Emory geneticist Tamara Caspary is an expert on the Hedgehog pathway, critical for brain development. In particular, she and her colleagues have been studying a gene that is part of the Hedgehog pathway called Arl13b, which is mutated in Joubert syndrome, affecting development of the cerebellum and brain stem.
The Arl13b protein was known to be enriched in primary cilia, tiny hair-like cellular structures with a signaling/navigation function in neuronal development. However Caspary’s lab, in a collaboration with Frederic Charron’s group in Montreal, has found that Arl13b can also function outside cilia: in axons and growth cones.
The Hedgehog pathway has several roles, some in specifying what embryonic cells will become, and others in terms of guiding growing axons, the scientists conclude in their new paper in Cell Reports.
“Arl13b regulates Shh [Sonic Hedgehog] signaling through two mechanisms: a cilia-associated one to specify cell fate and a cilia localization-independent one to guide axons,” they write. A related preprint, confirming Arl13b’s extra-ciliary role in mouse development, has been posted on bioRxiv.
Cilia are tiny hair-like structures on the outside of cells. Your memory of cilia may extend back to biology class, when you saw a picture of a paramecium or lung tissues, where cilia keep surfaces free of dirt and mucus.
Ciliated cells in the human oviduct
In the last few years, scientists have been learning more about cilia’s many roles in the body. Nearly all mammalian cells have cilia, and they are thought to act more like antennae, sending and receiving signals.Â Defects in cilia have been connected to lung, heart, kidney and eye diseases. Accordingly, Emory’s 15th BCMB training grant symposium focuses on cilia, beginning Thursday evening with a keynote talk by Susan Dutcher from Washington University, St. Louis and extending all day Friday.
At Emory, cell biologistÂ Winfield Sale’s laboratory uses the model system of the alga Chlamydomonas to study dynein, a molecular motor that drives the functions of cilia. In addition,Â geneticist Tamara Caspary’s laboratory is studying how defects in cilia can lead to altered embryonic development. Ping Chen’s group has been examining cilia in the context of inner ear development.
This week’s program is sponsored by Emory’s graduate program in Biochemistry, Cell and Developmental Biology, the Departments of Cell Biology, Biochemistry, Pharmacology, Biology, Microbiology and Immunology, Physics, the Graduate Division of Biological and Biomedical Sciences and the Woodruff Health Sciences Center.