Correlation between mutations and mRNA expression of APC and MUTYH genes: new insight into hereditary colorectal polyposis predisposition.
BACKGROUND
Transcript dosage imbalance may influence the transcriptome. To gain insight into the role of altered gene expression in hereditary colorectal polyposis predisposition, in the present study we analyzed absolute and allele-specific expression (ASE) of adenomatous polyposis coli (APC) and mutY Homolog (MUTYH) genes.


METHODS
We analyzed DNA and RNA extracted from peripheral blood mononuclear cells (PBMC) of 49 familial polyposis patients and 42 healthy blood donors selected according similar gender and age. Patients were studied for germline alterations in both genes using dHPLC, MLPA and automated sequencing. APC and MUTYH mRNA expression levels were investigated by quantitative Real-Time PCR (qRT-PCR) analysis using TaqMan assay and by ASE assays using dHPLC-based primer extension.


RESULTS
Twenty out of 49 patients showed germline mutations: 14 in APC gene and six in MUTYH gene. Twenty-nine patients did not show mutations in both genes. Results from qRT-PCR indicated that gene expression of both APC and MUTYH was reduced in patients analyzed. In particular, a significant reduction in APC expression was observed in patients without APC germline mutation vs control group (P < 0.05) while APC expression in the mutation carrier patients, although lower compared to control individuals, did not show statistical significance. On the other hand a significant reduced MUTYH expression was detected in patients with MUTYH mutations vs control group (P < 0.05). Altered ASE of APC was detected in four out of eight APC mutation carriers. In particular one case showed a complete loss of one allele. Among APC mutation negative cases, 4 out of 13 showed a moderate ASE. ASE of MUTYH did not show any altered expression in the cases analyzed. Spearman's Rho Test analysis showed a positive and significant correlation between APC and MUTYH genes both in cases and in controls (P = 0.020 and P < 0.001).


CONCLUSIONS
APC and MUTYH showed a reduced germline expression, not always corresponding to gene mutation. Expression of APC is decreased in mutation negative cases and this appears to be a promising indicator of FAP predisposition, while for MUTYH gene, mutation is associated to reduced mRNA expression. This study could improve the predictive genetic diagnosis of at-risk individuals belonging to families with reduced mRNA expression regardless of presence of mutation.
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. gaceto@unich.it.
Gitana Maria
GM
Aceto
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. f.fantini@unich.it.
Fabiana
F
Fantini
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. s.deiure@unich.it.
Sabrina
S
De Iure
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. m.dinicola@unich.it.
Marta
M
Di Nicola
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. gdpalka@unich.it.
Giandomenico
G
Palka
Department of Clinical Physiopathology, University of Florence, Florence, Italy. rosa.valanzano@unifi.it.
Rosa
R
Valanzano
Immunohaematology and Transfusional Medicine Service, "SS. Annunziata" Hospital, Chieti, Italy. patrizia.digregorio@asl2abruzzo.it.
Patrizia
P
Di Gregorio
Division of Gastroenterology and Digestive Endoscopy, Regina Elena National Cancer Institute, Rome, Italy. stigliano@ifo.it.
Vittoria
V
Stigliano
Institute of Medical Genetics, "A. Gemelli" School of Medicine, Catholic University of the Sacred Heart, Rome, Italy. m.genuardi@rm.unicatt.it.
Maurizio
M
Genuardi
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. p.battista@unich.it.
Pasquale
P
Battista
Department of Pharmacy, "G. d'Annunzio" University, Chieti, Italy. cama@unich.it.
Alessandro
A
Cama
Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University, Chieti, Italy. mc.curia@unich.it.
Maria Cristina
MC
Curia
D011125:Adenomatous Polyposis Coli / Q000175:diagnosis / Q000235:genetics*; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics*; D000328:Adult; D000368:Aged; D000483:Alleles; D016022:Case-Control Studies; D045647:DNA Glycosylases / Q000235:genetics*; D004252:DNA Mutational Analysis; D005786:Gene Expression Regulation; D020022:Genetic Predisposition to Disease; D018095:Germ-Line Mutation; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D012333:RNA, Messenger
D025601:Adenomatous Polyposis Coli Protein; D012333:RNA, Messenger; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase