A novel PIGN mutation and prenatal diagnosis of inherited glycosylphosphatidylinositol deficiency.

Glycosylphosphatidylinositol (GPI) anchors tether proteins to the extracellular face of eukaryotic plasma membranes. Defects in the human GPI anchor biosynthetic pathway cause inherited GPI deficiencies (IGDs) characterized by multiple congenital anomalies: dysmorphic faces, developmental delay, hypotonia, and epilepsy. We report the case of a 6-year-old boy with severe psychomotor developmental delay, epilepsy, and decreased granulocyte surface expression of GPI-anchored protein that suggested autosomal recessive GPI deficiency. The case underwent target exome sequencing to screen for IGDs. Target exome sequencing of the proband identified an apparently homozygous c.808T > C (p.Ser270Pro) mutation in PIGN, a gene involved in the GPI anchor biosynthetic pathway. As his parents were expecting another child, genetic carrier screening was conducted for the parents. Direct sequencing of the parents identified a heterozygous c.808T > C PIGN mutation in the father but none in the mother. To identify the mother's mutation, we performed semi-quantitative real-time PCR of the PIGN exons and long PCR, identifying a microdeletion in PIGN (del exons 2-14). The proband had inherited this microdeletion from his mother. Prenatal diagnosis of the fetus revealed that it was a heterozygous carrier of the mother's pathogenic allele. Here, we report a sporadic case of inherited GPI deficiency with a PIGN mutation and the first case of prenatal diagnosis for GPI deficiency.

Prenatal genetic testing for familial severe congenital protein C deficiency.

Severe congenital protein C (PC) deficiency is an autosomal recessive hereditary thrombophilia caused by mutations in PROC. The case manifested severe purpura fulminans, intracranial thrombosis or hemorrhage within 4 days after birth, resulting in blindness. We report the identification of inherited compound heterozygous mutations, including a novel nonsense mutation in PROC, and a prenatal genetic test for a subsequent pregnancy. Prenatal diagnosis may facilitate preemptive and radical therapy for severe PC deficiency.

Lateral diffusion of lipids separated from rotational and translational diffusion of a fluid large unilamellar vesicle.

A new method to separate lateral diffusion of lipids in spherical large unilamellar vesicles from the rotational and the translational diffusion of the vesicle as a whole is proposed. The lateral diffusion coefficient DL is obtained as a time-dependent part of the observed diffusion coefficient in vesicles of 800-nm diameters, by systematically changing the diffusion time interval of the high-field-gradient NMR measurement. Although the lipid is in a confined space, the DL of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is (1.5±0.6)×10(-11) m(2) s(-1) in the fluid state at 45°C, more than one order of magnitude faster than the rotational and the translational diffusion coefficients of the vesicle by the hydrodynamic continuum model. The method provides a potential for quantifying the lateral diffusion of lipids and proteins in fluid bilayer vesicles as model cell membranes in a natural manner.

Kinetics of binding and diffusivity of leucine-enkephalin in large unilamellar vesicle by pulsed-field-gradient 1H NMR in situ.

The kinetics of binding, the diffusivity, and the binding amount of a neuropeptide, leucine-enkephalin (L-Enk) to lipid bilayer membranes are quantified by pulsed-field-gradient (PFG) 1H NMR in situ. The peptide signal is analyzed by the solution of the Bloch equation with exchange terms in the presence of large unilamellar vesicles (LUVs) as confined, but fluid model cell membranes. Even in the case that the membrane-bound and the free states of L-Enk cannot be distinguished in the one-dimensional NMR spectrum, the PFG technique unveils the bound component of L-Enk after the preferential decay of the free component at the high field gradient. In 100-nm diameter LUVs consisting of egg phosphatidylcholine, the rate constants of the peptide binding and dissociation are 0.040 and 0.40 s-1 at 303 K. This means that the lifetime of the peptide binding is of the order from second to ten-second. The diffusivity of the bound L-Enk is 5×10-12m2/s, almost 60 times as restricted as the movement of free L-Enk at 303K. One-tenth of 5mM L-Enk is bound to 40mM LUV. The binding free energy is calculated to be -2.9 kJ/mol, the magnitude close to the thermal fluctuation, 2.5 kJ/mol. The result demonstrates the potential of PFG 1H NMR to quantify molecular dynamics of the peptide binding to membranes.

Regulation of mesodermal differentiation of mouse embryonic stem cells by basement membranes.

Basement membranes (BMs) have been implicated in cell fate determination during development. Embryoid bodies (EBs) derived from mouse embryonic stem cells deficient in the laminin gamma1 chain are incapable of depositing a BM, resulting in failure of primitive ectoderm epithelialization. To elucidate the mechanisms involved in this phenomenon, we compared the gene expression profiles of EBs with or without a BM to identify the genes showing BM-dependent expression. We found that the expressions of marker genes for the epithelial-mesenchymal transition (EMT), including the transcription factor Snai2, were up-regulated in LAMC1(-/-) EBs, whereas restoration of a BM to LAMC1(-/-) EBs suppressed the up-regulation of these genes. Overexpression of Snai2 induced the EMT in control EBs by molecular and morphological criteria, suggesting that suppression of the EMT regulatory genes is involved in BM-dependent epithelialization of primitive ectoderm. Despite the failure of primitive ectoderm epithelialization in BM-deficient EBs, mesodermal differentiation was not compromised, but rather accelerated. Furthermore, at later stages of control EB differentiation, the BM was disrupted at the gastrulation site where mesodermal markers were strongly expressed only in cells that had lost contact with the BM. Taken together, these results indicate that the BM prevents the EMT and precocious differentiation of primitive ectoderm toward mesoderm in EBs, implying that BMs are important for the control of mammalian gastrulation.

A novel large-scale production system for modified basement membrane matrices using gene-swapped parietal endoderm cells.

Parietal endoderm-like cells, including Engelbreth-Holm-Swarm tumor and differentiated F9 embryonal carcinoma cells, produce huge amounts of basement membrane components, including laminin-1 (alpha1beta1gamma1). We employed a double-lox system-based gene-swapping strategy in F9 cells to replace the laminin alpha1 gene with a laminin alpha5 minigene. The gene-swapped F9 cells secreted laminin-10 (alpha5beta1gamma1) consisting of the exogenous alpha5 subunit and endogenous beta1 and gamma1 subunits on differentiation. The laminin-10 concentration in the conditioned medium exceeded 10 mg/l, which is 10-fold higher than the concentrations achieved by conventional recombinant expression systems. The gene-swapped F9 cells deposited basement membrane-like matrices containing laminin-10 on culture dishes, offering a novel microenvironment for in vitro cell manipulation.

Sox7 plays crucial roles in parietal endoderm differentiation in F9 embryonal carcinoma cells through regulating Gata-4 and Gata-6 expression.

During early rodent development, the parietal endoderm appears from an inner cell mass and produces large amounts of basement membrane components, such as laminin-1 and collagen IV. To elucidate the regulatory network for gene expression during these procedures, we constructed a series of short interfering RNA expression vectors targeted to various transcription factors, transfected them into F9 embryonal carcinoma cells, and evaluated the effects of the gene silencing on the induction of parietal endoderm differentiation and basement membrane component production by treating F9 cells with all trans-retinoic acid and dibutyryl cyclic AMP. Among the transcription factors tested, silencing of Sox7 or combined silencing of Gata-4 and Gata-6 resulted in suppression of cell shape changes and laminin-1 production, which are the hallmarks of parietal endoderm differentiation. In cells silenced for Sox7, induction of Gata-4 and Gata-6 by retinoic acid and cyclic AMP treatment was inhibited, while induction of Sox7 was not affected in cells silenced for Gata-4 and Gata-6, indicating that Sox7 is an upstream regulatory factor for these Gata factors. Nevertheless, silencing of Sox7 did not totally cancel the action of retinoic acid, since upregulation of coup-tf2, keratin 19, and retinoic acid receptor beta2 was not abolished in Sox7-silenced F9 cells. Although overexpression of Sox7 alone was insufficient to induce parietal endoderm differentiation, overexpression of Gata-4 or Gata-6 in Sox7-silenced F9 cells restored the differentiation into parietal endoderm. Sox7 is therefore required for the induction of Gata-4 and Gata-6, and the interplay among these transcription factors plays a crucial role in parietal endoderm differentiation.

Establishment and characterization of a parietal endoderm-like cell line derived from Engelbreth-Holm-Swarm tumor (EHSPEL), a possible resource for an engineered basement membrane matrix.

Engelbreth-Holm-Swarm (EHS) tumor produces large amounts of basement membrane (BM) components, which are widely used as cell culture substrates mimicking BM functions. EHS tumor arose spontaneously in an ST/Eh strain mouse and has been propagated by transplantation. In the present study, we established a cell line, EHSPEL (EHS Parietal Endoderm-Like), which can be cultured ex vivo and preserves the capacity to form tumors in vivo. EHSPEL cells secreted large amounts of laminin-1 into the medium and deposited BM components onto dishes. To further characterize EHSPEL cells, their gene expression profile was compared to those of parietal endoderm cells from Reichert's membrane at embryonic day 13.5, differentiated F9 embryonal carcinoma cells, and PYS-2 parietal endoderm cells. These analyses outlined not only common features of parietal endoderm-like cells that underlie the efficient production of BM components, but also germline cell-like features of EHSPEL cells, at least some of which may play crucial roles in their capacity to form tumors that accumulate abundant BM components in vivo. Karyotyping of EHSPEL cells using chromosome painting probes showed a large number of interchromosomal rearrangements and partial chromosome hyperploidy. Exogenous introduction of a human laminin-alpha(4)-EGFP fusion protein into EHSPEL cells resulted in the production and deposition of human-mouse-hybrid laminin-8. This strategy should be applicable for creating efficient systems to produce chimeric laminins as well as BM-like gels with modified biological activity.