Refinement of the X-linked cleft palate and ankyloglossia (CPX) localisation by genetic mapping in an Icelandic kindred.

The gene responsible for X-linked cleft palate and ankyloglossia (CPX) has previously been localized to the proximal region of the q arm of the X chromosome in both Icelandic and North American Indian kindreds. In this study, further linkage analysis has been performed on the Icelandic family and has resulted in a significant reduction in the size of the interval containing the mutated gene. A new polymorphism at DXS95, together with DXS1002 and DXS349, defines the proximal boundary of the CPX interval, whereas DXYS1X defines the distal boundary. Multipoint analysis supports this localisation with a peak lod score of 12.7, more than 2 lod score units higher than the next most likely position. In order to assess the physical size of the CPX interval prior to initiating yeast artificial chromosome cloning, metaphase fluorescence in situ hybridisation analysis was performed with the closest flanking markers. The size of the interval between DXS95 and DXYS1X was estimated to be approximately 2-3 Mb.