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Updated: Apr 28, 2026
Dissection of the Auditory Bulla in Postnatal Mice: Isolation of the Middle Ear Bones and Histological Analysis
Published on: January 4, 2017
The genetics of auricular development and malformation: new findings in model systems driving future directions for
Timothy C Cox1, Esra D Camci2, Siddharth Vora2
1Center for Developmental Biology & Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA, USA; Department of Pediatrics (Craniofacial Medicine), University of Washington, Seattle, WA, USA; Department of Oral Health Sciences, University of Washington, Seattle, WA, USA; Department of Anatomy & Developmental Biology, Monash University, Clayton, Victoria, Australia.
Abstract:
Microtia is a term used to describe a wide array of phenotypic presentations of the outer ear. Although the majority of the cases are isolated in nature, much of our understanding of the causes of microtia has been driven by the identification of genes underlying syndromic forms where the anomaly co-presents with various other craniofacial and extra-craniofacial structural defects. In this review we discuss recent findings in mice deficient in Hoxa2, a key regulator of branchial arch patterning, which has necessitated a revision to the canonical model of pinna morphogenesis. The revised model will likely impact current classification schemes for microtia and, as we argue in this review, the interpretation of the developmental basis for various auricular malformations. In addition, we highlight recent studies in other mammalian species that are providing the first clues as to possible causes of at least some isolated anomalies and thus should now accelerate the search for the more elusive genetic contributions to the many isolated and non-syndromic cases of microtia. These findings, together with the application of new genome-level sequencing technologies and more thorough quantitative assessment of available mutant mouse resources, promise an exciting future for genetic studies in microtia.
Insights
Recent studies on Hoxa2 gene function in mice are revising the understanding of outer ear development (microtia). This research also sheds light on potential causes for isolated microtia cases in other mammals.
Area of Science:
- Developmental Biology
- Genetics
- Craniofacial Development
Background:
- Microtia encompasses diverse outer ear malformations.
- Understanding microtia causes is often linked to syndromic forms with other defects.
- Isolated microtia cases remain challenging to explain genetically.
Purpose of the Study:
- To review recent findings on Hoxa2 gene function in ear morphogenesis.
- To discuss the impact of new models on microtia classification and developmental interpretation.
- To highlight emerging insights into isolated microtia from studies in other mammalian species.
Main Methods:
- Review of recent research on Hoxa2-deficient mice.
- Analysis of findings from studies in other mammalian species.
- Consideration of new genome-level sequencing technologies and mutant mouse resources.
Main Results:
- Hoxa2 deficiency necessitates a revised model of outer ear (pinna) morphogenesis.
- New research in other mammals offers initial clues for isolated microtia causes.
- Advances in sequencing and mouse models are accelerating genetic research in microtia.
Conclusions:
- The revised model of pinna morphogenesis will influence microtia classification.
- Understanding Hoxa2 function is crucial for interpreting auricular malformations.
- Future research integrating new technologies promises to uncover genetic factors in isolated microtia.
