Human and mouse ISLR (immunoglobulin superfamily containing leucine-rich repeat) genes: Genomic structure and tissue expression

We have previously reported a transcript of the novel gene for human immuno globulin superfamily containing leucine-rich repeat (ISLR). By additional s creening of a human retina cDNA library, we isolated another type of transc ript with a 5' UTR different from that of the previously reported type, Gen omic sequencing of the ISLR gene revealed that these two types of transcrip ts, ISLR-1 and ISLR-2, originated from the same gene but are composed of di fferent first exons, Because the entire open reading frame is contained in the second exon, these two transcripts produce the same protein. Radiation hybrid mapping linked the ISLR gene to AFM248yh1, which is in the critical region of Bardet-Biedl syndrome type 4 (BBS4) on chromosome 15, Sequence an alysis of the ISLR gene in five BBS4 patients, however, showed no mutations , although a few polymorphic changes were detected. Cloning of the mouse ho molog of ISLR (Islr) revealed that the predicted protein consists of 428 am ino acids, 86% of which are identical to those of ISLR. The Islr gene was e xpressed in various mouse tissues, including retina, in which Islr mRNA was detected in the ganglion cell layer, the inner nuclear layer, and the inne r segment of the photoreceptor. (C) 1999 Academic Press.