IGP Genetics and Developmental Biology

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IGP Genetics and Developmental Biology
C. elegans Genetics
Lecture
Oct 21 Fri. 10 am Precocious development
reveals a novel gene regulatory pathway
Read
Rougvie, A. (2005) Intrinsic and extrinsic
regulators of developmental timing from miRNAs
to nutritional cues. Development 132, 3787-3798.
Interesting Reading
Lee, RC, Feinbaum, R, Ambros, V (2004) A short
history of short RNA. Cell S116,
S89-S92. Ruvkun, G Wightman, B, Ha, I, (2004).
The twenty years it took to recognize the
importance of tiny RNAs. Cell S116, S93-S96.
David Miller Cell
Develomental Biology 3154 MRB III
david.miller_at_vanderbilt.edu 343 3447
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C. elegans Life Cycle
0
49 hr
fertilization
molt
40 hr
hatch
14 hr
molt
33 hr
25 hr
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Hypodermis or nematode skin expands during
larval growth and secretes new cuticle at each
molt
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Seam cell are specialized hypodermal cells
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Seam cells give rise to alae at L4/Adult molt
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Hypodermal cells in L1 larva
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Hypodermal cells proliferate during larval
development
Larval seam cell lineage
Adult
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lin-14(0) results in precocious seam cell
lineage
lin-14(0)
Precocious seam cell lineage in lin-14(0)
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lin-14 is heterochronic switch gene
lin-14(gf)
lin-14(0)
Precocious seam cell lineage in lin-14(0)
Retarded seam cell lineage in lin-14(gf)
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MODEL LIN-14 is temporally regulated during
larval development
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LIN-14 is nuclear protein
L1 stage Larva stained with anti-LIN-14
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LIN-14 protein expression is highest in L1 lineage
lin-14()
lin-14(gf)
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How is LIN-14 down-regulated at the end of the L1?
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lin-4(0) phenocopies lin-14(gf)
lin-14(0)
lin-4(0)
lin-14(gf)
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lin-4 vs lin-14 epistasis experiment
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LIN-14 expression is regulated by the lin-14 3
UTR
Wightman, B, Ha, I, Ruvkun, G (1993)
Posttranscriptional regulation of the
heterochronic gene lin-14 by lin-4 mediates
temporal pattern formation in C. elegans. Cell
75, 855-862.
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Cloning lin-4
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lin-4 encodes two very small RNAs
70nt
22nt
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Noncomplementation screen for lin-4 mutations
Rhonda Feinbaum
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lin-4 miRNA complementary to 7 sites in lin-14
mRNA
3 UTR
LIN-14
CODING
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lin-4 may represent a class of developmental
regulatory genes that encode small antisense RNA
products
Lee et al., 1993
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let-7 miRNA regulates late larval development
Reinhart et al. 2000 Nature 403, 901-906
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et al. 2000 Nature 208, 86-89
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let-7 miRNA is temporally regulated in flies and
fish
Northern blots
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Plant development
WORMS
Neuronal Left/right asymmetry
Temporal fates
Roles for miRNAs
Apoptosis
hematopoiesis
Stem cell division
Fat metabolism
FLIES
MAMMALS
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RNAi components, Dicer and RISC, also mediate
gene silencing by microRNAs
small temporal RNA (microRNA)
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Temporal expression of a microRNA controls heart
development
Zhao et al. (2005) Serum response factor
regulates a muscle specific microRNA that targets
Hand2 during cardiogenesis Nature 436, 214-220