Conditional knockout of focal adhesion kinase in endothelial cells reveals its role in angiogenesis and vascular development in late embryogenesis

Focal adhesion kinase (FAK) is a critical mediator of signal transduction by integrins and growth factor receptors in a variety of cells including endothelial cells (ECs). Here, we describe EC-specific knockout of FAK using a Cre-loxP approach. In contrast to the total FAK knockout, deletion of FAK specifically in ECs did not affect early embryonic development including normal vasculogenesis. However, in late embryogenesis, FAK deletion in the ECs led to defective angiogenesis in the embryos, yolk sac, and placenta, impaired vasculature and associated hemorrhage, edema, and developmental delay, and late embryonic lethal phenotype. Histologically, ECs and blood vessels in the mutant embryos present a disorganized, detached, and apoptotic appearance. Consistent with these phenotypes, deletion of FAK in ECs isolated from the floxed FAK mice led to reduced tubulogenesis, cell survival, proliferation, and migration in vitro. Together, these results strongly suggest a role of FAK in angiogenesis and vascular development due to its essential function in the regulation of multiple EC activities.

Fetal Cells and Cell Free Fetal Nucleic Acids in Maternal Blood: New Tools to Study Abnormal Placentation?

The analysis of fetal cells, and more recently cell free fetal nucleic acids, in maternal blood has to date largely been concerned with the development of risk free methods for prenatal diagnosis. Although elevated feto-maternal cell trafficking has long been associated with preeclampsia, it has only recently been shown that this perturbation is an early event in these pregnancies, occurring well in advance of the onset of symptoms. In a separate development, analogous observations have been made concerning the levels of circulatory fetal nucleic acids in maternal plasma. Subsequent studies have shown that changes in these two parameters may also occur in other pregnancy related disorders including preterm labour, intra-uterine growth retardation, hyperemesis gravidarum or even pregnancies at high altitude. A striking finding of these examinations was that preterm labour was associated with an elevated release of cell free fetal nucleic acids but not with an increment in feto-maternal cell trafficking. This suggested that the analysis of the mechanisms regulating trans-placental cell trafficking or liberation of circulatory fetal nucleic acids may provide key insights into the fundamentally different placental lesions underlying these disorders. As such, circulatory fetal cells and nucleic acids may be viewed as new tools to study alterations in placentation.

Mutation of SENP1/SuPr-2 reveals an essential role for desumoylation in mouse development

The covalent modification of proteins by the small ubiquitin-like protein SUMO has been implicated in the regulation of numerous biological processes, including nucleocytoplasmic transport, genomic stability, and gene transcription. Sumoylation occurs by a multienzyme process similar to ubiquitination and, in Saccharomyces cerevisiae, is reversed by desumoylating enzymes encoded by the Ulp1 and Smt4/Ulp2 genes. The physiological importance of desumoylation has been revealed by mutations in either gene, which lead to nonoverlapping defects in cell cycle transition and meiosis. Several mammalian Ulp homologues have been identified, but, to date, nothing is known of the phenotypic effects of their loss of function. Here, we describe a random retroviral insertional mutation of one homolog, mouse SENP1/SuPr-2. The mutation causes increased steady-state levels of the sumoylated forms of a number of proteins and results in placental abnormalities incompatible with embryonic development. Our findings provide the first insight into the critical importance of regulating sumoylation in mammals.

[Early amnion rupture and fetal and newborn defects as an obstetrical and pathomorphological problem]

OBJECTIVES

Early amnion rupture (EAR, EARS, EAROD) may be the cause of amniotic bands and sheets development, which may lead to different fetal defects--from minor finger amputation, chiloschisis or palatoschisis to major amputation, acranius, deep paroschisis or broad body covering cleavage.

DESIGN

The aim of this report was to analyse cases of fetal malformation, which might have been caused by EARS.

MATERIALS AND METHODS

A retrospective analysis of 3173 autopsies performed within a span of 14 years (1989-2003).

RESULTS

Among 744 cases of malformations 14 cases of fetuses and newborns presented developmental anomalies, which probably were the consequences of EARS.

CONCLUSIONS

The EARS is probably more frequent than it is generally presumed, but it is very often impossible to find remnants of bands and sheets. Nevertheless, the presence of at least two typical anomalies excludes a different cause than early amnion rupture and amniotic bands.

Placental growth retardation due to loss of imprinting of Phlda2

The maternally expressed/paternally silenced genes Phlda2 (a.k.a. Ipl/Tssc3), Slc22a1l, Cdkn1c, Kcnq1, and Ascl2 are clustered in an imprinted domain on mouse chromosome 7. Paternal deletion of a cis-acting differentially methylated DNA element, Kvdmr1, causes coordinate loss of imprinting and over-expression of all of these genes and the resulting conceptuses show intrauterine growth restriction (IUGR). To test the specific contribution of Phlda2 to IUGR in the Kvdmr1-knockout, we crossed Kvdmr1(+/-) males with Phlda2(+/-) females. Conceptuses with the (Phlda2(+/+); Kvdmr1(+/-)) genotype showed fetal and placental growth retardation. Restoration of Phlda2 dosage to normal, as occurred in the conceptuses with the (Phlda2(-/+); Kvdmr1(+/-)) genotype, had a marginally positive effect on fetal weights and no effect on post-natal weights, but significantly rescued the placental weights. As we previously reported, loss of Phlda2 expression in the wild-type background (Phlda2(-/+); Kvdmr1(+/+) genotype) caused placentomegaly. Thus Phlda2 acts as a true rheostat for placental growth, with overgrowth after gene deletion and growth retardation after loss of imprinting. Consistent with this conclusion, we observed significant placental stunting in BAC-transgenic mice that over-expressed Phlda2 and one flanking gene, Slc22a1l, but did not over-express Cdkn1c.

Intrauterine growth restriction in humans is associated with abnormalities in placental insulin-like growth factor signaling

The IGFs promote the growth and development of the feto-placental unit during gestation, and impairment of their placental actions may result in altered intrauterine growth of the fetus. In this study, proteins involved in IGF signaling were investigated in human placentas from pregnancies complicated by intrauterine growth restriction (IUGR) compared with those from normal pregnancies. IUGR placentas exhibited 33% reduction in the protein content of IGF-I receptors, but no changes in insulin receptor protein levels. In addition, insulin receptor substrate-2 (IRS-2) protein levels were reduced in IUGR placentas, with no changes in IRS-1 or Shc protein content, and this was associated with a parallel decrease in IRS-2-associated phosphatidyl inositol 3-kinase. Akt protein expression was also reduced in IUGR, whereas phosphorylation of Akt and its substrate glycogen synthase kinase-3 was unchanged. Finally, in IUGR placentas there was impaired activation of multiple members of the MAPK family, because phosphorylation of p38 and c-Jun N-terminal kinase was reduced 70%. In conclusion, human placentas from pregnancies complicated by IUGR are characterized by decreased IGF-I receptor content, selective impairment of the IRS-2/ phosphatidyl inositol 3-kinase pathway, and reduced p38 and c-Jun N-terminal kinase activation. The observed abnormalities in IGF-I signaling may contribute to altered fetal growth and development in human IUGR.

Determinants of birthweight and intrauterine growth in liveborn twins

We explored the relationship of umbilical cord insertion and fusion of placentas with birthweight in monozygotic monochorionic (MZ MC), monozygotic dichorionic (MZ DC), and dizygotic (DZ) twins. In addition, we evaluated some of the possible factors responsible for the restricted intrauterine growth of twins compared with singletons. The birthweight of 4529 liveborn twin pairs of the East Flanders Prospective Twin Survey was prospectively recorded, placentas were examined, and site of umbilical cord insertion was determined after delivery. Birthweight of 76 490 liveborn singletons was obtained from the Study Centre for Perinatal Epidemiology (SPE). Infants with a peripheral cord insertion weighed 150 g less (P < 0.001) than infants with a central cord insertion. DZ infants had a significantly (P < 0.001) higher incidence of central cord insertion than MZ DC and MZ MC infants. MZ DC infants with fused placentas and a peripheral cord insertion weighed on average 300 g less (P < 0.01) than infants with separate placentas and a central cord insertion. In DZ infants, fusion of the placentas did not affect birthweight. Twins gain less weight per week of gestation than singletons from 32 weeks onwards (twins: 128 g, 156 g, 75 g and singletons: 118 g, 251 g, 149 g, weeks 27-31,32-36, 37-42 respectively). From week 32 onwards, parity, birth rank, cord insertion and number of placentas also influenced birthweight of twins. We conclude that the difference between the birthweights of DZ, MZ DC, and MZ MC infants may originate from the least favourable antenatal situation, namely fused placentas with a peripheral cord insertion, which occurs most frequently in MZ twins. Gestation is the main determinant of birthweight. Other placental and maternal factors have a modest but significant influence on prenatal growth.

Placental defects are associated with male lethality in bare patches and striated embryos deficient in the NAD(P)H Steroid Dehydrogenase-like (NSDHL) Enzyme

NSDHL is a 3beta-hydroxysterol dehydrogenase that is involved in the removal of C-4 methyl groups in one of the later steps of cholesterol biosynthesis. Mutations in the Nsdhl gene are associated with the X-linked male lethal mouse mutations bare patches (Bpa) and striated (Str), as well as with most cases of human CHILD syndrome. To begin to examine the pathogenesis of these disorders, we have determined that affected male embryos for several Nsdhl alleles die in midgestation, between E10.5 and 13.5, while the majority of affected male embryos for the most severe allele, Nsdhl(Bpa1H), die prior to E9.5. Although no consistent anomalies were identified in affected male embryos themselves, the labyrinth layer of the fetal placenta was always thinner, with fewer fetal vessels and decreased proliferation of labyrinth trophoblast cells. X-inactivation is non-random in females in most lineages of the rodent placenta with preferential inactivation of the paternal X chromosome. For primary defects involving these extraembryonic lineages, heterozygous females with a mutant maternal X chromosome would be expected to have an identical placental phenotype to that found in affected male embryos. We hypothesize that abnormalities in cells of the allantoic mesoderm that undergo random X-inactivation and form the endothelial lining of the fetal vessels of the labyrinth are associated with the male lethality, perhaps through disruption of an as yet unidentified signaling pathway.

Polybromo protein BAF180 functions in mammalian cardiac chamber maturation

BAF and PBAF are two related mammalian chromatin remodeling complexes essential for gene expression and development. PBAF, but not BAF, is able to potentiate transcriptional activation in vitro mediated by nuclear receptors, such as RXRalpha, VDR, and PPARgamma. Here we show that the ablation of PBAF-specific subunit BAF180 in mouse embryos results in severe hypoplastic ventricle development and trophoblast placental defects, similar to those found in mice lacking RXRalpha and PPARgamma. Embryonic aggregation analyses reveal that in contrast to PPARgamma-deficient mice, the heart defects are likely a direct result of BAF180 ablation, rather than an indirect consequence of trophoblast placental defects. We identified potential target genes for BAF180 in heart development, such as S100A13 as well as retinoic acid (RA)-induced targets RARbeta2 and CRABPII. Importantly, BAF180 is recruited to the promoter of these target genes and BAF180 deficiency affects the RA response for CRABPII and RARbeta2. These studies reveal unique functions of PBAF in cardiac chamber maturation.

Essential requirement of CCAAT/enhancer binding proteins in embryogenesis

The CCAAT/enhancer binding proteins C/EBPalpha and C/EBPbeta are related transcription factors that are important for the function of various organs in the postnatal mouse. Gene replacement and tissue culture experiments have suggested partial redundancy of both transcription factors. Here we show that mouse embryos deficient of both C/EBPalpha and C/EBPbeta (C/EBPalphabeta(-/-)) die between embryonic day 10 (E10) and E11 and display defective placentas. In situ hybridization revealed that C/EBPalpha and C/EBPbeta are coexpressed in the chorionic plate at E9.5 and later in the trophoblasts of the labyrinthine layer. In C/EBPalphabeta(-/-) placentas, allantoic blood vessels invaded the chorion; however, vessel expansion and development of the labyrinthine layer was impaired. Furthermore, a single copy of either C/EBPalpha in the absence of C/EBPbeta or C/EBPbeta in the absence of C/EBPalpha is sufficient to complete development, suggesting complementation of these C/EBPs during embryogenesis. A single copy of C/EBPalpha in the absence of C/EBPbeta, however, fails to rescue survival after birth, suggesting haploinsufficiency of C/EBPalpha in newborns. Our data thus reveal novel essential, redundant, and dosage dependent functions of C/EBPs.

Haploinsufficiency of delta-like 4 ligand results in embryonic lethality due to major defects in arterial and vascular development

Vascular development depends on the highly coordinated actions of a variety of angiogenic regulators, most of which apparently act downstream of vascular endothelial growth factor (VEGF). One potential such regulator is delta-like 4 ligand (Dll4), a recently identified partner for the Notch receptors. We generated mice in which the Dll4 gene was replaced with a reporter gene, and found that Dll4 expression is initially restricted to large arteries in the embryo, whereas in adult mice and tumor models, Dll4 is specifically expressed in smaller arteries and microvessels, with a striking break in expression just as capillaries merge into venules. Consistent with these arterial-specific expression patterns, heterozygous deletion of Dll4 resulted in prominent albeit variable defects in arterial development (reminiscent of those in Notch knockouts), including abnormal stenosis and atresia of the aorta, defective arterial branching from the aorta, and even arterial regression, with occasional extension of the defects to the venous circulation; also noted was gross enlargement of the pericardial sac and failure to remodel the yolk sac vasculature. These striking phenotypes resulting from heterozygous deletion of Dll4 indicate that vascular development may be as sensitive to subtle changes in Dll4 dosage as it is to subtle changes in VEGF dosage, because VEGF accounts for the only other example of haploid insufficiency, resulting in obvious vascular abnormalities. In summary, Dll4 appears to be a major trigger of Notch receptor activities previously implicated in arterial and vascular development, and it may represent a new opportunity for pro- and anti-angiogenic therapies.

Divergent genetic and epigenetic post-zygotic isolation mechanisms in Mus and Peromyscus

Interspecific hybridization in the rodent genera Peromyscus and Mus results in abnormal placentation. In the Peromyscus interspecies hybrids, abnormal allelic interaction between an X-linked locus and the imprinted paternally expressed Peg3 locus was shown to cause the placental defects. In addition, loss-of-imprinting (LOI) of Peg3 was positively correlated with increased placental size. As in extreme cases this placental dysplasia constitutes a post-zygotic barrier against interspecies hybridization, this finding was the first direct proof that imprinted genes may be important in speciation and thus in evolution. In the Mus interspecies hybrids, a strong role of an X-linked locus in placental dysplasia has also been detected. However, here we show by backcross and allele specific expression analyses that neither LOI of Peg3 nor abnormal interactions between Peg3 and an X-linked locus are involved in generating placental dysplasia in Mus hybrids, although the placental phenotypes observed in the two genera seem to be identical. In contrast to this, another dysgenesis effect common to Peromyscus and Mus hybrids, altered foetal growth, is caused at least in part by the same X-chromosomal regions in both genera. These findings first underline the strong involvement of the X-chromosome in the genetics of speciation. Secondly, they indicate that disruption of epigenetic states, such as LOI, at specific loci may be involved in hybrid dysgenesis effects in one group, but not in another. Thus, we conclude that even in closely related groups divergent molecular mechanisms may be involved in the production of phenotypically similar post-zygotic barriers against hybridization.

Antenatal sonographic detection of an unusual placental lake under the cord insertion

PRESENTATION

We detected an unusual placental lake under the membranes between the two lobes of a placenta bilobate with a turbulent blood flow in it. This was an extraordinary maternal lake: simply the accumulation of maternal blood inside the intervillous space in an area where villous structures were absent between the placental lobes. The lake reduced in size and became almost invisible during the Braxton Hicks contractions, and enlarged up to its previous dimensions at the end of contractions. This extraordinarily huge lake showed an interesting dynamic appearance on sonographic examination.

OUTCOME

Although it caused no complications during the course of the pregnancy it produced an obstetric hemorrhage, which took place during the second stage of the delivery. Pathologic examination confirmed the diagnosis of placenta bilobate. We present its interesting appearance and clinical outcome in this paper.

Placental findings in low-risk, singleton, term pregnancies after uncomplicated deliveries

Should all placentas be sent to pathology for examination after delivery room triage? A cohort of 88 placentas was prospectively obtained and examined from low-risk, singleton, term pregnancies after uneventful delivery. All patients had a normal prenatal testing and anatomy ultrasound. Fifty-one placentas (58%) were normal. Thirty-seven of the placental cohort (42%) had abnormal findings. Thirteen of the abnormal placentas (35.1%) showed pathology unassociated with fetal compromise. Twenty-four of the placentas (27.3% of the total cohort and 64.9% of the abnormal placentas) showed findings associated with fetal compromise. The most common pathologies were marginal cord insertion, chorioamnionitis, and abruption. Routine placental examination is not indicated, according to our data, in low-risk, singleton, and term pregnancy unless the placenta is determined to be abnormal at delivery examination.

Endothelium-specific ablation of PDGFB leads to pericyte loss and glomerular, cardiac and placental abnormalities

Platelet-derived growth factor-B (PDGFB) is necessary for normal cardiovascular development, but the relative importance of different cellular sources of PDGFB has not been established. Using Cre-lox techniques, we show here that genetic ablation of Pdgfb in endothelial cells leads to impaired recruitment of pericytes to blood vessels. The endothelium-restricted Pdgfb knockout mutants also developed organ defects including cardiac, placental and renal abnormalities. These defects were similar to those observed in Pdgfb null mice. However, in marked contrast to the embryonic lethality of Pdgfb null mutants, the endothelium-specific mutants survived into adulthood with persistent pathological changes, including brain microhemorrhages, focal astrogliosis, and kidney glomerulus abnormalities. This spectrum of pathological changes is reminiscent of diabetic microangiopathy, suggesting that the endothelium-restricted Pdgfb knockouts may serve as models for some of the pathogenic events of vascular complications to diabetes.

Maternal-Fetal Transplacental Leakage of Mitochondrial DNA in Bovine Nuclear Transfer Pregnancies: Potential Implications for Offspring and Recipients

The synepitheliochorial placenta of ruminants is constructed of multiple tissue layers that separate maternal and fetal blood. In nuclear transfer cloned ruminants, however, placental anomalies such as abnormal vascular development and hemorrhagic cotyledons have been reported. We have investigated the possible exchange of genetic material between somatic cell nuclear transfer cloned (SCNT) bovine fetuses and recipients at day 80 of gestation using mitochondrial DNA (mtDNA) as a marker. Twenty-three recovered SCNT-fetuses and their recipients were screened for divergent and thus informative mtDNA combinations. Twenty-one fetuses generated by in vitro fertilization (IVF) or multiple ovulation embryo transfer (MOET) and the corresponding recipients served as controls. A search for recipient mtDNA haplotype in DNA extracts from fetal blood by PCR-RFLP analysis revealed three cases of chimerism (two SCNT, one IVF) among a total of 19 informative fetus-recipient pairs (eight SCNT, seven IVF, four MOET). Placental anomalies have also been observed in some IVF fetuses and the present data therefore suggests transplacental leakage of cell components or cells from the recipient into some fetuses generated by in vitro techniques. Further studies are necessary to determine (i) the nature of leaked material, (ii) whether there is bi-directional leakage, and (iii) whether leaked material is present in recipients and calves after parturition, i.e. whether leakage takes place in vivo. If recipients were chimeric for DNA or cells derived from genetically modified SCNT (or IVF) embryos, their subsequent utilization might be affected.

Evidence on hereditary occurrence of placental anastomoses in heterosexual twins in sheep

Pedigree analysis of 22 heterosexual litters demonstrating the leukocyte chimerism (XX/XY) was carried out. The analysis revealed the familial occurrence of the chimerism in 15 litters. Eight litters were obtained from four ewes and the other seven ones were sired by three rams. Moreover, it was shown that ten chimeric litters had a common male ancestor. The coefficients of inbreeding ranged from 0.0 to 0.0625, with a mean of 0.019. These results suggest that the development of placental anastomoses in sheep is genetically controlled. A possible mode of the genetic control is discussed.

Cyclin F disruption compromises placental development and affects normal cell cycle execution

Human cyclin F was originally isolated as a cDNA capable of suppressing the temperature sensitivity of a Saccharomyces cerevisiae cdc4-1 mutant. Its tightly regulated expression and high conservation in the evolutionary progression from amphibians to mammals suggest that it coordinates the timing of a critical cell cycle event. The fact that it contains an F box and can form an SCF (Skp1-Cul1/Cdc53-F-box) complex in vivo further suggests that it may also function in proteolysis. To investigate the role of cyclin F in vivo, we generated mice deficient for cyclin F and conditionally deficient mice as well as mouse embryonic fibroblasts (MEFs) conditionally deficient for cyclin F. Heterozygous animals are normal and fertile, but CycF(-/-) animals, with a myriad of developmental anomalies due in large part to failures in yolk sac and chorioallantoic placentation, die around embryonic day 10.5. Tissue-specific deletion of cyclin F revealed that it was not required for the development and function of a number of different embryonic and adult tissues. In contrast, MEFs lacking cyclin F, while viable, do exhibit cell cycle defects, including reduced population-doubling time and a delay in cell cycle reentry from quiescence, indicating that cyclin F plays a role in cell cycle regulation.

Ultrasound abnormalities of the amniotic fluid, membranes, umbilical cord, and placenta

Prenatal ultrasound has expanded the ability to assess the umbilical cord, fetal membranes, amniotic fluid volume, and placenta. Evaluation of these structures provides information regarding the intrauterine environment. Umbilical cord abnormalities may be associated with fetal aneuploidy, structural anomalies, and fetal compromise. Estimating the amniotic fluid volume has become an integral part of a sonogram and provides immense information regarding possible fetal anomalies and perinatal outcome. Likewise, placental location or abnormalities may significantly impact obstetric management and prognosis. Early detection of several of these conditions may lead to increased vigilance that may improve perinatal outcome.

Knockout of ERK5 causes multiple defects in placental and embryonic development

Backgroud

ERK5 is a member of the mitogen activated protein kinase family activated by certain mitogenic or stressful stimuli in cells, but whose physiological role is largely unclear.

Results

To help determine the function of ERK5 we have used gene targeting to inactivate this gene in mice. Here we report that ERK5 knockout mice die at approximately E10.5. In situ hybridisation for ERK5, and its upstream activator MKK5, showed strong expression in the head and trunk of the embryo at this stage of development. Between E9.5 and E10.5, multiple developmental problems are seen in the ERK5-/- embryos, including an increase in apoptosis in the cephalic mesenchyme tissue, abnormalities in the hind gut, as well as problems in vascular remodelling, cardiac development and placental defects.

Conclusion

Erk5 is essential for early embryonic development, and is required for normal development of the vascular system and cell survival.

Cloning animals by somatic cell nuclear transfer--biological factors

Cloning by nuclear transfer using mammalian somatic cells has enormous potential application. However, somatic cloning has been inefficient in all species in which live clones have been produced. High abortion and fetal mortality rates are commonly observed. These developmental defects have been attributed to incomplete reprogramming of the somatic nuclei by the cloning process. Various strategies have been used to improve the efficiency of nuclear transfer, however, significant breakthroughs are yet to happen. In this review we will discuss studies conducted, in our laboratories and those of others, to gain a better understanding of nuclear reprogramming. Because cattle are a species widely used for nuclear transfer studies, and more laboratories have succeeded in cloning cattle than any other species, this review will be focused on somatic cell cloning of cattle.

Effect of maternal age on blood loss during parturition: a retrospective multivariate analysis of 10,053 cases

OBJECTIVE

An extensive study as to whether maternal age itself is a risk factor for blood loss during parturition.

METHOD

A total of 10,053 consecutive women who delivered a singleton infant were studied. The excess blood loss was defined separately for women with vaginal and cesarean deliveries as > or = 90th centile value for each delivery mode. The effects of 13 potential risk factors on blood loss were analyzed using multivariate analysis.

RESULTS

The 90th centile value of blood loss was 615 ml and 1,531 ml for women with vaginal and cesarean deliveries, respectively. A low lying placenta (odds ratio [OR], 4.4), previous cesarean (3.1), operative delivery (2.6), leiomyoma (1.9), primiparity (1.6), and maternal age > or = 35 years (1.5) were significant independent risk factors for excess blood loss in women with vaginal delivery. Placenta previa (6.3), leiomyoma (3.6), low lying placenta (3.3), and maternal age > or = 35 years (1.8) were significant independent risk factors for excess blood loss in women with cesarean sections.

CONCLUSION

A maternal age of > or = 35 years was an independent risk factor for excess blood loss irrespective of the mode of delivery, even after adjusting for age-related complications such as leiomyoma, placenta previa, and low lying placenta.

Targeted disruption of p185/Cul7 gene results in abnormal vascular morphogenesis

Cul1, a member of the cullin ubiquitin ligase family, forms a multiprotein complex known as SCF and plays an essential role in numerous cellular and biological activities. A Cul1 homologue, p185 (Cul7), has been isolated as an simian virus 40 large T antigen-binding protein. To understand the physiological role of p185, we generated mice lacking p185. p185-/- embryos are runted and die immediately after birth because of respiratory distress. Dermal and hypodermal hemorrhage is detected in mutant embryos at late gestational stage. p185-/- placentas show defects in the differentiation of the trophoblast lineage with an abnormal vascular structure. We demonstrate that p185 forms an SCF-like complex with Skp1, Rbx1, Fbw6 (Fbx29), and FAP68 (FAP48, glomulin). FAP68 has recently been identified as a gene responsible for familial glomuvenous malformation. These results suggest that p185 forms a multiprotein complex and plays an important role in vascular morphogenesis.

Hyrtl's anastomosis is normally developed in placentas from small for gestational age infants

BACKGROUND

The aim of this study was to investigate the occurrence and appearance of the anastomosis between the two umbilical arteries in placentas from infants small for gestational age (SGA).

METHODS

The arterial systems of 64 placentas from singleton pregnancies resulting in SGA infants were visualized by angiography. The method allowed study of the anastomosis between the umbilical arteries and calculation of the relative placental area supplied by each artery. The results were compared with findings in a previous study of appropriate for gestational age (AGA) infants. One-way analysis of variance (ANOVA) and chi2-analyses were used for statistics.

RESULTS

In 56 placentas the anastomosis was represented by a true vessel, in two by a fenestration, and in another two cases by fusion of the umbilical arteries. The anastomosis was absent in one case and another three cases had a single umbilical artery (SUA). When the diameter of the anastomosis was thinner than that of the umbilical arteries, their supply areas were significantly (p < or = 0.001) more symmetrical than in cases with a wider anastomosis. The anatomy of the anastomosis and the relationship between its width and the symmetry between the supply areas of each umbilical artery did not differ in placentas from SGA and AGA infants, despite various types of cord insertion and placentation.

CONCLUSION

Static measurements of Hyrtl's anastomosis do not indicate a contributing part for intrauterine growth retardation.