GSTCD and INTS12 Regulation and Expression in the Human Lung

Abstract

Genome-Wide Association Study (GWAS) meta-analyses have identified a strong association signal for lung function, which maps to a region on 4q24 containing two oppositely transcribed genes: glutathione S-transferase, C-terminal domain containing (GSTCD) and integrator complex subunit 12 (INTS12). Both genes were found to be expressed in a range of human airway cell types. The promoter regions and transcription start sites were determined in mRNA from human lung and a novel splice variant was identified for each gene. We obtained the following evidence for GSTCD and INTS12 co-regulation and expression: (i) correlated mRNA expression was observed both via Q-PCR and in a lung expression quantitative trait loci (eQTL) study, (ii) induction of both GSTCD and INTS12 mRNA expression in human airway smooth muscle cells was seen in response to TGFβ1, (iii) a lung eQTL study revealed that both GSTCD and INTS12 mRNA levels positively correlate with percent predicted FEV1, and (iv) FEV1 GWAS associated SNPs in 4q24 were found to act as an eQTL for INTS12 in a number of tissues. In fixed sections of human lung tissue, GSTCD protein expression was ubiquitous, whereas INTS12 expression was predominantly in epithelial cells and pneumocytes. During human fetal lung development, GSTCD protein expression was observed to be highest at the earlier pseudoglandular stage (10-12 weeks) compared with the later canalicular stage (17-19 weeks), whereas INTS12 expression levels did not alter throughout these stages. Knowledge of the transcriptional and translational regulation and expression of GSTCD and INTS12 provides important insights into the potential role of these genes in determining lung function. Future work is warranted to fully define the functions of INTS12 and GSTCD.

Translating Lung Function Genome-Wide Association Study (GWAS) Findings

“…This staining pattern in multiple cell types potentially confirms the role as a regulator of RNA processing and/or other functions in the nucleus and implies INTS12 function may be crucial in many cell types (Obeidat et al, 2013). Similarly, another lung function associated gene HTR4 (5q33) was found to be highly expressed in the GI tract and neuronal cells of the central nervous system and cerebellum of the brain.…”

“…Similarly, another lung function associated gene HTR4 (5q33) was found to be highly expressed in the GI tract and neuronal cells of the central nervous system and cerebellum of the brain. In the lung, bronchial epithelial cells were moderately immunopositive in the cytoplasm and membrane (Hodge et al, 2013). HTR4 protein expression was absent in the pneumocytes and macrophages.…”

“…has been used to provide further insight into the possible regulation of gene expression in this lung function associated locus (Obeidat et al, 2013). This approach identified a possibly shared promoter region for the INTS12 and GSTCD genes with evidence of H3K27 acetylation (Ac) histone mark, DNase hypersensitivity, transcription factor binding and CpG islands detected in-between the oppositely transcribed genes (Figure 8).…”

“…However, although SNPs within this putative regulatory region were predictive of INTS12 expression this was not observed for GSTCD suggesting there may be some gene specific effects. Finally, it is important to bear in mind that the regulatory features found enriched at the putative regulatory region were generated in cell lines that were not derived from lung-relevant cells (Obeidat et al, 2013). BEDtools suite for analysis of NGS data (Quinlan & Hall, 2010).…”

“…eQTL mapping can be particularly useful for identifying potential candidate genes contained within a broad association region. For example, our research group prioritized genes at locus 4q24 previously associated with the lung function measure FEV1 and risk of COPD by identifying eQTL SNPs in a range of datasets generated in lymphoblastoid cell line, liver and brain tissue (Obeidat et al, 2013 (Hao et al, 2012;Obeidat et al, 2015), blood cells (Westra et al, 2013) and airway epithelial cells (X. Li et al, 2015;Luo et al, 2015).…”