Retinal changes following rapid ascent to a high-altitude environment

PurposeTo determine what impact rapid ascension to a high-altitude environment has on the retina with the aim of preventing and treating high-altitude oculopathy.Patients and methodsParticipants in the study were members of the Chinese military assigned to the high-altitude environment of the Tibetan plateau. Ninety-one participants were enrolled in the study. Optical coherence tomography was used to measure the thickness of retina-related indicators. Measurements were taken before and after exposure to the high-altitude environment and upon return to the baseline altitude.ResultsFollowing exposure to the high-altitude environment in Tibet, there was a significant increase in retinal nerve fiber layer (RNFL) thickness in the temporal and nasal quadrants of the optic disc, whilst a significant decrease in RNFL thickness in the inferior optic disc was also observed. A significant increase in RNFL thickness in the superior and inferior macula was also evident, along with a significant increase in the ganglion cell layer thickness in the superior macula. Upon return to the baseline altitude, all measurements returned to baseline levels except for the RNFL of the inferior macula, which was significantly thicker. Pathological changes were also documented in the eyes of nine participants upon returning to baseline altitude, including ischemic optic neuropathy, myopia, and cortical amaurosis.ConclusionsThe high-altitude environment can have a negative impact on the health of the retina and may contribute to the incidence of various eye diseases. This study deepens the understanding of what impact a high-altitude environment has on retina and provides reliable data for blindness prevention and treatment.

109 Dosage Compensation of the X Chromosome in Ovine Embryos, Late Gestation, and Adult Somatic Tissues

Deviations from proper gene dosage of the autosome range from severe to lethal consequences in mammals. Eutherian males (XY), however, have reduced gene dosage compared with females (XX) due to a single X and deteriorating Y chromosome. This dosage imbalance is resolved through X chromosome dosage compensation, according to Ohno’s hypothesis: X-linked gene expression is doubled in both males and females to balance expression of the X chromosome and autosomes. To compensate for doubled X chromosome expression in females, X chromosome inactivation (XCI) inactivates a single X chromosome in each cell. Although these mechanisms have been well studied in mice and humans, controversies exist due to the analysis and interpretation of RNA sequencing data. Here we described X chromosome dosage compensation in the sheep. Twelve ewes were fed 100% (control), 60% (restricted), or 140% (overfed) of the National Research Council requirements for a ewe pregnant with twins (NRC, 1985; Nutrient Requirements of Sheep, 6th ed.). Day 135 brain, lung, and kidney tissues were collected from fetuses of the control, restricted, and overfed groups (n = 7, 4, and 4; respectively). RNA seq libraries were prepared using the Illumina TruSeq stranded mRNA kit and sequenced on the NextSEqn 500 (Illumina Inc., San Diego, CA, USA). Two additional RNA-seq datasets were downloaded from Sequence Read Archive (SRA), including Day 14 embryos (PRJNA254105), and adult and juvenile heart, brain, liver, muscle, rumen, and female- and male-specific tissues (PRJEB6169). The RNA-seq data were trimmed and mapped to the ovine reference genome assembly Oar_v4.0 using Hisat2 (version 2.0.5; https://ccb.jhu.edu/software/hisat2/index.shtml) aligner. The mRNA level of each gene was estimated by transformed transcripts per kilobase million (TPM) and was quantified using IsoEM (version 1.1.4; http://dna.engr.uconn.edu/). The relative expression of X to autosomal (A)(RXE) was calculated using RXE = log2(X expression) – log2(A expression) with an average of 486 X-linked genes and 13,001 autosomal genes after TPM >1 filtering. RXE ≥0 (or X:A ratio ≥ 1); <0, = –1 indicate complete, incomplete, or no dosage compensation; respectively. Control, restricted, and overfed ovine fetal somatic tissues displayed incomplete dosage compensation. Incomplete dosage compensation was also observed in juvenile and adult somatic major organs and female specific tissues. Brain tissues, apart from the cerebellum, displayed complete dosage compensation with an RXE range of 0 to 0.16. An interesting pattern was observed in the male specific tissues with complete dosage compensation in the epididymis (RXE = 0.32) and incomplete dosage compensation in the testes (RXE = –0.84). No significant RXE differences were observed between ovine female and male somatic tissues, supporting Ohno’s hypothesis of balanced expression of X-linked genes to autosomal genes. Our results indicate that a mechanism for dosage compensation exists in the sheep, although it is largely incomplete.

Protective effects of Nano-elemental selenium against chromium-vi-induced oxidative stress in broiler liver

The valuable role of selenium in mitigation of oxidative stress and heavy metal toxicity is well-known. Thus, the aim of the current study on broiler chickens was to examine whether nano elemental selenium (Nano-Se) supplementation can reduce the effects of chromium VI (K2Cr2O7) toxicity. For this purpose, a total of 150, one-day-old broiler chickens were allotted to five groups with three replicates: control group (standard diet), poisoned group (K2Cr2O7 via drinking water), protection group (K2Cr2O7 + Nano- Se), cure group (K2Cr2O7 for initial 2 weeks and then Nano-Se), and prevention group (opposite to the cure group). The broilers were detected by the activities of marker enzymes and oxidative stress markers including, aspartate aminotransferase (AST), alanine transaminase (ALT), gamma-glutamyl transferase (GGT) and superoxide dismutase (SOD), glutathione peroxidase (GSH-px), malondialdehyde (MDA), respectively. The (K2Cr2O7 administration caused histopathological damage in the liver of the chickens. Moreover, changes in serum biochemical indicators and oxidative stress parameters were also observed. Nano-Se supplementation increased the levels of GSH-px but reduced the activities of SOD, MDA, GGT, ALT and AST in the experimental groups (P less than 0.05). Our results showed that Nano-Se plays a protective role by preventing the oxidative stress induced by the chromium VI in broiler chickens.

Core@shell structured Co–CoO@NC nanoparticles supported on nitrogen doped carbon with high catalytic activity for oxygen reduction reaction

A composite with a hierarchical structure consisting of nitrogen doped carbon nanosheets with the deposition of nitrogen doped carbon coated Co–CoO nanoparticles (Co–CoO@NC/NC) has been synthesized by a simple procedure involving the drying of the reaction mixture containing Co(NO₃)₂, glucose, and urea and its subsequent calcination. The drying step is found to be necessary to obtain a sample with small and uniformly sized Co–CoO nanoparticles. The calcination temperature has a great effect on the catalytic activity of the final product. Specifically, the sample prepared at the calcination temperature of 800 °C shows better catalytic activity of the oxygen reduction reaction (ORR). Urea in the reaction mixture is crucial to obtain the sample with the uniformly sized Co–CoO nanoparticles and also plays an important role in improving the catalytic activity of the Co–CoO@NC/NC. Additionally, there exists a strong electronic interaction between the Co–CoO nanoparticles and the NC. Most interestingly, the Co–CoO@NC/NC is highly efficient for the ORR and can deliver an ORR onset potential of 0.961 V vs. RHE and a half-wave potential of 0.868 V vs. RHE. Both the onset and half-wave potentials are higher than those of most catalysts reported previously and even close to those of the commercial Pt/C (the ORR onset and half-wave potential of the Pt/C are 0.962 and 0.861 V vs. RHE, respectively). This, together with its high stability, strongly suggests that the Co–CoO@NC/NC could be used as an efficient catalyst for the ORR.

A simple method has been developed for the synthesis of Co–CoO@NC/NC, which exhibits high and stable performance for the ORR.

Exome sequencing identifies a TCF4 mutation in a Chinese pedigree with symmetrical acral keratoderma

BACKGROUND

Symmetrical acral keratoderma (SAK) is a rare skin disorder and its pathogenesis and inheritability are unknown.

OBJECTIVES

To investigate the inheritance and pathogenesis of SAK.

METHODS

Four SAK cases occurred in a four-generation Chinese family. Exome sequencing identified SNPs with potential SAK-related mutations, and a potentially responsible gene transcription factor 4 (TCF4) was identified. TCF4 was then sequenced in all 11 family members, and pedigree analysis was performed. Histopathology and immunohistochemistry evaluated TCF4 expression in skin lesions. The gene mutation was investigated in human keratinocytes for keratin-related protein expression.

RESULTS

A novel heterozygous missense mutation, c.85C>A (p.Pro29Thr) was found in TCF4. The mutation showed autosomal dominant inheritance and perfectly cosegregated with the SAK phenotype in all family members. In skin lesions, TCF4 was present in the cytoplasm and membranes of the basal layer, the stratum spinosum and the stratum granulosum of the epidermis. The mutant TCF4 induced overexpression of differentiation markers including KRT1, KRT14, loricrin and involucrin.

CONCLUSIONS

A SAK-related gene mutation in TCF4 may function through transcriptional regulation of keratin.

[Laryngeal endoscopic cricopharyngeal myotomy for cricopharyngeal achalasia post stroke]

Objective: To explore the safety and validity of endoscopic cricopharyngeal myotomy in patients with cricopharyngeal achalasia. Methods: A total of 19 patients with cricopharyngeal achalasia suffered from sustained dysphagia were enrolled in this study. The patients were divided into transcervical cricopharyngeal myotomy(CPM) group and endoscopic CPM (ECPM) group. Swallowing function and complications were evaluated.SPSS7.0 software was used to analyze the data. Results: The swallowing function improved significantly in seven patients in ECPM group, and 9 patients improved in CPM group.The video fluoroscopic swallowing study(VFSS)-swallowing score, VFSS-aspiration score and drinking test score were (3.1±1.1), (3.4±0.8) and (2.0±0.6)in post-ECPM, (3.4±1.4), (3.0±0.9) and (2.2±0.6)in post-CPM. No statistical difference was found in validity between CPM group and ECPM group(t=-0.435, t=1.086, t=-0.607, P>0.05). No statistical difference was observed on the occurrence of complication between two groups. Only one patient had subcutaneous emphysema after operation in ECPM. Conclusions: New surgical instruments and endoscopic surgical technique were safe and effective for cricopharyngeal achalasia. Because these instruments are cheaper, laryngeal endoscopic cricopharyngeal myotomy is easier to be popularized more easily than microscopic laser assistted CPM.

HLA-B*40:356, identified by next-generation sequence based typing in a Chinese tuberculosis patient

HLA-B*40:356 differs from B*40:02:01 by only one nucleotide transition, C>A 1040 in exon 6.

Sulfonated Holey Graphene Oxide (SHGO) Filled Sulfonated Poly(ether ether ketone) Membrane: The Role of Holes in the SHGO in Improving Its Performance as Proton Exchange Membrane for Direct Methanol Fuel Cells

Sulfonated holey graphene oxides (SHGOs) have been synthesized by the etching of sulfonated graphene oxides with concentrated HNO₃ under the assistance of ultrasonication. These SHGOs could be used as fillers for the sulfonated aromatic poly(ether ether ketone) (SPEEK) membrane. The obtained SHGO-incorporated SPEEK membrane has a uniform and dense structure, exhibiting higher performance as proton exchange membranes (PEMs), for instance, higher proton conductivity, lower activation energy for proton conduction, and comparable methanol permeability, as compared to Nafion 112. The sulfonated graphitic structure of the SHGOs is believed to be one of the crucial factors resulting in the higher performance of the SPEEK/SHGO membrane, since it could increase the local density of the -SO₃H groups in the membrane and induce a strong interfacial interaction between SHGO and the SPEEK matrix, which improve the proton conductivity and lower the swelling ratio of the membrane, respectively. Additionally, the proton conductivity of the membrane could be further enhanced by the presence of the holes in the graphitic planes of the SHGOs, since it provides an additional channel for transport of the protons. When used, direct methanol fuel cell with the SPEEK/SHGO membrane is found to exhibit much higher performance than that with Nafion 112, suggesting potential use of the SPEEK/SHGO membrane as the PEMs.

Blocking Smad2 signalling with loganin attenuates SW10 cell cycle arrest induced by TNF-α

The activity of Schwann cells (SWCs) is very important in trauma-induced nerve repair, and tumour necrosis factor-α (TNF-α) produced during tissue injury inhibits the viability of SWCs, which delays the repair of peripheral nerves. Loganin is an iridoid glycoside that has been shown to alleviate a variety of cytotoxic effects. In the current study, we evaluated the potential efficacy and the mechanism of action of loganin in TNF-α-induced cytotoxicity in SW10 cells. The experimental results indicated that loganin blocked TNF-α-mediated Smad2 activation, downregulated the expression of the G1 phase cell cycle inhibitor p15IN4KB, and upregulated the expression of the G1 phase cell cycle activator cyclin D1-CDK4/6, which upregulated E2F-1-dependent survivin expression and relieved TNF-α-induced apoptosis in SW10 cells. The protective effect of loganin on SWCs has potential medicinal value in the promotion of peripheral nerve repair and is significant for studies in the field of tissue regeneration.

Measurement of the Neutrino Mixing Angle θ_{23} in NOvA

This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of 6.05×10^{20} protons on target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal θ_{23} mixing (θ_{23}=π/4). Assuming the normal mass hierarchy, we find Δm_{32}^{2}=(2.67±0.11)×10^{-3}  eV^{2} and sin^{2}θ_{23} at the two statistically degenerate values 0.404_{-0.022}^{+0.030} and 0.624_{-0.030}^{+0.022}, both at the 68% confidence level. Our data disfavor the maximal mixing scenario with 2.6σ significance.

[Distribution of electroencephalograph power density in patients with severe obstructive sleep apnea during different sleep stages]

Objective: To investigate the variation of electroencephalograph(EEG) power density during different sleep stages in OSA for understanding of the mechanisms underlying the brain dysfunction in OSA as well as its earlier diagnosis and treatment. Methods: Sixteen-channel EEGs from OSA patients and normal controls in stage wake, sleep stage 1, sleep stage 2, sleep stage 3 and rapid eye movement stage were analyzed by time-frequency analysis method. The EEG power density in different frequency bands (including δ, θ, α, σ, β and γ) was respectively compared between the 2 groups. The correlation between the variation in the EEG power and primary indices of polysomnography was further analyzed. Results: The EEG power density in δ band in stage wake [OSA: (0.82±0.13) μV(2)/Hz, Control: (0.66±0.02) μV(2)/Hz, t=4.309, P<0.05], stage 1 [OSA: (1.28±0.07) μV(2)/Hz, Control: (0.92±0.04) μV(2)/Hz, t=-3.369, P<0.05] and stage 3 [OSA: (2.74±0.22) μV(2)/Hz, Control: (2.04±0.07) μV(2)/Hz, t=-2.669, P<0.05] was significantly higher in OSA, compared with that in the control. Statistical analysis showed that the EEG power density was significantly higher in frontal and central regions in stage wake [frontal: OSA: (0.90±0.02) μV(2)/Hz, Control: (0.66±0.02) μV(2)/Hz, t=8.539, P<0.01; central: OSA: (1.15±0.06) μV(2)/Hz, Control: (0.72±0.02) μV(2)/Hz, t=6.669, P<0.01] and stage 1 [frontal: OSA: (1.23±0.03) μV(2)/Hz, Control: (0.99±0.03) μV(2)/Hz, t=5.983, P<0.01; central: OSA: (1.52±0.05) μV(2)/Hz, Control: (1.14±0.04) μV(2)/Hz, t=5.714, P<0.01], as well as central region in stage 3 [OSA: (3.24±0.17) μV(2)/Hz, Control: (2.71±0.08) μV(2)/Hz, t=2.707, P<0.05]. The correlation analysis showed that the power density in central region in stage 1 and stage 3 was positively correlated with arousal index (r=0.877 in stage 1, 0.656 in stage 3), implying that sleep fragmentation was closely related to the variation of EEG power density during nocturnal sleep in OSA. Conclusions: The feature stages for OSA are stage wake, stage 1 and stage 3. The EEG power density in OSA (δ band) was significantly higher than that in the control. The EEG power density in OSA and the control shows differences in frontal and central regions in stage wake and stage 1, as well as in central region in stage 3. The results indicate that low-frequency EEG power density giving priority to frontal area and central area has improved in severe OSA, which may be related to the neurologic deficits in corresponding brain areas.

Transition Metal Chelator Induces Progesterone Production in Mouse Cumulus-Oocyte Complexes and Corpora Lutea

Progesterone production is upregulated in granulosa cells (cumulus and mural) after the LH surge, but the intra-follicular mechanisms regulating this transition are not completely known. Recent findings show that the transition metal chelator, N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN), impairs ovarian function. In this study, we provide evidence that chelating transition metals, including zinc, enhances progesterone production. The findings show that TPEN (transition metal chelator) increases abundance of Cyp11a1 and Star messenger RNA (mRNA) between 8- and 20-fold and progesterone production more than 3-fold in cultured cumulus-oocyte complexes (COC). Feeding a zinc-deficient diet for 10 days, but not 3 days, increased Star, Hsd3b, and prostaglandin F2 alpha receptor (Ptgfr) mRNA ~2.5-fold, suggesting that the effect of TPEN is through modulation of zinc availability. Progesterone from cumulus cells promotes oocyte developmental potential. Blocking progesterone production with epostane during maturation reduced subsequent blastocyst formation from 89 % in control to 18 % in epostane-treated complexes, but supplementation with progesterone restored blastocyst developmental potential to 94 %. Feeding a zinc-deficient diet for 5 days before ovulation did not affect the number of CL, STAR protein, or serum progesterone. However, incubating luteal tissue with TPEN increased abundance of Star, Hsd3b, and Ptgfr mRNA 2-3-fold and increased progesterone production 3-fold. TPEN is known to abolish SMAD2/3 signaling in cumulus cells. However, treatment of COC with the SMAD2/3 phosphorylation inhibitor, SB421542, did not by itself induce steroidogenic transcripts but did potentiate EGF-induced Star mRNA expression. Collectively, the results show that depletion of transition metals with TPEN acutely enhances progesterone biosynthesis in COC and luteal tissue.

Rapid in-focus corrections on quantitative amplitude and phase imaging using transport of intensity equation method

Transport of intensity equation (TIE) method can acquire sample phase distributions with high speed and accuracy, offering another perspective for cellular observations and measurements. However, caused by incorrect focal plane determination, blurs and halos are induced, decreasing resolution and accuracy in both retrieved amplitude and phase information. In order to obtain high-accurate sample details, we propose TIE based in-focus correction technique for quantitative amplitude and phase imaging, which can locate focal plane and then retrieve both in-focus intensity and phase distributions combining with numerical wavefront extraction and propagation as well as physical image recorder translation. Certified by both numerical simulations and practical measurements, it is believed the proposed method not only captures high-accurate in-focus sample information, but also provides a potential way for fast autofocusing in microscopic system.

MicroRNA-34c promotes osteoclast differentiation through targeting LGR4

MicroRNAs have emerged as important regulators of osteoclast differentiation in recent years. Of these, miR-34c has been reported to play an important role in bone development. However, its role and the underlying mechanism in osteoclast differentiation remains poorly understood. In this study, we aimed to investigate the precise role and molecular mechanism of miR-34c in osteoclast differentiation. We found an obvious increase in miR-34c expression during osteoclast differentiation in osteoclast precursors induced by receptor activator of nuclear factor κB (NF-κB) ligand and macrophage colony-stimulating factor in vitro. Further experiments showed that overexpression of miR-34c significantly promoted osteoclast differentiation while suppression of miR-34c showed the opposite effect. Interestingly, bioinformatics analysis and dual-luciferase reporter assays showed that miR-34c targets the 3'-untranslated region of leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4). The expression of LGR4 was regulated by miR-34c in osteoclasts. Moreover, miR-34c regulated NF-κB and glycogen synthase kinase 3-β signaling during osteoclast differentiation. Overexpression of LGR4 partially reversed the promoting effect of miR-34c overexpression on osteoclast differentiation. Taken together, our study suggests that miR-34c contributes to osteoclast differentiation by targeting LGR4, providing novel insights into understanding the molecular mechanism underlying osteoclast differentiation.

FBXL4 defects are common in patients with congenital lactic acidemia and encephalomyopathic mitochondrial DNA depletion syndrome

Mutations in FBXL4 have recently been recognized to cause a mitochondrial disorder, with clinical features including early onset lactic acidosis, hypotonia, and developmental delay. FBXL4 sequence analysis was performed in 808 subjects suspected to have a mitochondrial disorder. In addition, 28 samples from patients with early onset of lactic acidosis, but without identifiable mutations in 192 genes known to cause mitochondrial diseases, were examined for FBXL4 mutations. Definitive diagnosis was made in 10 new subjects with a total of 7 novel deleterious variants; 5 null and 2 missense substitutions. All patients exhibited congenital lactic acidemia, most of them with severe encephalopathic presentation, and global developmental delay. Overall, FBXL4 defects account for at least 0.7% (6 out of 808) of subjects suspected to have a mitochondrial disorder, and as high as 14.3% (4 out of 28) in young children with congenital lactic acidosis and clinical features of mitochondrial disease. Including FBLX4 in the mitochondrial diseases panel should be particularly important for patients with congenital lactic acidosis.

125 INCOMPLETE COMPENSATORY UP-REGULATION OF X-LINKED GENES IN BOVINE GERMLINE, EARLY EMBRYOS, AND SOMATIC TISSUES

The maintenance of a proper gene dosage is essential in cellular networks. To resolve the dosage imbalance between eutherian females (XX) and male (XY), X chromosome inactivation (XCI) occurs in females, while X-chromosome dosage compensation up-regulates the active X to balance its expression with that of autosome pairs [Ohno’s hypothesis; Ohno 1967 Sex Chromosomes and Sex-linked Genes (Springer-Verlag), p. 99]. These phenomena have been well studied in humans and mice, despite many controversies over the existence of such up-regulation. Using RNA sequencing data, we determined X chromosome dosage compensation in the bovine by analysing the global expression profiles of germ cells, embryos, and somatic tissues. Eight bovine RNA-seq data sets were obtained in from the Gene Expression Omnibus, covering bovine immature/mature oocytes (GSE59186 and GSE52415), pre-implantation conceptuses (GSE59186, GSE52415, and GSE56513), extra-embryonic tissues (PRJNA229443), and male/female somatic tissues (GSE74076, GSE63509, PRJEB6377, and GSE65125). The RNAseq data were trimmed and non-uniquely (paralogs included) mapped to the bovine reference genome assembly UMD3.1.1 using Hisat2 (version 2.0.5) aligner. The mRNA level of each gene, estimated by transformed transcripts per kilobase million was quantified by IsoEM (version 1.1.5). These RNA-seq data sets represented 4 chromosome scenarios in cells: XXXX:AAAA (diploid immature oocyte with DNA duplication), XX:AA (haploid mature oocyte with DNA duplication), XX:AA and X:AA (gradual changed X status in bovine pre-implantation conceptuses), and X:AA (extra-embryonic tissues and somatic cells in female with one active X or XY male) were analysed for dosage compensation. A total of 959 X-linked genes and 20,316 autosome genes were used to calculate the relative X to autosomal gene (A) expression (RXE): log2 (X expression) − log2 (A expression). The following dosage determinations were made: RXE values ≥ 0: complete dosage compensation (or X: A ratio ≥ 1); RXE values < 0: in-complete dosage compensation; RXE value = −1: no dosage compensation (or X: A ratio = 0.5). Our analyses showed a decreased RXE after fertilization, from −0.33 in matured oocytes to −0.50 at the 2-cell stage, indicating that the sperm that undergo meiotic sex chromosome inactivation (MSCI) bring in inactive X chromosomes to the matured oocytes. Subsequently, the activation of the bovine embryonic genome at the 4- to 8-cell stage increased RXE from −0.54 to −0.05. This was followed by a sharp RXE decline from −0.02 at the 16-cell stage, 0.1 at the 32-cell stage to −0.29 at the compact morula stage, which is known as paternal X inactivation stage in the bovine. Finally, RXE was stabilised from blastocysts −0.19 through the Day 19 conceptuses −0.25 to somatic tissue average −0.21 with a pattern of incomplete X compensation. These findings support X expression up-regulation as proposed by Ohno. No significant RXE differences were observed between bovine female and male somatic tissues, further supporting Ohno’s hypothesis, which predicts a balance in the expression of X-linked genes to that of autosomes. This study confirms Ohno’s hypothesis of X dosage compensation in bovine germ cells, early embryos, and somatic tissues.

130 A CATALOG OF REFERENCE GENES WITH HIGH, MEDIUM, AND LOW LEVELS OF EXPRESSION DURING BOVINE IN VIVO PRE-IMPLANTATION DEVELOPMENT

Appropriate reference genes for accurate normalization in RT-PCR are essential for the study of gene expression. Ideal reference genes should not only have stable expression across stages of embryo development, but also be expressed at comparable levels to the target genes. Using RNA-seq data from in vivo-produced bovine oocytes and embryos from the 2-cell to blastocyst stage (Jiang et al., 2014 BMC Genomics 15, 756), we tried to establish a catalogue of all reference genes for RT-PCR analysis. One-way ANOVA generated 4055 genes that did not differ across stages. To reduce this list, we used the entire RNA-seq data set and first removed genes with a FPKM (fragments per kilobase of transcript per million mapped reads) of <1, and then rescaled each gene’s expression values within a range of 0 to 1. We subsequently calculated the expression variance for each gene across all stages. By assuming that the calculated variances follow a Gaussian distribution and that the majority of the genes do not have a stable expression level, a gene was classified as a reference if its variance significantly deviated (P < 0.05) from these assumptions. We identified 346 potential reference genes, all of which were among the candidates from the ANOVA analysis. We arbitrarily assigned genes in this list to high (FPKM ≥ 100), medium (10 < FPKM < 100), and low expression levels (FPKM ≤ 10), and 37, 154, and 155 genes, respectively, fell into these groups. Surprisingly, none of the commonly used reference genes, such as GAPDH, PPIA, ACTB, PRL15, GUSB, and H3F2A, were identified as being stably expressed across in vivo development. This is consistent with findings of prior RT-PCR studies (Robert et al. 2002 Biol. Reprod. 67, 1465–1472; Ross et al. 2010 Cell Reprogram. 12, 709–717). The following gene ontology terms were significantly enriched for the 346 genes: cell cycle, translation, transport, chromatin, cell division, and metabolic process, indicating that the early embryos maintained constant levels of genes involved in fundamental biological functions. Finally, we performed RT-PCR to validate the RNA-seq results using different bovine in vivo-derived oocytes and embryos (n = 3/stage). We successfully validated 10 selected genes, including those in the high (CS, PGD, and ACTR3), medium (CCT5, MRPL47, COG2, CRT9, and HELLS), and low expression groups (CDC23 and TTF1). In conclusion, we recommend the use of reference genes that are expressed at comparable levels to target genes. This study offers a useful resource to aid in the appropriate selection of reference genes, which will improve the accuracy of quantitative gene expression analyses across bovine embryo pre-implantation development.