Abstract
Purpose: :
Congenital fibrosis of the extraocular muscles (CFEOM) refers to several rare strabismus disorders characterized by non-progressive ophthalmoplegia primarily affecting extraocular muscles innervated by the oculomotor nerve. One recessive (FEOM2) and three dominant (FEOM1,3,4) CFEOM genetic loci are mapped, and PHOX2A and KIF21A identified as the FEOM2 and FEOM1 genes, respectively. Previously, we reported a consanguineous Yemenite family in which affected children reduced to homozygosity across the dominant FEOM1 locus. We now exclude KIF21A and PHOX2A, and provide evidence for a new recessive CFEOM locus.
Methods: :
DNA samples from 2 affected and 6 unaffected family members were sequenced for KIF21A and PHOX2A.An Affymetrix 10K SNP chip II genome-wide screen and multipoint linkage analysis were performed.
Results: :
No mutations in PHOX2A or KIF21A were identified. Assuming recessive inheritance, the maximum LOD score of 2.12 was obtained in regions of chromosomes 8, 12 and 18. Within each region, both affected family members reduced to homozygosity.
Conclusions: :
CFEOM is a genetically heterogeneous disorder for which an understanding of the underlying disease causing genes has given new insights into neuronal differentiation and axonal pathfinding. Our data provides candidate loci for a new recessive CFEOM gene. Genes within each region can now be screened for mutations.
Keywords: strabismus • genetics • extraocular muscles: development