SSCP analysis by RT-PCR for the prenatal diagnosis of Niemann-Pick disease type C

A functional, genome-wide evaluation of liposensitive yeast identifies the "ARE2 required for viability" (ARV1) gene product as a major component of eukaryotic fatty acid resistance

The toxic subcellular accumulation of lipids predisposes several human metabolic syndromes, including obesity, type 2 diabetes, and some forms of neurodegeneration. To identify pathways that prevent lipid-induced cell death, we performed a genome-wide fatty acid sensitivity screen in Saccharomyces cerevisiae. We identified 167 yeast mutants as sensitive to 0.5 mm palmitoleate, 45% of which define pathways that were conserved in humans. 63 lesions also impacted the status of the lipid droplet; however, this was not correlated to the degree of fatty acid sensitivity. The most liposensitive yeast strain arose due to deletion of the "ARE2 required for viability" (ARV1) gene, encoding an evolutionarily conserved, potential lipid transporter that localizes to the endoplasmic reticulum membrane. Down-regulation of mammalian ARV1 in MIN6 pancreatic β-cells or HEK293 cells resulted in decreased neutral lipid synthesis, increased fatty acid sensitivity, and lipoapoptosis. Conversely, elevated expression of human ARV1 in HEK293 cells or mouse liver significantly increased triglyceride mass and lipid droplet number. The ARV1-induced hepatic triglyceride accumulation was accompanied by up-regulation of DGAT1, a triglyceride synthesis gene, and the fatty acid transporter, CD36. Furthermore, ARV1 was identified as a transcriptional of the protein peroxisome proliferator-activated receptor α (PPARα), a key regulator of lipid homeostasis whose transcriptional targets include DGAT1 and CD36. These results implicate ARV1 as a protective factor in lipotoxic diseases due to modulation of fatty acid metabolism. In conclusion, a lipotoxicity-based genetic screen in a model microorganism has identified 75 human genes that may play key roles in neutral lipid metabolism and disease.

Impact of selected inborn errors of metabolism on prenatal and neonatal development

In general, data regarding maturational processes of different metabolic pathways in the very vulnerable fetal and neonatal period are rare. This review is to substantiate the impact of selected inborn errors of metabolism on this critical period of life and their clinical manifestation. Significant adaptation of mitochondrial/energy-, carbohydrate-, lysosomal-, and amino acid-metabolism occurs during early prenatal and neonatal development. In utero, metabolic environment has an impact on the development of the fetus as well as fetal organ maturation. Defects of distinct metabolic pathways could therefore already be of significant relevance in utero and for clinical manifestations in the early fetal and neonatal period. Disturbances of these pathways may influence intrauterine growth and health. Production of a toxic intrauterine milieu, energy-deficiency, modification of membrane function, or disturbance of the normal intrauterine expression of genes may be responsible for fetal compromise and developmental disorders. Three categories of metabolic disorders will be discussed: the "intoxication type" (classical galactosemia, ornithine transcarbamylase deficiency, and "maternal phenylketonuria"), the "storage type" (Morbus Niemann Pick type C), and the "energy deficient type" (including long-chain fatty acid oxidation disorders, pyruvate dehydrogenase deficiency, and respiratory chain defects). For these disorders, the pathophysiology of early manifestation, special aspects regarding the prenatal and neonatal period, and diagnostic as well as therapeutic options are presented.

Niemann-Pick Disease Type C: from molecule to clinic

1. Niemann-Pick Type C disease (NPC) is an incurable cholesterol-storage disorder that stems from inherited deficiencies of lysosomal proteins involved in intracellular lipid-trafficking proteins. The condition manifests as progressive neurological impairment and leads to death at an early age. 2. To improve clinical recognization and investigate therapeutic strategies, recent studies using molecular and genetic approaches have led to significant advances in the creation of animal models of NPC, as well as in the understanding of the cellular and molecular mechanisms underlying the pathogenesis of NPC. 3. Patients with NPC are divided into four groups based on age at presentation, whereas the clinical features of NPC can be divided into five categories based on the severity of the disease. Progressive neuronal loss, especially of cerebellar Purkinje cells, is a hallmark of NPC. Ballooned neurons, axonal abnormalities and astroglyosis are among the pathological changes seen. Severe demyelination is also present in the mouse model of NPC. 4. Mutations in the NPC1 gene cause approximately 95% of cases of NPC, whereas mutations in the NPC2 gene account for the remainder of cases. NPC1 is a transmembrane protein and NPC2 is a soluble protein involved in lipid trafficking in lysosomes. Loss-of-function mutations in the NPC1 gene lead to a failure of the calcium-mediated fusion of endosomes with lysosomes, resulting in the accumulation of cholesterol and other lipids in late endosomes and lysosomes. 5. The present review updates the disorders of NPC from clinical features to animal models and molecular mechanisms.

Genomic and transcription studies as diagnostic tools for a prenatal detection of X-linked dilated cardiomyopathy due to a dystrophin gene mutation

X-linked dilated cardiomyopathy (XLDC) represents a form of dystrophinopathy with exclusive heart involvement. Here a prenatal diagnosis of this condition performed in a family with XLDC is described. In this family, the causative mutation was a pure intronic deletion, which induces the splicing of a novel, aberrant, and out-of-frame exon into the dystrophin transcript. The genetic test was performed by defining both the DNA (villous) and the RNA (amniocyte) configuration. The prenatal diagnosis determined that the fetus was female, and a carrier of the genomic deletion. RNA analysis on cultured amniocytes revealed the presence of an easily detectable dystrophin transcript, as well as the co-existence of both the wild-type and the abnormal splicing profile. Our analysis represents the first report of a prenatal diagnosis in XLDC and also indicates the feasibility of dystrophin mutation detection on RNA from amniocytes. This finding suggests that the dystrophin splicing pattern in amniocytes and skeletal muscle is similar, and that, therefore, this approach could be used in other prenatal dystrophin mutation detection, where abnormal RNA splicing is thought to play a role, or for specific cases in which no mutations have been identified in the coding regions.

Increased NPC1 mRNA in skin fibroblasts from Niemann-Pick disease type C patients

Niemann-Pick disease type C (NP-C) is an autosomal recessive lipid-storage disease that is characterized by progressive neurodegeneration and hepatosplenomegaly. Since identification of the NPC1 gene in 1997, a total of 120 disease-causing mutations have been reported. In this study, two novel mutations were identified, namely c.2508[-2509]A del (837Fs-838X) in exon 16 and T3194G (V1065G) in exon 21. To explore the impact of NPC1 mutations on transcription of this gene, we analyzed NPC1 mRNA levels in skin fibroblasts derived from NP-C patients. Fibroblasts from patients with missense mutations showed increased levels of NPC1 mRNA while fibroblasts from patients with a specific frameshift mutation showed mRNA levels similar to those of normal control subjects. These results suggest that NPC1 transcription levels are altered in cells with mutations in the NPC1 gene.

Prenatal diagnosis of Niemann-Pick diseases types A, B and C

Prenatal diagnosis of Niemann-Pick disease types A and B is routinely accomplished by sphingomyelinase assay. For Niemann-Pick type C disease, demonstration of an abnormal intracellular cholesterol trafficking is a complex procedure, and mutational analysis (NPC1 or NPC2/HE1 gene), whenever feasible, represents a major advance.