Tubby Like Protein 1 (TULP1)

North et al. (1997) identified the more distantly related TULP1 and TULP2 genes in humans. All 3 genes encode proteins with different N termini but with conserved C-terminal regions (63 to 90% amino acid identity) of approximately 200 amino acid residues. They also have distinct tissue expression patterns; TUB is expressed in many tissues including retina, whereas TULP1 is expressed exclusively in retina and TULP2 in retina and testis.

The mutation was homozygous in all 33 affected individuals and heterozygous in all 50 obligate carriers. The mutation was not observed in 210 unrelated controls. The data from the 2 studies indicated that mutation in TULP1 is a rare cause of recessive RP and that TULP1 plays an essential role in the physiology of photoreceptors.