Ghosh, Auyon

Abstract Rationale Reliable data about the natural history of lung function decline in alpha-1 antitrypsin (AAT)-deficient Pi*MZ heterozygotes is largely missing. Objectives We hypothesized that, in adults with a tobacco smoking history, lung function deteriorates faster in Pi*MZ compared with the Pi*MM genotype. Methods We identified 1,856 Pi*MM and 79 Pi*MZ participants with ⩾20 pack-years tobacco smoking history from the SPIROMICS (Subpopulations and Intermediate Outcomes Measures in COPD Study) cohort by DNA sequencing and followed them over a median of 4.8 years, comparing radiographic and clinical characteristics between the two groups over time using regression models. Results Adjusted for age, sex, race, smoking pack-year history, and smoking status, Pi*MZ participants had a lower baseline percent predicted forced expiratory volume in 1 second (FEV1) (65.4% vs. 75.1%; difference 95% confidence interval [CI], −15.4% to −3.9%), more radiographic emphysema (<−950 Hounsfield units%, 12.9% vs. 7.8%; difference 95% CI, 2.8% to 7.5%), and nonsignificantly lower lung density. In the longitudinal analysis, the FEV1 annual rate of decline was similar in both groups over the course of the study (−34.5 ml/yr vs. −34.6 ml/yr for Pi*MZ and Pi*MM; difference 95% CI, −16.9 to 17.1 ml/yr). There were no significant differences between Pi*MZ and Pi*MM individuals in the annualized change in lung density, emphysema, patient-reported outcomes, exacerbations, or survival. The proportion with faster FEV1 decline (annual loss ⩾40 ml) was similar in Pi*MZ and Pi*MM groups. In both groups, faster FEV1 decline was associated with more air trapping and small airway disease at baseline. In Pi*MZ only, faster decline was associated with higher blood eosinophil counts (310 vs. 220 cells/μl; difference 95% CI, 30 to 140 cells/μl). In the subgroup analysis limited to a small number of currently smoking participants, no significant differences in longitudinal outcomes were found. Conclusions Despite a lower FEV1 and more emphysema at enrollment, the longitudinal analysis did not demonstrate significantly greater lung function decline or lung density loss in Pi*MZ compared with Pi*MM participants with tobacco smoking history. Limited sample size and duration of longitudinal follow-up constrain generalizability of our findings, thus prohibiting the conclusion that longitudinal trajectories did not differ between these groups. However, our results may suggest that earlier life events could be responsible for more extensive lung disease at enrollment in Pi*MZ compared with Pi*MM tobacco-exposed individuals.

Abstract Rationale Dysanapsis refers to a mismatch between airway tree caliber and lung size arising early in life. Dysanapsis assessed by computed tomography (CT) is evident by early adulthood and associated with chronic obstructive pulmonary disease (COPD) risk later in life. Objectives By examining the genetic factors associated with CT-assessed dysanapsis, we aimed to elucidate its molecular underpinnings and physiological significance across the lifespan. Methods We performed a genome-wide association study of CT-assessed dysanapsis in 11,951 adults, including individuals from two population-based and two COPD-enriched studies. We applied colocalization analysis to integrate genome-wide association study and gene expression data from whole blood and lung. Genetic variants associated with dysanapsis were combined into a genetic risk score that was applied to examine association with lung function in children from a population-based birth cohort (n = 1,278) and adults from the UKBiobank (n = 369,157). Measurements and Main Results CT-assessed dysanapsis was associated with genetic variants from 21 independent signals in 19 gene regions, implicating HHIP (hedgehog interacting protein), DSP, and NPNT as potential molecular targets based on colocalization of their expression. A higher dysanapsis genetic risk score was associated with obstructive spirometry among 5-year-old children and among adults in the fifth, sixth, and seventh decades of life. Conclusions CT-assessed dysanapsis is associated with variation in genes previously implicated in lung development, and dysanapsis genetic risk is associated with obstructive lung function from early life through older adulthood. Dysanapsis may represent an endophenotype link between the genetic variations associated with lung function and COPD.

Abstract Rationale Constantly exposed to the external environment and mutagens such as tobacco smoke, human lungs have one of the highest somatic mutation rates among all human organs. However, the relationship of these mutations to lung disease and function is not known. Objectives To identify the prevalence and significance of clonal somatic mutations in chronic lung diseases. Methods We analyzed the clonal somatic mutations from 1,251 samples of normal and diseased noncancerous lung tissue RNA sequencing with paired whole-genome sequencing from the Lung Tissue Research Consortium. We examined the associations of somatic mutations with lung function, disease status, and computationally deconvoluted cell types in two of the most common diseases represented in our dataset, chronic obstructive pulmonary disease (COPD; 29%) and idiopathic pulmonary fibrosis (IPF; 13%). Measurements and Main Results Clonal somatic mutational burden was associated with reduced lung function in both COPD and IPF. We identified an increased prevalence of clonal somatic mutations in individuals with IPF compared with normal control subjects and individuals with COPD independent of age and smoking status. IPF clonal somatic mutations were enriched in disease-related and airway epithelial–expressed genes such as MUC5B in IPF. Patients who were MUC5B risk variant carriers had increased odds of developing somatic mutations of MUC5B that were explained by increased expression of MUC5B. Conclusions Our identification of an increased prevalence of clonal somatic mutation in diseased lung that correlates with airway epithelial gene expression and disease severity highlights for the first time the role of somatic mutational processes in lung disease genetics.

Abstract Rationale In addition to rare genetic variants and the MUC5B locus, common genetic variants contribute to idiopathic pulmonary fibrosis (IPF) risk. The predictive power of common variants outside the MUC5B locus for IPF and interstitial lung abnormalities (ILAs) is unknown. Objectives We tested the predictive value of IPF polygenic risk scores (PRSs) with and without the MUC5B region on IPF, ILA, and ILA progression. Methods We developed PRSs that included (PRS-M5B) and excluded (PRS-NO-M5B) the MUC5B region (500-kb window around rs35705950-T) using an IPF genome-wide association study. We assessed PRS associations with area under the receiver operating characteristic curve (AUC) metrics for IPF, ILA, and ILA progression. Measurements and Main Results We included 14,650 participants (1,970 IPF; 1,068 ILA) from six multi-ancestry population-based and case–control cohorts. In cases excluded from genome-wide association study, the PRS-M5B (odds ratio [OR] per SD of the score, 3.1; P = 7.1 × 10−95) and PRS-NO-M5B (OR per SD, 2.8; P = 2.5 × 10−87) were associated with IPF. Participants in the top PRS-NO-M5B quintile had ∼sevenfold odds for IPF compared with those in the first quintile. A clinical model predicted IPF (AUC, 0.61); rs35705950-T and PRS-NO-M5B demonstrated higher AUCs (0.73 and 0.7, respectively), and adding both genetic predictors to a clinical model yielded the highest performance (AUC, 0.81). The PRS-NO-M5B was associated with ILA (OR, 1.25) and ILA progression (OR, 1.16) in European ancestry participants. Conclusions A common genetic variant risk score complements the MUC5B variant to identify individuals at high risk of interstitial lung abnormalities and pulmonary fibrosis.

Abstract Rationale Multiple studies have demonstrated an increased risk of chronic obstructive pulmonary disease (COPD) in heterozygous carriers of the AAT (alpha-1 antitrypsin) Z allele. However, it is not known if MZ subjects with COPD are phenotypically different from noncarriers (MM genotype) with COPD. Objectives To assess if MZ subjects with COPD have different clinical features compared with MM subjects with COPD. Methods Genotypes of SERPINA1were ascertained by using whole-genome sequencing data in three independent studies. We compared outcomes between MM subjects with COPD and MZ subjects with COPD in each study and combined the results in a meta-analysis. We performed longitudinal and survival analyses to compare outcomes in MM and MZ subjects with COPD over time. Measurements and Main Results We included 290 MZ subjects with COPD and 6,184 MM subjects with COPD across the three studies. MZ subjects had a lower FEV1% predicted and greater quantitative emphysema on chest computed tomography scans compared with MM subjects. In a meta-analysis, the FEV1was 3.9% lower (95% confidence interval [CI], −6.55% to −1.26%) and emphysema (the percentage of lung attenuation areas <−950 HU) was 4.14% greater (95% CI, 1.44% to 6.84%) in MZ subjects. We found one gene, PGF(placental growth factor), to be differentially expressed in lung tissue from one study between MZ subjects and MM subjects. Conclusions Carriers of the AAT Z allele (those who were MZ heterozygous) with COPD had lower lung function and more emphysema than MM subjects with COPD. Taken with the subtle differences in gene expression between the two groups, our findings suggest that MZ subjects represent an endotype of COPD.