The role of hdac4 in zebrafish craniofacial development Vishesh Khanna University of Oregon PI: Prof. Charles Kimmel Mentor: Dr. April DeLaurier Hypothesis:

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