Mutations are not uniformly distributed throughout the OCRL1 gene in Lowe syndrome patients

Lowe syndrome (OCRL) is an X-linked disorder involving the eyes, kidney, and nervous system that is caused by loss of function in the OCRL1 gene. OCRL1 contains 24 exons (23 of which are coding) and encodes a 105-kDa enzyme with phosphatidylinositol 4,5 bisphosphate (PtdIns[4,5]P-2) 5-phosphatase activity. We published previously (1,2) 13 different mutations in 15 patients. Here we report another 8 mutations in 10 families. Four are missense mutations in highly conserved PtdIns(4,5)Pz 5-phosphatase domains, two are premature terminations caused by nonsense mutations, and three others are premature terminations caused by frameshift mutations. One frameshift, a GT deletion in exon 21, has been observed previously in two unrelated Lowe syndrome patients, suggesting that it may be a relative "hotspot" for mutation in a disorder marked otherwise by allelic heterogeneity. We have also seen two other recurrent mutations. One is a nonsense mutation <(C)under bar GA> > <(T)under bar GA> in exon 22 observed in two patients and the second is a missense mutation CGA > CA in exon 15 present in two unrelated patients. These 21 distinct mutations we have found in 25 Lowe syndrome patients occur in only 9 of the 24 exons: 10, 12, 13, 14, 15, 18, 19, 21, and 22. interestingly missense mutations have occurred only in exons 12 through 15 in highly conserved residues among the phosphatidylinositol 5-phosphatases, These observations suggest useful strategies for mutation screening in OCRL, (C) 1998 Academic Press.