Congress Abstracts - Society for Developmental Biology

Program/Abstract # 382
Amplitude of growth factor signaling tunes craniofacial morphology
Szabo-Rogers, Heather L.; Cusack, Brian (University of Pittsburgh, USA)
Human orofacial clefting (OFC) is the most common human congenital anomaly, occurring in approximately of 1/700 live births and
has a complex multifactorial, multigenic origin. While significant work has been done to identify the genomic regions associated with
increased risk for human OFC, the molecular and morphogenetic consequences are unexplored. The previously identified human
OFC risk genes are enriched in effectors of the transforming growth factor beta, hedgehog, Wnt and Fibroblast growth factor signaling
pathways. There are no clear functional consequences within the human loci for these genes associated with OFC and most traditional
mouse models do not have overt craniofacial phenotypes. We hypothesized that the OFC risk-genes are modulating the output of
these signaling pathways which results in abnormal morphogenesis. We chose to modify these pathways in the zebrafish embryo
during three distinct time periods of craniofacial development: neural crest migration, patterning and differentiation. We found both
dose and stage dependent changes to facial morphology and in particular to the shape and size of the ethmoid plate- the surrogate
zebrafish palate. Interestingly, we found that muscles can still develop in the absence of jaw cartilage. We conclude that careful
dissection of the timing and amplitude of pathway activation will provide insights into human OFC.
Program/Abstract # 383
The role of kinin-kallikrein signaling in craniofacial development
Jacox, Laura (Whitehead Institute- MIT & Harvard GSAS, USA); Sindelka, Radek; Sive, Hazel (Whitehead Institute, USA)
The mouth is the initial opening between the gut and outside of the embryo, and forms from juxtaposed ectoderm and endoderm. In
Xenopus, mouth formation involves multiple steps, including cell migration and death, dissolution of basement membrane, cell layer
thinning and intercalation, and cell sheet perforation. Several signaling pathways are required for this process, including BMP, Wnt,
Hedgehog and most recently, the kinin-kallikrein pathway. This latter pathway acts in adults as a regulator of blood pressure and
inflammation, but has not been previously described in embryos. The pathway converges on production of the signaling molecule
nitric oxide (NO). Using an unbiased microarray approach, three members of the kinin-kallikrein pathway were found to be
preferentially expressed in the presumptive mouth region, relative to surrounding regions. These are carboxypeptidase-N, kininogen
and neural nitric-oxide synthase. Requirement of all three members for mouth formation was determined by loss of function. Loss of
function was associated with gross craniofacial abnormalities, histological aberrations in facial basement membranes and tight
junctions, and reduced neural crest marker expression and migration, suggesting broad and diverse roles for the kinin-kallikrein
pathway in craniofacial development. Further, loss of function phenotypes were rescued by downstream kinin-kallikrein peptides and
exogenous nitric oxide (NO). Kinin-kallikrein signaling is a novel regulator of craniofacial development in Xenopus.
Program/Abstract # 384
Genetic and molecular characterization of the avian ciliopathic model Talpid2
Brugmann, Samantha A.; Chang, Ching-Fang; Schock, Elizabeth (Cincinnati Children's Hospital, USA); Robb, Elizabeth (UC Davis,
USA); Snyder, Jon (Cincinnati Children's Hospital, USA); Dodgson, Jerry (Michigan State University, USA); Cheng, Hans (USDA-
ARS, USA); Muir, William (Purdue University, USA); Delany, Mary (UC Davis, USA)
The chicken Talpid2 is an autosomal recessive mutant with a myriad of Hedgehog (Hh) dependent malformations, including
polydactyly and facial clefting. Although the Talpid2 has been used as a disease model for numerous studies of limb and craniofacial
development, the causal genetic element has yet to be identified. To determine the genetic cause for the Talpid2 phenotype we
performed 60K SNP array and Next-gen sequencing analyses and mapped the Talpid2 locus to a region on chromosome1 containing
the avian homolog of c2cd3, a vertebrate specific C2 domain-containing protein essential for ciliogenesis. Reverse transcriptase-PCR
(RT-PCR) using primers to the first and last exons of c2cd3 revealed an abnormal distribution of transcripts in Talpid2 relative to
controls embryos. The molecular consequence of c2cd3-dependent loss of ciliary function was disrupted post-translational processing
of the down-stream transcription factors of the Hh pathway, Gli2 and Gli3 in the developing facial prominences. We found that
whereas both Gli2 and Gli3 processing was disrupted in Talpid2 mutants, only nuclear Gli3A levels were significantly altered between
control and Talpid2 embryos. These results are the first to identify the causal genetic element for Talpid2 and show that it is a distinct
ciliary mutant from Talpid3. Furthermore, ours are the first to perform an in-depth cellular and molecular analysis of the Talpid2 facial
phenotype. Taken together, these results shed light on how craniofacial tissues utilize primary cilia to process a Hh signal and
characterize the Talpid2 as a novel disease model system for ciliopathies.
Program/Abstract # 385
Mortalin plays a protective role in cell survival through the regulation of the unfolded protein response pathway during mouse
embryonic development.
Frisdal, Aude (Stowers Institute, USA); Walker, Macie (University of Colorado-Denver, USA); Trainor, Paul (Stowers Institute, USA)
Neural crest cells (NCC) give rise to the majority of skeletal elements and connective tissue of the head and face. Most craniofacial
malformations therefore are associated with defects in NCC development. It is thus important to understand the mechanisms that
govern NCC formation, migration and differentiation. To identify new genes involved in craniofacial development, we performed an
ENU mutagenesis screen in mice and here we describe arco piccolo which exhibits craniofacial malformation. NCC migration is
110