We performed supervised clustering of samples with NNNS profiles using 339 Hg-associated loci (see Supplemental Material, Figure S1), but observed no obvious clustering pattern of high-risk neurobehavioral profile.
We then examined the average extent of methylation across all of the EMID2 loci in the NNNS subset, comparing those infants in the high-risk and non-high-risk groups.
In this analysis, 16 infants were observed to have a high-risk NNNS profile.
Limitations to this study include undetermined Hg exposure sources, infant toenail Hg as a proxy for prenatal exposure, use of term placentas, a relatively small sample size (including n = 16 high-risk NNNS profile infants), independent sample sets for Hg and neurobehavior analyses, which limits our ability to examine direct relationships between them, and a large proportion of samples falling below the limit of detection.
125 were analyzed for associations with high-risk NNNS profile in an independent set of 151 samples with NNNS data.
Abnormal findings in case Neurobehavioral NNNS exam symptoms Displayed hypertonicity in Excessive or trunk, neck, and upper/lower above-normal extremities muscle tone or tension; the infant's musculature becomes "stiff" or rigid, and the infant shows marked resistance to passive movements.
Ten singleton infants in the cohort were referred to a physician for abnormal NNNS findings after the 1-month examination.
The NNNS is a validated tool to assess neurobehavior during early infancy (Lester and Tronick 2004).