Glycotope-centric in depth spatial glycomic analysis of mouse brain
Intro - The characteristic complex type N-glycans of mouse brain are known to comprise truncated structures with 2 to 3 non-galactosylated GlcNAc termini, and bi- to multi-antennary structures elaborated with a combination of ±sialyl LacNAc and Lewis X termini. Other less abundant glycotopes including disialylated LacNAc and various sulfated structures have also been reported on specific isolated glycoproteins but not in the context of global glycomic analyses of single mouse brain. We have undertaken in depth glycomic analyses of tissues derived from different mouse brain regions by a nanoLC-MS2/MS3-based glycotope-centric glycomic workflow.
We not only identified all previously reported glycotopes but additionally resolved the relative amount of isomeric i) fucosylated LacNAc glycotopes (LeX, LeA, H1, H2); ii) terminal disialyl unit (NeuAc-NeuAc-Hex-HexNAc) versus disialylated type 1 structure (NeuAc-Hex-3(NeuAc6)HexNAc, as well as such di- and trisialyl units extending from O-glycans; and iii) Gal-3-O-, Gal-6-O- versus GlcNAc-6-O-sulfated glycotopes. Remarkably, we found a high abundance of terminal sulfated GlcNAc on the truncated structures, and both mono- and di-sulfated LacNAc, LeX, and sialyl LacNAc, not previously reported. Importantly, some of the sialyl sulfo glycotopes identified may serve as preferred cognate ligands of microglial receptors, including the sialic acid binding Siglecs implicated in neurodegenerative diseases.
Reduced terminal di and oligosialylation on glycoproteins from mouse brain deficient in ST8Sia3
We further demonstrated a significant reduction of these terminal NeuAc-NeuAc-disialyl units in glycomic samples derived from ST8Sia3 KO mouse and Huntington mouse (R6/2). Strikingly, ST8Sia3 is the only notable glycogene among striatal-enriched transcripts compared to other brain region and that its expression is significantly reduced in Huntington disease, in which the most severe damage occurs in the striatum. Moreover, ST8Sia3 KO selectively impact the sialylation of several important striatal proteins that are involved in motor response to drug targeting. [Functional roles of ST8SIA3-mediated sialylation of striatal dopamine D2 and adenosine A2A receptors. (2019). Lin et al Transl Psychiatry 9(1): 209.]
Reduced terminal di and oligosialylation on glycoproteins from mouse brain deficient in ST8Sia3
We further demonstrated a significant reduction of these terminal NeuAc-NeuAc-disialyl units in glycomic samples derived from ST8Sia3 KO mouse and Huntington mouse (R6/2). Strikingly, ST8Sia3 is the only notable glycogene among striatal-enriched transcripts compared to other brain region and that its expression is significantly reduced in Huntington disease, in which the most severe damage occurs in the striatum. Moreover, ST8Sia3 KO selectively impact the sialylation of several important striatal proteins that are involved in motor response to drug targeting. [Functional roles of ST8SIA3-mediated sialylation of striatal dopamine D2 and adenosine A2A receptors. (2019). Lin et al Transl Psychiatry 9(1): 209.]
