Photoreceptor localization of the KIF3A and KIF3B subunits of the heterotrimeric microtubule motor kinesin II in vertebrate retina

The heterotrimeric microtubule motor kinesin II has been shown to be requir ed for morphogenesis and maintenance of both motile flagella and immotile s ensory cilia. Recently, we showed that the KIF3A subunit of kinesin II is c oncentrated in the inner segment and connecting cilium of fish photorecepto rs. Here we report the gene structure of human KIF3A (HsKIF3A) and describe its localization in human and monkey retina. We also describe the localiza tion of both KIF3A and KIF3B kinesin II subunits in Xenopus retina. Using a portion of HsKIF3A we had amplified from adult human retinal cDNA, we found by a GenBank database search that an identical sequence had alread y been obtained by the Human Genome Center at Lawrence Berkeley National La boratories in a direct sequencing analysis of 680 kb of human chromosome 5q 31. By comparing the genomic sequence of HsKIF3A to the open reading frame (ORF) of the highly homologous mouse Kif3A, we determined that the HsKIF3A gene has 17 exons and an ORF of similar to 2.1 kb, predicting a protein of 80.3 kDa. Antibodies against sea urchin KRP85, a KIF3A homologue, bound to a single b and of similar to 85 kDa in immunoblots of total retina protein from human, monkey and Xenopus. In these same samples, a single band of similar to 95 kDa is recognized by antibodies against Xklp3, a Xenopus KIF3B homologue. I n sections of Xenopus retina, both antibodies strongly labelled photorecept or inner segments and the outer limiting membrane. Both antibodies also lab elled photoreceptor axonemes. The axonemal localization of kinesin II subun its suggests that kinesin II may play a role in transport of materials from the photoreceptor cell body to the outer segment. (C) 1999 Academic Press.