Maternal vitamin D deficiency impairs heart formation in mouse offspring through a change in 3D-chromatin structure

The origins of congenital heart diseases, the most common congenital diseases are still largely unknown. Environmental factors are now emerging as major causes of these diseases. Vitamin D deficiency has become a public health burden, notably for childbearing age, pregnant and breastfeeding women. Since maternal 25-hydroxyvitamin D (25(OH)D) determined fetal and neonatal 25(OH)D status, foetuses exposed to insufficient levels of vitamin D, may feature developmental defects. Herein, we investigated the effects of maternal vitamin D deficiency on cardiovascular defects in early and later life of offsprings in two generations as well as the molecular mechanisms underlying vitamin D effect. Eight weeks before and during pregnancy, C57BL/6JRj female mice received a sufficient or vitamin D deficient diet ((1.0 IU/g in control vs 0.0 IU/g in Vitamin D Deficient (VDD) group). E16.5 Embryos of maternal VDD diet featured hypertrophic heart revealed by a thicker left ventricular (LV) wall and septum. RNAseq analysis of LV revealed 1555 transcripts differentially expressed in the VDD group and among them cardiac transcription factors and constitutive cardiac genes (tbx5, gata4, myl2). Anti-Vitamin D receptor (VDR) Chip-seq from chromatin of E16.5 LV uncovered different targeting of tbx5 and tbx3 loci by VDR in the VDD vs control embryos. Anti-CTCF ChIP-loop experiments focusing on the Tbx3 and Tbx5 loci uncovered a change in the Topology Associated Domains associated with these loci. Echocardiography of 2-months-old VDD offspring revealed a significantly thicker left ventricle and increased fractional shortening while 6-months-old mice featured cardiac decompensation and in turn failing LV. Maternal vitamin D deficiency severely affects heart formation following a change in chromatin conformation on cardiac gene loci and impacts function of adult hearts in two generations. These defects are likely to be at the origin of cardiovascular diseases in the adulthood.