Int. J. Dev. Biol. 61: 557 - 563 (2017)
doi: 10.1387/ijdb.170155jb
© UPV/EHU Press

Temporal and spatial expression patterns of Hedgehog receptors in the developing inner and middle ear

Jeong-Oh Shin1, Harinarayana Ankamreddy1,3, Naga Mahesh Jakka1, Seokwon Lee4,5, Un-Kyung Kim4,5 and Jinwoong Bok*,1,2,3

1Department of Anatomy, 2Department of Otorhinolaryngology, 3BK21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, 4Department of Biology, College of Natural Sciences and 5School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, Republic of Korea

ABSTRACT The mammalian inner ear is a complex organ responsible for balance and hearing. Sonic hedgehog (Shh), a member of the Hedgehog (Hh) family of secreted proteins, has been shown to play important roles in several aspects of inner ear development, including dorsoventral axial specification, cochlear elongation, tonotopic patterning, and hair cell differentiation. Hh proteins initiate a downstream signaling cascade by binding to the Patched 1 (Ptch1) receptor. Recent studies have revealed that other types of co-receptors can also mediate Hh signaling, including growth arrest-specific 1 (Gas1), cell-adhesion molecules-related/down-regulated by oncogenes (Cdon), and biregional Cdon binding protein (Boc). However, little is known about the role of these Hh co-receptors in inner ear development. In this study, we examined the expression patterns of Gas1, Cdon, and Boc, as well as that of Ptch1, in the developing mouse inner ear from otocyst (embryonic day (E) 9.5) until birth and in the developing middle ear at E15.5. Ptch1, a readout of Hh signaling, was expressed in a graded pattern in response to Shh signaling throughout development. Expression patterns of Gas1, Cdon, and Boc differed from that of Ptch1, and each Hh co-receptor was expressed in specific cells and domains in the developing inner and middle ear. These unique and differential expression patterns of Hh co-receptors suggest their roles in mediating various time- and space-specific functions of Shh during ear development.

Keywords:

inner ear, hedgehog, Gas1, Cdon, Boc

*Corresponding author e-mail: bokj@yuhs.ac