Randa Stringer

Neurodevelopmental alcohol exposure elicits long-term changes to gene expression that alter distinct molecular pathways dependent on timing of exposure

BackgroundMaternal alcohol consumption is known to adversely affect fetal neurodevelopment. While it is known that alcohol dose and timing play a role in the cognitive and behavioral changes associated with prenatal alcohol exposure, it is unclear what developmental processes are disrupted that may lead to these phenotypes.MethodsMice (n=6 per treatment per developmental time) were exposed to two acute doses of alcohol (5 g/kg) at neurodevelopmental times representing the human first, second, or third trimester equivalent. Mice were reared to adulthood and changes to their adult brain transcriptome were assessed using expression arrays. These were then categorized based on Gene Ontology annotations, canonical pathway associations, and relationships to interacting molecules.ResultsThe results suggest that ethanol disrupts biological processes that are actively occurring at the time of exposure. These include cell proliferation during trimester one, cell migration and differentiation during trimester two, and cellular communication and neurotransmission during trimester three. Further, although ethanol altered a distinct set of genes depending on developmental timing, many of these show interrelatedness and can be associated with one another via ‘hub’ molecules and pathways such as those related to huntingtin and brain-derived neurotrophic factor.ConclusionsThese changes to brain gene expression represent a ‘molecular footprint’ of neurodevelopmental alcohol exposure that is long-lasting and correlates with active processes disrupted at the time of exposure. This study provides further support that there is no neurodevelopmental time when alcohol cannot adversely affect the developing brain.

Reduced expression of brain cannabinoid receptor 1 (Cnr1) is coupled with an increased complementary micro-RNA (miR-26b) in a mouse model of fetal alcohol spectrum disorders

BackgroundPrenatal alcohol exposure is known to result in fetal alcohol spectrum disorders, a continuum of physiological, behavioural, and cognitive phenotypes that include increased risk for anxiety and learning-associated disorders. Prenatal alcohol exposure results in life-long disorders that may manifest in part through the induction of long-term gene expression changes, potentially maintained through epigenetic mechanisms.FindingsHere we report a decrease in the expression of Canabinoid receptor 1 (Cnr1) and an increase in the expression of the regulatory microRNA miR-26b in the brains of adult mice exposed to ethanol during neurodevelopment. Furthermore, we show that miR-26b has significant complementarity to the 3’-UTR of the Cnr1 transcript, giving it the potential to bind and reduce the level of Cnr1 expression.ConclusionsThese findings elucidate a mechanism through which some genes show long-term altered expression following prenatal alcohol exposure, leading to persistent alterations to cognitive function and behavioural phenotypes observed in fetal alcohol spectrum disorders.

Western Database of Lipid Variants (WDLV): a catalogue of genetic variants in monogenic dyslipidemias.

BACKGROUND Next-generation sequencing (NGS) is nearing routine clinical application, especially for diagnosis of rare monogenic cardiovascular diseases. But NGS uncovers so much variation in an individual genome that filtering steps are required to streamline data management. The first step is to determine whether a potential disease-causing variant has been observed previously in affected patients. METHODS To facilitate this step for lipid disorders, we developed the Western Database of Lipid Variants (WDLV) of 2776 variants in 24 genes that cause monogenic dyslipoproteinemias, including conditions characterized primarily by either high or low low-density lipoprotein cholesterol, high or low high-density lipoprotein cholesterol, high triglyceride, and some miscellaneous disorders. We incorporated quality-control steps to maximize the likelihood that a listed mutation was disease causing. RESULTS The details of each mutation found in a dyslipidemia, together with a mutation map of the causative genes, are shown in graphical display items. CONCLUSIONS WDLV will help clinicians and researchers determine the potential pathogenicity of mutations discovered by DNA sequencing of patients or research participants with lipid disorders.

Third Trimester-Equivalent Ethanol Exposure Is Characterized by an Acute Cellular Stress Response and an Ontogenetic Disruption of Genes Critical for Synaptic Establishment and Function in Mice

The developing brain is remarkably sensitive to alcohol exposure, resulting in the wide range of cognitive and neurobehavioral characteristics categorized under the term fetal alcohol spectrum disorders (FASD). The brain is particularly susceptible to alcohol during synaptogenesis, a process that occurs heavily during the third trimester and is characterized by the establishment and pruning of neural circuitry; however, the molecular response of the brain to ethanol during synaptogenesis has not been documented. To model a binge-like exposure during the third-trimester neurodevelopmental equivalent, neonate mice were given a high (5 g/kg over 2 h) dose of ethanol at postnatal day 7. Acute transcript changes within the brain were assessed using expression arrays and analyzed for associations with gene ontology functional categories, canonical pathways, and gene network interactions. The short-term effect of ethanol was characterized by an acute stress response and a downregulation of energetically costly cellular processes. Further, alterations to a number of genes with roles in synaptic transmission and hormonal signaling, particularly those associated with the neuroendocrine development and function, were evident. Ethanol exposure during synaptogenesis was also associated with altered histone deacetylase and microRNA transcript levels, suggesting that abnormal epigenetic patterning may maintain some of the persistent molecular consequences of developmental ethanol exposure. The results shed insight into the sensitivity of the brain to ethanol during the third-trimester equivalent and outline how ethanol-induced alterations to genes associated with neural connectivity may contribute to FASD phenotypes.

Common Low-Density Lipoprotein Receptor p.G116S Variant Has a Large Effect on Plasma Low-Density Lipoprotein Cholesterol in Circumpolar Inuit Populations

Background—Inuit are considered to be vulnerable to cardiovascular disease because their lifestyles are becoming more Westernized. During sequence analysis of Inuit individuals at extremes of lipid traits, we identified 2 nonsynonymous variants in low-density lipoprotein receptor (LDLR), namely p.G116S and p.R730W. Methods and Results—Genotyping these variants in 3324 Inuit from Alaska, Canada, and Greenland showed they were common, with allele frequencies 10% to 15%. Only p.G116S was associated with dyslipidemia: the increase in LDL cholesterol was 0.54 mmol/L (20.9 mg/dL) per allele (P=5.6×10−49), which was >3× larger than the largest effect sizes seen with other common variants in other populations. Carriers of p.G116S had a 3.02-fold increased risk of hypercholesterolemia (95% confidence interval, 2.34–3.90; P=1.7×10−17), but did not have classical familial hypercholesterolemia. In vitro, p.G116S showed 60% reduced ligand-binding activity compared with wild-type receptor. In contrast, p.R730W was associated with neither LDL cholesterol level nor altered in vitro activity. Conclusions—LDLR p.G116S is thus unique: a common dysfunctional variant in Inuit whose large effect on LDL cholesterol may have public health implications.Inuit were long-believed to have lower CVD risk than non-indigenous populations.1–3 However, re-evaluation of population studies indicates that ischemic heart disease rates are similar between Inuit and non-Indigenous people.4 Furthermore, ongoing Westernization in many Inuit communities has intensified their exposure to CVD risk factors such as smoking, calorie-dense processed foods, and a more comfortable but also sedentary lifestyle, all of which affect CVD risk and prevalence.4–10 Among classical CVD risk factors, Inuit adults tend to have higher plasma concentrations of LDL cholesterol than non-indigenous populations.11–15 The predominant monogenic cause of elevated LDL cholesterol concentration in most global populations is familial hypercholesterolemia (FH, Online Mendelian Inheritance in Man [OMIM] 143890).16 Heterozygous FH (HeFH) prevalence may be as high as 1:200 in certain European populations, and it is a potent predisposition state for early CVD.11–13 To date, DNA sequencing and biochemical studies have identified >1,600 rare loss-of-function mutations in the gene encoding the LDL receptor (LDLR), which can increase LDL cholesterol levels by 100% or more, and underlie >95% of cases of molecularly diagnosed FH.16 But despite the relatively high levels of LDL cholesterol observed in some Inuit, the role of LDLR gene variation has not been systematically studied.13–15 We thus investigated the LDLR locus in Inuit and tested for association of variants therein with plasma lipids. Through Sanger sequencing and targeted genotyping, we found two new LDLR variants common to five Inuit subgroups from across North America and Greenland: 1) p.G116S was both dysfunctional in vitro and associated with a relatively large increase in plasma LDL cholesterol levels; while 2) p.R730W had minimal dysfunction and impact on the lipid profile.

Common Low-Density Lipoprotein Receptor p.G116S Variant Has a Large Effect on Plasma Low-Density Lipoprotein Cholesterol in Circumpolar Inuit PopulationsCLINICAL PERSPECTIVE

Background—Inuit are considered to be vulnerable to cardiovascular disease because their lifestyles are becoming more Westernized. During sequence analysis of Inuit individuals at extremes of lipid traits, we identified 2 nonsynonymous variants in low-density lipoprotein receptor (LDLR), namely p.G116S and p.R730W. Methods and Results—Genotyping these variants in 3324 Inuit from Alaska, Canada, and Greenland showed they were common, with allele frequencies 10% to 15%. Only p.G116S was associated with dyslipidemia: the increase in LDL cholesterol was 0.54 mmol/L (20.9 mg/dL) per allele (P=5.6×10−49), which was >3× larger than the largest effect sizes seen with other common variants in other populations. Carriers of p.G116S had a 3.02-fold increased risk of hypercholesterolemia (95% confidence interval, 2.34–3.90; P=1.7×10−17), but did not have classical familial hypercholesterolemia. In vitro, p.G116S showed 60% reduced ligand-binding activity compared with wild-type receptor. In contrast, p.R730W was associated with neither LDL cholesterol level nor altered in vitro activity. Conclusions—LDLR p.G116S is thus unique: a common dysfunctional variant in Inuit whose large effect on LDL cholesterol may have public health implications.Inuit were long-believed to have lower CVD risk than non-indigenous populations.1–3 However, re-evaluation of population studies indicates that ischemic heart disease rates are similar between Inuit and non-Indigenous people.4 Furthermore, ongoing Westernization in many Inuit communities has intensified their exposure to CVD risk factors such as smoking, calorie-dense processed foods, and a more comfortable but also sedentary lifestyle, all of which affect CVD risk and prevalence.4–10 Among classical CVD risk factors, Inuit adults tend to have higher plasma concentrations of LDL cholesterol than non-indigenous populations.11–15 The predominant monogenic cause of elevated LDL cholesterol concentration in most global populations is familial hypercholesterolemia (FH, Online Mendelian Inheritance in Man [OMIM] 143890).16 Heterozygous FH (HeFH) prevalence may be as high as 1:200 in certain European populations, and it is a potent predisposition state for early CVD.11–13 To date, DNA sequencing and biochemical studies have identified >1,600 rare loss-of-function mutations in the gene encoding the LDL receptor (LDLR), which can increase LDL cholesterol levels by 100% or more, and underlie >95% of cases of molecularly diagnosed FH.16 But despite the relatively high levels of LDL cholesterol observed in some Inuit, the role of LDLR gene variation has not been systematically studied.13–15 We thus investigated the LDLR locus in Inuit and tested for association of variants therein with plasma lipids. Through Sanger sequencing and targeted genotyping, we found two new LDLR variants common to five Inuit subgroups from across North America and Greenland: 1) p.G116S was both dysfunctional in vitro and associated with a relatively large increase in plasma LDL cholesterol levels; while 2) p.R730W had minimal dysfunction and impact on the lipid profile.

The common LDLR p.G116S variant has a large effect on plasma LDL cholesterol in circumpolar Inuit populations

Background—Inuit are considered to be vulnerable to cardiovascular disease because their lifestyles are becoming more Westernized. During sequence analysis of Inuit individuals at extremes of lipid traits, we identified 2 nonsynonymous variants in low-density lipoprotein receptor (LDLR), namely p.G116S and p.R730W. Methods and Results—Genotyping these variants in 3324 Inuit from Alaska, Canada, and Greenland showed they were common, with allele frequencies 10% to 15%. Only p.G116S was associated with dyslipidemia: the increase in LDL cholesterol was 0.54 mmol/L (20.9 mg/dL) per allele (P=5.6×10−49), which was >3× larger than the largest effect sizes seen with other common variants in other populations. Carriers of p.G116S had a 3.02-fold increased risk of hypercholesterolemia (95% confidence interval, 2.34–3.90; P=1.7×10−17), but did not have classical familial hypercholesterolemia. In vitro, p.G116S showed 60% reduced ligand-binding activity compared with wild-type receptor. In contrast, p.R730W was associated with neither LDL cholesterol level nor altered in vitro activity. Conclusions—LDLR p.G116S is thus unique: a common dysfunctional variant in Inuit whose large effect on LDL cholesterol may have public health implications.Inuit were long-believed to have lower CVD risk than non-indigenous populations.1–3 However, re-evaluation of population studies indicates that ischemic heart disease rates are similar between Inuit and non-Indigenous people.4 Furthermore, ongoing Westernization in many Inuit communities has intensified their exposure to CVD risk factors such as smoking, calorie-dense processed foods, and a more comfortable but also sedentary lifestyle, all of which affect CVD risk and prevalence.4–10 Among classical CVD risk factors, Inuit adults tend to have higher plasma concentrations of LDL cholesterol than non-indigenous populations.11–15 The predominant monogenic cause of elevated LDL cholesterol concentration in most global populations is familial hypercholesterolemia (FH, Online Mendelian Inheritance in Man [OMIM] 143890).16 Heterozygous FH (HeFH) prevalence may be as high as 1:200 in certain European populations, and it is a potent predisposition state for early CVD.11–13 To date, DNA sequencing and biochemical studies have identified >1,600 rare loss-of-function mutations in the gene encoding the LDL receptor (LDLR), which can increase LDL cholesterol levels by 100% or more, and underlie >95% of cases of molecularly diagnosed FH.16 But despite the relatively high levels of LDL cholesterol observed in some Inuit, the role of LDLR gene variation has not been systematically studied.13–15 We thus investigated the LDLR locus in Inuit and tested for association of variants therein with plasma lipids. Through Sanger sequencing and targeted genotyping, we found two new LDLR variants common to five Inuit subgroups from across North America and Greenland: 1) p.G116S was both dysfunctional in vitro and associated with a relatively large increase in plasma LDL cholesterol levels; while 2) p.R730W had minimal dysfunction and impact on the lipid profile.