Journal: bioRxiv

Article Title: Reduced enteric BDNF-TrkB signaling drives glucocorticoid-mediated GI dysmotility

doi: 10.1101/2024.12.13.628260

Figure Lengend Snippet: Graphical representation of the proportions of various Bdnf isoforms whose transcripts were detected in the murine ileal LM-MP layer in two different sexes across three different ages of 1-month (juvenile), 6-month (mature adult), and 17-month (aging). This representation shows that stress-responsive Bdnf VI is the dominant isoform found in the murine ileal LM-MP at all ages, with its proportions accounting for >80% of all isoforms. The isoform Bdnf V is the second most represented isoform at all ages in the murine LM-MP layer but little is known about the mechanisms that regulate its expression. In addition to Bdnf VI, Bdnf IV is another stress-responsive isoform detected in the juvenile and adult mice but is not detected in aging murine ileal LM-MP. In contrast to Bdnf IV, Bdnf II isoform is detected in the adult and aging ileal tissues, but not in the juvenile tissues. Finally, Bdnf III isoform is detected only in the adult ileal LM-MP and not at the other ages.

Article Snippet: The levels of BDNF in the LM-MP tissues cultured with and without dexamethasone were measured using the BDNF DuoSet kit (R&D Systems; DY248).

Techniques: Expressing

Journal: bioRxiv

Article Title: Reduced enteric BDNF-TrkB signaling drives glucocorticoid-mediated GI dysmotility

doi: 10.1101/2024.12.13.628260

Figure Lengend Snippet: (A) Bdnf expression is detected in 1-month, 6-month, and 17-month-old mice. Isoform-level abundance estimates were collapsed to gene-level after inter-library normalization with edgeR (TMM method). Across all ages, average expression of Bdnf is 0.38 ± 0.02 TPM. Independently, gene-level differential expression across age was conducted with DESeq2 (counts ∼ age + RIN + batch, Wald test) and Bdnf was not identified as differential by age across any comparison. (B) Abundance estimates of individual Bdnf isoforms identify the e6 isoform (ENSMUST00000111045) as the majority isoform in each condition. The average expression of this isoform is 0.32 ± 0.08 TPM. Other lowly detected isoforms include e5 (ENSMUST00000176893), e4 (ENSMUST00000111050), e3 (ENSMUST00000111046), and e2 (ENSMUST00000111047), while remaining isoforms were not detected. Differential isoform usage by age was tested via the DEXSeq wrapper within IsoformSwitchAnalyzeR (Likelihood ratio test, full model: ∼ sample + exon + age:exon, reduced model: ∼ sample + exon). No Bdnf isoforms were identified as having significant differential usage by age. (C) Isoform level expression was transformed to isoform fraction (IF) measures by age (for each age, sum of IF’s is 1).

Article Snippet: The levels of BDNF in the LM-MP tissues cultured with and without dexamethasone were measured using the BDNF DuoSet kit (R&D Systems; DY248).

Techniques: Expressing, Comparison, Transformation Assay

Journal: bioRxiv

Article Title: Reduced enteric BDNF-TrkB signaling drives glucocorticoid-mediated GI dysmotility

doi: 10.1101/2024.12.13.628260

Figure Lengend Snippet: Transcriptomic and proteomic evidence of neuronal expression of BDNF. (A) Confocal microscopy image of a 14 μm thick section of adult murine ileal LM-MP tissue which was probed with RNAScope-probes against all Bdnf (green) , Ntrk2 (red) transcripts and against the pan-neuronal Tubb3 (grey) transcript show that off (i, ii) all the Tubb3 -expressing myenteric neurons, distinct neurons express Bdnf (yellow arrow, (i, iii)) and Ntrk2 (TrkB, red arrow, (i, iv)). That Bdnf and Ntrk2 expressing neurons are distinct neurons can also be observed in (v) an image representation where the dominant Tubb3 transcripts are not visualized. No other cellular subset inside or outside the ganglia shows expression of Bdnf or Ntrk2 transcripts providing evidence that BDNF and TrkB in the adult small intestine are neuronally restricted. Nuclei are labeled with DAPI (blue). Scale bar represents 10 μm. (B) Immunostaining a human small intestinal tissue section with antibodies against BDNF also shows that while the secreted form of BDNF is present inside and outside of the myenteric ganglia, the highly enriched presence of BDNF in the cytoplasm of a myenteric neuron (black arrow) suggests its likely source of expression. Scale bar represents 100 μm.

Article Snippet: The levels of BDNF in the LM-MP tissues cultured with and without dexamethasone were measured using the BDNF DuoSet kit (R&D Systems; DY248).

Techniques: Expressing, Confocal Microscopy, RNAscope, Labeling, Immunostaining

Journal: bioRxiv

Article Title: Reduced enteric BDNF-TrkB signaling drives glucocorticoid-mediated GI dysmotility

doi: 10.1101/2024.12.13.628260

Figure Lengend Snippet: (A) Adult male mice dosed with dexamethasone (Dexa) and sacrificed 4 hours later showed a significant down regulation in the expression of stress and glucocorticoid-responsive Bdnf IV and Bdnf VI transcripts in their small intestinal LM-MP tissues, when compared to age- and sex-matched mice that were dosed with vehicle. *p < 0.05, **p < 0.01, Students’ t-test. (B) Small intestinal LM-MP tissues from adult male mice that were cultured with Dexa for 4 hours showed a significant down regulation in the expression of stress and glucocorticoid-responsive Bdnf IV and Bdnf VI transcripts in their small intestinal LM-MP tissues, when compared to tissues from age- and sex-matched mice that were cultured with vehicle. *p < 0.05, Students’ t-test. (C) Small intestinal LM-MP tissues from adult male mice that were cultured with Dexa for 4 hours showed a significant reduction in the abundance of BDNF protein as assessed by ELISA, when compared to tissues from age- and sex-matched mice that were cultured with vehicle. **p < 0.01, Students’ t-test. (D) Dexa-treated adult male mice that were also dosed with the synthetic and specific agonist of TrkB HIOS showed significant reduction in their whole gut transit time of orally gavaged carmine-red dye, and hence improved gut motility, when compared to age- and sex-matched mice that were dosed only with Dexa.

Article Snippet: The levels of BDNF in the LM-MP tissues cultured with and without dexamethasone were measured using the BDNF DuoSet kit (R&D Systems; DY248).

Techniques: Expressing, Cell Culture, Enzyme-linked Immunosorbent Assay