My name is Micheal Buszczak and I am a member of
the Department of Molecular Biology at the UT Southwestern Medical Center in Dallas.
As part of the Legacy of Drosophila Genetics series,
I will present a lecture on drosophila stem cells.
The study of drosophila stem cells and their associated niches have greatly
influenced our understanding of stem cell biology across tissues and across species.
These studies span well over a decade and were carried out by many different groups.
I'll present published work and cite the appropriate references along the way.
It is important to note that many other interesting discoveries have been
made through the study of other drosophila stem cell population,
such as those found within the testis.
However, in the interest of time,
I will focus here on the adult germline stem cells of the drosophila ovary,
and describe the insights that have emerged through
the careful study of this one stem cell model.
A stem cell, pictured here in green,
can be defined as a cell that undergoes self-renewing divisions.
When a stem cell divides,
it forms two daughters.
One will remain a stem cell,
while the other can differentiate,
represented here by the red cell,
or it can remain a stem cell depending on the cellular context that it finds itself.
Stem cells are vitally important for the development of
multicellular organisms and for proper tissue homeostasis,
particularly in tissues that experience a high rate of cell turnover such as the skin,
intestine or hematopoietic system.
One of the central paradigms in stem cell biology is the idea that in vivo,
stem cells often reside in specialized micro-environments called niches.
The stem cell niche concept was first proposed by Schofield in
1978 as a model to explain observations made in the mammalian hematopoietic system.
However, because of the difficulty of observing
mammalian stem cells at single-cell resolution in vivo,
the experimental underpinnings of the niche model had been largely developed by
studying invertebrate models such
as the one that will be described throughout this lecture.
Simply defined, niches are formed by specialized groups of cells,
pictured here in blue, that produce factors that
keeps stem cells in an undifferentiated state.
Niches create asymmetries within tissues so that when a stem cell divides,
any daughter that remains within this niche,
retains its stem cell identity,
while daughters displaced away from the niche differentiate.