EXTL3 encodes alpha1,4-N-acetylglucosaminyltransferases I and II enzymes, which are involved in chain initiation and elongation of heparan sulfate (HS) biosynthesis. HS proteoglycans are critically involved in a variety of biological phenomena at various levels of complexity in adult and embryonic lives. Dedicated functions of HS proteoglycans are due to variable HS chains that interact with different cellular proteins, and can be regulated by their synthesizing enzymes. EXTL3 protein is also a putative receptor for Reg protein, a growth signal mediator for the beta-cells of the pancreas. The present Northern blot analysis revealed two EXTL3 transcripts (6.2 and 3.4 kb), which were differentially expressed in different mouse adult tissues. The strongest expression was in the adult brain and pancreas. In the adult pancreas, a comparable intensity of both signals was detected. In the embryonic pancreas, the longer transcript was predominant, and showed a biphasic expression pattern with a peak at E11.5, whereas the shorter one showed a steady level of expression throughout the whole period of pancreatic development. By in situ hybridization, the acini of adults and embryos were strong positive for EXTL3 mRNA. Mature islets of Langerhans gave a weak signal, whereas the developing islets showed moderately positive reaction albeit less intense than the acini. In situ hybridization revealed a wide and differential expression pattern of EXTL3 mRNA in embryonic tissues. At the early stages, intense reaction was found in the developing neurons of the brain and spinal cord and in the epithelia of the developing GIT, pancreas, liver and kidney of embryos. Our data suggested that EXTL3 expression is developmentally regulated, and may contribute to the regulated production of HS in different adult and embryonic tissues.

No abstract

Aging is associated with reduced hippocampal neurogenesis, which may in turn contribute to cognitive impairment. We assessed the effect of Ginkgo biloba (Gb) on hippocampal neurogenesis in elderly male mice using immunohistochemistry. We used anti-caspase-3 as a marker of apoptosis, anti-GFAP as a marker of neural stem cells, anti-Ki-67 as a specific marker for cellular proliferation and anti-doublecortin (DCX) to detect newly born neurons in the hippocampal dentate gyrus (DG) of aged male mice. The 24-month-old male mice were divided into two groups: a control group treated with distilled water and a group fed with Gb at a dose of 100 mg/kg once daily for 28 days. A sharp decrease in apoptotic cells in Gb-treated compared to nontreated mice was observed by anti-csapase-3 immunostaining. A large number of GFAP+ve cells was found in the subgranular zone of the DG of Gb-treated mice, suggesting an increase in the pool of neural stem cells by Gb treatment. There was also an increase in Ki-67 immunoreactive cells, indicating increased cell proliferation in the DG in the Gb-treated compared to nontreated group. A significant increase in newborn DCX+ve neurons with well-developed tertiary dendrites was also found in the Gb-treated compared to nontreated group. Using Western blot analysis, the expression of DCX protein in the Gb group was also significantly increased compared to the control. The results support a beneficial role of Gb on hippocampal neurogenesis in the context of brain aging.

No abstract