Congress Abstracts - Society for Developmental Biology

condition. Kanyon embryos have a mid-facial cleft, ocular anomolies (micropthalmia) and a variable mid-brain exencephaly,
phenotypes that mimic human fronotonasal dysplasia. The facial cleft often varies in severity, from a disastrous lesion completely
disrupting the face to a discrete cleft lip and palate phenotype. Thus, kanyon in its mildest form may also be a model for cleft lip and
palate. Characterisation of these ENU mouse mutant strains will highlight the fundamental mechanisms responsible for normal
development of the craniofacial structures. This data will facilitate the identification of underlying mutations in correlating human
conditions.
Program/Abstract # 212
Fgf signaling in the control of craniofacial and tracheal gland development
May, Alison; Tucker, Abigail S. (King's College London, UK)
The submucosal glands (SMGs) of the respiratory system are specialized structures essential for maintaining human airway
homeostasis. The significance of these glands is highlighted by their involvement in serious respiratory diseases such as cystic
fibrosis, asthma and chronic bronchitis where both their phenotype and function are severely altered. Uncovering the normal
developmental journey of SMGs of the conductive airways is essential to elucidate their role in these disorders, however, very little is
known about their development and differentiation. To start to understand the molecular mechanisms involved we have investigated
the development of both nasal and tracheal SMGs in the Fgf10 mutant mouse. Fgf10 is expressed in the mesenchyme around the
developing SMGs, and in heterozygous mice the tracheal glands are reduced in number at a very early age, with an altered A/P
distribution of the glands postnatally, a deficit that is not recovered in adults. This change in distribution is not due to a change in the
tracheal cartilage rings and indicates that Fgf10 is required for the first stages of SMG bud initiation and branching morphogenesis. In
the nasal glands, some but not all glands were lost in the homozygous mutant, indicating that not all glands require Fgf10 for
initiation. Some of the SMGs present in the Fgf10 homozygote were missing in the Fgfr2b mutant, suggesting compensation by
another Fgf ligand. We aim to uncover the expression patterns of a number of Fgfs during early gland morphogenesis and to study the
functional consequence of the reduction of SMGs in Fgf10 heterozygotes by assessing the ability of these mice to respond to
respiratory challenges, compared to wildtype littermates.
Program/Abstract # 213
Foxi3 is an essential regulator of tooth development
Jussila, Maria; Shirokova, Vera; Aalto, Anne; Sanz Navarro, Maria (University of Helsinki, Finland); Ohyama, Takahiro; Groves,
Andrew (Baylor College of Medicine, USA); Mikkola, Marja; Thesleff, Irma (Institute of Biotechnology, University of Helsinki,
Finland)
Transcription factor Foxi3 has been identified as the causative gene for the phenotype of the hairless dog breeds. These dogs have
missing and misshapen teeth in addition to the hair phenotype. The function of Foxi3 in tooth development has not been studied
previously. We show that Foxi3 is expressed in the dental epithelium throughout tooth development, as well as in the epithelial stem
cell niche of mouse incisors. We have studied the role of Foxi3 in tooth development by analyzing the phenotype of a conditional
Foxi3 knock-out mouse line (Foxi3 cKO). To investigate downstream targets of Foxi3, we have performed a microarray analysis on
teeth of Foxi3 cKO and wild type embryos. To study the upstream regulation of Foxi3, we have analyzed Foxi3 expression in different
mutant mouse lines. In addition, we have used different proteins to induce Foxi3 expression in embryonic skin and tooth, and analyzed
the results with qRT-PCR. Foxi3 expression is upregulated in K14-Eda mice overexpressing Ectodysplasin (Eda) and downregulated
in Eda-deficient Tabby mice. In line with this Foxi3 expression is induced in embryonic Tabby skin treated with Eda protein. In
addition, Foxi3 expression is induced in wild type skin and teeth treated with Activin A protein. We are currently analyzing the
phenotype of the Foxi3 cKOs and the microarray data. Our results show that Foxi3 is a new epithelial regulator of tooth development
and that Foxi3 lies downstream of Eda signaling. The phenotype of the hairless dogs resembles symptoms of ectodermal dysplasia,
which is cause by mutations in the Eda pathway. Our data suggests the ectodermal dysplasia can be partly caused by reduced Foxi3
expression.
Program/Abstract # 214
The Cadherin23, Harmonin, Myosin7aa, and Ift88 Usher syndrome protein complex assembles at the ER and is required for
Usher protein trafficking
Blanco-Sanchez, Bernardo Blanco-San; Clement, Aurelie; Fierro Jr., Javier; Washbourne, Phillip; Westerfield, Monte (University of
Oregon, USA)
In vertebrates, the scaffold and motor proteins, Harmonin and Myosin7a (Myo7a), interact physically with the cytoplasmic tail of the
transmembrane protein Cadherin23 (Cdh23). These molecular interactions result in the formation of a macromolecular complex that is
required for hearing, balance, and vision. In humans, mutations that disrupt the function any one of these or 8 other proteins result in
Usher Syndrome, the most common cause of deafblindness. Little is known, however, about where, how, and which particular Usher
proteins assemble together at the cellular level. We analyzed potential binding of the Cadherin23, Harmonin, and Myosin7aa Usher
proteins, and whether Ift88 is required for their trafficking and localization in zebrafish. We used confocal microscopy of
mechanosensory hair cells in conjunction with an in vivo whole-mount protein-protein proximity assay. Our data suggest that these
four proteins are required not only for structural integrity of the mechanoreceptor, but also for its morphogenesis. We also found all
four proteins in close proximity, consistent with them forming a complex. Analysis of mutants and morpholino-injected animals
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