Single Nucleotide Polymorphisms in MicroRNA Processing and Susceptibility to the Effects of Black Carbon on Cognition in a Cohort of Older Men.

Colicino E, Giuliano G, Power MC, Wilker EH, Vokonas P, Spiro A, Weisskopf MG, Schwartz J, Baccarelli AA Background • Declining cognition in older adults is associated with loss of independence, hospitalization and mortality

• Air pollution exposure: – has been linked with accelerated cognitive aging – specific associations reported with Black Carbon (BC), taken as a marker of traffic air-pollution

• The biological process by which air pollution may impact cognition is not fully known 2 (miRNAs)

• Small non-coding RNAs (18-23 nucleotides): – Powerful inhibitors of – Key roles in neuronal programming

• MiRNA processing genes: – Generate mature miRNAs from longer precursor molecules (primi-/pre- miRNAs) – Levels of mature miRNAs may vary due to single nucleotide polymorphisms (SNPs) in miRNA- processing genes

3 Single Nucleotide Polymorphisms (SNPs) and MicroRNAs (miRNAs)

miRNA

Adapted from: Wilker EH, 2010, EHP 18:943–8. 4 Single Nucleotide Polymorphisms (SNPs) and MicroRNAs (miRNAs)

AGO1 rs595961 AGO2 rs4961280 GEMIN4 rs7813, rs1062923, rs3744741, rs4968104, rs910925, TRBP rs784567 rs2740348, rs910924, rs910924

DGCR8 rs3757, rs1640299 GEMIN3 rs197414, rs197388, rs197412 RAN rs14035 rs6877842 DICER1 rs13078

XPO5 rs11077

Adapted from: Wilker EH, 2010, EHP 18:943–8. 5 Objectives

• x Environment (GxE) study: BC Cognition ? SNPs in miRNA-processing genes

• Functional study: Expression of SNPs ? candidate miRNAs

6 Data - Participants 536 Normative Aging Study (NAS) participants

Free chronic disease or stroke Greater Boston (MA) area older men (71yo in average)

baseline visit 2 visit 3 visit 4 1996 2007 1 year 3-5 years3-5 years 3-5 years

BC exposure At each visit: assessment • Lab and physical exams • demographic and life style information • 7 cognitive tests 7 Data - Cognitive measures

• Mini-Mental State Examination (MMSE): – dichotomized for low performance (≤25)

• Global cognitive function : – includes: • digit span backward • verbal fluency task • constructional praxis • immediate and delayed recall • pattern comparison task – summarized in a global score • individual test scores converted to z-scores • global score = mean of the z-scores

8 Data – Exposure assessment • Estimates of BC exposure as surrogates for individual exposure to local traffic • Spatio-temporal land-use regression model to get daily estimates • Long term exposure: average of 365 daily estimates for the year before baseline visit

9 Data – SNPs and MiRNAs • GxE study : – 18 miRNAs-related SNPs in 10 genes – No linkage disequilibrium (LDPlotter tool) – Dominant genetic model: • hm major vs hz + hm minor • Functional study (miRNA expression) : – 14 candidate miRNAs in blood samples of a subset of 93 participants – miRNA selected due to their potential roles in oxidative stress and inflammatory pathways 10 Statistical analysis in GxE study Models • MMSE – logistic regression with generalized estimating equations – empirical variance estimates • Global Function – random-effects linear mixed models – random intercept for the study participant – random intercept for each of the cognitive scores • Results considered noteworthy at False Discovery Rates (FDRs) <0.20 11 Effect of BC on lower MMSE

12 Odds ratio for each doubling of 1-yr BC concentration levels Effect of BC on global function

Change in global function for each doubling of 1-yr BC concentration levels 13 Single Nucleotide Polymorphisms (SNPs) and MicroRNAs (miRNAs)

AGO1 rs595961 AGO2 rs4961280 GEMIN4 rs4968104 , rs910924 , rs7813, rs1062923, rs3744741, TRBP rs784567 rs910925, rs2740348, rs910924

DGCR8 rs3757, rs1640299 GEMIN3 rs197388, rs197414, rs197412 RAN rs14035 DROSHA rs6877842 DICER1 rs13078

XPO5 rs11077

Adapted from: Wilker EH, 2010, EHP 18:943–8. 14 Functional Study: Association between SNPs and miRNA expression rs11077 in XPO5 AA AC/CC miRNA Mean SE Mean SE p-value FDR miR9 0.68 0.11 0.33 0.13 0.02 0.10 miR96 1.37 0.41 0.91 0.51 0.08 0.12 rs197388 in GEMIN3 TT TA/AA miRNA Mean SE Mean SE p-value FDR miR96 1.52 0.30 1.24 0.50 0.02 0.10 rs4968104 in GEMIN4 TT TA/AA miRNA Mean SE Mean SE p-value FDR miR96 1.52 0.36 0.83 0.49 0.10 0.12 rs910924 in GEMIN4 CC CT/TT miRNA Mean SE Mean SE p-value FDR miR96 1.50 0.37 0.84 0.49 0.09 0.12

15 Conclusions

• GxE study : Selected SNPs in miRNA-processing genes modified the association between long-term exposure to BC and cognitive function in a cohort of older men

• Functional study The miRNA-processing SNPs that modified BC cognitive effect also affected miRNA expression levels in blood samples

16 Thank you!

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