Abstract
Purpose:
We analyzed a sample of eight ostensibly unrelated families for mutations in FRMD7 in order to expand the range of mutations in FRMD7 and to identify pedigrees not linked to the X-chromosome.<br /> Congenital motor nystagmus is transmitted according to the three patterns of inheritance classically observed in single gene Mendelian diseases: autosomal dominant and recessive and X-linked. The individually most common form of inheritance is X-linked, caused by mutations in FRMD7 at Xq26.2; a total of 53 mutations are known in this gene, nine of which have been discovered in the last two years.
Methods:
We analyzed eight families with congenital motor nystagmus. The mode of inheritance was X-linked in four, presumed autosomal recessive in one and simplex in three families. All living affected and potentially informative family members underwent an ocular evaluation; peripheral blood samples were obtained for DNA extraction after informed consent was secured; the study was approved by the Internal Review Board. DNA was isolated using the iPrep gDNA blood kit (Invitrogen, Grand Island, NY). One sample per family was sequenced in search of mutations in FRMD7 gene using Sanger sequencing.
Results:
We identified three novel mutations (c.781C>T, c.818A>G and c.1403G>A) in four families, one twice (c.781C>T); one previously identified mutation (c.691T>G) was found in two families; no mutation was identified in two families.
Conclusions:
New mutations in FERMD7 are still being identified since we identified three novel mutations in this study; they mapped to exons 9 and 12. The majority of mutations were found in the FERM domain and the FERM adjacent FA. The two patients without mutations in FRMD7 are presumed to have mutations in one of the unidentified genes in the previously mapped loci or at still unknown loci.