Dynamics of BCL-2 family of proteins in early pancreatic progenitors and β-cells

BCL-2 family proteins play an important role in the regulation of cell survival and death. However, there are also certain members that exhibit tissue- and developmental stage-specific expression and function. Here, I report a unique reciprocal relationship between BCL-xL (not BCL2) and BAK during early human pancreatic differentiation. The association of BCL-xL but not BCL2 with BAK has also been reported to keep apoptosis in check, albeit not specifically during pancreatic development. This is consistent with our findings that the compensatory increase in BCL2 protein expression upon BCL-xL inhibition with WEHI-539 is insufficient to curb the BAK mediated increase in cleaved caspase 3 and the triggering of the caspase cascade. I also found that the downregulation of BCL2L1/BCL-xL expression and function resulted in a decrease in early pancreatic gene and protein expression. However, BCL-xL is known to be dispensable during rodent beta cell development but rather is important for protection against apoptotic stimuli in mature beta cells (Carrington et al., 2009). Therefore, I propose that BCL-xL might be indirectly involved in human pancreatic specification that is ultimately crucial for proper beta cell function.Doctor of Philosoph

Elucidating the role of SCD1 in B cell development and function

Stearoyl-coenzyme A (CoA) desaturase (SCD) enzymes are a family of δ-9 fatty acid desaturases that catalyse the de novo synthesis of monounsaturated fatty acids (MUFAs) from endogenous or dietary saturated fatty acids (SFAs). Here, we reported the loss of SCD1 leads to the down-regulation of B1 cells in the peritoneal cavity, providing a further insight on the role of SCD1 in B cell development. In this case, the comparison of B cell activation markers between the C57/BL6J and Scd1ab-2J/ab-2 B cells did not reveal any distinct differences. Also, further investigations into immunoglobulin production by B cells did not reveal significant differences between the C57/BL6J and Scd1f/fCd19Cre/+mice. However, Scd1f/fCd19Cre/+mice did show significant increased frequency of antibody-secreting cells in the spleen. The study in this work should allow us to gain a further insight on SCD1 role in B cell development and functions.​Master of Scienc

Insight into muscle stem cell regeneration and mechanobiology

Abstract Stem cells possess the unique ability to differentiate into specialized cell types. These specialized cell types can be used for regenerative medicine purposes such as cell therapy. Myosatellite cells, also known as skeletal muscle stem cells (MuSCs), play important roles in the growth, repair, and regeneration of skeletal muscle tissues. However, despite its therapeutic potential, the successful differentiation, proliferation, and expansion processes of MuSCs remain a significant challenge due to a variety of factors. For example, the growth and differentiation of MuSCs can be greatly influenced by actively replicating the MuSCs microenvironment (known as the niche) using mechanical forces. However, the molecular role of mechanobiology in MuSC growth, proliferation, and differentiation for regenerative medicine is still poorly understood. In this present review, we comprehensively summarize, compare, and critically analyze how different mechanical cues shape stem cell growth, proliferation, differentiation, and their potential role in disease development (Fig. 1). The insights developed from the mechanobiology of stem cells will also contribute to how these applications can be used for regenerative purposes using MuSCs

The molecular functions of hepatocyte nuclear factors - in and beyond the liver

The hepatocyte nuclear factors (HNFs) namely HNF1α/β, FOXA1/2/3, HNF4α/γ and ONECUT1/2 are expressed in a variety of tissues and organs, including the liver, pancreas and kidney. The spatial and temporal manner of HNF expression regulates embryonic development and subsequently the development of multiple tissues during adulthood. Though the HNFs were initially identified individually based on their roles in the liver, numerous studies have now revealed that the HNFs cross-regulate one another and exhibit synergistic relationships in the regulation of tissue development and function. The complex HNF transcriptional regulatory networks have largely been elucidated in rodent models, but less so in human biological systems. Several heterozygous mutations in these HNFs were found to cause diseases in humans but not in rodents, suggesting clear species-specific differences in mutational mechanisms that remain to be uncovered. In this review, we compare and contrast the expression patterns of the HNFs, the HNF cross-regulatory networks and how these liver-enriched transcription factors serve multiple functions in the liver and beyond, extending our focus to the pancreas and kidney. We also summarise the insights gained from both human and rodent studies of mutations in several HNFs that are known to lead to different disease conditions.ASTAR (Agency for Sci., Tech. and Research, S’pore)NMRC (Natl Medical Research Council, S’pore

An Integrative Glycomic Approach for Quantitative Meat Species Profiling

It is estimated that food fraud, where meat from different species is deceitfully labelled or contaminated, has cost the global food industry around USD 6.2 to USD 40 billion annually. To overcome this problem, novel and robust quantitative methods are needed to accurately characterise and profile meat samples. In this study, we use a glycomic approach for the profiling of meat from different species. This involves an O-glycan analysis using LC-MS qTOF, and an N-glycan analysis using a high-resolution non-targeted ultra-performance liquid chromatography-fluorescence-mass spectrometry (UPLC-FLR-MS) on chicken, pork, and beef meat samples. Our integrated glycomic approach reveals the distinct glycan profile of chicken, pork, and beef samples; glycosylation attributes such as fucosylation, sialylation, galactosylation, high mannose, α-galactose, Neu5Gc, and Neu5Ac are significantly different between meat from different species. The multi-attribute data consisting of the abundance of each O-glycan and N-glycan structure allows a clear separation between meat from different species through principal component analysis. Altogether, we have successfully demonstrated the use of a glycomics-based workflow to extract multi-attribute data from O-glycan and N-glycan analysis for meat profiling. This established glycoanalytical methodology could be extended to other high-value biotechnology industries for product authentication

FGFR-mediated ERK1/2 signaling contributes to mesendoderm and definitive endoderm formation in vitro

Summary: The differentiation of human pluripotent stem cells into the SOX17+ definitive endoderm (DE) germ layer is important for generating tissues for regenerative medicine. Multiple developmental and stem cell studies have demonstrated that Activin/Nodal signaling is the primary driver of definitive endoderm formation. Here, we uncover that the FGF2-FGFR-ERK1/2 signaling contributes to mesendoderm and SOX17+ DE formation. Without ERK1/2 signaling, the Activin/Nodal signaling is insufficient to drive mesendoderm and DE formation. Besides FGF2-FGFR-mediated signaling, IGF1R signaling possibly contributes to the ERK1/2 signaling for DE formation. We identified a temporal relationship between Activin/Nodal-SMAD2 and FGF2-FGFR-ERK1/2 signaling in which Activin/Nodal-SMAD2 participates in the initiation of mesendoderm and DE specification that is followed by increasing activity of FGF2-FGFR-ERK1/2 to facilitate and permit the successful generation of SOX17+ DE. Overall, besides the role of Activin/Nodal signaling for DE formation, our findings shed light on the contribution of ERK1/2 signaling for mesendoderm and DE formation

Defective insulin receptor signaling in hPSCs skews pluripotency and negatively perturbs neural differentiation

10.1016/j.jbc.2021.100495Journal of Biological Chemistry29610049

Brief exposure to directionally-specific pulsed electromagnetic fields stimulates extracellular vesicle release and is antagonized by streptomycin: A potential regenerative medicine and food industry paradigm

10.1016/j.biomaterials.2022.121658BIOMATERIALS28