Validity of the Hfm transgenic mouse as a model for hemifacial microsomia.

Abstract Objective: Our comprehension of hemifacial microsomia (HFM) has been hindered by its diverse phenotype and unclear etiopathogenesis. The conventional view has been that HFM's facial defects result from embryonic hemorrhages in the region of the first and second branchial arches. A more recent model based on a transgenic mutation of a locus termed Hfm (B1 to B3 on chromosome 10) appears to provide an insight into HFM causation. This study investigated the validity of this model by examining the Hfm craniofacial phenotype and histological development of the embryonic head (E13.5 to 17.5). Results: The results confirmed that although the loss-of-function mutation was transmitted in an autosomal dominant manner, the penetrance rate was significantly reduced and only Hfm heterozygotes were viable. The observations here extend the Hfm phenotype beyond microtia and jaw asymmetry to include structural and positional anomalies affecting the external auditory meatus, middle ear, cranial base, maxilla, and ...