Download Course Name: Advanced Topics in Developmental Biology Course

Course Name: Advanced Topics in Developmental Biology
Course number: 47020634
Lecturer: Dr. Claytus Davis ([email protected])
Hours: one two-hour session once a week for one semester
Format: student-led discussion/argument based on research articles.
Topics: are all chosen for their controversial nature and include, among others: Redundancy in embryonic
development, Regeneration, Prokaryotic multicellularity, epigenetic inheritance.
Marking: 50% will be a written work, 50% will be a subjective evaluation of participation in discussion
Language: English with Hebrew as needed.
Course is limited to 15 students maximum
More detailed information is at URL: http://fohs.bgu.ac.il/develop/db2.html
1. Haploid/Prokaryotic development
Although most organisms on the planet are bacteria, almost all complex multicellular organisms belong
to the plants or animals. Although all of these plants and animals have haploid/diploid lifecycles, it
almost always the diploid phase that forms a complex organism. Why?
2. Redundancy in developmental programs
Seventy years ago, Hans Spemann suggested that some developmental events were so important that
the organisms developed two independent, redundant mechanisms to ensure that the event proceeded
normally (double assurance). More recently, it has been shown that a large number of genes thought to
be involved in regulating mouse development show no phenotype when they are "knocked out". Are
they part of double assurance pathways? The idea of double assurance makes the evolutionary biologists
uneasy. Who is right?
3. Is the mouse an upside-down lobster?
The location of the neural tube, the primary dorsal/ventral asymmetry of the basic body plan, is ventral
in the arthropods and dorsal in the vertebrates. Over a hundred and fifty years ago it was suggested that
both the vertebrates and the invertebrates had the same fundamental body plan - one of them was just
living on its back. This idea was thoroughly ridiculed. New molecular data suggests a reassessment.
4. Human embryonic stem cells: the shape of science and ethics
Embryonic stem cell are derived from the very early embryo and are totipotent – capable of becoming
any cell type in the body. They can also be modified genetically in vitro. We can produce designer mice
and we can almost certainly produce designer humans. Where do we stop?
5. Regeneration and Spallanzani’s mouse
A bisected planaria is able to regenerate the entire organism. A cockroach can regenerate a missing leg.
Some lizards can do the same. Humans can regenerate nothing more complicated than a finger tip. Why
are we so bad at regeneration compared to many other animals?
6. L/R axis formation
In all vertebrates the left side of the animal is different than the right side. Failure to place the organs
on the proper side can be lethal. The left-right axis is the last embryonic axis defined during
embryogenesis. Once the anterio-posterior and dorsoventral axes are set, there is only one possible left
and right. But how does the embryo know which side is which?
7. When does development end?
Embryonic development is the execution of a genetic program. From the point of view of the
organism, birth or hatching just marks a change of environment. Genetically programmed changes in
structure and function continue at least until sexual maturity. Does the program stop there? Is
senescence genetically programmed?
8. A phylotypic stage?
Haekel proposed that all vertebrate embryos pass through a phylotypic stage – an embryonic stage
where all vertebrates look the same – at this stage a fish embryo looks just like a human embryo. Is
there such a thing?
9. Losing your ancestral genes
Embryonic development is the result of the execution of a genetic program. Some of the pieces of this
program are genes that play central roles in regulating this process. They have been conserved for
hundreds of millions of years. Now that we have started looking at whole genomes we find that some
of these genes have been lost in some animals. How is this possible? How can an ancient, conserved,
and important gene be lost without negative effect?
10. Epigenetic inheritance
The information used during embryonic development to construct the body is considered to be encoded
in the genome. But is this always true? To what extent can an epigenetic state be transmitted through
the germ line into the next generation? Was Lamark perhaps a little bit right?
11. The heart never forgets
It is the brain that thinks. But does it think alone? Is thinking a cooperative process - with other body
parts participating? For instance, do your thoughts belong, in part, to your heart?
12. Where are all those disease genes?
We were very successful identifying genes associated with simple single-locus, mendelian-inheritance
genetic diseases. Some more complicated inheritances, like that of X-linked mental retardation took a
little longer. The human haplotype and single nucleotide polymorphism maps were supposed to help us
identify the collection of genes associated with more complex diseases, like type2 diabetes. The results
have been disappointing. What’s going on? Why are we failing?
13. Why are sponges stupid?
What started with the human genome has now advanced to the sponge. Surprise. They have many of
the genes that regulate complex embryonic development, for instance the genes defining muscle and
brain. Why does a thing that has been sitting on the bottom for 700 million years without moving or
reacting have these genes?
14. What is life?
- the title of Irwin (let’s make waves) Schrödinger’s 1944 book. So, 66 years later, and as we are
discovering planets in the “Goldilocks Zone” of other stars, how would you like to define life?