No abstract

Many common disorders of pregnancy are attributed to insufficient invasion of the uterine lining by trophoblast, fetal cells that are the major cell type of the placenta. Interactions between fetal trophoblast and maternal uterine NK (uNK) cells -specifically interactions between HLA-C molecules expressed by the fetal trophoblast cells and killer Ig-like receptors (KIRs) on the maternal uNK cells -influence placentation in human pregnancy. Consistent with this, pregnancies are at increased risk of preeclampsia in mothers homozygous for KIR haplotype A (KIR AA). In this study, we have demonstrated that trophoblast expresses both paternally and maternally inherited HLA-C surface proteins and that maternal KIR AA frequencies are increased in affected pregnancies only when the fetus has more group 2 HLA-C genes (C2) than the mother. These data raise the possibility that there is a deleterious allogeneic effect stemming from paternal C2. We found that this effect also occurred in other pregnancy disorders (fetal growth restriction and recurrent miscarriage), indicating a role early in gestation for these receptor/ligand pairs in the pathogenesis of reproductive failure. Notably, pregnancy disorders were less frequent in mothers that possessed the telomeric end of the KIR B haplotype, which contains activating KIR2DS1. In addition, uNK cells expressed KIR2DS1, which bound specifically to C2 + trophoblast cells. These findings highlight the complexity and central importance of specific combinations of activating KIR and HLA-C in maternal-fetal immune interactions that determine reproductive success. IntroductionThe main tissue location where maternal allo-recognition of the fetus occurs is in the uterus at the site of placentation, where fetal extravillous trophoblast cells (EVTs) invade and intermingle with maternal leukocytes (1). Uterine NK (uNK) cells account for approximately 70% of decidual leukocytes and are likely to be involved in placentation and thus fetal growth and development. We proposed that placentation is regulated as a result of interactions between maternal killer immunoglobulin-like receptors (KIRs) expressed by uNK cells and their cognate ligands, HLA-C molecules, displayed by invading fetal trophoblast cells (2, 3). The importance of NK cell KIR/HLA-C interactions in mediating allorecognition in the artificial context of BM transplantation (BMT) is well known (4). The only physiological situation in which NK allo-recognition occurs is during pregnancy.The function of EVT is to access the maternal blood supply during placentation, when trophoblast invades the walls of the spiral arteries, converting them to high-conductance vessels (1).

Clefts of the lip and/or palate (CL/P) are among the most common birth defects worldwide. The majority are non-syndromic where CL/P occurs in isolation of other phenotypes. Where one or more additional features are involved, clefts are referred to as syndromic. Collectively CL/P has a major clinical impact requiring surgical, dental, orthodontic, speech, hearing and psychological treatments or therapies throughout childhood. The etiology of CL/P is complex and thought to involve both major and minor genetic influences with variable interactions from environmental factors. Using a combination of gene targeting technology and traditional developmental techniques in both mouse and chick, significant progress has been made in the identification of numerous genes and gene pathways critical for craniofacial development. Despite this, it has been a particular source of frustration that mutation screening of specific candidates, association studies and even genome-wide scans have largely failed to reveal the molecular basis of human clefting. Nevertheless, some important findings have recently come from studies involving syndromic forms of the disorder. These include several genes which have now been shown to contribute a major effect on the etiology of CL/P. Furthermore, these genes can also be used to demonstrate a significant overlap between syndromic and non-syndromic CL/P. The study of these syndromic genes and their molecular pathways will provide a useful and informative route with which to gain a better understanding of human craniofacial pathology.

Imprinted genes play crucial roles in mammalian development and disruption of their expression is associated with many human disorders including tumourigenesis; yet, the actual number of imprinted genes in the human genome remains a matter of debate. Here, we report on the unexpected finding that the chromosome 19 microRNA cluster (C19MC), the largest human microRNA gene cluster discovered so far, is regulated by genomic imprinting with only the paternally inherited allele being expressed in the placenta. DNA methylation profiling identified a differentially methylated region (C19MC-DMR1) that overlaps an upstream CpG-rich promoter region associated with short tandem repeats. It displays a maternal-specific methylation imprint acquired in oocytes and generates a complex population of large, compartimentalized non-coding RNA (ncRNA) species retained in close proximity to the C19MC transcription site. This occurs adjacent to, but not within, a poorly characterized nuclear Alu-rich domain. Interestingly, C19MC maps near another imprinted gene, the maternally expressed ZNF331 gene, and therefore may define a novel, previously unrecognized large imprinted primate-specific chromosomal domain. Altogether, our study adds C19MC to the growing list of imprinted repeated small RNA gene clusters and further strengthens the potential involvement of small ncRNAs in the function and/or the evolution of imprinted gene networks.

Congenital melanocytic nevi (CMN) can be associated with neurological abnormalities and an increased risk of melanoma. Mutations in NRAS, BRAF, and Tp53 have been described in individual CMN samples; however, their role in the pathogenesis of multiple CMN within the same subject and development of associated features has not been clear. We hypothesized that a single postzygotic mutation in NRAS could be responsible for multiple CMN in the same individual, as well as for melanocytic and nonmelanocytic central nervous system (CNS) lesions. From 15 patients, 55 samples with multiple CMN were sequenced after site-directed mutagenesis and enzymatic digestion of the wild-type allele. Oncogenic missense mutations in codon 61 of NRAS were found in affected neurological and cutaneous tissues of 12 out of 15 patients, but were absent from unaffected tissues and blood, consistent with NRAS mutation mosaicism. In 10 patients, the mutation was consistently c.181C>A, p.Q61K, and in 2 patients c.182A>G, p.Q61R. All 11 non-melanocytic and melanocytic CNS samples from 5 patients were mutation positive, despite NRAS rarely being reported as mutated in CNS tumors. Loss of heterozygosity was associated with the onset of melanoma in two cases, implying a multistep progression to malignancy. These results suggest that single postzygotic NRAS mutations are responsible for multiple CMN and associated neurological lesions in the majority of cases.