Looking for the appropriate size:
genetics under control
Crazy about Biomedicine– May 2013
Ana Ferreira
Development and Growth Control Lab
Summary
I. Genetics
Definition
Mendelian Genetics
Drosophila melanogaster: The Fruit Fly
Historical view of the fly
Drosophila as a model organism
II. Developmental Biology
Definition
Historial view
III. Growth Control:
The different parameters
Our system: the fly wing
Systemic vs Organ-autonomous Growth Control
Size Control and Human Disease
I. Genetics
Genetics
is a discipline of biology, is the science of genes, heredity, and
variation in living organisms
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
GENETICS + ORGANISM EXPERIENCES
=
FINAL OUTCOME
Mendelian and Classic Genetics
Gregor Mendel
(1822 - 1884)
studied the nature of inheritance in plants
observed that organisms inherit traits by way
of discrete units of inheritance, which are now
called genes
traced the inheritance patterns of certain
traits in plants and described them
mathematically
Discrete Inheritance and Mendel’s Laws
studied the segregation of heritable traits in pea plants
29,000 pea plants
Grow easily, develop pure-bred strains, and control their pollination
Pisum sativum
Discrete Inheritance and Mendel’s Laws
Discrete Inheritance and Mendel’s Laws
Dominant trait
Alleles: is one of a number of alternative forms of the same gene
Discrete Inheritance and Mendel’s Laws
Discrete Inheritance and Mendel’s Laws
3:1 ratio
diploid species: each individual has two copies of each gene, one inherited from each parent
organisms with two copies of the same allele
of a given gene are called homozygous
organisms with two different alleles of a given gene are called
heterozygous
Discrete Inheritance and Mendel’s Laws
homozygous heterozygous homozygous
(WW)
(Ww)
(ww)
Purple
Purple
White
Discrete Inheritance and Mendel’s Laws
homozygous heterozygous homozygous
Genotype
(set of alleles)
Phenotype
(observable traits)
(WW)
(Ww)
(ww)
Purple
Purple
White
W
W
one allele is called other allele is called
dominant
recessive
Discrete Inheritance and Mendel’s Laws
Discrete Inheritance and Mendel’s Laws
Discrete Inheritance and Mendel’s Laws
3:1 ratio
Discrete Inheritance and Mendel’s Laws
Discrete Inheritance and Mendel’s Laws
1
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
Discrete Inheritance and Mendel’s Laws
1
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
2
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
Discrete Inheritance and Mendel’s Laws
1
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
2
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
3
The Law of Independent Assortment: alleles responsible for different
traits are distributed to gametes (and thus the offspring) independently
of each other
Drosophila melanogaster
Drosophila melanogaster: the fruit fly
Drosophila melanogaster: the fruit fly
Historical view of Drosophila
Charles W. Woodworth
(1865 - 1940)
1900 – First to breed Drosophila in the Lab
Historical view of Drosophila
Thomas Hunt Morgan (1866 - 1945)
1900 – Started to work with Drosophila
(study of mutation)
1910 – First mutation was found (white)
1911 – Genes are on chromosomes
1933 – Nobel Prize in Physiology or Medicine
for the role played by chromosomes in
heredity
Historical view of Drosophila
Historical view of Drosophila
Hermann Joseph Müller
(1890 - 1967)
1946 – Nobel Prize in Physiology or Medicine
for the discovery of the genetics effects
of Radiation (X-ray mutagenesis)
Historical view of Drosophila
Eric Wieschaus
(1947 - )
Janni Nusslein-Volhard Edward B. Lewis
(1942 - )
(1918 - 2004)
1995 – Nobel Prize in Physiology or Medicine for revealing
the genetic control of embryonic development
Historical view of Drosophila
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 ?
Why Drosophila melanogaster is such a good model organism ?
Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)
Each Female lays 400-500 eggs
Easy to maintain in the Lab (low cost)
Suitable of Genetic Manipulation
Extensive set of genetic tools available
Simple karyotype: 4 pairs of chromosomes (3 autosomes + sexual chromosomes)
Gene Sequence Conservation with humans: 60%
Functional conservation of regulatory and biochemical pathways with humans
Why Drosophila melanogaster is such a good model organism ?
Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)
Each Female lays 400-500 eggs
Easy to maintain and manipulate in the Lab (low cost)
Suitable of Genetic Manipulation
Extensive set of genetic tools available
Simple karyotype: 4 pairs of chromosomes (3 autosomes + sexual chromosomes)
Gene Sequence Conservation with humans: 60%
Functional conservation of regulatory and biochemical pathways with humans
Why Drosophila melanogaster is such a good model organism ?
Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)
Each Female lays 400-500 eggs
Easy to maintain and manipulate in the Lab (low cost)
Suitable of Genetic Manipulation
Extensive set of genetic tools available
Simple karyotype: 4 pairs of chromosomes (3 autosomes + sexual chromosomes)
Gene Sequence Conservation with humans: 60%
Functional conservation of regulatory and biochemical pathways with humans
Why Drosophila melanogaster is such a good model organism ?
Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)
Each Female lays 400-500 eggs
Easy to maintain and manipulate in the Lab (low cost)
Suitable of Genetic Manipulation
Extensive set of genetic tools available
Simple karyotype: 4 pairs of chromosomes (3 autosomes + sexual chromosomes)
Gene Sequence Conservation with humans: 60%
Functional conservation of regulatory and biochemical pathways with humans
Why Drosophila melanogaster is such a good model organism ?
Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)
Each Female lays 400-500 eggs
Easy to maintain and manipulate in the Lab (low cost)
Suitable of Genetic Manipulation
Extensive set of genetic tools available
Simple karyotype: 4 pairs of large chromosomes (3 autosomes + sexual chromosomes)
Gene Sequence Conservation with humans: 60%
Functional conservation of regulatory and biochemical pathways with humans
Why Drosophila melanogaster is such a good model organism ?
Short Life Cycle (Temperature Dependent – 10 days @ 25ºC)
Each Female lays 400-500 eggs
Easy to maintain and manipulate in the Lab (low cost)
Suitable of Genetic Manipulation
Extensive set of genetic tools available
Simple karyotype: 4 pairs of large chromosomes (3 autosomes + sexual chromosomes)
Gene Sequence Conservation with humans: 60%
Functional conservation of regulatory and biochemical pathways with humans
Why Drosophila melanogaster is such a good model organism ?
Drosophila melanogaster Life Cycle
Growth Phase
Drosophila melanogaster: why is such a potent genetic organism ?
Genome fully sequenced
Mutant animals are readily obtainable
Huge amount of transgenic lines available
Targeting gene expression in a temporal and spatial fashion
Targeting gene expression: Gal4-UAS System
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”)
Historical Perspective - Renaissance
Leonardo da Vinci
(1452 - 1519)
Dissection of human corpses
Drawings of the vascular and system
First drawing of the human fetus in the
utero
Views of a Fetus in the Womb
Leonardo da Vinci, ca. 1510-1512
Historical Perspective - Renaissance
Historical Perspective - Renaissance
Antonie van Leeuwenhoek
(1632 - 1723)
Discovered the microorganisms: animacules
Discovered the spermatozoa
“…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”
Historical Perspective - Renaissance
PREFORMATIONISM
organisms develop from
miniature versions of themselves
Nicolaas Hartsoeker in 1695
Historical Perspective - Renaissance
Reiner de Graaf
(1641 - 1673)
Discovered the follicles of the ovary (known as
Graafian follicles), in which the individual egg
cells are formed
Rejecting the preformationism
Historical Perspective
"ontogeny recapitulates phylogeny”
Ernst Haeckel
(1834 - 1919)
Recapitulation Theory /
Embryological Parallelism
developing from embryo to
adult, animals go through
stages
resembling
representing
or
successive
stages in the evolution of
their remote ancestors
Historical Perspective
Karl Ernst von Baer
(1792 - 1876)
Opposing view that the early general forms
diverged into four major groups of specialized
forms without ever resembling the adult of
another species
Historical Perspective
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
Historical Perspective
Experimental Embryology
Wilhelm Roux
1888 – Experiment destroying the frog embryo (in the two cells stage)
Hans Driesch
1892 – Separates de early 4 cells stage embryo of the sea urchin
Hans Spemann and Hilde Mangold
1918-1924 – 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 = number of cells + size of the cells + space between cells
Size of an organ/animal = number of cells + size of the cells
Cell Number
Cell Number
+
Cell Size
Cell Size
similar
Cell Division
+
Cell Death
Cell Growth
What determines differences in size ?
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)
Cell Cycle
How organs achieve a particular size and pattern ?
Drosophila imaginal discs: proliferative tissues
Drosophila wing imaginal disc
20-30 cells
Embryo
Larvae
wing
Adult
notum
50,000 cells
Drosophila wing imaginal disc development
Body Size Regulation
Systemic vs organ-autonomous growth control
 Long range signaling molecules
(hormones…)
 Cell autonomous growth promoters
 Environmental factors
(nutrition…)
 Morphogens, signaling molecules
Systemic growth control
SYSTEMIC GROWTH CONTROL
GROWTH RATE
DEVELOPMENTAL TIMING
(moults+pupariation)
Systemic growth control
DEVELOPMENTAL TIMING
Ecdysone
Ring gland
Fat body
Insulin
Brain
nutrients
Hemolymph (fly ‘blood’)
FEEDING
GROWTH
Gut
Organ-autonomous growth control
Transplants Experiments: when a small organ is transplanted into an adult
organism it grows to its normal final size (even in between different species)
Regeneration Experiments
Size Control and Human Disease
Cancer:
tumor initiation,
metastasis
Organ hypertrophy
or atrophy
Growth Pathways
Insulin pathway
dMyc oncogene
Hippo pathway
TGFb signaling (Dpp)
Wnt signaling (Wg)
Diabetes
and
Obesity
Regeneration
and Stem
Cell Biology
Drosophila was, is and will be important for Human Biology
Thank you
Development and Growth Control Lab
Crazy about
B omedicine
Transformation in flies