MULTIPOINT LINKAGE ANALYSIS IN X-LINKED OCULAR ALBINISM OF THE NETTLESHIP-FALLS TYPE

An extensive linkage analysis was performed by studying ten Xp22 loci in ten families segregating for X-linked ocular albinism of the Nettleship-Falls type (XOA). Linkage was confirmed between the XOA locus (OA1) and both DXS16 (theta-max = 0.10, Z(max) = 4.09) and DXS237 (theta-max = 0.12, Z(max) = 2.53). Linkage was found between OA1 and the loci DXS85 (theta-max = 0.00, Z(max) = Z(max) = 4.37), DXS143 (theta-max = 0.04, Z(max) = 3.74), STS (theta-max = 0.05, Z(max) = 2.48), DXF30S1 (DXS278) (theta-max = 0.07, Z(max) = 8.79) and DXF30S2/3 (DXS278) (theta-max = 0.00, Z(max) = 14.93). An indication for linkage was found between OA1 and the loci DXS43 (theta-max = 0.10, Z(max) = 1.58) and DXS31 (theta-max = 0.12, Z(max) = 1.55). The analysis of multiple informative meioses suggests the order Xpter-(DXS31, DXS89)-(DXF30S1, DXS237)-(DXF30S2/3, OA1)-DXS143-(DXS16, DXS43)-Xcen. Various multipoint linkage analyses using the DNA loci order DXF30S1-STS-DXS237-DXS143-DXS16 significantly favour the position of OA1 between DXS237 and DXS143. These results further determine the genetic map around the XOA locus on the distal Xp and may be useful for DNA diagnosis in families with XOA.