No evidence for mutations in NLRP7 and KHDC3L in women with androgenetic hydatidiform moles

Abstract

Objective: The objective of this study was to evaluate the mutational spectrum of NLRP7 and KHDC3L (C6orf221) in women with sporadic and recurrent androgenetic complete hydatidiform moles (AnCHM) and biparental hydatidiform moles (BiHM) to address the hypothesis that autosomal recessive mutations in these genes are only or primarily associated with BiHM.

Method: We recruited 16 women with suspected recurrent and sporadic AnCHM and five women with suspected BiHM in addition to their reproductive partners into our study. We then sequenced the coding exons of NLRP7 and KHDC3L from DNA isolated from either blood or saliva from the study subjects.

Results: Sequence analysis of NLRP7 and KHDC3L revealed previously described single nucleotide polymorphisms in patients with AnCHM. However, in patients with BiHM, we identified a novel homozygous mutation and a previously described intragenic duplication of exons 2 to 5 in NLRP7, both of which are likely to be disease causing. We did not identify mutations in KHDC3L in patients with either form of hydatidiform moles.

Conclusions: The absence of mutations in women with AnCHM supports a role for NLRP7 or KHDC3L in BiHM only. The absence of mutations in KHDC3L in women with BiHM is consistent with its minor role in this disease compared with NLRP7, the major BiHM gene.

© 2013 John Wiley & Sons, Ltd.

Figures

Figure 1. Tandem intragenic duplication of exons 2-5 of NLRP7 in women with recurrent BiHM

(A) A 32bp region of homology between intron 5 and intron 1 mediates recombination resulting in tandem duplication. (B) A PCR based strategy to detect the presence of the tandem duplication. A forward primer placed in intron 4 and reverse primer in intron 2 amplified a 1,221bp product in #8 (Lane 1), #14 (Lane 2) and #12 (Lane 3) but not in a control female (Lane 4).

Figure 2. A novel, damaging mutation in patient #14

A homozygous mutation in exon 5 of a patient (A, forward orientation) and (B, reverse orientation) with recurrent HM resulting in a C>T transition. This change was not seen in 200 control chromosomes (C and D). The c.1981C>T mutation changes a leucine to phenylalanine at amino acid position 661 in the NLRP7 transcript variant 3 which links the NAD and LRR domains (E). The leucine at this position in NLRP7 is conserved across primates and in the ancestral NLRP2 as well (F).