From early stress to 12-month development in very preterm infants: Preliminary findings on epigenetic mechanisms and brain growth

<div><p>Very preterm (VPT) infants admitted to Neonatal Intensive Care Unit (NICU) are at risk for altered brain growth and less-than-optimal socio-emotional development. Recent research suggests that early NICU-related stress contributes to socio-emotional impairments in VPT infants at 3 months through epigenetic regulation (i.e., DNA methylation) of the serotonin transporter gene (<i>SLC6A4</i>). In the present longitudinal study we assessed: (a) the effects of NICU-related stress and <i>SLC6A4</i> methylation variations from birth to discharge on brain development at term equivalent age (TEA); (b) the association between brain volume at TEA and socio-emotional development (i.e., Personal-Social scale of Griffith Mental Development Scales, GMDS) at 12 months corrected age (CA). Twenty-four infants had complete data at 12-month-age. <i>SLC6A4</i> methylation was measured at a specific CpG previously associated with NICU-related stress and socio-emotional stress. Findings confirmed that higher NICU-related stress associated with greater increase of <i>SLC6A4</i> methylation at NICU discharge. Moreover, higher <i>SLC6A4</i> discharge methylation was associated with reduced anterior temporal lobe (ATL) volume at TEA, which in turn was significantly associated with less-than-optimal GMDS Personal-Social scale score at 12 months CA. The reduced ATL volume at TEA mediated the pathway linking stress-related increase in <i>SLC6A4</i> methylation at NICU discharge and socio-emotional development at 12 months CA. These findings suggest that early adversity-related epigenetic changes might contribute to the long-lasting programming of socio-emotional development in VPT infants through epigenetic regulation and structural modifications of the developing brain.</p></div

From early stress to 12-month development in very preterm infants: Preliminary findings on epigenetic mechanisms and brain growth - Fig 2

<p><b>Brain MRI segmentation: A. axial and B. coronal view T1 images.</b> Note. Colors highlight anterior temporal lobe (ATL) lateral part left (ATL-LPL, yellow) and right (ATL-LPR, dark blue) as well as ATL medial part left (ATL-M;PL, light blue) and right (ATL-MPR, pink).</p

Effects of NICU-related stress and SLC6A4 methylation on brain volumes.

<p>Effects of NICU-related stress and SLC6A4 methylation on brain volumes.</p

Schematic time-line of the longitudinal project, limitedly to the variables of interest.

<p>Note. NICU, Neonatal Intensive Care Unit; <i>SLC6A4</i>, serotonin transporter gene; <i>Δ</i>_<i>met</i>, mean change in <i>SLC6A4</i> methylation from birth to NICU discharge at CpG chr17: 28562786–28562787; ATL, anterior temporal lobe; MRI, Magnetic Resonance Imaging; GMDS, Griffith Mental Development Scales; PCA, Post-Conceptional Age; TEA, term-equivalent age; CA, Corrected Age for prematurity.</p

Effects of brain volumes on GMDS Personal-Social scale.

<p>Effects of brain volumes on GMDS Personal-Social scale.</p

Descriptive statistics for the included subjects.

<p>Descriptive statistics for the included subjects.</p

Molecular cloning of the 5;15 translocation in case 1.

<p>A, magnified view of the chromosome 5 breakpoint boundary detected by array-CGH using a 244 K oligonucleotide-based whole-genome microarray. The shaded area indicates a loss in DNA copy number (deletion) detected by three oligonucleotide probes (green dots). Black dots represent probes with no changes in copy number (non-deleted region). B, whole chromosome view (left) and magnified view (right) of the chromosome 15 breakpoint boundaries detected by custom oligonucleotide-based 15q11-q13 microarray. The shaded areas indicate a deletion (majority of green dots) and a gain in DNA copy number (duplication) detected by red dots (see arrow). The area containing few widely spaced probes represents BP3, a large region containing paralogous sequences. The last deleted oligomer is at 26,210,153 bp within <i>HERC2</i>, corresponding to BP3; the duplicated region is between 26,996,914 (first duplicated) and 27,106,557 bp (last duplicated) with first normal oligomer at 27,108,882 bp just distal to BP3, within the <i>APBA2</i> gene. An arrowhead points to the two black spots possibly indicating a single copy region between the deletion and the duplication. C, schematic representation of the rearrangement showing the two chromosomes involved, the position and orientation of the duplicated region, and the location of the two junctions (arrows). D, DNA sequences spanning the chromosome 5 deletion/15 duplication junction (Jc1) aligned with the reference sequences. E, dot-plot diagram, made with PipMaker software <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039180#pone.0039180-Schwartz1" target="_blank">[45]</a>, showing the relative location of the inverted chromosome 15 duplication boundaries (Jc1 and Jc2, arrows) and of the <i>GOLGA8E</i>-associated inverted low copy repeat. The duplicated portion is represented by an orange arrow box.</p

Physical map of the 15q11.2-q14 region.

<p>The six segmental duplication sites responsible for specific recurrent rearrangements in this region, known as BP1-6, are represented by black boxes. All genes in the region are shown. The position of the chromosome 15 breakpoints of the five translocation cases we have examined are represented by thin arrows. The positions of the eight translocation cases (MR1-8) described by Mignon-Ravix <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039180#pone.0039180-MignonRavix1" target="_blank">[10]</a> are indicated by thick arrows.</p

Phenotype, karyotype and molecular characterization of the five cases with unbalanced translocations.

*<p>The minor cell line has been confirmed, by classical cytogenetics, in fibroblasts, with a similar mosaicism percentage (45, XX, der(15;18)(q13;q23)[83]-15/45, X, der (X;15)(q28;q13),-15<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039180#pone.0039180-Carrozzo1" target="_blank">[3]</a>*).</p