Comprehensive genotype-phenotype correlations between NLRP7 mutations and the balance between embryonic tissue differentiation and trophoblastic proliferation

BACKGROUND

Hydatidiform mole (HM) is a human pregnancy with excessive trophoblastic proliferation and abnormal embryonic development that may be sporadic or recurrent. In the sporadic form, the HM phenotype is driven by an abnormal ratio of paternal to maternal genomes, whereas in the recurrent form, the HM phenotype is caused by maternal-recessive mutations, mostly in NLRP7, despite the diploid biparental origin of the HM tissues. In this study, we characterised the expression of the imprinted, maternally expressed gene, CDKN1C (p57(KIP2)), the genotype, and the histopathology of 36 products of conception (POC) from patients with two defective alleles in NLRP7 and looked for potential correlations between the nature of the mutations in the patients and the various HM features.

METHODS/RESULTS

We found that all the 36 POCs are diploid biparental and have the same parental contribution to their genomes. However, some of them expressed variable levels of p57(KIP2) and this expression was strongly associated with the presence of embryonic tissues of inner cell mass origin and mild trophoblastic proliferation, which are features of triploid partial HMs, and were associated with missense mutations. Negative p57(KIP2) expression was associated with the absence of embryonic tissues and excessive trophoblastic proliferation, which are features of androgenetic complete HMs and were associated with protein-truncating mutations.

CONCLUSIONS

Our data suggest that NLRP7, depending on the severity of its mutations, regulates the imprinted expression of p57(KIP2) and consequently the balance between tissue differentiation and proliferation during early human development. This role is novel and could not have been revealed by any other approach on somatic cells.

Earliest ultrasound finding of implantation?

PURPOSE

Our purpose was to verify our earlier observation of an altered endometrial echo character during the periimplantation period, signifying the earliest detection of implantation by ultrasound.

METHODS

The transvaginal ultrasound study used a 7.5-MHz probe on day 6 following preembryo transfer.

RESULTS

Of 31 embryo transfers studied. 8 (25.8%) were positive for this sign on day 6, whereas 9 patients later showed a gestational sac, giving an accuracy of this sign of 88.8% (8 of 9).

CONCLUSIONS

The normal secretory-phase endometrium shows a typical, evenly distributed hyperechogenecity described earlier by Hackeloer (1). In some cases of proliferative phases, too, this echo pattern has been reported by others (2, 3), and observed by us in stimulated and unstimulated cycles, and has been named type A endometrium by Gonen et al. (4) Both these varieties are seen to have an even, unbroken outline at the anterior and posterior myometrial-endometrial interphase. We report what we believe to be the earliest ultrasound picture of implantation, resembling this variety of endometrial echo but having an irregular outline (Fig. 2).