Backgrounds. Congenital motor nystagmus CMN is a subtype of Congenital nystagm and usually diagnosed after sensory defect nystagmus is excluded. Although four sites have been located on X chromosome but we think there is still another disease gene on X chromosome. So in our study, we will narrow down the candidate region and identify the candidate gene for X-linked CMN of two Congenital motor nystagmus families.
Methods. Two families with CMN were investigated. Genotyping and linkage analysis were conducted in these two Chinese families.
Results. These two families were affected by X-linked CMN with incomplete penetrance. Two-point linkage analysis revealed significant maximum logarithm of odds (LOD) scores of 8.55 (DXS1047, sita = 0) and 3.91 (DXS1211 and DXS1205, sita = 0) at the family nys-01 and the family nys-02 respectively. Haplotype construction and multipoint linkage analysis also confirmed the locus and refined the locus to a 7.1 cM interval between the markers DXS8044 and DXS8041 in chromosome Xq25-q26.3.
Conclusion. We have mapped the nystagemus gene to an interval of 7.1 cM, at the location of Xq15-q26.3, such interval shares no overlap with previous Xq26-q27 locus.