Lowe's oculocerebrorenal syndrome (OCRL) is a human X-linked developmental disorder of unknown pathogenesis and has a pleiotropic phenotype affecting the lens, brain and kidneys. The OCRL locus has been mapped to Xq25-q26 by linkage and by finding de novo X; autosome translocations at Xq25-q26 in two unrelated females with OCRL. Here we use yeast artificial chromosomes with inserts that span the X chromosomal breakpoint from a female OCRL patient in order to isolate complementary DNAs for a gene that is interrupted by the translocation. We show that the transcript is absent in both female OCRL patients with X; autosome translocations and that it is absent or abnormally sized in 9 of 13 unrelated male OCRL patients with no detectable genomic rearrangement. The open reading frame encodes a new protein with 71% similarity to human inositol polyphosphate-5-phosphatase. Our results suggest that OCRL may be an inborn error of inositol phosphate metabolism.

Phosphatidylinositol 3,4,5-trisphosphate is a phospholipid signaling molecule involved in many cellular functions including growth factor receptor signaling, cytoskeletal organization, chemotaxis, apoptosis, and protein trafficking. Phosphorylation at the 3 position of the inositol ring is catalyzed by many different 3-kinases (classified as types I A , I B , II, and III), but the physiological roles played by each of the different 3-kinase isozymes during embryonic development and in homeostasis in animals is incompletely understood. Mammalian type I A kinase isozymes are heterodimers that are active at 37°C when the catalytic 110-kDa subunit interacts through an amino-terminal binding domain with a regulatory 85-or 55-kDa subunit. Using gene targeting in embryonic stem cells, we deleted this binding domain in the gene encoding the ␣ isoform of the 110-kDa catalytic subunit (Pik3ca) of the ␣ isozyme of the type I A kinases, leading to loss of expression of the p110 catalytic subunit. We show that Pik3ca del/del embryos are developmentally delayed at embryonic day (E) 9.5 and die between E9.5 and E10.5. E9.5 Pik3ca del/del embryos have a profound proliferative defect but no increase in apoptosis. A proliferative defect is supported by the observation that fibroblasts from Pik3ca del/del embryos fail to replicate in Dulbecco's modified Eagle's medium and fetal calf serum, even with supplemental growth factors.Phosphorylated phosphoinositides generated by phosphoinositide (PI) 1 3-kinases play crucial roles in signaling through receptors at the cell surface as well as in membrane trafficking mechanisms in Golgi and endosomal compartments, cytoskeletal organization, and regulation of apoptosis (1-9). The genes for many PI 3-kinases have been isolated from a wide range of tissues and organisms. They are divided into three major classes based on their amino acid sequence, the homology among their lipid-kinase domains, and substrate specificities (6, 9). Class I PI 3-kinases phosphorylate the 3Ј sites of PtdIns, PtdIns 4-phosphate, and PtdIns 4,5-diphosphate to form PtdIns 3-phosphate, PtdIns 3,4-diphosphate, and PtdIns 3,4,5-trisphosphate. Class I PI 3-kinases can be further divided into two subclasses. The class I A PI 3-kinases, which include at least three isozymes, ␣, ␤, and ␦, are heterodimers of a catalytic 110-kDa subunit (p110) and a regulatory subunit of 85 or 55 kDa (p85/p55) (10 -14). The interaction of p85/p55 and p110 via the inter-Src homology 2 domain on p85/p55 and the aminoterminal 123 amino acids of p110 is critical for achieving maximal activity of this class of PI 3-kinases in mammalian cells at 37°C (11,15,16).Despite a wealth of knowledge of the biochemistry and cell biological effects of phosphoinositides, very little information is available on the particular physiological roles played by these different enzymes and isozymes during mammalian development. Inhibitors of PI 3-kinases such as wortmannin (17) and LY294002 (18) are very useful for probing the functions of these enzymes but as with a...

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We performed positional cloning of genes carried on yeast artificial chromosomes that span a human translocation breakpoint associated with a human disease and isolated by chance human and bovine genes with strong homology to the S. cerevisiae genes, SNF2/SWI2 and STH1, and the D. melanogaster gene brahma. We report here sequence analysis, expression data, and functional studies for this human SNF2-like gene (hSNF2L) and its bovine homolog (bovSNF2L). Despite strong homology at the amino acid level, hSNF2L is not capable of complementing the yeast mutations snf2 or sth1 in S. cerevisiae. Furthermore, in contrast to SNF2 itself, a fusion protein consisting of the DNA binding domain of LexA and hSNF2L did not transactivate a reporter gene downstream of LexA binding sites in a yeast expression system. The strong similarity between hSNF2L and these yeast and drosophila genes suggest that the mammalian genes are part of an evolutionarily conserved family that has been implicated as global activators of transcription in yeast and fruitflies but whose function in mammals remains unknown.

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The mitochondrial copper concentrations and cytochrome C oxidase activity of the fibroblasts from the patients with Menkes syndrome were investigated. Both the mitochondrial copper concentrations and cytochrome C oxidase activity of fibroblasts from patients with Menkes syndrome were lower than those of the control fibroblasts. These data indicate that the mitochondria of fibroblasts from patients with Menkes syndrome are in a state of copper deficiency. The activity decline of cytochrome C oxidase, a mitochondrial cuproenzyme, seems to be caused by copper deficiency in the mitochondria.

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