Abstract
Purpose: :
To identify mutations in five Chinese families with congenital fibrosis of the extraocular muscles (CFEOM) and to characterize their clinical phenotypes.
Methods: :
Detailed clinical investigations were undertaken and genomic DNA was extracted from blood samples. Detection of known mutations in KIF21A gene was performed initially. Then Linkage analysis by exclusive mapping was conducted in the remaining families. At last, direct genomic sequencing was used to evaluate all the rest of exons and flanking intron sequences of the KIF21A gene. A restriction assay was used to confirm the novel mutation status in family.
Results: :
Four of the 5 families were classified as CFEOM1 and one as CFEOM3 by clinical evaluations. Firstly, heterozygous mutations 2860C/T and 2861G/A were identified in 2 CFEOM1 families and a CFEOM3 family respectively. Subsequently, in the rest of 2 CFEOM1 families, one was consistent with linkage to FEOM1, the other was consistent with linkage to both FEOM1 and FEOM3. Finally, a novel heterozygous mutation (84C/G, C28W) was detected in one family. The mutation co-segregated completely with the disease phenotype, but was absent in the unaffected relatives and 200 reference control alleles. The remaining CFEOM1 family did not harbor mutations in KIF21A.
Conclusions: :
A novel mutation (84C/G) in the KIF21A gene caused CFEOM in a Chinese CFEOM1 family studied. Its different location from that of the mutations identified previously within KIF21A suggested different pathogenesis of CFEOM. Furthermore, our findings provided evidence of genetic heterogeneity of both CFEOM1 and CFEOM3, implying the necessities of classification of CFEOM based on both genetic etiology and clinical presentations.
Keywords: gene screening • strabismus: etiology