The overall hypothesis to be tested is: women with the molecular phenotype of highly skewed X chromosome inactivation are at increased risk of spontaneous abortion.~We will investigate this hypothesis through two complimentary aims. In the Background and Significance section, we first present data on a 53-member pedigree segregating an X-linked recessive lethal defect that results in skewed X inactivation in the carrier females via secondary selection against those cells with the defective X chromosome active. We have characterized this deletion to be a 500 kb (approximate) deletion in distal Xq28. Moreover, the carrier females show a statistically significant increase in the frequency of spontaneous abortion as compared to non-deletion carrying relatives. Secondly, in the Preliminary Studies section, we present data from a population based case-control study wherein highly skewed X chromosome inactivation is significantly correlated with idiopathic recurrent spontaneous abortion. This protocol attempts to elucidate the mechanism underlying this association.~The first specific aim is to determine if women with highly skewed X chromosome inactivation are at risk of pregnancy loss. This will be accomplished through a prospective protocol, analyzing X chromosome inactivation patterns in pregnant women and investigating a possible association between X chromosome inactivation and pregnancy outcome. The second aim will study the nature of pregnancy loss in women with skewed X chromosome inactivation. This aim will correlate maternal X inactivation patterns with abortus karyotype.
The overall hypothesis to be tested is: women with the molecular phenotype of highly skewed X chromosome inactivation are at increased risk of spontaneous abortion.