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Chris Doe
Professor of Biology
Ph.D., Stanford University;
B.S., New College
Member of:
- Institute of Neuroscience
- Institute of Molecular Biology
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Office: Streisinger
Hall Room 365E
Telephone: 541-346-4877
Lab: Streisinger Hall Room 365
Telephone: 541-346-3041
Fax: 541-346-4736
ION Webpage
Email |
Research Interests
- Generation of Cell Polarity, Temporal Identity, an Neural Diversity
in Drosophila
We investigate Drosophila CNS development. Current interests
are (1) how stem cell-like neural precursors (neuroblasts) establish cell polarity
and divide asymmetrically; (2) how neuroblasts maintain stem cell-like features
as they divide to produce differentiating progeny; (3) how transcription factors
regulate temporal identity within neuroblast lineages; and (4) the genetic program
governing the production of motoneurons, serotonergic interneurons, or glia. |
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Asymmetric cell division of neural precursors
Drosophila neural precursors
(called neuroblasts) repeatedly divide along their apical/basal axis to
regenerate an apical neuroblast and bud off a smaller basal daughter cell
(called a GMC) that differentiates into a neurons or glia. Normal asymmetric
division requires alignment of the mitotic spindle along the apical/basal
axis as well as polarized localization of cell fate determinants to the
apical or basal poles of the cell -- which allows two molecularly distinct
daughter cells to be produced.
We are interested how neuroblasts establish cell polarity, and
how cell polarity is used to generate two different cell types at each cell division.
Work from our lab and others has identified basally-localized mRNA and proteins
(e.g. prospero RNA and Miranda, Prospero, and Numb proteins) as well as
apically-localized proteins (e.g. Baz, Par-6, and aPKC). We have done genetic
screens to identify new genes involved in apical protein localization, spindle
orientation, and basal protein localization, and have identified 12 loci that
are required for one or more of these events. A graduate student in the lab, Sarah
Siegrist, has developed methods for timelapse imaging of asymmetric neuroblast
division both in vivo and in vitro, which is providing new insights
into wild type and mutant cell division phenotypes. |
| Two former graduate students, Chian-Yu Peng and Roger Albertson,
have characterized three basal localization mutants, the previously identified
"tumor suppressor genes" lethal giant larvae (lgl), discs large (dlg),
and scribble. All three mutants show normal apical protein localization
and spindle orientation, but a loss of basal protein targeting. Interestingly,
these phenotypes can be suppressed by reducing the level of non-muscle myosin
II protein, and mimicked by a pan-myosin inhibitor, leading to a model in which
both positive and negative myosins regulate basal transport of Miranda and Numb
proteins. A third graduate student, Karsten Siller, is working on the role of
the dynactin complex and Lis1 in regulating basal protein targeting and spindle
orientation in neuroblasts. Karsten has show that Lis1 is essential for normal
asymmetric division (both basal targeting and spindle orientation). His results
are likely to aid in our understanding of the human Lissencephaly phenotype, which
has yet to be characterized at the cellular level. Our work on cell polarity and
asymmetric cell division has been supported by HHMI and the NIH. |
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Temporal regulation of cell fate within neuroblast cell lineages
Producing the right cells at the right
time is essential for normal development, yet it is not well understood
how an embryonic precursor cell or a stem cell reproducibly generates a
characteristic sequence of different cell types. To begin to study this
question, we have done comprehensive cell lineage studies to identify the
clone of neurons and glia produced by all 30 different embryonic neuroblasts
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as well as the precise birth-order of all progeny for selected neuroblasts. (http://www.neuro.uoregon.edu/doelab/lineages/) |
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We recently showed that nearly all of the 30 different Drosophila neuroblasts in each segment sequentially express the transcription factors Hunchback -> Krüppel -> Pdm -> Castor, raising the possibility
of a molecular "clock" for distinguishing GMC birth-order (Isshiki et al., 2001, Cell 106:511). Interestingly, while neuroblast only transiently
expressed each gene, the daughter GMCs born during each window of expression
maintained expression of that gene as they differentiated. Thus, first-born
GMCs maintain Hunchback as they differentiate, whereas second-born GMCs maintain
Kruppel as they differentiate. Mutant and misexpression studies show that Hunchback
is necessary and sufficient for first-born cell fates, whereas Krüppel is necessary
and sufficient for second-born cell fates; we observe this in multiple neuroblast
lineages and is independent of the cell type involved. We postulate that Hunchback -> Krüppel -> Pdm -> Castor are "temporal coordinate
genes" that act together with "spatial coordinate genes" known to specify each
neuroblast identity to uniquely specify the identity of each neuron or glia
in the CNS.
More recently, Bret Pearson in the lab has shown that Hunchback has
the potential to "restart" the lineage of older neuroblasts, revealing a surprising
degree of plasticity in neuroblast developmental potential. Bret has also shown
that transient expression of Hunchback can produce long-term heritable specification
of first-born cell fate, suggesting that Hunchback-mediated chromatin remodeling
may be involved in the specification of neuronal temporal identity, similar
to the role of Hunchback in establishing heritable HOX gene expression.
Other questions that we are interested in are: Do Pdm and Castor
have similar functions in specifying later-born fates? What regulates the timing
of the gene expression "clock" that controls Hunchback -> Krüppel -> Pdm -> Castor? And, do hunchback and Krüppel orthologs have similar functions during vertebrate neurogenesis or hematopoiesis?
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Generation of motoneuron, interneuron, and glial cell fates
A long-term interest of the lab
has been to understand how neural diversity is generated. A graduate student
in the lab, Joanne Odden, is investigating how specific types of motoneurons
are produced. Her initial work has been on the Drosophila homologue
of homeodomain transcription factor HB9/MNR2. Drosophila HB9 is expressed
in a subset of motoneurons that project to the lateral body wall muscles;
these are distinct from the pool of Eve+ motoneurons that project to dorsal
body wall muscles and from a small pool of motoneurons that project to the
ventral-most muscles. RNAi and misexpression experiments are consistent
with a model that HB9 is necessary and sufficient for motoneuron targeting
to lateral muscles. Additional studies on other transcription factors expressed
in some or all motoneurons are ongoing.
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| A postdoctoral fellow in the lab, Marc Freeman, has begun a comprehensive
analysis of glial development. Marc is using a novel computational method, microarray
technology, and saturation mutagenesis to identify new genes involved in glial
development. The computational method identifies putative target genes for the
glial cells missing transcription factor, a "master regulator" of glial development.
The microarray method looks for genes upregulated following Gcm overexpression
in the CNS. These two approaches have already given us over 40 new genes that
are involved in glial specification, migration, differentiation, or function.
Most of these genes have murine or human orthologs, so it will be interesting
to see if they play similar roles in Drosophila and vertebrate gliogenesis. |
Siller KH, Cabernard C, Doe CQ. The NuMA-related Mud protein binds Pins and regulates spindle orientation in Drosophila neuroblasts.Nat Cell Biol. 2006 Jun;8(6):594-600
Cleary MD, Doe CQ. Regulation of neuroblast competence: multiple temporal identity factors specify distinct neuronal fates within a single early competence window. Genes Dev. 2006 Feb 15;20(4):429-34
Siegrist SE, Doe CQ. Extrinsic cues orient the cell division axis in Drosophila embryonic neuroblasts. Development. 2006 Feb;133(3):529-36.
Siegrist SE, Doe CQ. Microtubule-induced Pins/Galphai cortical polarity in Drosophila neuroblasts. Cell. 2005 Dec 29;123(7):1323-35.
Lee CY, Robinson KJ, Doe CQ. Lgl, Pins and aPKC regulate neuroblast self-renewal versus differentiation. Nature. 2006 Feb 2;439(7076):594-8.
Cheesman S.E., M.J. Layden, T. Von Ohlen, C.Q. Doe, and J.S. Eisen
(2004) Zebrafish and fly Nkx6 proteins have similar CNS expression patterns
and regulate motoneuron formation. Development 131:5221-32.
Pearson, B. and C.Q. Doe (2003) Regulation of neuroblast competence
and temporal identity if Drosophila Nature 425:624-8.
Isshiki, T., B. Pearson, S. Holbrook, and C.Q.
Doe (2001) Drosophila neuroblasts sequentially express transcription factors
which specify the temporal identity of their neuronal progeny. Cell 106:511-21. |
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