Linkage analysis inUshersyndrome typeI (USH1)families fromSpain

Ushersyndrome(USH)is an autosomal recessive hereditary disorder characterisedbycongenital sensorineural hearing lossandgradualvisual impairment secondarytoretinitis pigmentosa (RP).The disorder isclinically andgenetically heterogeneous. WithregardtoUshertypeI (USHI),several subtypes havebeendescribed, themost frequent beingUSHIB located on chromosomeIlqI3.5. Of 18 USH1 families studied bylinkage analysis, 12(67%)showedsignificant lodscore values forlocusDllS527(Zmax=14.032, 0=0.000) situated on chromosomellq. Ourfindings suggestconsiderable genetic heterogeneity intheSpanishUSH1 population. Itisimportant tonotethatone of our families linkedto theUSHIB locus showsinteresting intrafamilial clinical variability. As regards theremaining six USHI families, thelinkage analysis did notprovide conclusive data,although two ofthem showslight linkage to markers located on chromosome3q(Zmax=1.880, 0=0.000forD3S1279), thesame location thathadpreviously beenassigned tosome USH3 families. (7MedGenet 1998;35:391-398)