2011)

2011 – Nobel Prize in Physiology or Medicine for the discovery of the dendritic cell and its role in adaptive immunity


Why Drosophila melanogaster is such a good model organism ?


Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)

Easy to maintain in the Lab (low cost)

Suitable of Genetic Manipulation

Simple karyotype: 4 pairs of chromosomes (3 autosomes + sexual chromosomes)

Extensive set of genetic tools available

Functional conservation of regulatory and biochemical pathways with humans

Gene Sequence Conservation with humans: 60%

Each Female lays 400-500 eggs


Easy to maintain and manipulate in the Lab (low cost)










Simple karyotype: 4 pairs of large chromosomes (3 autosomes + sexual chromosomes)







Drosophila melanogaster Life Cycle

Growth Phase

Drosophila melanogaster: why is such a potent genetic organism ?

Mutant animals are readily obtainable

Targeting gene expression in a temporal and spatial fashion

Genome fully sequenced

Huge amount of transgenic lines available

Driver line Responder line

Big collection of both Driver and Responder Lines available

Temperature Dependence of the Driver Line

Targeting gene expression: Gal4-UAS System

Targeting gene expression: Gal4-UAS System

II. Developmental Biology

Developmental Biology

Historical Perspective – The first steps

Aristotle (384 – 322 AC)

Study of the Development of the chick

The semen of the male provides the “form” or soul and the female the unorganized matter (menstrual blood) allowing the embryo to grow: EPIGENESIS

Theory of Preformationism: organs with their own shape expand

Theory of Spontaneous Generation: life of invertebrates emerges from non-living matter (“nothing”)

Views of a Fetus in the WombLeonardo da Vinci, ca. 1510-1512

Dissection of human corpses

Drawings of the vascular and system

First drawing of the human fetus in theutero

Historical Perspective - Renaissance

Leonardo da Vinci (1452 - 1519)


Antonie van Leeuwenhoek(1632 - 1723)

“…now that I have discovered that the animalcules also occur in the male seed of quadrupeds, birds and fishes…, I assume with even greater certainty than before that a human being originates not from an egg but from an animalcule that is found in the male semen”

Discovered the microorganisms: animacules

Discovered the spermatozoa

Nicolaas Hartsoeker in 1695


PREFORMATIONISM

organisms develop from

miniature versions of themselves


Discovered the follicles of the ovary (known as

Graafian follicles), in which the individual egg

cells are formed

Reiner de Graaf(1641 - 1673)

Rejecting the preformationism

Historical Perspective

Ernst Haeckel(1834 - 1919)

Recapitulation Theory /

Embryological Parallelism

developing from embryo to

adult, animals go through

stages resembling or

representing successive

stages in the evolution of

their remote ancestors

"ontogeny recapitulates phylogeny”

Opposing view that the early general forms

diverged into four major groups of specialized

forms without ever resembling the adult of

another species

Karl Ernst von Baer(1792 - 1876)


August Weismann(1834 - 1914)


Germ plasm theory

inheritance only takes place by means of the germ cells—the gametes

Other cells of the body—somatic cells—do not function as agents of heredity


Experimental Embryology

Wilhelm Roux1888 – Experiment destroying the frog embryo (in the two cells stage)

Hans Driesch1892 – Separates de early 4 cells stage embryo of the sea urchin

Hans Spemann and Hilde Mangold1918-1924 – Transplants of cells from one embryo to another induced particular

tissues or organs – embryonic induction. Nobel Prize in 1935

Are Developmental Biology and Genetic Linked ?

III. Growth Control

How are differences in size achieved ?

What determines differences in size ?

Size of an organ/animal =

similarSize of an organ/animal = number of cells + size of the cells

Cell Number

Cell Size

Cell Number+

Cell Size

Cell Division+

Cell Death

Cell Growth

number of cells + size of the cells + space between cells

Cell Division / Proliferation: increase in cell number by one cell (the

"mother cell") dividing to produce two "daughter cells"

Cell Death / Apoptosis: is death of a cell in any form, mediated by an

intracellular program (DNA fragmentation and protein degradation)

Cell Growth: increase in cell mass (protein synthesis and organelle

biogenesis)

What determines differences in size ?

Cell Cycle

How organs achieve a particular size and pattern ?

Drosophila imaginal discs: proliferative tissues

notum

wing

20-30 cells

50,000 cells

Drosophila wing imaginal disc

Embryo

Larvae

Adult

Drosophila wing imaginal disc development

Body Size Regulation

Cell autonomous growth promoters

Morphogens, signaling molecules

Long range signaling molecules (hormones…)

Environmental factors (nutrition…)

Systemic vs organ-autonomous growth control

Systemic growth control

SYSTEMIC GROWTH CONTROL

GROWTH RATE DEVELOPMENTAL TIMING(moults+pupariation)

Gut

Fat body

Brain

Ring gland

nutrients

Insulin

GROWTH

Systemic growth control

FEEDING

Hemolymph (fly ‘blood’)

Ecdysone

DEVELOPMENTAL TIMING

Organ-autonomous growth control

Regeneration Experiments

Transplants Experiments: when a small organ is transplanted into an adult

organism it grows to its normal final size (even in between different species)

Size Control and Human Disease

Cancer: tumor initiation,

metastasis

Diabetesand

Obesity

Organ hypertrophy or atrophy

Insulin pathwaydMyc oncogeneHippo pathway

TGFb signaling (Dpp)Wnt signaling (Wg)

Regenerationand Stem

Cell Biology

Growth Pathways

Drosophila was, is and will be important for Human Biology

Crazy aboutB omedicine

Thank you

Development and Growth Control Lab

Transformation in flies

looking for the appropriate size: genetics under control

Documents

medical genetics

combination of genetics

patterns of inheritance

nature of inheritance

different alleles

organisms size

behavior of organisms

gene behavior