Jerome F. Strauss III, M.D., Ph.D., dean of the Virginia Commonwealth University School of Medicine, and colleagues found that a change in a single nucleotide in the gene sequence, known as a single nucleotide polymorphism (SNP), in the SERPINH1 gene may be responsible for the increased risk of preterm premature rupture of membranes (PPROM) in women of African descent. The SERPINH1 gene encodes a heat shock protein known as Hsp47, which is essential for collagen production. Collagen lends strength to the membranes that surround the fetus and amniotic fluid.
The genetic variant identified reduces the amount of Hsp47 made and thus the collagen in the membranes, making them more prone to rupture. Other published research has reported that reduced collagen content has been found in PPROM fetal membranes. PPROM is the leading identifiable cause of preterm birth and occurs more frequently in African-American women.
"Our discovery of an association between a gene variation that is more common in individuals of African descent and a cause of premature birth, can explain in part the disparity in prematurity rates in African-Americans," said Strauss, who led the study.
"More importantly, the genetic signature can help us identify women at risk of early breakage of the "bag of waters" so that appropriate monitoring and therapy can be applied in order to prevent this serious pregnancy complication."
In this study, the researchers compared amnion samples carrying the minor "T" allele to samples carrying the major "C" allele. The minor "T" allele is a genetic variant that occurs with greater frequency among those with African ancestry. A reduction in the promoter activity of the amnion cells in the minor "T" allele compared to the major "C" allele was observed. According to Strauss, as a result, women carrying the minor "T" allele may produce decreased amounts of Hsp47 protein and thus, produce reduced amounts of collagen and a weaker amnion that is more prone to rupture.