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General Comment |
The pivotal roles of the NOD-like receptors with a PYD domain, NLRPs, in oocytes and early embryo development. Amoushahi M et al. (2019) Nucleotide-binding oligomerization domain (NOD)-like receptors with a pyrin domain (PYD), NLRPs, are pattern-recognition receptors, well recognized for their important roles in innate immunity and apoptosis. However, several NLRPs have received attention for their new, specialized roles as maternally contributed genes important in reproduction and embryo development. Several NLRPs have been shown to be specifically expressed in oocytes and preimplantation embryos. Interestingly, and in line with divergent functions, NLRP genes reveal a complex evolutionary divergence. The most pronounced difference is the human-specific NLRP7 gene, not identified in rodents. However, mouse models have been extensively used to study maternally contributed NLRPs. The NLRP2 and NLRP5 proteins are components of the subcortical maternal complex (SCMC), which was recently identified as essential for mouse preimplantation development. The SCMC integrates multiple proteins, including KHDC3L, NLRP5, TLE6, OOEP, NLRP2, and PADI6. The NLRP5 (also known as MATER) has been extensively studied. In humans, inactivating variants in specific NLRP genes in the mother are associated with distinct phenotypes in the offspring, such as biparental hydatidiform moles (BiHMs) and preterm birth. Maternal-effect recessive mutations in KHDC3L and NLRP5 (and NLRP7) are associated with reduced reproductive outcomes, BiHM, and broad multi-locus imprinting perturbations. The precise mechanisms of NLRPs are unknown, but research strongly indicates their pivotal roles in the establishment of genomic imprints and post-zygotic methylation maintenance, among other processes. Challenges for the future include translations of findings from the mouse model into human contexts and implementation in therapies and clinical fertility management.//////////////////
NLRPs, the subcortical maternal complex and genomic imprinting. Monk D et al. (2017) Before activation of the embryonic genome, the oocyte provides many of the RNAs and proteins required for the epigenetic reprogramming and the transition to a totipotent state. Targeted disruption of a subset of oocyte-derived transcripts in mice results in early embryonic lethality and cleavage stage embryonic arrest as highlighted by the members of the Subcortical Maternal Complex (SCMC). Maternal-effect recessive mutations of NLRP7, KHDC3L and NLRP5 in humans are associated with variable reproductive outcomes, biparental hydatidiform moles (BiHM) and widespread multi-locus imprinting disturbances. The precise mechanism of action of these genes is unknown, but the maternal effect phenomenon suggests a function during early pre-implantation development, while biochemical and genetic studies implement them as SCMC members or interacting partners. In this review article we discuss the role of the NLRP family members and the SCMC proteins in the establishment of genomic imprints and post-zygotic methylation maintenance, the recent advances made in the understanding of the biology involved in BiHM formation and the wider roles of the SCMC in mammalian reproduction.//////////////////
NCBI Summary:
This gene encodes a member of the NACHT, leucine rich repeat, and PYD containing (NLRP) protein family. It has an N-terminal pyrin domain, followed by a NACHT domain, a NACHT-associated domain (NAD), and a C-terminal leucine-rich repeat (LRR) region. NLRP proteins are implicated in the activation of proinflammatory caspases through multiprotein complexes called inflammasomes. This gene may act as a feedback regulator of caspase-1-dependent interleukin 1-beta secretion. Alternative splicing results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Jul 2008]
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Mutations |
2 mutations
Species: human
Mutation name:
type: naturally occurring
fertility: embryonic lethal
Comment: Live births in women with recurrent hydatidiform mole and two NLRP7 mutations. Akoury E et al. (2015) Hydatidiform mole (HM) is an aberrant human pregnancy with abnormal embryonic development and excessive proliferation of the trophoblast. Recessive mutations in NLRP7 are responsible for recurrent HM (RHM). Women with recessive NLRP7 mutations fail to have normal pregnancies from spontaneous conceptions with the exception of three out of 131 reported patients. Because there is no treatment for RHM and maternal-effect genes are needed in the oocytes to sustain normal embryonic development until the activation of the embryonic genome, one patient with recessive NLRP7 mutations tried ovum donation and achieved a successful pregnancy. This study reports three additional live births from donated ova to two patients with recessive NLRP7 mutations. The occurrence of two live births from spontaneous conceptions to two other patients is also reported. The reproductive outcomes and mutations of all reported patients were reviewed and it was found that live births are associated with some missense mutations expected to have mild functional consequences on the protein. The data support a previous observation that ovum donation appears the best management option for these patients to achieve normal pregnancies and provide an explanation for the rare occurrence of live births from natural spontaneous conceptions in patients with two NLRP7 mutations.//////////////////
Species: human
Mutation name:
type: naturally occurring
fertility: embryonic lethal
Comment: Absence of Maternal Methylation in Biparental Hydatidiform Moles from Women with NLRP7 Maternal-Effect Mutations Reveals Widespread Placenta-Specific Imprinting. Sanchez-Delgado M et al. (2015) Familial recurrent hydatidiform mole (RHM) is a maternal-effect autosomal recessive disorder usually associated with mutations of the NLRP7 gene. It is characterized by HM with excessive trophoblastic proliferation, which mimics the appearance of androgenetic molar conceptuses despite their diploid biparental constitution. It has been proposed that the phenotypes of both types of mole are associated with aberrant genomic imprinting. However no systematic analyses for imprinting defects have been reported. Here, we present the genome-wide methylation profiles of both spontaneous androgenetic and biparental NLRP7 defective molar tissues. We observe total paternalization of all ubiquitous and placenta-specific differentially methylated regions (DMRs) in four androgenetic moles; namely gain of methylation at paternally methylated loci and absence of methylation at maternally methylated regions. The methylation defects observed in five RHM biopsies from NLRP7 defective patients are restricted to lack-of-methylation at maternal DMRs. Surprisingly RHMs from two sisters with the same missense mutations, as well as consecutive RHMs from one affected female show subtle allelic methylation differences, suggesting inter-RHM variation. These epigenotypes are consistent with NLRP7 being a maternal-effect gene and involved in imprint acquisition in the oocyte. In addition, bioinformatic screening of the resulting methylation datasets identified over sixty loci with methylation profiles consistent with imprinting in the placenta, of which we confirm 22 as novel maternally methylated loci. These observations strongly suggest that the molar phenotypes are due to defective placenta-specific imprinting and over-expression of paternally expressed transcripts, highlighting that maternal-effect mutations of NLRP7 are associated with the most severe form of multi-locus imprinting defects in humans.//////////////////
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