Mapping Far (First arch) in relation to molecular markers on mouse chromosome 2

Review of the etiologic heterogeneity of the oculo-auriculo-vertebral spectrum (Hemifacial Microsomia)

Hemifacial microsomia is a congenital asymmetry of the lower face that may be associated with other cranial and extracranial anomalies. The variability of its severity, and wide range of anomalies that have been reported with it in some cases has resulted in these composite manifestations being given a number of names, including oculo-auriculo-vertebral spectrum (OAVS). Etiology is often stated to be a perturbation of embryonic blood flow in the developing region, although other factors may also play a role in some cases. Depending on what is considered to be minimum criteria for affected classification, what is often to be presumed to be a sporadic event in a family may be the more severe manifestation of a familial condition. Etiological factors are clearly heterogeneous, the investigation of which is confounded by not only the lack of a refined affected phenotype, but also the apparent influence of genetic factors in some instances that directly influence phenotype perhaps through alteration of mesodermal development, or indirectly through increased susceptibility to vascular disruption. Future studies likely to advance knowledge in this area will need to incorporate an analysis of who may be minimally affected in families, so that advances in genotyping will have greater power to distinguish genetic factors that may influence OVAS through interaction with environmental factors in particular families. The same genetic-environmental factors and or etiological mechanisms may then be investigated in apparently sporadic cases.

The lidgap-Gates (lgGa) mutation for open eyelids at birth maps to mouse chromosome 13

Complex nonadditive interactions between specific alleles at multiple loci may underlie many so-called multifactorial threshold birth defects. The open-eyelids-at-birth defect in mice is a good model for these defects, and an understanding of its genetic complexity begins with mapping the participating loci. The open-eyelids defect can be part of a syndrome or can occur with no other obvious phenotypic effects. Of the latter nonsyndromic forms, the lidgap series includes four extant mutations that are considered to be alleles based on complementation tests. All show genetic complexity in segregation ratios. None has been mapped previously. On the basis of a strategy of mapping the mutation with the simplest inheritance pattern first, we generated an extensive exclusion map for lidgap-Gates, lgGa, using morphological and protein polymorphisms. We then screened the non-excluded regions in a congenic strain, AEJ.LGG-lgGa, for SSLP markers and located the differential chromosome segment containing the lgGa locus in a region near the distal end of mouse Chromosome (Chr) 13. This linkage was confirmed and refined by typing SSLPs in 64 F2 and 74 BC1 progeny of a cross of LGG/Bc (lgGa/lgGa) to SWV/Bc. The lgGa mutation maps to a 1- to 2-cM region between D13Mit76 and D13Mit53. Integrin alpha 1 and integrin alpha 2, which map to the same general region, are possible candidate loci, based on their embryonic expression and cellular function. Evidence is also presented for a common unlinked recessive suppressor of the open eyelids trait caused by lgGa.

The major locus for multifactorial nonsyndromic cleft lip maps to mouse chromosome 11

Cleft lip with or without cleft palate, CL(P), a common human birth defect, has a genetically complex etiology. An animal model with a similarly complex genetic basis is established in the A/WySn mouse strain, in which 20% of newborns have CL(P). Using a newly created congenic strain, AEJ.A, and SSLP markers, we have mapped a major CL(P)-causing gene derived from the A/WySn strain. This locus, here named clf1 (cleft lip) maps to Chromosome (Chr) 11 to a region having linkage homology with human 17q21-24, supporting reports of association of human CL(P) with the retinoic acid receptor alpha (RARA) locus.