Characterization of the larynx in ephrin-B2 knockout mice: A novel animal model for laryngeal clefts

Objective: To identify and classify laryngeal clefts in a novel mouse model. Design: In vivo animal study. Setting: Academic research laboratory. Subjects: 129/CD1 mice with the ephrin-B2 gene disrupted by the β-galactosidase ( lacZ ) gene were humanely killed at embryonic day 18 (E18) and evaluated for the presence and characterization of a laryngeal cleft. Homozygous and heterozygous lacZ knockout mice as well as wild-type littermates were evaluated. Main Outcome Measures: Microsurgical dissection of the oral cavity and pharynx allowed for a pseudoendoscopic view of the larynx to determine the presence or absence of a cleft. The specimens were also histologically sectioned and examined for characterization and classification of the cleft. Results: A laryngeal cleft was identified in 12 of 27 ephrin-B2 homozygous lacZ knockout mice (44%). Laryngeal clefts were not identified in heterozygous ephrin-B2 knockout mice or in wild-type littermates. Conclusions: Disruption of ephrin-B2 reverse signaling results in laryngeal clefts in lacZ knockout mice. This presents a novel mouse model in which future investigations into etiology of laryngeal clefts may be examined.