Characterization of Carbohydrate Surface Markers on Mouse Embryonic Stem Cells

Research Article

J Stem Cell Res Transplant. 2016; 3(1): 1022.

Characterization of Carbohydrate Surface Markers on Mouse Embryonic Stem Cells

Zhenwei He1,2, Yue An1,3, Gang Shi1,4, Yingwei Lin1,3, Jiliang Hu5* and Yali Li¹*

¹Department of Biochemistry and Molecular Biology, Dalian Medical University, China

¹Department of Neurology, Forth Affiliated Hospital of China Medical University, China

³Department of Clinical Laboratory, The Second Affiliated Hospital of Dalian Medical University, China

4Department of Colorectal Surgery, Liaoning Cancer Hospital and Institute, Cancer Hospital of China Medical University, China

5Department of Neurosurgery, The Shenzhen People’s Hospital, The Second Clinical Medical Collage of Jinan University, China

*Corresponding author: Yali Li, Department of Biochemistry and Molecular Biology, Dalian Medical University, China

Jiliang Hu, Department of Neurosurgery, The Shenzhen People’s Hospital, The Second Clinical Medical Collage of Jinan University, China

Received: April 19, 2016; Accepted: July 13, 2016; Published: July 15, 2016


Glycosylation of proteins and lipids on cell surface have been shown to be important in maintaining pluripotency and stem cell fate in embryonic stem cells. Lectins have been widely used to characterize carbohydrate modifications on cell surface of embryonic stem cells to determine pluripotency and stem cell fate. In the present study, a panel of 14 lectins and carbohydrate antibodies was used to characterize the carbohydrate surface markers of mouse Embryonic Stem (ES) cells. SSEA-1-positive mouse ES cells were firstly enriched and the carbohydrate profile of the cells was determined by flow cytometry and immunocytochemistry. Enrichment of mouse ES cells yielded approximately 99.95 ± 0.87% of SSEA-1-positive mouse ES cells. A uniform and high percentage of binding was observed for PNA, DSL, JAC, GNL, PSA and LTL, with PNA, DSL, JAC and GNL having similar percentage of binding to SSEA- 1 (99.9%), while PSA and LTL binding were approximately 95%-99%. Partial binding of WFL, SNA and AAL were observed in mouse ES cells which was also reflected by the respective immunocytochemistry images. A very low percentage of binding was observed for MAA and UEAI. The data showed that high expression of mannose, N-acetyllactosamine and galactose are present on the cell surface of mouse ES cells. Some reliable surface markers that can be used to determine pluripotency are PNA, DSL, JAC and GNL, which showed similar binding to SSEA-1, a well-established pluripotent marker. Taken together, the data has provided information on the cell surface carbohydrate profile of mouse ES cells.

Keywords: Mouse embryonic stem cells; SSEA-1; Lectins


mouse ESCs: mouse Embryonic Stem Cells; SSEA-1: Stage Specific Embryonic Antigen-1; GalNAc: N-acetylgalactosamine; LIF: Leukemia Inhibitory Factor; MEF: Mouse Embryonic Fibroblast; PBS: Phosphate Buffered Saline; BSA: Bovine Serum Albumin; UEAI: Ulex Europaeus Agglutinin I; LTL: Lotus Tetragonolobus Lectin; PSA: Pisum Sativum Agglutinin; GNL: Galanthus Nivalis Lectin; AAL: Aleuria Aurantia Lectin; PNA: Peanut agglutinin; JAC: Jacalin; MAA, MALII: Maackia Amurensis Lectin II; SNA, SBNL: Sambucus Nigra Agglutinin, Elderberry Bark Lectin; DSL: Datura Stramonium Lectin; WFL: Wisteria Floribunda Lectin; FITC: Fluorescein Isothiocyanate


Mouse Embryonic Stem (ES) cells were first derived from inner cell mass of mouse blastocysts isolated from pre-implantation embryos on feeder layers [1,2]. The use of mouse ES cells provided a deeper understanding of the mechanisms of cell differentiation and observations of the physiological consequences of genetic mutations. Most importantly, the pluripotent nature of mouse ES cells enabled the generation of transgenic and knockout mice, which has revolutionized genetic research, allowing the development of countless animal models for human diseases [3].

Key regulators of pluripotency and self-renewal including Oct4 and Nanog are well known markers of mouse ES cells [4]. These transcription factors regulate the expression of numerous genes responsible for stem cell fate and pluripotency such as Sox2, Foxd3, Setb1, Rif1 and Esrrb [4]. Apart from transcription factors, cell surface markers of mouse ES cells for pluripotency have also been identified. The most common cell surface carbohydrate antigen specifically found on murine ES cells is the stage specific embryonic antigen 1 (SSEA-1) – also known as Lewis x or CD15 – which is important for cell-cell adhesion in tightly compacted colonies of mouse ES cells [5,6,7]. Other surface markers include CD324, CD90, CD117, CD9 and CD326 [8].

Carbohydrate modifications of proteins and lipids on cell surface of ES cells have also been reported to be important in maintenance of pluripotency and stem cell fate [9]. Glycosylation, a process by which glycans or carbohydrate are attached to proteins or lipids, are common post-translational carbohydrate modifications. Glycans play essential roles in biological process such as cell development and differentiation. Lectins are proteins that bind to glycans and are universally present in animals, plants and bacteria. Lectin profiles are widely used to characterize carbohydrates of glycoproteins, glycolipids or polysaccharides. Venable et al. [10] was the first to characterize carbohydrate patterns through lectin profiles in SSEA- 4-enriched human ES cells. Additionally, a panel of lectin biomarkers has been identified for the isolation of pluripotent human ES cells [9]. Lectin probes and more recently, lectin microarrays have also been utilized to distinguish undifferentiated from differentiated ES cells in both human and mouse ES cells [11,12,13].

In the present study, carbohydrate profiles of ES-D3 and ESC57BL/ 6 mouse ES cell lines were analyzed. These cell lines have been shown to express SSEA-1, the pluripotency marker in mouse ES cells [14,15]. SSEA-1-positive cells were enriched by flow cytometry before carbohydrate analysis using a panel of 14 carbohydrate antibodies and lectins. The study showed distinct expression and localization of carbohydrate and lectins on cell surface of the mouse ES cells.

Materials and Methods


All cell culture reagents were purchased from Invitrogen Life Technologies (Merelbeke, Belgium), unless indicated otherwise. Anti-SSEA-1 antibody was purchased from Santa Cruz Biotechnology Inc. Rat anti-mouse IgM-microbeads and LS+ positive selection column were purchased from Miltenyi Biotec Inc. (Miltenyi Biotec. Inc., Bergisch Gladbach, Germany). L3, L4 and L5 antibodies were produced as previously described and presented by Melitta in Hamberg University [16,17,18]. R-Phycoerythin (R-PE)-conjugated mouse anti-rat monoclonal, R-Phycoerythin (R-PE)-conjugated rat anti-mouse IgM monoclonal Ab, PerCP-CY5.5-conjugated rat antimouse IgM monoclonal, PerCP-CY5.5-conjugated mouse antirat IgM monoclonal Ab, PerCP-CY5.5-conjugated streptavidin and R-PE-conjugated rat anti-mouse IgM monoclonal antibodies were purchased from BD Biosciences (Franklin Lakes, NJ, USA). Biotinylated lectins and Texas Red Avidin D were purchased from Vector Laboratories, Inc. (Burlingame, CA, USA). FITC-conjugated rat anti-mouse IgM Ab and Cy3-conjugated mouse anti-rat IgM Ab were purchased from Invitrogen Detection Technologies, Oregon, USA. Leukemia Inhibitory Factor (LIF) was purchased from Chemicon Incorporation, Temecula, CA, USA.

Cell culture

All cell culture reagents were purchased from Invitrogen Life Technologies (Merelbeke, Belgium) unless indicated otherwise. ES-D3 embryonic stem cell line derived from the blastocysts of 129 S2/SvPas mouse and ES-C57BL/6 embryonic stem cell line derived from the C57BL/6J mouse were purchased from ATCC (Global Bioresource CenterTM, Manassas, USA). ES cells were grown in ESDMEM supplemented with 15% ES-FBS, 1 × non-essential amino acids, 2 mM L-glutamine, 50 U/mL penicillin, 50μg/mL streptomycin, and 0.1 mM 2-mercaptoethanol. Undifferentiated ES cells were grown on Mitomycin C-Treated Mouse Embryonic Fibroblasts (MEFs) in the presence of 1,000 U/mL Leukemia Inhibitory Factor (LIF; Chemicon Inc.). ES cells were passaged every 2 or 3 days using 0.05% trypsin/0.04% EDTA for 2-3 minutes or mechanical dissection with BD Medimachine. Flow cytometry assay was performed using routinely maintained adherent mouse ES cell colonies.

Enrichment of SSEA-1 positive mouse Embryonic Stem Cells (ESCs)

Murine ES cells were grown in 10cm dishes and trypsin/EDTA passaged into single cell suspensions as described above. Cells were incubated at 4°C for 30 minutes in 1:10 dilution of purified antimouse IgM in D/G buffer. D/G buffer consisted of 0.5% BSA and 2 mM EDTA in Phosphate Buffered Saline (PBS), pH7.4. After incubation, 2 ml D/G buffer was added and cells were re-suspended and centrifuged at 300g for 5 minutes. Supernatant was removed, leaving the cell pellet intact, and cells were washed again in D/G buffer and re-suspended. After centrifugation, cells were incubated at 4°C for 30 minutes in 1:10 dilution of SSEA-1 antibody in D/G buffer. After washing with D/G buffer for 3 times, a 1:4 dilution of secondary anti-mouse IgM-beads in D/G buffer were added to the cell pellet, and the re-suspended pellet was incubated at 4°C for 5 minutes. After incubation, 5 ml of D/G buffer was added to wash the cell pellet, followed by centrifugation (300g) for 5 minutes. This process was repeated two more times with 5 ml D/G buffer. The cells were finally re-suspended in 500 μl of D/G buffer before being applied to a prewashed magnetic beads column. The flow through from the column was collected and applied to the magnetic beads column thrice. Then, 5 ml of D/G buffer was applied to the magnetic beads column to obtain the eluate. The eluate was collected and cells were counted. Cells were then subjected to flow cytometry. Flow cytometry results presented here are from mouse ES cells that were used immediately after the enrichment.

Flow cytometry assay

Cell surface carbohydrate expression of SSEA-1 enriched mouse ES cells was assessed by indirect immunofluorescence detected by flow cytometry to provide a quantitative binding percentage and fluorescence intensity of SSEA-1 Ab, carbohydrate antibodies and lectins. FACSCalibur (Becton-Dickinson, San Jose, USA) equipped with an argon laser with emission wavelength at 488 nm was used. Flow cytometry results presented here are from mESCs that were used immediately after the SSEA-1 positive cell enrichment procedure. Cell Quest Pro software (Becton-Dickinson) was used for cell acquisition and analysis. Mouse ES cells were prepared, cultured and harvested into single cell suspensions using trypsinization as described above. The cells were digested with 0.05% trypsin and washed twice with PBS (Gibco, Long Island, USA). Single cell suspension was prepared in PBS with 10%FBS with the concentration adjusted to 107 cells/ ml for indirect antibody labeling. The SSEA-1 positive ES cells were enriched as described above. Then, cells were placed in 4 ml sterile conical tubes (Falcon, Becton-Dickison) in aliquots of 500,000 cells each and stained with one of the 14 carbohydrate antibodies and lectins. Cells were washed 3 times with PBS and subsequently stained with primary antibodies. Cells were double stained with one of the 14 carbohydrate antibodies and lectins and SSEA-1 Ab, then stained with secondary antibodies after washing with PBS. The secondary antibodies were chosen so that there would not be any overlap in the emission/excitation wavelengths and so that double staining could be performed. Unstained, enriched mouse ES cells and enriched mouse ES cells stained with secondary antibodies alone were used as controls. Flow cytometry was performed using a Beckman Coulter Cytomics FC 500 Flow Cytometer. Data analysis was performed using the RXP Analysis Software by Beckman Coulter and Windows Multi Document Interface for Flow Cytometry (WinMDI 2.8). At least three independent assays were carried out using both ES-D3 cell line and ES-C57BL/6 mouse ES cell line.

Immunocytochemical staining

Immunocytochemistry staining was used to analyze the localization and staining patterns of cell surface carbohydrate expression and SSEA-1 on routinely maintained adherent cultures of mouse ES cells. Mouse ES cells were fixed in 4% paraformaldehyde in PBS for 30 minutes and then washed 3 times with PBS. After blocking in 1% BSA for 1 hour, cells were double stained with one of the 11 biotinylated lectins, 3 carbohydrate antibodies and SSEA-1 Ab for 1 hour, followed by washing with PBS thrice. Cells were stained with secondary antibodies for 1 hour and then washed 3 times with PBS. After drying, cells were mounted with Hard SetTM fluorescence mounting medium (Vector Laboratories, Inc. Burligame, CA, USA) including DAPI to detect cell nuclei. Controls of unstained cells were obtained by incubation with secondary antibodies alone. All slides were visualized using a LSM510 laser microscope. Individual color channels were captured separately and merged using the LSM510 software.

Statistical analysis

All data were expressed as mean ± S.E.M. Statistical evaluations were achieved by one-way analysis of variance and Student’s t-test. Differences were considered to be significant when p < 0.05.


Carbohydrate analysis using flow cytometry

To decrease non-specific binding, purified anti-mouse IgM was used to block mouse ES cells. After blocking, the non-specific binding was decreased from 14.36% to 3.61% (Figure S1). To obtain undifferentiated mouse ES cells, magnetic beads sorting method was used to enrich SSEA-1 positive mouse ES cells. After enrichment, about 99.95 ± 0.87% of mouse ES cells were SSEA-1 positive (Figure 1). To determine the presence and binding percentage of 14 chosen carbohydrate Abs and lectins on pluripotent mouse ES cell surfaces, both karyotypically normal mouse ES cell lines (ES-D3 and ESC57BL/ 6) were analyzed using flow cytometry with the panel of Abs and lectins together with the pluripotency marker, SSEA-1. A broad range of binding percentages was observed (Figure 2). The highest binding percentages were detected using PNA, DSL, JAC, GNL, PSA, AAL and LTL. The binding percentages for PNA, DSL, JAC and GNL were similar to that of SSEA-1, which showed over 99.9% of positive binding in enriched mouse ES cells. Figure 3B and 3C show the shifted histogram plots of GNL and DSL, as representatives of these high percentage binding Abs and lectins. The flurorescence intensity of DSL binding was higher than GNL binding. The binding percentages of PSA, AAL and LTL ranged from 95-99% of enriched mouse ES cells. Two lectins, MAA and UEAI, binding percentage were very low. Analysis of MAA and UEAI histograms showed a little peak shifts using these lectins (Figure 3E and 3F).