RESUMO
BACKGROUND AND AIMS: Susceptibility genes and the underlying mechanisms for the majority of risk loci identified by genome-wide association studies (GWAS) for colorectal cancer (CRC) risk remain largely unknown. We conducted a transcriptome-wide association study (TWAS) to identify putative susceptibility genes. METHODS: Gene-expression prediction models were built using transcriptome and genetic data from the 284 normal transverse colon tissues of European descendants from the Genotype-Tissue Expression (GTEx), and model performance was evaluated using data from The Cancer Genome Atlas (n = 355). We applied the gene-expression prediction models and GWAS data to evaluate associations of genetically predicted gene-expression with CRC risk in 58,131 CRC cases and 67,347 controls of European ancestry. Dual-luciferase reporter assays and knockdown experiments in CRC cells and tumor xenografts were conducted. RESULTS: We identified 25 genes associated with CRC risk at a Bonferroni-corrected threshold of P < 9.1 × 10-6, including genes in 4 novel loci, PYGL (14q22.1), RPL28 (19q13.42), CAPN12 (19q13.2), MYH7B (20q11.22), and MAP1L3CA (20q11.22). In 9 known GWAS-identified loci, we uncovered 9 genes that have not been reported previously, whereas 4 genes remained statistically significant after adjusting for the lead risk variant of the locus. Through colocalization analysis in GWAS loci, we additionally identified 12 putative susceptibility genes that were supported by TWAS analysis at P < .01. We showed that risk allele of the lead risk variant rs1741640 affected the promoter activity of CABLES2. Knockdown experiments confirmed that CABLES2 plays a vital role in colorectal carcinogenesis. CONCLUSIONS: Our study reveals new putative susceptibility genes and provides new insight into the biological mechanisms underlying CRC development.
Assuntos
Biomarcadores Tumorais/genética , Neoplasias Colorretais/genética , Predisposição Genética para Doença , Modelos Genéticos , Alelos , Carcinogênese/genética , Estudos de Casos e Controles , Estudos de Coortes , Neoplasias Colorretais/epidemiologia , Técnicas de Silenciamento de Genes , Estudo de Associação Genômica Ampla , Humanos , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas/genética , RNA-Seq , Fatores de Risco , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
In vivo function of CDK5 and Abl enzyme substrate 2 (Cables2), belonging to the Cables protein family, is unknown. Here, we found that targeted disruption of the entire Cables2 locus (Cables2d) caused growth retardation and enhanced apoptosis at the gastrulation stage and then induced embryonic lethality in mice. Comparative transcriptome analysis revealed disruption of Cables2, 50% down-regulation of Rps21 abutting on the Cables2 locus, and up-regulation of p53-target genes in Cables2d gastrulas. We further revealed the lethality phenotype in Rps21-deleted mice and unexpectedly, the exon 1-deleted Cables2 mice survived. Interestingly, chimeric mice derived from Cables2d ESCs carrying exogenous Cables2 and tetraploid wild-type embryo overcame gastrulation. These results suggest that the diminished expression of Rps21 and the completed lack of Cables2 expression are intricately involved in the embryonic lethality via the p53 pathway. This study sheds light on the importance of Cables2 locus in mouse embryonic development.
Assuntos
Proteínas de Ciclo Celular/genética , Gastrulação/genética , Expressão Gênica , Proteínas Ribossômicas/genética , Transdução de Sinais , Proteína Supressora de Tumor p53/metabolismo , Animais , Feminino , Masculino , Camundongos , Camundongos Endogâmicos ICR , Fenótipo , Ativação Transcricional , Proteína Supressora de Tumor p53/genética , Regulação para CimaRESUMO
Two members of the CDK5 and ABL enzyme substrate (CABLES) family, CABLES1 and CABLES2, share a highly homologous C-terminus. They interact and associate with cyclin-dependent kinase 3 (CDK3), CDK5, and c-ABL. CABLES1 mediates tumor suppression, regulates cell proliferation, and prevents protein degradation. Although Cables2 is ubiquitously expressed in adult mouse tissues at RNA level, the role of CABLES2 in vivo remains unknown. Here, we generated bicistronic Cables2 knock-in reporter mice that expressed CABLES2 tagged with 3×FLAG and 2A-mediated fluorescent reporter tdTomato. Cables2-3×FLAG-2A-tdTomato (Cables2Tom) mice confirmed the expression of Cables2 in various mouse tissues. Interestingly, high intensity of tdTomato fluorescence was observed in the brain, testis and ovary, especially in the corpus luteum. Furthermore, immunoprecipitation analysis using the brain and testis in Cables2Tom/Tom revealed interaction of CABLES2 with CDK5. Collectively, our new Cables2 knock-in reporter model will enable the comprehensive analysis of in vivo CABLES2 function.