HMGA2 is regulated by LIN28 and BRCA1 in human placental cells.

The chromatin associated transcription factor HMGA2 is a downstream target of let-7 miRNAs and binds to chromatin to regulate gene expression. Inhibition of let-7 miRNAs by RNA-binding proteins LIN28A and LIN28B is necessary during early embryogenesis to ensure stable expression of HMGA2. In addition to LIN28, HMGA2 is regulated by a BRCA1/ZNF350/CtIP repressor complex. In normal tissues, the BRCA1/ZNF350/CtIP complex binds to the HMGA2 promoter to prevent transcription. However, in many cancers the oncomiR miR-182 targets BRCA1, preventing BRCA1 translation and allowing for increased HMGA2. Little is known about the regulation of HMGA2 during early placental development; therefore, we hypothesized that both LIN28 and BRCA1 can regulate HMGA2 in placental cells. Using siRNA and CRISPR gene editing techniques, we found that knockdowns of both LIN28A and LIN28B increase HMGA2 levels in ACH-3P cells. These cells also demonstrated deficiencies in cell differentiation, seemingly differentiating solely towards the syncytiotrophoblast sublineage, secreting higher amounts of hCG, and displaying upregulated ERVW-1. Additionally, we found that a knockout of both LIN28A and LIN28B caused a significant increase of miR-182 and a decrease in BRCA1 allowing HMGA2 mRNA levels to increase and protein levels to remain the same. Using chromatin immunoprecipitation, we saw binding of the BRCA1 repressor complex to HMGA2. We also saw a decrease in binding to HMGA2's promoter in the LIN28A/B knockout cells. These findings suggest a novel role for BRCA1 during early human placental development.

Global gene expression analysis of bovine somatic cell nuclear transfer blastocysts and cotyledons.

Low developmental competence of bovine somatic cell nuclear transfer (SCNT) embryos is a universal problem. Abnormal placentation has been commonly reported in SCNT pregnancies from a number of species. The present study employed Affymetrix bovine expression microarrays to examine global gene expression patterns of SCNT and in vivo produced (AI) blastocysts as well as cotyledons from day-70 SCNT and AI pregnancies. SCNT and AI embryos and cotyledons were analyzed for differential expression. Also in an attempt to establish a link between abnormal gene expression patterns in early embryos and cotyledons, differentially expressed genes were compared between the two studies. Microarray analysis yielded a list of 28 genes differentially expressed between SCNT and AI blastocysts and 19 differentially expressed cotyledon genes. None of the differentially expressed genes were common to both groups, although major histocompatibility complex I (MHCI) was significant in the embryo data and approached significance in the cotyledon data. This is the first study to report global gene expression patterns in bovine AI and SCNT cotyledons. The embryonic gene expression data reported here adds to a growing body of data that indicates the common occurrence of aberrant gene expression in early SCNT embryos.

Chorionic somatomammotropin impacts early fetal growth and placental gene expression.

Several developmental windows, including placentation, must be negotiated to establish and maintain pregnancy. Impaired placental function can lead to preeclampsia and/or intrauterine growth restriction (IUGR), resulting in increased infant mortality and morbidity. It has been hypothesized that chorionic somatomammotropin (CSH) plays a significant role in fetal development, potentially by modifying maternal and fetal metabolism. Recently, using lentiviral-mediated in vivo RNA interference in sheep, we demonstrated significant reductions in near-term (135 days of gestation; dGA) fetal and placental size, and altered fetal liver gene expression, resulting from CSH deficiency. We sought to examine the impact of CSH deficiency on fetal and placental size earlier in gestation (50 dGA), and to examine placental gene expression at 50 and 135 dGA. At 50 dGA, CSH-deficient pregnancies exhibited a 41% reduction (P ≤ 0.05) in uterine vein concentrations of CSH, and significant (P ≤ 0.05) reductions (≈21%) in both fetal body and liver weights. Placentae harvested at 50 and 135 dGA exhibited reductions in IGF1 and IGF2 mRNA concentrations, along with reductions in SLC2A1 and SLC2A3 mRNA. By contrast, mRNA concentrations for various members of the System A, System L and System y+ amino acid transporter families were not significantly impacted. The IUGR observed at the end of the first-third of gestation indicates that the near-term IUGR reported previously, began early in gestation, and may have in part resulted from deficits in the paracrine action of CSH within the placenta. These results provide further compelling evidence for the importance of CSH in the progression and outcome of pregnancy.

Bovine nuclear transfer embryo development using cells derived from a cloned fetus.

Many different cell types have been used to generate nuclear transfer embryos and fetuses. However, little is known about the potential of fibroblasts derived from a nuclear transfer fetus as donor cells for nuclear transfer. The ability of cloned fetuses or animals to be cloned themselves is of great interest in determining whether successive generations of clones remain normal or accumulate genetic or phenotypic abnormalities. We generated a bovine fibroblast cell line from a cloned fetus, that continued to divide beyond 120 days (94 doublings,18 passages) in continuous culture. As long-term survival of cells in culture is a desirable characteristic for use in transgenic cell production, passage 2 and 18 cells were compared as donor cells for nuclear transfer (NT). When cells from passage 2 (2 weeks in culture) and passage 18 (4 months in culture) were used for nuclear transfer, there was no significant difference in development rate to blastocyst (35.4 versus 44.6%, P=0.07). A greater proportion of late passage cells were in G0/G1 whether under serum-fed (64 versus 56%, P<0.01) or serum-starved (95 versus 88%, P<0.01) culture conditions. Following embryo transfer, equivalent day 30 pregnancy rates were observed for each group (P 2: 2/19 versus P 18: 2/13). A slightly retarded fetus was surgically removed at day 56 and the remaining three fetuses died in utero by day 60 of gestation. Our results show that fibroblast cells derived from regenerated cloned fetuses are capable of both in vitro and in vivo development. The longevity of this regenerated cell line would allow more time for genetic manipulations and then to identify stable transfected cells prior to their use as NT donor cells. Although no live fetuses were produced in this study the results provide encouraging data to show that a cloned fetus can itself be recloned to produce another identical cloned fetus. Further studies on this and other recloned fetuses are necessary to determine whether the failure to produce live offspring was a result of inadequate sample size or due to the cell type selected.

IGF paracrine and autocrine interactions between conceptus and oviduct.

Development in vitro is influenced by embryo density, serum, somatic cell co-culture and the production of 'embryotrophic' paracrine and autocrine factors. Research in our laboratory has focussed principally on the insulin-like growth factor (IGF) family. We have demonstrated that pre-attachment bovine and ovine embryos express mRNAs encoding a number of growth factor ligand and receptor genes including all members of the IGF ligand and receptor family throughout this developmental interval. In addition, early embryos express mRNAs encoding IGF-binding proteins (IGFBPs) 2-5 from the one-cell to the blastocyst stage and IGFBP5 mRNA at the blastocyst stage. Cultured bovine blastocysts release up to 35 pg per embryo in 24 h, whereas release of IGF-I was below detectable values. Analysis extended to bovine oviductal cultures has also demonstrated that mRNAs encoding these IGF family members are present throughout an 8 day culture period. Transcripts encoding IGFBPs 2-6 were also present. Release of both IGFs was recorded over an 8 day culture period. IGF-II release was significantly greater than that observed for IGF-I. Therefore, the IGFs are present throughout the maternal environment during early embryo development. The oocyte, within the follicle, is held in an environment high in IGFs and IGFBPs. The zygote, after fertilization, is maintained in an IGF-rich environment while free-living in the oviduct and the uterus. This review is focused on the IGF family and IGFBPs and their roles in enhancing development up to the blastocyst stage.

Characterization of a bovine cDNA encoding citrate synthase, and presence of citrate synthase mRNA during bovine pre-attachment development.

Citrate synthase is a key regulatory metabolic enzyme that catalyzes the first step in the tricarboxylic acid (TCA) cycle, the synthesis of citrate from acetyl coenzyme A and oxaloacetate. Aerobic metabolism via the TCA cycle is high in bovine embryos at the 4-cell stage then decreases until the compact morula stage before increasing at the expanded blastocyst stage. This study characterizes the presence of citrate synthase mRNA in bovine pre-attachment embryos to determine if a variation in mRNA transcript expression patterns is associated with previous reports of the patterns of TCA cycle activity. The reverse transcription-polymerase chain reaction (RT-PCR) method was used to detect citrate synthase mRNA from the 1-cell to blastocyst stage of bovine embryo development, and in embryos cultured under either an atmosphere of 5% CO(2) in air or 5% CO(2)/5% O(2)/90%N(2). The nucleotide sequence encoding citrate synthase was determined from bovine heart cDNA by the rapid amplification of cDNA ends (RACE) technique. This 1455-bp nucleotide fragment contained an open reading frame that encoded a deduced protein of 466 amino acids. The bovine nucleotide sequence was 92.1% and 93.8% identical to the human and porcine coding sequence, respectively. The amino acid sequence predicted from the bovine sequence is 95.1% identical to the human sequence and 96.3% identical to the porcine sequence. The porcine sequence contains a stop codon that results in a peptide truncated by 2 amino acids. The detection of citrate synthase transcripts from the 1-cell to blastocyst stage demonstrates that the decrease in TCA cycle activity observed following the 4-cell stage is not associated with an absence of citrate synthase mRNA.

Genetic reprogramming of lactate dehydrogenase, citrate synthase, and phosphofructokinase mRNA in bovine nuclear transfer embryos produced using bovine fibroblast cell nuclei.

Adult animal cloning has progressed to allow the production of offspring cloned from adult cells, however many cloned calves die prenatally or shortly after birth. This study examined the expression of three important metabolic enzymes, lactate dehydrogenase (LDH), citrate synthase, and phosphofructokinase (PFK), to determine if their detection in nuclear transfer (NT) embryos mimics that determined for in vitro produced embryos. A day 40 nuclear transfer produced fetus derived from an adult cell line was collected and fetal fibroblast cultures were established and maintained. Reconstructed NT embryos were then produced from this cell line, and RT-PCR was used to evaluate mRNA reprogramming. All three mRNAs encoding these enzymes were detected in the regenerated fetal fibroblast cell line. Detection patterns were first determined for IVF produced embryos (1-cell, 2-cell, 6-8 cell, morula, and blastocyst stages) to compare with their detection in NT embryos. PFK has three subunits: PFK-L, PFK-M, and PFK-P. PFK-L and PFK-P were not detected in bovine oocytes. PFK subunits were not detected in 6-8 cell embryos but were detected in blastocysts. Results from NT embryo RT-PCR demonstrated that PFK was not detected in 8-cell NT embryos but was detected in NT blastocysts indicating that proper nuclear reprogramming had occurred. Citrate synthase was detected in oocytes and throughout development to the blastocyst stage in both bovine IVF and NT embryos. LDH-A and LDH-B were detected in bovine oocytes and in all stages of IVF and NT embryos examined up to the blastocyst stage. A third subunit, LDH-C was not detected at the blastocyst stage in IVF or NT embryos but was detected in all earlier stages and in mature oocytes. In addition, LDH-C mRNA was detected in gonad isolated from the NT and an in vivo produced control fetus. These results indicate that the three metabolic enzymes maintain normal expression patterns and therefore must be properly reprogrammed following nuclear transfer.

Development rates of male bovine nuclear transfer embryos derived from adult and fetal cells.

This study compared the nuclear transfer (NT) embryo development rates of adult and fetal cells within the same genotype. The adult fibroblast cells were obtained from a 21-yr-old Brahman bull. The fetal cells were derived from a Day 40 NT fetus previously cloned using cells from the Brahman bull. Overall, similar numbers of blastocysts developed from both adult (53 of 190; 28%) and fetal (39 of 140; 28%) donor cells. Improved blastocyst development rates were observed when fetal cells were serum-starved (serum-fed 12% vs. serum-starved 43%; P < 0.01) whereas there was no similar benefit when adult cells were serum-starved (both serum-fed and serum-starved 28%). Day 30 pregnancy rates were similar for blastocysts derived from adult (6 of 26; 23%) or fetal (5 of 32; 16%) cells. Day 90 pregnancy rates were 3 of 26 for adult and 0 of 32 for the fetal cell lines. One viable bull calf derived from a 21-yr-old serum-starved adult skin fibroblast was born in August 1999. In summary, somatic NT embryo development rates were similar whether adult or fetal cells, from the same genotype, were used as donor cells. Serum starvation of these adult donor cells did not improve development rates of NT embryos to blastocyst, but when fetal cells were serum-starved, there was a significant increase in development to blastocyst.

Bovine parthenogenesis is characterized by abnormal chromosomal complements: implications for maternal and paternal co-dependence during early bovine development.

The present study was conducted to examine the karyotypes of parthenogenetic bovine embryos arising from the application of standard oocyte activation and diploidization methods. Bovine cumulusoocyte complexes were collected and matured in vitro for 24 hr prior to oocyte activation with either 5 microM ionomycin or 7% ethanol for 5 min. Groups of activated oocytes were further treated with 5 micrograms/ml cytochalasin D or 1.9 mM 6-dimethylaminopurine (DMAP) for 6 hr. Cleavage varied significantly (P < .05) among the treatment groups with 68.0% of the ethanol- and DMAP-treated oocytes dividing. Blastocyst development did not vary with 18.4 +/- 2.5% of all treated oocytes progressing to this stage. Blastocyst development did not occur in groups subjected to oocyte activation alone. Blastocysts displayed haploid (2.3%), diploid (11.4%), tetraploid (40.9%), octaploid (4.5%), and mixoploid chromosomal complements (40.9%). Two-cell stage parthenogenotes resulting from ethanol or ionomycin treatment alone displayed haploid (66.7%), diploid (16.7%), tetraploid (4.2%), and mixoploid (12.5%) complements. Our results demonstrate that diploid bovine parthenogenotes arising from these procedures are a minority, with the majority of parthenogenotes displaying polyploid and mixoploid chromosomal complements. The events contributing to these abnormal chromosomal complements occur as early as completion of the first cell cycle, possibly linking these events with the absence of a paternally supplied centrosome.

Bovine oviductal and embryonic insulin-like growth factor binding proteins: possible regulators of "embryotrophic" insulin-like growth factor circuits.

Bovine oviductal monolayer and vesicle primary cultures express insulin-like growth factor (IGF)-I and -II mRNAs and polypeptides. Early bovine embryos also express IGF-I, IGF-II, IGF-I receptor, IGF-II receptor, and insulin receptor mRNAs. This study reports the expression of IGF binding protein (IGFBP) mRNAs and polypeptides in bovine oviduct primary cultures and IGFBP mRNAs in preattachment embryos. Release of immunoreactive IGF-I and IGF-II by oviduct cultures and bovine blastocysts was also determined. IGFBP-2, -3, -4, and -5 transcripts were observed in oviduct primary cultures throughout an 8-day interval. IGFBP-1 and -6 mRNAs were consistently not detected in the oviduct. Messenger RNAs encoding IGFBPs -2, -3, and -4 were detected throughout bovine preattachment development, while transcripts encoding IGFBP-5 were detected only in blastocysts. IGFBP-1 and -6 transcripts were not detected in early embryos. Ligand blot analysis with 125I-labeled IGF-II revealed the presence of four prominent polypeptide bands of approximate molecular masses 24, 31, and 36 kDa, and a broad band extending from 46 to 53 kDa, in conditioned media samples prepared from oviduct primary cultures. Western immunoblot analysis confirmed the identity of the 24-kDa, 31-kDa, and 36-kDa species as IGFBP-4, -5, and -2, respectively. Levels of the release of IGF-II from oviductal vesicle cultures were significantly greater than levels observed for monolayer cultures (p < 0.005). No significant difference in the levels of IGF-I release between monolayer and vesicle cultures was observed. Pools of 10 blastocysts released on average 36.2 +/- 3.9 pg of IGF-II per embryo, while the release of embryonic IGF-I was below the levels of detection for our assay. The results suggest that maternally derived IGF may be regulated by IGFBPs to support bovine preattachment development.

Evidence for placental abnormality as the major cause of mortality in first-trimester somatic cell cloned bovine fetuses.

The production of cloned animals is, at present, an inefficient process. This study focused on the fetal losses that occur between Days 30-90 of gestation. Fetal and placental characteristics were studied from Days 30-90 of gestation using transrectal ultrasonography, maternal pregnancy specific protein b (PSPb) levels, and postslaughter collection of fetal tissue. Pregnancy rates at Day 30 were similar for recipient cows carrying nuclear transfer (NT) and control embryos (45% [54/120] vs. 58% [11/19]), although multiple NT embryos were often transferred into recipients. From Days 30-90, 82% of NT fetuses died, whereas all control pregnancies remained viable. Crown-rump (CR) length was less in those fetuses that were destined to die before Day 90, but no significant difference was found between the CR lengths of NT and control fetuses that survived to Day 90. Maternal PSPb levels at Days 30 and 50 of gestation were not predictive of fetal survival to Day 90. The placentas of six cloned and four control (in vivo or in vitro fertilized) bovine pregnancies were compared between Days 35 and 60 of gestation. Two cloned placentas showed rudimentary development, as indicated by flat, cuboidal trophoblastic epithelium and reduced vascularization, whereas two others possessed a reduced number of barely discernable cotyledonary areas. The remaining two cloned placentas were similar to the controls, although one contained hemorrhagic cotyledons. Poor viability of cloned fetuses during Days 35-60 was associated with either rudimentary or marginal chorioallantoic development. Our findings suggest that future research should focus on factors that promote placental and vascular growth and on fetomaternal interactions that promote placental attachment and villous formation.