A GENE (SRPX) ENCODING A SUSHI-REPEAT-CONTAINING PROTEIN IS DELETED IN PATIENTS WITH X-LINKED RETINITIS-PIGMENTOSA

X-linked retinitis pigmentosa (XLRP) is characterized by retinal degen eration with night blindness and progressive reduction of the visual f ields. By linkage and deletion analysis a gene locus (RP3) has been ma pped-to the short arm of the X chromosome between the genes CYBB and O TC. Analysis of transcripts in this region has revealed a gene which i s abundantly expressed in human retina and encodes a putative membrane protein with significant homologies to short consensus repeat (SCR/su shi) domains known from selectins and complement proteins. The gene, t ermed SRPX (sushi-repeat-containing protein, X chromosome) is deleted in an RP patient who also suffers from chronic granulomatous disease a nd McLeod syndrome. A 75 kb deletion removing exon 1 of the gene was a lso found in two brothers of a second XLRP family. However, no further functionally significant mutations were detected by SSCP screening of ail 10 exons in 34 unrelated XLRP patients nor by full length RT-PCR sequencing in two RP3 families. The role of this highly conserved reti nal gene in the pathogenesis of RP therefore remains to be determined.