Development of Immunoglobulin A Nephropathy-Like Disease in β-1, 4-Galactosyltransferse-I- Deficient Mice

取得学位 : 博士（医学）, 学位授与番号 : 医博甲第1833号, 学位授与年月日 : 平成19年3月22日, 学位授与大学 : 金沢大学, 主査教授 : 大島 正伸, 副査教授 : 金子 周一, 山岸 正

Galactosyl carbohydrate residues on hematopoietic stem/progenitor cells are essential for homing and engraftment to the bone marrow

骨髄移植における造血幹細胞の生着にはガラクトース糖鎖が必須であることを解明. 京都大学プレスリリース. 2019-05-16.The role of carbohydrate chains in leukocyte migration to inflamed sites during inflammation and trafficking to the lymph nodes under physiological conditions has been extensively characterized. Here, we report that carbohydrate chains also mediate the homing and engraftment of hematopoietic stem/progenitor cells (HSPCs) to the bone marrow (BM). In particular, we found that transplanted BM cells deficient in β-1, 4-galactosyltransferase-1 (β4GalT-1) could not support survival in mice exposed to a lethal dose of irradiation. BM cells obtained from mice deficient in β4GalT-1 showed normal colony-forming activity and hematopoietic stem cell numbers. However, colony-forming cells were markedly rare in the BM of recipient mice 24 h after transplantation of β4GalT-1-deficient BM cells, suggesting that β4GalT-1 deficiency severely impairs homing. Similarly, BM cells with a point mutation in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase gene, encoding a key enzyme in sialic acid biosynthesis, showed mildly impaired homing and engraftment abilities. These results imply that the galactosyl, but not sialyl residues in glycoproteins, are essential for the homing and engraftment of HSPCs to the BM. These findings suggest the possibility of modifying carbohydrate structures on the surface of HSPCs to improve their homing and engraftment to the BM in clinical application

Lactosylceramide synthases encoded by B4galt5 and 6 genes are pivotal for neuronal generation and myelin formation in mice

糖脂質ガングリオシドが脳の形成に必須であることを解明 --神経系の構築異常のモデルを提示--. 京都大学プレスリリース. 2018-08-28.It is uncertain which β4-galactosyltransferase (β4GalT; gene name, B4galt), β4GalT-5 and/or β4GalT-6, is responsible for the production of lactosylceramide (LacCer) synthase, which functions in the initial step of ganglioside biosynthesis. Here, we generated conditional B4galt5 knockout (B4galt5 cKO) mice, using Nestin-Cre mice, and crossed these with B4galt6 KO mice to generate B4galt5 and 6 double KO (DKO) mice in the central nervous system (CNS). LacCer synthase activity and major brain gangliosides were completely absent in brain homogenates from the DKO mice, although LacCer synthase activity was about half its normal level in B4galt5 cKO mice and B4galt6 KO mice. The DKO mice were born normally but they showed growth retardation and motor deficits at 2 weeks and died by 4 weeks of age. Histological analyses showed that myelin-associated proteins were rarely found localized in axons in the cerebral cortex, and axonal and myelin formation were remarkably impaired in the spinal cords of the DKO mice. Neuronal cells, differentiated from neurospheres that were prepared from the DKO mice, showed impairments in neurite outgrowth and branch formation, which can be explained by the fact that neurospheres from DKO mice could weakly interact with laminin due to lack of gangliosides, such as GM1a. Furthermore, the neurons were immature and perineuronal nets (PNNs) were poorly formed in DKO cerebral cortices. Our results indicate that LacCer synthase is encoded by B4galt5 and 6 genes in the CNS, and that gangliosides are indispensable for neuronal maturation, PNN formation, and axonal and myelin formation

Development of Immunoglobulin A Nephropathy- Like Disease in β-1,4-Galactosyltransferase-I-Deficient Mice

β4 Galactosylation of glycoproteins plays important roles in protein conformation, stability, transport, and clearance from the circulation. Recent studies have revealed that aberrant glycosylation causes various human diseases. Here we report that mice lacking β-1,4-galactosyltransferase (β4GalT)-I, which transfers galactose to the terminal N-acetylglucosamine of N- and O-linked glycans in a β-1,4 linkage, spontaneously developed human immunoglobulin A nephropathy (IgAN)-like glomerular lesions with IgA deposition and expanded mesangial matrix. β4GalT-I-deficient mice also showed high serum IgA levels with increased polymeric forms as in human IgAN. IgAN is the most common form of glomerulonephritis, and a significant proportion of patients progress to renal failure. However, pathological molecular mechanisms of IgAN are poorly understood. In humans, abnormal character of serum IgA, especially serum IgA1 with aberrant galactosylation and sialylation of O-glycans in its hinge region is thought to contribute to the pathogenesis of IgAN. Mouse IgA has N-glycans but not O-glycans, and β4-galactosylation and sialylation of the N-glycans on the serum IgA from β4GalT-I-deficient mice was completely absent. This is the first report demonstrating that genetic remodeling of protein glycosylation causes IgAN. We propose that carbohydrates of serum IgA are involved in the development of IgAN, whether the carbohydrates are O-glycans or N-glycans