title: DNA methylation analysis of Homeobox genes implicates HOXB7 hypomethylation as risk factor for neural tube defects.
abstract: Neural tube defects (NTDs) are common birth defects of complex etiology. Though family- and population-based studies have confirmed a genetic component, the responsible genes for NTDs are still largely unknown. Based on the hypothesis that folic acid prevents NTDs by stimulating methylation reactions, epigenetic factors, such as DNA methylation, are predicted to be involved in NTDs. Homeobox (HOX) genes play a role in spinal cord development and are tightly regulated in a spatiotemporal and collinear manner, partly by epigenetic modifications. We have quantified DNA methylation for the different HOX genes by subtracting values from a genome-wide methylation analysis using leukocyte DNA from 10 myelomeningocele (MMC) patients and 6 healthy controls. From the 1575 CpGs profiled for the 4 HOX clusters, 26 CpGs were differentially methylated (P-value < 0.05; β-difference > 0.05) between MMC patients and controls. Seventy-seven percent of these CpGs were located in the HOXA and HOXB clusters, with the most profound difference for 3 CpGs within the HOXB7 gene body. A validation case-control study including 83 MMC patients and 30 unrelated healthy controls confirmed a significant association between MMC and HOXB7 hypomethylation (-14.4%; 95% CI: 11.9-16.9%; P-value < 0.0001) independent of the MTHFR 667C>T genotype. Significant HOXB7 hypomethylation was also present in 12 unaffected siblings, each related to a MMC patient, suggestive of an epigenetic change induced by the mother. The inclusion of a neural tube formation model using zebrafish showed that Hoxb7a overexpression but not depletion resulted in deformed body axes with dysmorphic neural tube formation. Our results implicate HOXB7 hypomethylation as risk factor for NTDs and highlight the importance for future genome-wide DNA methylation analyses without preselecting candidate pathways.
authors.affiliation: a Department of Cardiovascular Sciences; Center for Molecular and Vascular Biology ; University of Leuven ; Leuven , Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Rochtus
authors.forename: Benedetta
authors.initials: B
authors.lastname: Izzi
authors.forename: Elise
authors.initials: E
authors.lastname: Vangeel
authors.forename: Sophie
authors.initials: S
authors.lastname: Louwette
authors.forename: Christine
authors.initials: C
authors.lastname: Wittevrongel
authors.forename: Diether
authors.initials: D
authors.lastname: Lambrechts
authors.forename: Yves
authors.initials: Y
authors.lastname: Moreau
authors.forename: Raf
authors.initials: R
authors.lastname: Winand
authors.forename: Carla
authors.initials: C
authors.lastname: Verpoorten
authors.forename: Katrien
authors.initials: K
authors.lastname: Jansen
authors.forename: Chris
authors.initials: C
authors.lastname: Van Geet
authors.forename: Kathleen
authors.initials: K
authors.lastname: Freson
mesh_terms: D000328:Adult; D000818:Animals; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008591:Meningomyelocele / Q000235:genetics*; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D015027:Zebrafish
chemical_list: C490538:HOXB7 protein, human; D018398:Homeodomain Proteins; C573423:MTHFR protein, human; D042965:Methylenetetrahydrofolate Reductase (NADPH2)
keywords: DNA methylation; HOX genes; HOXB7; Myelomeningocele; epigenetics; neural tube defects