Role of phosphoinositide-specific phospholipase C η2 in isolated and syndromic mental retardation

Phospholipase C: underrated players in microbial infections

During bacterial infections, one or more virulence factors are required to support the survival, growth, and colonization of the pathogen within the host, leading to the symptomatic characteristic of the disease. The outcome of bacterial infections is determined by several factors from both host as well as pathogen origin. Proteins and enzymes involved in cellular signaling are important players in determining the outcome of host-pathogen interactions. phospholipase C (PLCs) participate in cellular signaling and regulation by virtue of their ability to hydrolyze membrane phospholipids into di-acyl-glycerol (DAG) and inositol triphosphate (IP3), which further causes the activation of other signaling pathways involved in various processes, including immune response. A total of 13 PLC isoforms are known so far, differing in their structure, regulation, and tissue-specific distribution. Different PLC isoforms have been implicated in various diseases, including cancer and infectious diseases; however, their roles in infectious diseases are not clearly understood. Many studies have suggested the prominent roles of both host and pathogen-derived PLCs during infections. PLCs have also been shown to contribute towards disease pathogenesis and the onset of disease symptoms. In this review, we have discussed the contribution of PLCs as a determinant of the outcome of host-pathogen interaction and pathogenesis during bacterial infections of human importance.

Identification of new genes and quantitative trait locis associated with growth curve parameters in F2 chicken population using genome-wide association study

The markers which are correlated with the growth curve parameters help in understanding the characteristics of individual growth during the rearing of livestock. This study aimed to identify a set of biomarkers through a GWAS for growth curve parameters in crossbred chickens using the Illumnia 60K chicken SNP Beadchip. Growth data were collected from a total of 301 birds from cross of a broiler line and native chickens. Using the Gompertz-Laird model, two growth curve parameters, the instantaneous growth rate per day (L) and the coefficient of relative growth or maturing index (k), were estimated. The L and k were used to estimate five derived parameters, namely asymptotic (mature) body weight, body weight at inflection point, age at the inflection point, average growth rate and maximum growth rate. These parameters were considered as phenotypic values in the GWAS based on generalized linear models. The results of the GWAS indicated 21 significant markers, which were located near or within 46 genes. A number of these genes, such as GH, RET, GRB14, FTSJ3 and CCK, are important for growth and meat quality in chickens, and some of them are growth related in other species such as sheep and cattle (GPI, XIRP2, GALNTL6, BMS1, THSD4, TRHDE, SHISA9, ACSL6 and DYNC1LI2). The other genes are associated with developmental biological pathways. These genes are particuarly related to body weight, average daily gain and growth QTL. The results of this study can shed light on the genetic mechanism of biological functions of growth factors in broiler chickens, which is useful for developing management practices and accelerating genetic progress in breeding programs.

Clustering by phenotype and genome-wide association study in autism

Autism spectrum disorder (ASD) has phenotypically and genetically heterogeneous characteristics. A simulation study demonstrated that attempts to categorize patients with a complex disease into more homogeneous subgroups could have more power to elucidate hidden heritability. We conducted cluster analyses using the k-means algorithm with a cluster number of 15 based on phenotypic variables from the Simons Simplex Collection (SSC). As a preliminary study, we conducted a conventional genome-wide association study (GWAS) with a data set of 597 ASD cases and 370 controls. In the second step, we divided cases based on the clustering results and conducted GWAS in each of the subgroups vs controls (cluster-based GWAS). We also conducted cluster-based GWAS on another SSC data set of 712 probands and 354 controls in the replication stage. In the preliminary study, which was conducted in conventional GWAS design, we observed no significant associations. In the second step of cluster-based GWASs, we identified 65 chromosomal loci, which included 30 intragenic loci located in 21 genes and 35 intergenic loci that satisfied the threshold of P < 5.0 × 10^-8. Some of these loci were located within or near previously reported candidate genes for ASD: CDH5, CNTN5, CNTNAP5, DNAH17, DPP10, DSCAM, FOXK1, GABBR2, GRIN2A5, ITPR1, NTM, SDK1, SNCA, and SRRM4. Of these 65 significant chromosomal loci, rs11064685 located within the SRRM4 gene had a significantly different distribution in the cases vs controls in the replication cohort. These findings suggest that clustering may successfully identify subgroups with relatively homogeneous disease etiologies. Further cluster validation and replication studies are warranted in larger cohorts.

Phospholipase C

Phospholipase C (PLC) family members constitute a family of diverse enzymes. Thirteen different family members have been cloned. These family members have unique structures that mediate various functions. Although PLC family members all appear to signal through the bi-products of cleaving phospholipids, it is clear that each family member, and at times each isoform, contributes to unique cellular functions. This chapter provides a review of the current literature on PLC. In addition, references have been provided for more in-depth information regarding areas that are not discussed including tyrosine kinase activation of PLC. Understanding the roles of the individual PLC enzymes, and their distinct cellular functions, will lead to a better understanding of the physiological roles of these enzymes in the development of diseases and the maintenance of homeostasis.

Phosphoinositide-specific phospholipase C in normal human liver and in alcohol abuse

The phosphoinositide (PI) signal transduction pathway participates in liver metabolism. Abnormal activity or expression of PI-specific phospholipase C (PLC) enzymes has been described in different liver diseases. We resume the role of the PI metabolism in liver and PLC abnormalities in different liver diseases. Moreover, we present the results of PLC analyses in a normal human liver and an alcohol-damaged liver. PLC enzymes and the expression of the corresponding genes in liver biopsies from individuals deceased for complications of the alcoholic liver disease (ALD) at different stages compared with normal controls (deceased individuals with histologically normal livers without alcohol addiction anamnesis) were analyzed by using immunohistochemistry and molecular biology techniques. The expression panel of PLCs was described in normal and alcohol abuse liver. Our observations suggest that the regulation of PLC expression might be due to posttranscriptional events and that alcohol affects the epigenetic control of PLC expression belonging to PI signaling. We also describe the alternate expression of PLCB1 and PLCH1 genes in liver. Our results corroborate literature data suggesting that PLC enzymes are differently expressed in normal versus pathological liver, playing a role in the histopathogenesis of liver tissue damage. The expression and/or localization of selected PLC isoforms is especially affected in alcohol-related liver tissue histopathology. Our present observations confirm that the modulation of protein synthesis plays a role in the regulation of PLC enzymes. We also suggest that this modulation might act at the transcription level. Further studies are required to investigate related epigenetic mechanisms.

Application of high-resolution array comparative genomic hybridization in children with unknown syndromic microcephaly

BackroundMicrocephaly can either be isolated or it may coexist with other neurological entities and/or multiple congenital anomalies, known as syndromic microcephaly. Although many syndromic cases can be classified based on the characteristic phenotype, some others remain uncertain and require further investigation. The present study describes the application of array-comparative genomic hybridization (array-CGH) as a diagnostic tool for the study of patients with clinically unknown syndromic microcephaly.MethodsFrom a cohort of 210 unrelated patients referred with syndromic microcephaly, we applied array-CGH analysis in 53 undiagnosed cases. In all the 53 cases except one, previous standard karyotype was negative. High-resolution 4 × 180K and 1 × 244K Agilent arrays were used in this study.ResultsIn 25 out of the 53 patients with microcephaly among other phenotypic anomalies, array-CGH revealed copy number variations (CNVs) ranging in size between 15 kb and 31.6 Mb. The identified CNVs were definitely causal for microcephaly in 11/53, probably causal in 7/53, and not causal for microcephaly in 7/53 patients. Genes potentially contributing to brain deficit were revealed in 16/53 patients.ConclusionsArray-CGH contributes to the elucidation of undefined syndromic microcephalic cases by permitting the discovery of novel microdeletions and/or microduplications. It also allows a more precise genotype-phenotype correlation by the accurate definition of the breakpoints in the deleted/duplicated regions.

LPS, Oleuropein and Blueberry extracts affect the survival, morphology and Phosphoinositide signalling in stimulated human endothelial cells

Endothelial cells (EC) act as leading actors in angiogenesis. Understanding the complex network of signal transduction pathways which regulate angiogenesis might offer insights in the regulation of normal and pathological events, including tumours, vascular, inflammatory and immune diseases. The effects of olive oil and of Blueberry extracts upon the phosphoinositide (PI)-specific phospholipase C (PLC) enzymes were evaluated both in quiescent and inflammatory stimulated human umbilical vein EC (HUVEC) using molecular biology (multiliquid bioanalysis) and immunofluorescence techniques. Oleuropein significantly increased the number of surviving HUVEC compared to untreated controls, suggesting that it favours the survival and proliferation of EC. Our results suggest that Oleuropein might be useful to induce EC proliferation, an important event during angiogenesis, with special regard to wound healing. Blueberry extracts increased the number of surviving HUVEC, although the comparison to untreated controls did not result statistically significant. Lipopolysaccharide (LPS) administration significantly reduced the number of live HUVEC. LPS can also modify the expression of selected PLC genes. Adding Blueberry extracts to LPS treated HUVEC cultures did not significantly modify the variations of PLC expression induced by LPS. Oleuropein increased or reduced the expression of PLC genes, and statistically significant results were identified for selected PLC isoforms. Oleuropein also modified the effects of LPS upon PLC genes' expression. Thus, our results corroborate the hypothesis that Oleuropein owns anti-inflammatory activity. The intracellular localization of PLC enzymes was modified by the different treatments we used. Podosome-like structures were observed in differently LPS treated HUVEC.

Phospholipase C-η2 interacts with nuclear and cytoplasmic LIMK-1 during retinoic acid-stimulated neurite growth

Neurite growth is central to the formation and differentiation of functional neurons, and recently, an essential role for phospholipase C-η2 (PLCη2) in neuritogenesis was revealed. Here we investigate the function of PLCη2 in neuritogenesis using Neuro2A cells, which upon stimulation with retinoic acid differentiate and form neurites. We first investigated the role of the PLCη2 calcium-binding EF-hand domain, a domain that is known to be required for PLCη2 activation. To do this, we quantified neurite outgrowth in Neuro2A cells, stably overexpressing wild-type PLCη2 and D256A (EF-hand) and H460Q (active site) PLCη2 mutants. Retinoic acid-induced neuritogenesis was highly dependent on PLCη2 activity, with the H460Q mutant exhibiting a strong dominant-negative effect. Expression of the D256A mutant had little effect on neurite growth relative to the control, suggesting that calcium-directed activation of PLCη2 is not essential to this process. We next investigated which cellular compartments contain endogenous PLCη2 by comparing immunoelectron microscopy signals over control and knockdown cell lines. When signals were analyzed to reveal specific labeling for PLCη2, it was found to be localized predominantly over the nucleus and cytosol. Furthermore in these compartments (and also in growing neurites), a proximity ligand assay revealed that PLCη2 specifically interacts with LIMK-1 in Neuro2A cells. Taken together, these data emphasize the importance of the PLCη2 EF-hand domain and articulation of PLCη2 with LIMK-1 in regulating neuritogenesis.

Neuropathology of brain and spinal malformations in a case of monosomy 1p36

Monosomy 1p36 is the most common subtelomeric chromosomal deletion linked to mental retardation and seizures. Neuroimaging studies suggest that monosomy 1p36 is associated with brain malformations including polymicrogyria and nodular heterotopia, but the histopathology of these lesions is unknown. Here we present postmortem neuropathological findings from a 10 year-old girl with monosomy 1p36, who died of respiratory complications. The findings included micrencephaly, periventricular nodular heterotopia in occipitotemporal lobes, cortical dysgenesis resembling polymicrogyria in dorsolateral frontal lobes, hippocampal malrotation, callosal hypoplasia, superiorly rotated cerebellum with small vermis, and lumbosacral hydromyelia. The abnormal cortex exhibited “festooned” (undulating) supragranular layers, but no significant fusion of the molecular layer. Deletion mapping demonstrated single copy loss of a contiguous 1p36 terminal region encompassing many important neurodevelopmental genes, among them four HES genes implicated in regulating neural stem cell differentiation, and TP73, a monoallelically expressed gene. Our results suggest that brain and spinal malformations in monosomy 1p36 may be more extensive than previously recognized, and may depend on the parental origin of deleted genes. More broadly, our results suggest that specific genetic disorders may cause distinct forms of cortical dysgenesis.

Phosphoinositide pathway and the signal transduction network in neural development

The development of the nervous system is under the strict control of a number of signal transduction pathways, often interconnected. Among them, the phosphoinositide (PI) pathway and the related phospholipase C (PI-PLC) family of enzymes have been attracting much attention. Besides their well-known role in the regulation of intracellular calcium levels, PI-PLC enzymes interact with a number of molecules belonging to further signal transduction pathways, contributing to a specific and complex network in the developing nervous system. In this review, the connections of PI signalling with further transduction pathways acting during neural development are discussed, with special regard to the role of the PI-PLC family of enzymes.

Phospholipase C

Phospholipase C (PLC) family members constitute a family of diverse enzymes. Thirteen different family members have been cloned. These family members have unique structures that mediate diverse functions. Although PLC family members all appear to signal through the bi-products of cleaving phospholipids, it is clear that each family member, and at times each isoform, contributes to unique cellular functions. This chapter provides a review of the current literature. In addition, references have been provided for more in depth information regarding areas that are discussed. Ultimately, understanding the roles of the individual PLC enzymes, and their distinct cellular functions, will lead to a better understanding of the development of diseases and the maintenance of homeostasis.