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The role of hdac4 in zebrafish craniofacial development
Vishesh KhannaUniversity of Oregon
PI: Prof. Charles KimmelMentor: Dr. April DeLaurier
Hypothesis: hdac4 patterns anterior craniofacial development
through upregulation of shh
hdac = Histone Deacetylase• Transcriptional repressors• SNPs in the human hdac4 gene are linked to
cleft palate-like defects (Park et al. 2006) and skeletal defects in mice (Vega et al. 2004)
• Zebrafish may serve as a good model by whichto study craniofacial disordersin humans
Images from Ida.org.in and Kimmel et. al 2001
Hypothesis: hdac4 patterns neurocranium formation through upregulation of shh
Images from Kimmel et al. 2001
Morpholino (MO) knockdowns of hdac4 mRNA result in neurocranial
defects
WT 6dpf
hdac4 MO6dpf
Photos courtesy of Dr. April DeLaurier
hdac4 MO6dpf
hdac4 MO6dpf
hdac4 MO6dpf
sonic hedgehog (shh) and hdac4• shh plays a crucial role in
craniofacial development
• Zebrafish shh- mutantsshow variable neurocraniumdefects (Eberhart et al. 2006)
• Loss of Hdac proteins resultsin reduction of shh expression inchick limb buds (Zhao et al. 2009)
4 dpf -- Photo from Wada et al, 2005
WT
shh and hdac4• Two shh signals are required for neurocranium
development:1) Shh signals to the stomodeal (mouth) precursors2) Stomodeum signals to post-migratory neural
crest cells
Images adapted from Eberhart et al. 2006
At 10 and 14 hpf, loss of hdac4 ≠ loss of shh
shh shh shhWT 10 hpf MO 10 hpf MO 10 hpf
shhshhshhWT 14 hpf MO 14 hpf MO 14 hpf
At 36 hpf, loss of hdac4 = loss of shh
36 hpf 36 hpf
shh shh
shh
shh
WT
WT
MO
MO
Conclusion• Hypothesis: hdac4 patterns anterior craniofacial
development through upregulation of shh.
• hdac4 knockdown does not result in downregulation of shh at early stages (10 & 14 hpf) but may affect shh expression at later (36 hpf) stages of development
• My hypothesis can be rejected at early stages but may hold true for later stages
Future Directions• Repeat in-situ hybridizations of shh expression at
later stages • Look for a genetic interaction between hdac4 and
pdgfra (platelet-derived growth factor receptor alpha) and factors in the pdgf pathway– Factors in the pdgf pathway is important for
neural crest cell migration and its loss is associated with anterior neurocranium defects
Acknowledgments• Professor Chuck Kimmel• Dr. April DeLaurier• The Kimmel Lab• Dr. Peter O’Day• Blakely Strand• The SPUR participants