A Genome-wide Association Analysis in Four Populations Reveals Strong Genetic Heterogeneity For Birth Weight

Association of the FCN2 Gene Promoter Region Polymorphisms with Very Low Birthweight in Preterm Neonates

Single nucleotide polymorphisms (SNPs) localised to the promoter region of the FCN2 gene are known to influence the concentration of ficolin-2 in human serum and therefore potentially have clinical associations. We investigated the relationships between SNPs at positions −986 (A > G), −602 (G > A), −64 (A > C) and −4 (A > G) and clinical complications in 501 preterms. Major alleles at positions −986 and −64 and A/A homozygosity for both polymorphisms were less frequent among babies with very low birthweight (VLBW, ≤1500 g) compared with the reference group (OR = 0.24, p = 0.0029; and OR = 0.49, p = 0.024, respectively for A/A genotypes). A lower frequency of G/G homozygosity at position −4 was associated with gestational age <33 weeks and VLBW (OR = 0.38, p = 0.047; and OR = 0.07, p = 0.0034, respectively). The AGAG haplotype was protective for VLBW (OR = 0.6, p = 0.0369), whilst the GGCA haplotype had the opposite effect (OR = 2.95, p = 0.0249). The latter association was independent of gestational age. The AGAG/GGAA diplotype favoured both shorter gestational age and VLBW (OR = 1.82, p = 0.0234 and OR = 1.95, p = 0.0434, respectively). In contrast, AGAG homozygosity was protective for lower body mass (OR = 0.09, p = 0.0155). Our data demonstrate that some FCN2 variants associated with relatively low ficolin-2 increase the risk of VLBW and suggest that ficolin-2 is an important factor for fetal development/intrauterine growth.

Genetic variants in the glucocorticoid pathway genes and birth weight

PURPOSE

The aim of this study was to examine associations between single nucleotide polymorphisms (SNPs) that tag genetic variation in the glucocorticoid pathways (particularly in maternal genes FKBP5, NR3C1, and CRHR1) and birth weight.

METHODS

The Franconian Maternal Health Evaluation Study (FRAMES) recruited healthy pregnant women prospectively for the assessment of maternal and fetal health. Germline DNA was collected from 375 pregnant women. Nine SNPs in the above-mentioned genes were genotyped. After reconstruction of haplotypes for each gene, a linear regression model was applied to the data to describe the association between haplotypes and birth weight.

RESULTS

Female sex in the newborn (compared to male) was associated with lower birth weight, whereas a later week of gestation, higher body mass index pre-pregnancy, and higher parity were associated with higher birth weight. No association with birthweight was shown for the haplotypes of the selected SNPs.

CONCLUSIONS

In this cohort of healthy unselected pregnant women, the analyzed candidate haplotypes in FKBP5, NR3C1, and CRHR1 did not show any association with birth weight. This might be in line with several other studies that have found no influence of fetal polymorphisms in the glucocorticoid receptor gene or triggers of the maternal HPA axis such as stress and psychosocial problems on birth weight. However, the small sample size in this study and the lack of consideration of individual risk factors and levels of stress in this cohort needs to be taken into account when interpreting the results.