Lethal Contractural Syndrome Type 3 (LCCS3) Is Caused by a Mutation in PIP5K1C, Which Encodes PIPKIγ of the Phophatidylinsitol Pathway

Abstract

Lethal congenital contractural syndrome (LCCS) is a severe form of arthrogryposis. To date, two autosomal recessive forms of the disease (LCCS and LCCS2) have been described and mapped to chromosomes 9q34 and 12q13, respectively. We now describe a third LCCS phenotype (LCCS3)--similar to LCCS2 yet without neurogenic bladder. Using 10K single-nucleotide-polymorphism arrays, we mapped the disease-associated gene to 8.8 Mb on chromosome 19p13. Further analysis using microsatallite markers narrowed the locus to a 3.4-Mb region harboring 120 genes. Of these genes, 30 candidates were sequenced, which identified a single homozygous mutation in PIP5K1C. PIP5K1C encodes phosphatidylinositol-4-phosphate 5-kinase, type I, gamma (PIPKI gamma ), an enzyme that phophorylates phosphatidylinositol 4-phosphate to generate phosphatidylinositol-4,5-bisphosphate (PIP(2)). We demonstrate that the mutation causes substitution of aspartic acid with asparagine at amino acid 253 (D253N), abrogating the kinase activity of PIPKI gamma . Thus, a defect in the phosphatidylinositol pathway leading to a decrease in synthesis of PIP(2), a molecule active in endocytosis of synaptic vesicle proteins, culminates in lethal congenital arthrogryposis.

Clathrin Regulates the Association of PIPKIγ661 with the AP-2 Adaptor β2 Appendage

“…Thus molecular mechanisms appear to exist to align cycles of PtdIns(4,5)P 2 formation and hydrolysis with progression of the coated assemblage toward the final fission step. In this study, we confirm that PIPKI␥, a vital lipid kinase (12)(13)(14) and the major phosphatidylinositol 4-phosphate kinase at the synapse (32), binds to AP-2 chiefly through the functionally autonomous appendage domain of the large ␤2 chain. We show that this depends on an interaction surface positioned upon the sandwich subdomain of the ␤2 appendage, a site also engaged by clathrin and eps15.…”

“…This raises the question of whether the prevailing PtdIns(4,5)P 2 concentration at the cell surface is simply permissive and sufficient for nucleation and sustained clathrin-coated vesicle assembly and budding or whether, in addition to basal PtdIns(4,5)P 2 that might act as an initial compartmental cue, regional synthesis of this lipid is also necessary for clathrin coat assembly and progression. Supporting the first possibility is the general decrease in PtdIns(4,5)P 2 levels in the brains of type I␥ phosphatidylinositol 4-phosphate 5-kinase (PIPKI␥) nullizygous mice that parallels major synaptic vesicle recycling aberrations in neurons of these animals, which die before (12,13) or shortly after (14) birth. Also, activated P2Y purinergic receptors, which trigger phospholipase C-mediated cleavage of PtdIns(4,5)P 2 , diminish clathrin-mediated uptake of insulin (15), suggesting that signaling and endocytic processes can utilize a common phosphoinositide pool.…”

The desmosterolosis phenotype: spasticity, microcephaly and micrognathia with agenesis of corpus callosum and loss of white matter

“…3 EBV transformation of lymphocytes of affected individuals was carried out as previously described. 5 RNA was extracted from cultured cells of EBV-transformed lymphoblastoid cell lines using the RNeasy Mini Kit (Qiagen, Petach Tikva, Israel) and cDNA was reverse transcribed by the Verso RT-PCR Kits (TAMAR, Mevaseret Zion, Israel) according to the protocol of the manufacturer. 6 Primer pairs for cDNA and/or exons of genomic DNA (including flanking intron sequences) of eight genes in the putative 1p33-1p32.3 locus were designed based on the known mRNA and genomic sequences using Primer3.…”

“…We then proceeded to perform genome-wide linkage analysis of four patients, four obligatory carriers (parents of affected individuals) and one healthy sibling (IV1, IV2, V1, V2, IV3, III5, V4, V7 and IV5, depicted in Figure 1), using 250K SNP Arrays (GeneChip Human Mapping 500K Array Set (Affymetrix)) as previously described. 3,5 A single region of homozygosity on chromosome 1p33-1p32.3 was identified, that was common to all affected individuals. Fine mapping 2,6 testing the 18 available DNA samples with polymorphic markers narrowed down the locus to 6.75 cM (7.25 Mb) between D1S2824 and D1S200, with a maximum multipoint LOD score of six calculated using SUPERLINK 4 (data not shown).…”

Deficiency in the mRNA export mediator Gle1 impairs Schwann cell development in the zebrafish embryo

“…LCCS2 is caused by mutation of ERBB3 (Narkis et al, 2007b), a member of the ERBB family of receptor tyrosine kinases; LCCS3 is caused by mutation of PIP5K1C (Narkis et al, 2007a), which encodes phosphatidylinositol-4-phosphate 5-kinase, type I, gamma (PIPKIγ); LCCS5 is caused by homozygous Dynamin 2 (DNM2) mutation (Koutsopoulos et al, 2013); while another study linked mutations in CNTNAP1 (encoding contactin associated protein 1) and ADCY6…”