ABSTRACT
Newborn screening is an incredibly useful tool for the early identification of many metabolic disorders, including fatty acid oxidation (FAO) disorders. In many cases, molecular tests are necessary to reach a final diagnosis, highlighting the need for a thorough evaluation of genes implicated in FAO disorders. Using the ClinGen (Clinical Genome Resource) clinical validity framework, thirty genes were analyzed for the strength of evidence supporting their association with FAO disorders. Evidence was gathered from the literature by biocurators and presented to disease experts for review in order to assign a clinical validity classification of Definitive, Strong, Moderate, Limited, Disputed, Refuted, or No Reported Evidence. Of the gene-disease relationships evaluated, 22/30 were classified as Definitive, three as Moderate, one as Limited, three as No Reported Evidence and one as Disputed. Gene-disease relationships with a Limited, Disputed, and No Reported Evidence were found on two, six, and up to four panels out of 30 FAO disorder-specific panels, respectively, in the National Institute of Health Genetic Testing Registry, while over 70% of the genes on panels are definitively associated with an FAO disorder. These results highlight the need to systematically assess the clinical relevance of genes implicated in fatty acid oxidation disorders in order to improve the interpretation of genetic testing results and diagnosis of patients with these disorders.
Subject(s)
Fatty Acids/metabolism , Genetic Testing , Lipid Metabolism, Inborn Errors/diagnosis , Lipid Metabolism, Inborn Errors/genetics , Genetic Predisposition to Disease , Humans , Infant, Newborn , Neonatal Screening , Oxidation-Reduction , Reproducibility of ResultsABSTRACT
BACKGROUND: This work was conducted in an effort to establish an oral intake model system in which the effects of ethanol insult that occur during early stages of embryogenesis can be easily examined and in which agents that may modulate ethanol's teratogenicity can be readily tested in vivo. The model system described utilizes the alcohol deprivation effect to obtain teratogenic levels of maternal ethanol intake on days 7 and 8 of pregnancy in C57Bl/6J mice. Ocular defects including microphthalmia and uveal coloboma, which have previously been shown to result from ethanol administered by gavage or via intraperitoneal injection on these days, served as the developmental end point for this study. The ocular defects are readily identifiable and their degree of severity is expected to correlate with concurrently developing defects of the central nervous system (CNS). METHODS: Female C57Bl/6J mice were maintained on an ethanol-containing (4.8% v/v) liquid diet for 14 days and then mated during a subsequent abstinence period. Mice were then reexposed to ethanol on days 7 and 8 of pregnancy only. Control as well as ethanol-exposed dams were killed on their 14th day of pregnancy. Fetuses were then weighed, measured for crown rump length, photographed, and analyzed for ocular abnormalities. Globe size, palpebral fissure length, and pupil size and shape were noted for both the right and left eyes of all fetuses and informative comparisons were made. RESULTS: This exposure paradigm resulted in peak maternal blood alcohol concentrations that ranged from 170 to 220 mg/dL on gestational day (GD) 8. Compared with the GD 14 fetuses from the normal control group, the pair-fed, acquisition controls, as well as the ethanol-exposed fetuses, were developmentally delayed and had reduced weights. Confirming previous studies, comparison of similarly staged control and treated GD 8 embryos illustrated reductions in the size of the forebrain in the latter. Subsequent ocular malformations were noted in 33% of the right eyes and 25% of the left eyes of the 103 GD 14 ethanol-exposed fetuses examined. This incidence of defects is twice that observed in the control groups. Additionally, it was found that the palpebral fissure length is directly correlated with globe size. CONCLUSIONS: The high incidence of readily identifiable ocular malformations produced by oral ethanol intake in this model and their relevance to human fetal alcohol spectrum disorders (FASD) makes this an excellent system for utilization in experiments involving factors administered to the embryo that might alter ethanol's teratogenic effects. Additionally, the fact that early ethanol insult yields ocular and forebrain abnormalities that are developmentally associated allows efficient specimen selection for subsequent detailed analyses of CNS effects in this in vivo mammalian FASD model.
