LINKAGE ANALYSIS OF 2 CANADIAN FAMILIES SEGREGATING FOR X-LINKED SPONDYLOEPIPHYSEAL DYSPLASIA

X linked spondyloepiphyseal dysplasia (SED) is caused by a growth defe ct of the vertebral bodies leading to characteristic changes in the ve rtebral bodies and a short trunk. The gene responsible for this disord er has previously been mapped to Xp22, with a maximum likelihood locat ion between markers DXS16 and DXS92. We present linkage data using mic rosatellite markers on two Canadian X linked SED families, one of Norw egian descent and the other from Great Britain. In the Xp22 region, th ree recombination events have occurred in these families, two between markers SXS996 and DXS1043 and one between DXS999 and DXS989. One fami ly shows a maximal lod score of 3.0 at theta = 0 with marker DXS1043 a nd the other family has a maximal lod score of 1.2 at theta = 0 with m arkers DXS1224 and DXS418. Both families therefore support the previou sly reported gene localisation.