The characteristic expression pattern of BMI-1 and SALL4 genes in placenta tissue and cord blood
- Shaohua Chen†1, 2,
- Sichu Liu†1,
- Ling Xu†1,
- Lijian Yang1,
- Zhenyi Jin1,
- Yu Ma1,
- Bo Li1,
- Xiuli Wu1,
- Jianchang Yang3,
- Yupo Ma3 and
- Yangqiu Li1, 2Email author
© Chen et al.; licensee BioMed Central Ltd. 2013
Received: 16 March 2013
Accepted: 26 April 2013
Published: 30 April 2013
SALL4 and BMI-1 are important factors in hematopoiesis. Placental tissue (PT) and umbilical cord blood (CB) are rich in hematopoietic stem/progenitor cells (HSCs/HPCs), but their SALL4 and BMI-1 expression levels remain unknown.
Real-time PCR was used to determine the expression level of these genes in PT and CB from ten cases, and ten healthy donors were used as controls.
A significantly higher BMI-1 and SALL4 gene expression level was found in PT (median: 17.548 and 34.362, respectively) than in cord blood mononuclear cells (CBMCs) (median: 2.071 and 11.300, respectively) (P = 0.0001 and P = 0.007) and healthy peripheral blood mononuclear cells (PBMCs) (median: 0.259 and 0.384, respectively) (P = 0.001 and P <0.0001), and their expression level was lower in PBMCs than in CBMCs (P = 0.029 and P = 0.002). A positive correlation between the BMI-1 and SALL4 genes was found in the PT and CB groups, while there was no significant correlation between these genes in the healthy group. There was also no significant correlation between the expression level of each gene in PT and CB.
These results describe the characteristic features of the BMI-1 and SALL4 gene expression pattern in placental tissue and cord blood. Placental tissue with higher expression level of both genes may be considered as a potential resource for SALL4-related HPC expansion.
KeywordsBMI-1 gene Cord blood Placenta Real-time PCR SALL4 gene
Umbilical cord blood (CB) is a valuable alternative hematopoietic stem cells (HSC) source for transplantations for patients who lack a suitable sibling donor [1–3]. It has been demonstrated previously that CB-derived progenitors can express Oct3/4, SRY-related HMG-box 2 (Sox2), Nanog and reduced expression-1 (Rex1), which are pluripotent/multilineage markers and could potentially differentiate into multiple lineages [4, 5]. However, different gene expression pattern may determine the use of human CB-derived HSCs/hematopoietic progenitor cells (HPCs) as functional tissues or cells .
Sal-like protein 4 (SALL4) and B cell-specific MLV integration site 1 (BMI-1) are important factors in hematopoiesis and are expressed in hematopoietic stem/progenitor cells (HSCs/HPCs) and myeloid leukemia cells . Placental tissue (PT) and CB comprise rich HSCs/HPCs; however, little is known about the difference in the expression level of SALL4 and BMI-1 in PT and CB.
SALL4, a newly identified zinc-finger transcription factor that is a member of the SALL gene family, was originally cloned based on its sequence homology to Drosophila spalt (sal) [7, 8]. This protein plays important roles in maintaining embryonic stem cells (ESC) pluripotency and HSC/HPC self-renewal properties, and it has been recently proposed for use in CB expansion . Recently, it was demonstrated that BMI-1 is a direct SALL4 target gene. BMI-1 is a member of the polycomb group of proteins, and it was initially identified in Drosophila as a repressor of homeotic genes [7, 10]. This protein is highly expressed in purified HSCs, its expression declines with differentiation [7, 11], and it plays an essential role in regulating adult, self-renewing HSCs/HPCs [7, 11–13]. The induction of SALL4 expression is associated with increased levels of histone H3-K4 and H3-K79 methylation in the BMI-1 promoter, indicating a novel connection between SALL4 and the polycomb group proteins .
In this study, we sought to characterize the expression pattern of the BMI-1 and SALL4 genes in PT and CB.
Materials and methods
Ten placental tissue samples were obtained from full-term deliveries, and umbilical cord blood was obtained at the same time from full-term healthy babies with the mothers’ consent. All human tissue and cell samples were obtained with consent from the human subjects. Peripheral blood samples from ten healthy donors with informed consent were used as control. All of the procedures were conducted according to the guidelines of the Medical Ethics Committees of the Health Bureau of the Guangdong Province of China, and ethical approval was obtained from the Ethics Committee of Medical School of Jinan University for this study.
Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR)
Mononuclear cells were isolated from cord blood samples (CBMCs) and healthy peripheral blood (PBMCs) by Ficoll-Hypaque gradient centrifugation. The placental tissue (approximately 100 mg) was obtained by curettage of the central portion of the placenta (decidua in majority). RNA isolation and cDNA synthesis were performed according to the manufacturer’s protocol .
The expression level of BMI-1, SALL4, and the β2 microglobulin (β2-MG) reference gene was determined by SYBR Green I real-time PCR as previously described .
Differences in mRNA expression between two groups were analyzed using the Mann-Whitney test. Data are presented as the median. Spearman’s rank correlation analysis was used to analyze the SALL4 and BMI-1 mRNA levels in different samples. Differences were considered statistically significant with a P <0.05.
Results and Discussion
We determined the expression characteristics of BMI-1 and SALL4 in placental tissue and cord blood. The results of this study may contribute to a better understanding of the expression characteristics and correlation of SALL4 and BMI-1 in placenta tissue. Placental tissue with higher expression level of both genes may be considered as a potential resource for SALL4-related HPC expansion.
B cell-specific MLV integration site 1 gene
umbilical cord blood
cord blood mononuclear cells
embryonic stem cells
hematopoietic progenitor cells
hematopoietic stem cells
healthy peripheral blood mononuclear cells
quantitative real-time reverse transcription-polymerase chain reaction
reduced expression 1
Sal-like protein 4 gene
SRY-related HMG-box 2
This study was supported by grants from the National Natural Science Foundation of China (no. 81270604), the Collaborated grant for HK-Macao-TW of Ministry of Science and Technology (2012DFH30060), the Fundamental Research Funds for Central Universities (no. 21612116), and, in part, an NIH grant to YM (no. R01HL087948).
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