Abstract
It has been shown previously that homozygous and compound-heterozygous variants affecting protein function in the human NLRP genes impact reproduction and/or fetal imprinting patterns. These variants represent so-called 'maternal effect mutations', that is, although female variant carriers are healthy, they are at risk of reproductive failure, and their offspring may develop aberrant methylation and imprinting disorders. In contrast, the relevance to reproductive failure of maternal heterozygous NLRP7 variants remains unclear. The present report describes the identification of a heterozygous NLRP7 variant in a healthy 28-year-old woman with a history of recurrent reproductive failure, and the molecular findings in two of the deceased offspring. Next-generation sequencing (NGS) for NLRP variants was performed. In the tissues of two offspring (one fetus; one deceased premature neonate) methylation of imprinted loci was tested using methylation-specific assays. Both pregnancies had been characterized by the presence of elevated human chorionic gonadotropin (hCG) levels and ovarian cysts. In the mother, a heterozygous nonsense 2-bp deletion in exon 5 of the NLRP7 gene was identified (NM_001127255.1:c.2010_2011del, p.(Phe671Glnfs*18)). In the two investigated offspring, heterogeneous aberrant methylation patterns were detected at imprinted loci. The present data support the hypothesis that heterozygous NLRP7 variants contribute to reproductive wastage, and that these variants represent autosomal dominant maternal effect variants which lead to aberrant imprinting marks in the offspring. Specific screening and close prenatal monitoring of NLRP7 variant carriers is proposed. Egg donation might facilitate successful pregnancy in heterozygous NLRP7 variant carriers.